Global Volcanism Program

Etna

Google Earth Placemark with Features

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Italy
Sicily Volcanic Province
Composite | Stratovolcano(es)
2024 CE

Country
Volcanic Region
Landform | Volc Type
Last Known Eruption

37.748°N
14.999°E
3,357 m
11,014 ft
211060

Latitude
Longitude
Summit
Elevation
Volcano
Number

Most Recent Weekly Report: 16 October-22 October 2024 Cite this Report

Sezione di Catania - Osservatorio Etneo (INGV) reported that during 14-20 October activity at Etna was characterized by continuous intra-crater explosive activity at NE Crater, mild and sporadic ash emissions from SE Crater, and degassing activity from the summit craters, based on webcam images. During 17-20 October weather conditions prevented clear observations. The Aviation Color Code was raised from Yellow to Orange at 1538 on 21 October.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

Most Recent Bulletin Report: August 2023 (BGVN 48:08) Cite this Report

Intermittent Strombolian activity, lava flows, and ash plumes during March-June 2023

Etna, on the Italian island of Sicily, has had documented eruptions dating back to 1500 BCE. Activity typically originates from multiple cones at the summit, where several craters have formed and evolved. The currently active craters are Northeast Crater (NEC), Voragine (VOR), and Bocca Nuova (BN), and the Southeast Crater (SEC); VOR and BN were previously referred to as the “Central Crater”. The original Southeast crater formed in 1978, and a second eruptive site that opened on its SE flank in 2011 was named the New Southeast Crater (NSEC). Another eruptive site between the SEC and NSEC was referred to as the "cono della sella" (saddle cone) and developed during early 2017. The current eruption period began in November 2022 and has been characterized by new, active vents, and lava flows (BGVN 48:03). This report updates activity during March through June 2023, which includes Strombolian activity, lava flows, and ash plumes, based on weekly and special reports by the Osservatorio Etneo (OE), part of the Catania Branch of Italy's Istituo Nazionale di Geofisica e Vulcanologica (INGV) and satellite data.

Variable fumarolic degassing was reported at all summit craters Bocca Nuova (BN), Voragine (VOR), Northeast Crater (NEC), and Southeast Crater (SEC) throughout the entire reporting period. The MIROVA (Middle InfraRed Observation of Volcanic Activity) volcano hotspot detection system based on the analysis of MODIS data showed frequent but low-power thermal anomalies throughout the reporting period (figure 393). There was a short break in activity during mid-April and a pulse of stronger thermal activity during late May. Infrared satellite imagery captured a persistent thermal anomaly at the central summit crater area (figure 394). On 7 May a second thermal anomaly was also visible in SEC. Accompanying thermal activity were occasional sulfur dioxide plumes that exceeded 2 Dobson Units (DUs) recorded by the TROPOMI instrument on the Sentinel-5P satellite (figure 395). During 21-22 May notably strong sulfur dioxide plumes drifted E and occurred around the same time as the strong pulse in thermal activity as shown on the MIROVA graph.

Table 14. Summary of activity at the four primary crater areas at the summit of Etna during March-June 2023. Information is from INGV weekly reports.

Month	Bocca Nuova (BN)	Voragine (VOR)	Northeast Crater (NEC)	Southeast Crater (SEC)
Mar 2023	Continuous degassing.	Weak fumarolic degassing.	Weak fumarolic degassing.	Variable fumarolic degassing at the crater rim and fractures along the cone.
Apr 2023	Continuous degassing.	Weak fumarolic degassing.	Weak fumarolic degassing.	Intense fumarolic degassing at the crater rim and fractures along the cone.
May 2023	Continuous degassing. Strombolian activity.	Fumarolic degassing.	Fumarolic degassing.	Continuous degassing. Strombolian activity. Lava flows.
Jun 2023	Continuous degassing.	Weak degassing.	Weak degassing.	Continuous degassing.

Figure 393. Frequent thermal activity at Etna was relatively low during March through June 2023, as indicated by this MIROVA plot (Log Radiative Power). A short break in activity occurred during mid-April. There was a brief pulse of strong thermal activity during late May. Courtesy of MIROVA.

Figure 394. Infrared (bands B12, B11, B4) satellite images showing a strong thermal anomaly at Etna’s central crater area on 13 March 2023 (top left), 27 April 2023 (top right), 7 May 2023 (bottom left), and 18 June 2023 (bottom right). On 7 May a second thermal anomaly was visible in the Southeast Crater area. Courtesy of Copernicus Browser.

Figure 395. Sulfur dioxide plumes that exceeded 2 Dobson Units (DUs) rose above Etna on 19 March 2023 (top left), 4 April 2023 (top right), 21 May 2023 (bottom left), and 22 May 2023 (bottom right). The plumes drifted S, SE, and E, respectively. Two significant sulfur dioxide plumes were captured during late May, which drifted E. Courtesy of NASA Global Sulfur Dioxide Monitoring Page.

Activity during March and April was relatively low and mainly consisted of variable degassing at the summit craters. According to INGV weak explosions that ejected ash were detected on 8 and 14 May at SEC. During 18-19 May eruptive activity resumed, consisting of Strombolian activity at BN and SEC, though there were only short periods of visibility due to weather conditions. Strombolian activity from SEC began at 0456 on 18 May, based on webcam images taken from a camera at Montagnola. The Aviation Color Code (ACC) was raised to Yellow (the second lowest level on a four-color scale) at 1242 after a sudden increase in volcanic tremor amplitude that began at 1210. A seismic swarm in the summit area at 1644 was immediately followed by ground deformation recorded at the Punta Lucia and Pizzi Deneri summit stations. On 18 May at 1700 explosive activity was observed in BN based on infrared webcam images from Bronte (13 km WNW). The ACC was raised to Orange (the second highest level on a four-color scale) at 1751. On 19 May around 0456 weak intra-crater Strombolian activity was also recorded at SEC based on images taken by the Montagnola webcam. INGV reported that it was possible intermittent explosive activity occurred during 19-20 May.

There was a sharp increase in volcanic tremors at 0720 on 21 May. During 0730-1140 on 21 May the explosive activity at SEC evolved to lava fountaining, accompanied by an ash plume that drifted as far as 10 km and ashfall to the SW, S, and SE (figure 396). The ACC was raised to Red (the highest level on a four-color scale) at 0937 due to ash and lapilli on the SW flank, affecting the area between Adrano village at 560 m elevation and Catania as well as Aci Castello. According to news reports the ashfall caused the Catania-Fontanarossa Airport in Sicily to close until 0900 on 22 May. The runway had been covered in ash and at least 68 flights to and from the airport were cancelled. In addition, lava flows were also reported from SEC that moved S and E from the summit; the flows expanded to the W part of BN and near Monte Frumento Supino, as seen in Landsat 8 data. The S flow reached about 2 km in length, while the one in the Valle del Bove was 1.9 km long and extended E. According to quantitative estimates, the lava covered 300,000 m² and expanded to 2.3 km in length (figure 397). A strong sulfur dioxide plume that drifted E was also captured in satellite imagery (figure 395). The ACC was lowered to Orange at 0601 on 22 May, though the lava flows remained active. During 23-24 May weak intra-crater explosive activity was observed at SEC (figure 398) and some flashes of incandescence were visible at BN. The ACC was lowered to Yellow at 0840 on 23 May and then to Green at 1051. A drone overflight was conducted on 27 May that observed the lava flows and tephra deposits emplaced during 21 May. Flows had traveled 2.3 km and descended to 2,650 m elevation. During a field inspection on 28 May volcanologists observed gas emissions rising from BN and fumarolic activity at both VOR and NEC.

Figure 396. Photo of ashfall near Etna from explosive activity at the Southeast crater on 21 May 2023. Courtesy of Boris Behncke, INGV.

Figure 397. Map of the new lava flows (yellow and orange) at SEC (CSE) of Etna on 21 May 2023. The background image is a shaded model of the terrain of the summit area obtained by processing drone images acquired during several overflights made on 15 and 21 September 2022 and 6, 21, and 23 October 2022, superimposed on the shaded model from a Pleiades image taken on 22 August 2020. CSE = Southeast Crater; CNE = Northeast Crater; BN = Bocca Nuova; VOR = Voragine. Courtesy of INGV (Report 22/2023, ETNA, Bollettino Settimanale, 22/05/2023 - 28/05/2023).

Figure 398. Photo of weak intra-crater explosive activity at Etna’s Southeast Crater on the evening of 23 May 2023. Photo has been color corrected. Courtesy of Boris Behncke, INGV.

During June, activity was relatively low and mainly consisted of degassing at each of the summit craters. On 8 June during 2248-2250 a thermal anomaly was visible on the S flank of SEC in webcam images. An analysis of the image noted that this was due to a collapse in an unstable part of the cone, which exposed hot material. In addition, based on visual and thermal surveillance cameras on Montagnola, a short series of hot material moved down the slope.

Information Contacts: Sezione di Catania - Osservatorio Etneo, Istituto Nazionale di Geofisica e Vulcanologia (INGV), Sezione di Catania, Piazza Roma 2, 95123 Catania, Italy (URL: http://www.ct.ingv.it/it/); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); NASA Global Sulfur Dioxide Monitoring Page, Atmospheric Chemistry and Dynamics Laboratory, NASA Goddard Space Flight Center (NASA/GSFC), 8800 Greenbelt Road, Goddard MD 20771, USA (URL: https://so2.gsfc.nasa.gov/); Copernicus Browser, Copernicus Data Space Ecosystem, European Space Agency (URL: https://dataspace.copernicus.eu/browser/); Boris Behncke, Istituto Nazionale di Geofisica e Vulcanologia (INGV), Sezione di Catania, Piazza Roma 2, 95123 Catania, Italy (Twitter: https://twitter.com/etnaboris); MSN, Mount Etna eruption: Flights canceled after Catania Airport runway covered in volcanic ash (URL: https://www.msn.com/en-us/travel/news/mount-etna-eruption-flights-canceled-after-catania-airport-runway-covered-in-volcanic-ash/ar-AA1bxuub).

Weekly Reports - Index

16 October-22 October 2024 Cite this Report

Source: Sezione di Catania - Osservatorio Etneo (INGV)

25 September-1 October 2024 Cite this Report

Sezione di Catania - Osservatorio Etneo (INGV) reported that continuous gas emissions rose from Etna’s summit craters during 23-29 September. Explosive activity at NE Crater that began at around 2300 on 23 September continued through the week, though with less frequently, based on webcam images.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

18 September-24 September 2024 Cite this Report

Sezione di Catania - Osservatorio Etneo (INGV) reported that mainly gas emissions rose from Etna’s summit craters during 16-23 September. The activity was strongest at Bocca Nuova Crater where the gas emissions were dense and continuous, and occasionally contained ash. A series of explosions at NE Crater began at 2310 on 23 September and were visible in webcam images.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

21 August-27 August 2024 Cite this Report

INGV reported that activity at Etna’s summit craters continued during 19-25 August, though weather conditions often prevented visual observations during daylight hours. Continuous gas emissions were visible from the summit craters, especially at SE Crater (SEC). At 2154 on 23 August a thermal anomaly and a short-lived sequence of ash emissions from the E vent at SEC were visible in thermal webcam images.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

14 August-20 August 2024 Cite this Report

INGV reported that activity at Etna’s summit craters continued during 12-18 August. Strombolian activity at Voragine Crater during 12-13 August ejected lava fragments that fell on the cone’s flanks. The seismic network recorded significant increases in tremor levels during 1700-2000 on 14 August and webcam images showed that Strombolian activity at Voragine Crater intensified. The Strombolian activity become lava fountaining by 0030 on 15 August and lava overflowed the W crater rim at Bocca Nuova Crater. Ash plumes at the peak of the activity rose as high as 9.5 km a.s.l. (about 6.2 km above the summit) and drifted SSW and ESE. Tephra fell in several areas including Belpasso, Pedara, Nicolosi, Ragalna, Mascalucia, Tremestieri Etneo, Gravina di Catania, Catania, Viagrande, Milo, Zafferana, Santa Tecla, Giarre, Santa Venerina Aci Bonaccorso, and Syracuse. According to a news article the Aeroporto de Catania (also called the Catania-Fontanarossa Airport) closed due to ashfall on the runways, with flights either being canceled, rescheduled, or diverted to other airports. The lava fountaining began to decrease at around 0230 and ceased at 0320. A two-minute-long explosion was recorded at 0328 and was followed by moderate level of Strombolian activity that gradually decreased. During a field inspection on 15 August scientists observed the new lava flows and noted that they overlapped the 4 August flows and descended farther SW. Lava from the fountaining event continued to fill in Bocca Nuova Crater and partially filled in NE Crater.

Two explosion sequences at Bocca Nuova Crater were recorded at 0430 and 0459 on 18 August and lasted four and six minutes, respectively. The explosions produced eruptive clouds that drifted ENE and rapidly dissipated. The explosions may have reopened the N vent because a thermal anomaly and almost continuous gas emissions from Bocca Nuova followed the events. Strombolian activity at Voragine Crater was also observed on 18 August.

Sources: Sezione di Catania - Osservatorio Etneo (INGV); Euronews

31 July-6 August 2024 Cite this Report

INGV reported that activity at Etna’s summit craters continued during 29 July-4 August. On 29 July ongoing Strombolian activity at the Voragine crater generated a small ash emission that quickly dispersed from the summit area. Around 0408 on 4 August the Strombolian activity at Voragine crater began to increase in intensity and frequency, with volcanic tremor amplitude reaching very high levels around 0430 and increasing further by 0520 when activity transitioned to lava fountains. At 0445 the Aviation Color Code was raised from Orange to Red, though the ash cloud height could not be estimated. The fountains produced an SO2-rich eruption plume that by 0542 had reached about 6.5 km above the summit (to about 10 km a.s.l.) and was drifting SE; significant tephra (ash and lapilli) fell towards the E, affecting areas such as Fleri (14 km SE), Fornazzo (10.5 km E), Zafferana (11 km SE), Milo (11 km ESE), Santa Venerina (14 km SE), Giarre (17 km E), Riposto (18 km E), Stazzo (20 km SE), Torre Archirafi (20 km E), San Giovanni La Punta (20 km SSE), Viagrande (17 km SE), Aci Sant'Antonio, Aci Catena (20 km SE), Aci Castello (23 km SE), Aci Trezza (23 km SE), and Acireale (20 km SE). An ash advisory at 1058 noted that a second plume with a high ash concentration had reached 6.2 km a.s.l., and both it and the higher plume were drifting SSE. The high tremor amplitude decreased after 0910, explosive activity decreased over the next few hours, and at 1318 the Aviation Color Code was lowered from Red to Orange, though there were still sporadic emissions with ashfall confined to the summit area. Operations at the Aeroporto de Catania were reduced to six arrivals per hour during part of this period of elevated activity. During the lava fountaining, INGV observers noted that lava from Voragine had completely filled the Bocca Nuova (BN) crater, resulting in lava overflows from its W rim. There was an also an active flow moving NW to an elevation of about 3,000 m, and a flow was present between the Voragine and BN craters.

Sources: Sezione di Catania - Osservatorio Etneo (INGV); Toulouse Volcanic Ash Advisory Centre (VAAC); Aeroporto di Catania

24 July-30 July 2024 Cite this Report

INGV reported that activity at Etna’s summit craters continued during 24-28 July. Volcanologists conducted a field inspection of the summit area on 24 July, the day after intense activity that included Strombolian explosions and lava fountaining at Voragine Crater, and lava overflows at Bocca Nuova Crater. Explosive activity at Voragine Crater occurred at intervals of 35-40 minutes during the inspection and ejected material beyond the crater rim. Lava flows originated from three breaches along Bocca Nuova Crater’s WNW, W, and SW rim and continued to advance. The WNW flow traveled the farthest, reaching 2,905 m elevation, followed by the W and SW flows that reached 2,950 and 3,026 m elevations, respectively. The total volume of the lava flows that breached the crater rim, the flows that pooled within the crater, and ejected pyroclastic deposits, were estimated to be 2.4 x 10^6 cubic meters. Activity at Voragine Crater on 25 July was characterized by intermittent explosive activity and a period of Strombolian activity.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

17 July-23 July 2024 Cite this Report

INGV reported that activity at Etna’s summit craters continued during 14-23 July. Explosive activity at both Voragine Crater and NE Crater began to slowly intensify at around 1500 on 14 July and ash emissions from both craters rapidly dispersed. Infrasound data showed increasing activity at NW Crater at around 1600.

Strombolian activity at Voragine Crater persisted on 15 July, and that same day minor ash emissions from Voragine and NE craters were visible in webcam images. Volcanic tremor amplitude values fluctuated at average values for most of the day, then began to increase. Activity at Voragine was observed in infrasound data. Strombolian activity at Voragine slowly intensified beginning around 2100 and volcanic tremor amplitude reached very high levels, peaking at 2140. Activity continued to intensify, and lava fountaining began at 2154. Ash plumes reached about 6 km a.s.l., or about 2.6 km above the summit, and drifted SE. Ashfall was reported in areas downwind including Viagrande (16 km SSE) and Aci Castello (26 km SSE). Lava flowed over the NW rim of Bocca Nuova Crater and descended to about 3,000 m elevation. The average volcanic tremor amplitude remained at very high levels and peaked again at 0100 on 16 July. Infrasound data showed a decrease in the frequency of events. Lava fountaining decreased and had ceased by 0210 on 16 July, though Strombolian activity persisted until around 0500. Reddish ash plumes occasionally rose from NE Crater throughout the day. Strombolian activity at NE Crater began at around 2300 and ejected large bombs several tens of meters above the crater rim. The lava flow continued to be fed though at a low rate.

INGV staff visited the summit area on 17 July and saw Strombolian activity in NE Crater; the activity was also visible in webcam images. The activity produced both fine and coarse material that was ejected tens of meters above the crater rim; the coarser material fell back inside the crater as well as onto the flanks. An explosion at NE Crater at 1956 produced an ash plume that rapidly dispersed.

Strombolian activity at Voragine Crater was again visible in webcam images on 22 July, though weather clouds mostly obscured observations. Volcanic tremor amplitude was low, though gradually increasing, through the day; the amplitude reached a high level by 1745 and remained high. Infrasound data indicated activity in Voragine. The Strombolian activity intensified and was characterized as strong by 0300 on 23 July. Ash emissions rose about the summit, volcanic tremor amplitude increased to very high levels, and by 0508 lava fountaining was underway that resulted in overflows of the Bocca Nuova Crater W rim. Lava fountaining persisted and by 0830 fountains were rising several hundred meters above the crater rim. Ash plumes rose around 8 km a.s.l., or about 4.6 km above the summit, and drifted ESE, then SSE. Ashfall was reported in Rifugio Sapienza (5 km S), Piano Vetore (6 km SSW), C.da Milia, Nicolosi (15 km S), Tremestieri Etneo (20 km SSE), and Catania (29 km SSE). The lava fountaining gradually decreased and then ceased by 1015. The lava flow produced during the activity was small, though due to weather clouds the total length was undetermined.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

10 July-16 July 2024 Cite this Report

Sezione di Catania - Osservatorio Etneo (INGV) reported that an eruption at Etna continued during 8-14 July. The eruption was characterized by a gradual increase of Strombolian activity within the Voragine Crater on 10 July, and ash emissions on 11 July. The Toulouse VAAC issued advisories for an ash emission that rose about 1 km above the summit (12,000 ft a.s.l.) and drifted S. After a few days of decreased activity, explosions gradually increased in the NE Crater (NEC) and Voragine on 14 July, generating ash emissions that quickly dispersed above the craters; light ash emissions continued afterwards from both craters. The amplitude of volcanic tremor rapidly fluctuated between medium and high levels. Signal locations shifted from an area just E of the Voragine crater to the SE Crater area on 12 July, and then shifted again to the NEC area on 14 July.

Sources: Sezione di Catania - Osservatorio Etneo (INGV); Toulouse Volcanic Ash Advisory Centre (VAAC)

3 July-9 July 2024 Cite this Report

Sezione di Catania - Osservatorio Etneo (INGV) reported that an eruption at Etna continued during 3-9 July, with activity intensifying on 4 July and producing substantial ashfall in areas downwind during 4-7 July. Strombolian activity at Voragine Crater intensified during 2-3 July and lava continued to flow into Bocca Nuova Crater. During the evening of 3 July Dipartimento della Protezione Civile raised the Alert Level to Yellow (the second lowest level on a four-level scale). Strombolian activity at Voragine notably intensified during the morning of 4 July and tremor amplitude further increased around 1420. Two lava flows from two vents located on the SE and NW sides of the growing scoria cone continued to flow into the Bocca Nuova. Bombs and scoria were ejected hundreds of meters high. The Strombolian activity changed to tall lava fountaining at 1815 and produced ash-and-gas plumes that rose to about 4.5 km a.s.l., or over 1.1 km above the summit, and drifted SE. Notable ashfall was reported in several areas downwind as far as Catania (29 km SSE). The lava fountaining gradually decreased through the night and ceased at around 0350 on 5 July; about an hour of Strombolian activity followed. Ash-and-gas emissions continued to rise to the same height as the previous day and drifted SE. Significant ashfall was reported in areas downwind and beyond Syracuse, 60-80 km SSE. According to a news article the airport in Catania closed due to ash on the runways; operations resumed by 1500, though some flight restrictions were in place.

The amplitude of volcanic tremor fluctuated between medium and high levels. Strombolian activity resumed during the afternoon on 6 July. The activity intensified at around 0000 on 7 July and changed to lava fountaining by around 0400. Ash emissions rose about 9 km a.s.l. (about 5 km above the summit) and drifted ESE, causing significant ashfall to the E, especially in the area between Zafferana Etnea (10 km SE) and Giarre (17 km ESE). At around 0850 lava overflowed the NW rim of Bocca Nuova Crater and traveled just over 500 m, stopping at around 3,000 m elevation. Sporadic ash emissions at Southeast Crater were observed. The lava fountaining gradually weakened and ceased at around 1000 and was followed by Strombolian activity that also gradually weakened and then ceased after about an hour. A more notable ash emission from Southeast Crater occurred at 1141 and rapidly dissipated. By 1228 minor ash emissions continued to occur and lava continued to flow from the summit craters.

Sources: Sezione di Catania - Osservatorio Etneo (INGV); Dipartimento della Protezione Civile; Reuters; Euronews

26 June-2 July 2024 Cite this Report

INGV reported that eruptive activity was recorded at Etna’s Bocca Nuova Crater, Southeast Crater, and Voragine Crater during the month of June. Gas emissions at Bocca Nuova Crater were variable and sometimes high-temperature pulses were visible as incandescent flashes at night. Occasional emissions of red ash were visible but quickly dissipated. At Southeast Crater fumarolic gas emissions rose from the E part of the cone and from the 2 April pit crater on the N crater rim. Diffuse ash emissions from the E vent were visible during 6-9 June. At Voragine Crater weak Strombolian activity began during 13-14 June at a vent located at the southern inner wall of a cinder cone formed during 2019-2021 activity. Initially explosions occurred about every 10 minutes and built small hornitos. Over a period of days, the material accumulated and formed a small scoria cone; Strombolian activity at two vents began to intensify on 26 June. The new cinder cone reached about 20 m high during 27-30 June. On 29 June lava from the SE side of the cone flowed into Bocca Nuova Crater and on 1 July a lava flow effused from a vent on the NW flank.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

19 June-25 June 2024 Cite this Report

INGV reported that Etna’s Voragine Crater began erupting on 14 June, after more than three years of quiescence, and continued to eject lava through at least 23 June. The activity gradually increased from spattering lava at a new vent to more vigorous with jets of incandescent lava that rose several tens of meters above the crater rim. A new scoria cone grew inside the crater.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

12 June-18 June 2024 Cite this Report

According to news reports, video of Etna’s Voragine Crater showed gas jetting from a vent followed by spattering lava on 15 June. INGV issued a Volcano Observatory Notice for Aviation (VONA) at 2016 on 17 June raising the Aviation Color Code to Yellow (the second highest color on a four-color scale) due to increased signs of unrest. The Aviation Color Code was raised to Orange at 2025 because explosive activity at the summit craters was visible in webcam images and observed by volcanologists in the field.

Sources: Sezione di Catania - Osservatorio Etneo (INGV); Local Team

10 April-16 April 2024 Cite this Report

INGV reported that at 2241 on 10 April a weak explosion at Etna’s Southeast Crater produced an ash emission that quickly dispersed based on webcam images. INGV issued a Volcano Observatory Notices for Aviation (VONA) on 12 and 16 April lowering the Aviation Color Code to Yellow and then Green, respectively.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

3 April-9 April 2024 Cite this Report

A small vent at Etna’s Southeast Crater began emitting unprecedented quantities of volcanic gas puffs that formed vortex rings during the evening of 2 April. INGV issued a Volcano Observatory Notice for Aviation (VONA) at 2016 on 2 April raising the Aviation Color Code to Yellow (the second highest color on a four-color scale) due to increased signs of unrest. The Aviation Color Code was raised to Orange at 2030 because explosive activity at the summit craters was visible in webcam images; ash emissions were not produced.

A series of six explosive events were recorded by the seismic network during 1501-1510 on 7 April. Coincident with the seismic signals a four-minute-long, dense ash emission from Bocca Nuova Crater rose to 5 km a.s.l., or about 1.6 km above the summit, and quickly dispersed to the S. A VONA issued at 1018 on 9 April noted sporadic activity at the summit craters.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

20 December-26 December 2023 Cite this Report

INGV reported that a seismic swarm at Etna was recorded during 1508-1517 on 21 December. Coincident with the swarm, light-gray ash emissions rose from Bocca Nuova Crater during 1513-1520 and drifted S, rapidly dissipating. At 0217 on 23 December a strong explosion at SE Crater ejected coarse material onto the flanks and produced an ash plume that was dispersed by wind. At 1223 a strong explosion at the same crater produced an ash plume that rapidly dissipated.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

29 November-5 December 2023 Cite this Report

INGV reported that Strombolian activity at Etna’s SE Crater (SEC) continued during 29 November-5 December. Over the longer period of 19 November-1 December there were over 250 Strombolian explosions counted. Eruptive episodes were quite regular, with episodes lasting 5-15 minutes separated by 60-70 minutes of quiet. At peak intensity there were strong explosions and incandescent jets as high as 200 m above the crater rim. Activity primarily took place at the western-most vent within the saddle of the SEC, but the eastern-most vent was also active. On 29 November eruptive activity began to intensify, and by 1 December the time between episodes was only about 5 minutes. Low pulsating lava fountains and small lava flows on the SW flank of the SEC were observed. A VONA was issued at 1708 and the Aviation Color Code was Red. A new paroxysmal episode began at approximately 1800 with sustained lava fountains sending material 400 m above the crater and producing lava flows down the SSW and ESE flanks to the base of the SEC. Lava flows reached about 2,860 m elevation on the SSW flank and 2,300 m on the SE flank. The Strombolian activity produced ash plumes that rose as high as 6 km a.s.l. and drifted ESE. Ashfall was reported in the towns of Fiumefreddo (20 km ENE), Calatabiano (24 km NE), and Naxos Gardens (25 km NE). The strong activity lasted around three hours, and started to gradually decrease around 2050. A VONA was issued at 2238 lowering the Aviation Color Code to Orange. On 2 December at 1136 and 1254 the Aviation Color Code was lowered to Yellow then Green respectively. During 2-5 December no explosive activity was observed, but degassing was observed from both the SEC and the Bocca Nuova craters.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

22 November-28 November 2023 Cite this Report

INGV reported that Strombolian activity at Etna’s SE Crater (SEC) was periodically visible during 20-26 November; weather clouds often prevented visual observations. The frequency of the eruptive activity was on the scale of hours, and explosions were most intense during 25-26 November. The explosions ejected material that fell within the crater or nearby on the flanks and produced ash emissions that rapidly dispersed near the summit. Lava overflowed the crater starting at 1810 on 24 November and produced a slow-moving lava flow that descended the S flank to the base of the cone. The lava flowed down the same ravine as one of the three flows emplaced on 12 November and was no longer being fed by 0450 on 25 November. During periods of more intense Strombolian activity on 26 November ejected lava that accumulated on the upper S flank and was visible in thermal webcam images. Activity at Bocca Nuova Crater was characterized by pulsating gas emissions and flashes of incandescence generated by the hot gases.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

15 November-21 November 2023 Cite this Report

INGV reported that Strombolian activity resumed at Etna’s SE Crater (SEC) on 22 October and became more continuous and intense through early November. An increase in the frequency of explosions occurred on 4 November, with one occurring about every three minutes. A small new cone formed on the NW flank, near the saddle, that effused lava for a few hours and produced two lava flows that traveled a maximum of 10 m. Strombolian activity at SEC was recorded during 10-12 November, and at 1000 on the 12th a small lava flow was produced. The activity intensified during the afternoon and lava fountaining commenced at around 1730, though weather clouds hindered views. Two main explosive vents were discernable and produced an ash plume that rose almost 1.2 km above the summit and drifted ESE. Ash and lapilli fell in areas from Milo to Zafferana and from Torre Archirafi to Pozzillo. Starting at around 2040 several pyroclastic flows descended the SSE flank and reached the W part of the Valle del Bove. Eruptive activity decreased at around 2100. Minor Strombolian activity continued, and several lava flows traveled S, SE, SSW, and SW.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

8 November-14 November 2023 Cite this Report

INGV-OE reported that eruptive activity continued at Etna during 8-14 November. Lava fountaining began on 12 November at 1700 UTC and ended at 1930 UTC; an eruptive column rose to 4.5 km a.s.l. At 1940, a pyroclastic flow originated from the SE Crater area and traveled SSE. Effusive lava flowed SE, S, and SW from the SE Crater area and began to cool. The seismic network recorded high-amplitude tremor mainly localized to the SE Crater between 1800 and 1900 on 12 November. The average amplitude of the tremor signals decreased drastically and returned to baseline levels by 2000. Deviations in deformation measurements also returned to normal.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

16 August-22 August 2023 Cite this Report

INGV reported that an eruption at Etna began on 13 August. Tremor amplitude suddenly increased at around 2000 on 13 August and reached high values within 20 minutes. Significant infrasonic activity coincided with the tremor increase. Strombolian activity at SE Crater began to gradually intensify starting at 2040. Seismic activity continued to increase. The Aviation Color Code was raised to Yellow (second lowest level on a four-color scale) at 2126 and then to Orange at 2129 due to above-background activity. By 2333 the Strombolian activity had evolved into lava fountaining and lava overflowed the S flank of SE Crater. Ash, gas, and steam plumes drifted S and caused ashfall in areas downwind, on the volcano’s flanks and beyond. The Aviation Color Code was raised to Red at 2241 based on strong explosive activity and ashfall in Rifugio Sapienza-Piano Vetore at 1,700 m elevation on the S flank.

Seismic and infrasonic activity continued to intensify, reached a peak at around 0320 on 14 August, then rapidly decreased to pre-eruptive levels between 0450 and 0530. Coincident with the decreasing seismicity, fountaining ceased at around 0520. The Aviation Color Code was lowered to Orange as volcanic ash was confined to the summit area. Sporadic, minor ash emissions continued throughout the day. At 1415 the Aviation Color Code was lowered to Yellow and then lowered to Green at 1417. According to a news source the ash emissions caused the closure of the Catania airport, about 50 km S, from 0238 until 2000; the airport averages about 200 flights a day. Though activity decreased at the beginning of the day, ashfall continued to impact the area. The mayor banned the use of motorcycles until 16 August and banned drivers from driving over 30 kilometers per hour.

At 2346 an explosion at SE Crater produced a volcanic cloud that rapidly dispersed. The Aviation Color Code was raised to Yellow at 2355 on 14 August due to increasing unrest and lowered back to Green at 0954 on 15 August. At 2030 on 15 August a report noted that during the day the amplitude of volcanic tremor fluctuated widely and was mostly centered beneath SE Crater and E of the central craters. By 1700 infrasonic activity increased and coincided with more intense periods of tremor; the signals indicated that the source of the activity was at Bocca Nuova Crater. Gas emissions rose from both the SE and Bocca Nuova craters. The Aviation Color Code was raised to Yellow at 1944. During 15-20 August gas emissions rose from Bocca Nuova Crater and from the SE Crater’s E vent and numerous fumaroles located along the crater rim.

An 18 August satellite image was used to estimate the extent of the flow field, though the analysis was difficult due to weather clouds obscuring features in the image. The image revealed that a fissure had opened on the SW flank of SE Crater, was about 350 m long, and oriented NNE-SSW. The lava flow reached 2,790 m elevation, W of Frumento Supino, and had an estimated volume of 900,000 cubic meters and an area of 300,000 square meters.

Sources: Sezione di Catania - Osservatorio Etneo (INGV); Euronews

12 July-18 July 2023 Cite this Report

INGV reported that during 10-16 July gas emissions rose from some of Etna’s summit craters and Strombolian activity was visible at SE Crater. Pulsating gas emissions at Bocca Nuova Crater were accompanied by roaring noises and nighttime crater incandescence. Fumarolic activity at NE Crater was visible; no activity occurred at Voragine. During most of the week activity at SE Crater was characterized by continuous gas emissions interspersed with ash emissions that rapidly dissipated. Strombolian activity began at 2034 on 14 July from a vent on the E part of the crater and an ash emission rose from the crater at 2037.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

5 July-11 July 2023 Cite this Report

INGV reported that during 9-10 July explosive activity at Etna’s SE Crater produced ash emissions that rapidly dispersed near the summit.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

24 May-30 May 2023 Cite this Report

INGV reported that during 23-24 May activity at Etna was characterized by weak intra-crater explosive activity at the SE Crater and minor incandescence at Bocca Nuova Crater based on webcam images. A drone survey of the lava flows and tephra deposits emplaced during the 21 May paroxysmal eruption was conducted on 27 May. Lava flows had traveled 2.3 km, reaching 2,650 m elevation. During a field inspection on 28 May volcanologists observed gas emissions rising from Bocca Nuova and fumarolic activity at both Voragine Crater and NE Crater.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

17 May-23 May 2023 Cite this Report

Strong explosive eruptions were reported at Etna by INGV starting on 18 May after continuous degassing and moderate seismicity over the previous few days, with significant Strombolian activity and a paroxysmal event at SE Crater on 21 May. Views were often obscured by persistent weather cloud cover. Strombolian activity from SE Crater at 0456 on 18 May was seen in webcam images from the camera located at Montagnola. The Aviation Color Code was raised to Yellow (second lowest level on a four-color scale) at 1242 following a sudden increase in volcanic tremor amplitude that began at 1210. The signal amplitude decreased for a short time but then increased to an even higher level at 1330. A seismic swarm in the summit area at 1644 was immediately followed by ground deformation recorded at the Punta Lucia and Pizzi Deneri summit stations. At 1656 weak intra-crater Strombolian activity at SE Crater was observed in images taken by the INGV thermal camera at La Montagnola (3 km S). Explosive activity from Bocca Nuova crater starting at 1700 was visible in thermal images from the Bronte (13 km WNW) webcam, concurrent with infrasonic signals. The Aviation Color Code was raised to Orange at 1751. The activity likely persisted for a few hours based on satellite images; weather conditions prevented confirmation with webcams. Tremor fluctuated and by 0927 on 19 May levels had begun to decrease.

Intermittent explosive activity persisted at SE Crater during 19-20 May, with pulsating gas emissions rising from the crater. A sharp increase in volcanic tremors at 0720 on 21 May was a precursor to significant tall lava fountaining during 0730-1140, with ash plumes that rose to 10 km and drifted SW, S, and SE. At 0937 the Aviation Color Code was raised to Red after INGV field personnel observed ash and lapilli fall on the SW flank and ashfall in Adrano at 560 m elevation. Lava flows from SE Crater descended the W part of the Valle del Bove as far as 1.9 km E and the S flank as far as 2 km. Satellite data showed a large sulfur dioxide plume drifting E. Weather clouds prevented views of the activity. Tremor levels sharply decreased starting at 1135 and had stabilized by 1200. Ashfall was also reported in Catania and Aci Castello. According to news reports the ashfall caused the Catania-Fontanarossa Airport in Sicily to close until 0900 on 22 May. The runway had been covered in ash and at least 68 flights to and from the airport were cancelled.

The Aviation Color Code was lowered to Orange at 0601 on 22 May, though lava flows were still active. By 0832 on 23 May monitoring data indicated that eruptive activity had ceased, and webcam images showed that the lava flows were cooling. The Aviation Color Code was lowered to Yellow at 0840 and then to Green at 1051.

Sources: Sezione di Catania - Osservatorio Etneo (INGV); Advanced geospatial Data Management Platform (ADAM); MSN

10 May-16 May 2023 Cite this Report

INGV reported that an explosion at Etna’s SE Crater occurred at 0839 on 14 May and produced an ash emission that rapidly dispersed around the summit area. The Aviation Color Code was raised to Yellow at 0902 and then lowered back to Green at 1830 on 14 May. No significant variations in the seismic data were associated with the explosion.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

3 May-9 May 2023 Cite this Report

INGV reported that a sudden explosion at Etna’s SE Crater occurred at 2325 on 6 May and produced a diffuse ash emission that rapidly dispersed around the crater area. The Aviation Color Code was raised to Yellow at 2358 and then lowered back to Green at 1148 on 7 May. Neither seismic nor infrasound data recorded changes associated with the explosion.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

15 February-21 February 2023 Cite this Report

INGV reported that lava effusion had ended on 6 February from the vents at the NE base of Etna’s SE Crater, in the Valle del Leone at about 2,800 m elevation. The total area covered by the lava flows was an estimated 0.96 square kilometers and the estimated volume was 4,800,000-6,100,000 cubic meters. In a Volcano Observatory Notices for Aviation (VONA) posted on 7 February, the Aviation Color Code was lowered to Yellow (the second lowest level om a four-color scale) and INGV noted that although effusion had stopped unrest was ongoing. In a second VONA, posted on 14 February, the Aviation Color Code was lowered to Green as activity had decreased to background levels.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

1 February-7 February 2023 Cite this Report

INGV reported that the vents at the NE base of Etna’s SE Crater, in the Valle del Leone at about 2,800 m elevation, continued to feed lava flows during 30 January-5 February. The flow rate was highly variable with an increase on 1 February, a gradual decrease overnight during 1-2 February, and a complete cessation on the morning of 2 February. Later, during the afternoon of 2 February, lava again effused from the vent and traveled over pre-existing flows. The effusion rate started to decrease in the afternoon of 4 February and progressively decreased overnight into 5 February. By the afternoon of 5 February, the flows appeared to be cooling.

Intense gas emissions rose from Bocca Nuova Crater while gas emissions at Northeast Crater (NEC) and Voragine were minimal. Activity at Southeast Crater was characterized by fumarolic activity localized along the crater rim and from the May-June 2022 eruptive vent which also occasionally produced flashes of incandescence at night. Occasional diffuse ash emissions were also visible and rapidly dispersed with the wind.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

25 January-31 January 2023 Cite this Report

INGV reported that the vents at the NE base of Etna’s SE Crater, in the Valle del Leone at about 2,800 m elevation, continued to feed lava flows during 23-29 January, without notable changes compared to the week before. Intense gas emissions rose from Bocca Nuova Crater while gas emissions at Northeast Crater (NEC) and Voragine were minimal. Activity at Southeast Crater was characterized by fumarolic activity localized along the crater rim and from the May-June 2022 eruptive vent which also occasionally produced flashes of incandescence at night. Diffuse ash emissions rapidly dispersed with the wind.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

18 January-24 January 2023 Cite this Report

INGV reported that the vents at the NE base of Etna’s SE Crater, in the Valle del Leone at about 2,800 m elevation, continued to feed lava flows during 16-22 January, though the rate notably fluctuated. Lava effusion progressively decreased during 16-17 January and had possibly ceased by the late afternoon of 17 January. Effusion restarted in the early hours of 18 January, generating two lava flows. One of the flows traveled NE along the W edge of the lava field, and the other traveled E onto the steep W wall of Valle del Bove, reaching the base of the wall on 20 January. The effusion rate decreased on 21 January and the again increased during the evening. Late on 22 January a new lava flow descended the Valle del Bove, almost reaching the base of the W wall at around 2,200 m elevation.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

4 January-10 January 2023 Cite this Report

INGV reported that the vents at the NE base of Etna’s SE Crater, in the Valle del Leone at about 2,800 m elevation, continued to feed lava flows during 2-8 January. The active flow field consisted of overlapping lava flows that expanded into the Valle del Leone and the Valle del Bove and hornitos. By 7 January the longest active lava flow had descended to 2,170 m elevation, and the area of the flow field was an estimated 0.63 square kilometers. Gas emissions rose from the summit craters, mainly at Bocca Nuova.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

21 December-27 December 2022 Cite this Report

INGV reported that the vents at the NE base of Etna’s SE Crater, in the Valle del Leone at about 2,800 m elevation, continued to feed lava flows during 19-25 December. The active flow field consisted of overlapping lava flows that expanded into the Valle del Leone and the Valle del Bove. By 25 December the most active lava flow had descended to 2,150 m elevation. Gas emissions rose from the summit craters.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

14 December-20 December 2022 Cite this Report

INGV reported that the vents at the NE base of Etna’s SE Crater, in the Valle del Leone, continued to feed lava flows during 7-18 December. The active flow field consisted of a main lava flow and several breakouts that fed smaller lava flows. A small hornito formed at the vent area and ejected pieces of lava.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

30 November-6 December 2022 Cite this Report

INGV reported that a new vent, at the NE base of Etna’s SE Crater around 2,800 m elevation, was first seen at about 1800 on 27 November when weather conditions allowed for direct visual observations. The vent produced a lava flow that traveled 300 m E towards the Valle del Leone. Inclement weather conditions from 1000 on 28 November until the end of the next day prevented confirmation of continuing activity, though incandescent flashes in the clouds suggested ongoing effusion. The weather conditions improved on 30 November, and a second vent was observed, located upslope from the first at about 2,900 m elevation. A lava flow from the second vent had traveled about 450 parallel to and N of the first flow, reaching about 2,700 m elevation.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

23 November-29 November 2022 Cite this Report

INGV reported that at about 1800 on 27 November a vent opened at the NE base of Etna’s SE Crater, at 2,800 m elevation, and produced a lava flow. The flow slowly advanced a few hundred meters towards the Valle del Leone. Tremor levels at the time the vent opened showed no variations from the average trend recorded during the previous week, and no notable changes were identified in deformation data. Effusive activity continued through 30 November, with additional small lava flows emplacing over the first one. For a period of about an hour, beginning at 1700 on 29 November, tremor amplitude increased and then peaked; the amplitude fluctuated between medium and high values for a few hours afterwards. The source of the tremor was in an area between the SE Crater and Bocca Nuova Crater, at elevations of 2,000-2,600 m.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

15 June-21 June 2022 Cite this Report

INGV reported that during 13-19 June gas emissions rose from Etna’s Southeast Crater (SEC) and Bocca Nuova Crater (BN); the emissions from BN were dense and voluminous on 13 June and drifted SSW. Lava effusion from the vent located at about 2,700 m elevation, along the fissure that had opened on 29 May, had slowed by 13 June and stopped by that evening. Lava continued to erupt from a vent along the 7 June fissure, located at the base of the N wall of the Valle del Bove, advancing to 1,760 m elevation by 14 June. Effusion ceased overnight during 15-16 June.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

8 June-14 June 2022 Cite this Report

INGV reported that during 6-12 June explosive activity at Etna’s Southeast Crater (SEC) produced sporadic and minor ash emissions that rapidly dispersed. The fissure located at the upper part of the Valle del Bove, between 2,700 and 2,900 m elevation, continued to produce lava flows at a variable rate. The flows were most active between 2,000 and 2,100 m elevation but overall were visibly cooling during the week. Flows from the fissure that had opened on 7 June at the base of the N wall of the Valle del Bove, at 1,979 m elevation, had traveled 170 m and were also cooling. A new fissure with three active vents opened on 11 June around 1,900 m elevation. Lava effusion was slow, and the flow only traveled a few tens of meters.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

1 June-7 June 2022 Cite this Report

INGV reported that during 30 May-5 June the fissure located at the upper part of Etna’s Valle del Bove, between 2,700 and 2,900 m elevation, continued to produce lava flows at a variable rate. The flows branched and overlapped, reaching 1,900 m elevation by 5 June. Strombolian activity at Southeast Crater (SEC) varied in intensity and frequency, producing ash emissions that drifted SSE; the most intense activity occurred during 1-3 June. Ash plumes rose to around 5 km (16,400 ft) a.s.l. and drifted S on 3 June. On 7 June a new fissure opened at the base of the N wall of the Valle del Bove, in the Serracozzo area, at 1,900-1,950 m elevation. The fissure produced a lava flow that traveled a few tens of meters.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

25 May-31 May 2022 Cite this Report

INGV reported that during 23-29 May activity at Etna’s Southeast Crater (SEC) was characterized by intermittent Strombolian activity and occasional ash emissions. At 0805 on 29 May a fissure opened in the upper part of the Valle del Bove. Two vents along the fissure, located at 2,850 and 2,730 m elevation, produced slow-moving lava flows that had advanced E to 2,090 m elevation by the next day. During an aerial survey conducted on 30 May scientists observed a series of about four arc-shaped fractures on the E flank of SEC, between 3,000 and 3,200 m elevation, and unstable and slumped material which had moved downslope.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

18 May-24 May 2022 Cite this Report

INGV reported that at around 1900 on 12 May a new vent opened along the N flank of Etna’s Southeast Crater (SEC) at an elevation of 3,250 m, and produced ash emissions that rose to 3.5 km (11,500 ft) a.s.l. and drifted SW. Small pyroclastic flows descended the flank. Lava effused from the vent and traveled N and NE into the snowy Valle del Leone, where lava blocks that rolled onto the snow caused steam plumes. The lava flow slowly advanced during 13-22 May, reaching 2,300-2,400 m elevation by 17 May. Discontinuous Strombolian activity of variable intensities occurred at SEC; ash emissions were visible during more intense phases, though the plumes dissipated rapidly.

A new lava flow emerged from the vent on the N flank at around 2300 on 17 May and traveled N and NE alongside the previous lava flow. During fieldwork conducted on 18 May, scientists observed that lava had reached an elevation of 2,700 m in the Valle del Leone. A new vent opened on the N flank of SEC by 1730 on 20 May, at 3,250 m elevation, just NW of the previous vent. The vent produced a small lava flow that curved N and NE, joining the previous flow. By 21 May lava flows were not advancing below the summit area, at elevations of 2,700-2,800. Strombolian activity of varying intensity continued at SEC; periodic ash emissions generated ashfall in areas as far as Catania. At 2305 on 21 May a pyroclastic flow from the 20 May vent traveled 700 m NNE. Ash emissions intensified during 0300-0400 on 22 May. By that evening, lava flows from the 12 May vent had ceased and the 20 May vent produced short lava flows.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

11 May-17 May 2022 Cite this Report

INGV reported that at around 1900 on 12 May new vents opened along the N flank of Etna’s Southeast Crater (SEC) and produced ash emissions that rose to 3.5 km (11,500 ft) a.s.l. and drifted SW. Lava flowed from the vents and traveled to the N base of the crater. Lava effusion continued over the next several days, and by 17 May the flow had descended ENE into Valle del Leone, reaching 2,300-2,400 m elevation. Discontinuous Strombolian activity of variable intensities occurred at SEC; during more intense phases ash emissions were visible, though the plumes dissipated rapidly.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

23 February-1 March 2022 Cite this Report

INGV reported that during 23-25 February activity at Etna’s Southeast Crater (SEC) was characterized by Strombolian activity and occasional ash emissions that rapidly dispersed to the SSW and SSE. At 1338 on 24 February a forceful ash emission from Northeast Crater drifted SSE. A diffuse ash emission rose from the same crater at 1642. Emissions at Bocca Nuova Crater consisted mainly of gas with occasional minor ash content during 21-27 February.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

16 February-22 February 2022 Cite this Report

INGV reported that a thermal anomaly at Etna’s Southeast Crater (SEC) was first visible in webcam images at 0907 on 21 February, followed within an hour by weak Strombolian activity. Strombolian activity intensified and by noon lava fountaining was visible. An eruption plume had risen to 10 km above the summit and drifted SE. Lava overflowed the SEC at 1210 and traveled SW. The eruption plume reached an altitude of 12 km (39,400 ft) a.s.l., drifted SSE, and caused ashfall in Viagrande (16 km SSE), Trecastagni (16 km SE), Milo (about 11 km ESE), Aci Castello (26 km SSE), and Zafferana (10 km SE). Sometime after 1300 lava fountaining ceased, though the lava flow continued to be fed. Another flow traveling E to an elevation of 2,900 m was visible in webcam images and by scientists observing the eruption in the field. Explosivity activity ceased in the afternoon. Weather conditions hindered views over the next day but by 1900 on 22 February webcam observations were again possible. Weak Strombolian activity at SEC was visible and the E lava flow had advanced.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

9 February-15 February 2022 Cite this Report

INGV reported that a notable eruption at Etna’s Southeast Crater (SEC) occurred during 9-10 February and changed the morphology of the cone. The eruption began with incandescence from explosive activity within SEC that was visible in webcam images at night during 9-10 February. Sporadic ash emissions rose above the crater. Lava began to effuse at 1520 on 10 February and flows descended WSW. Strombolian activity varied in intensity and frequency, though at 1700 there was a clear intensification. Lava flows continued to be fed and had descended S and SE to 2,900 m elevation. Strombolian activity transitioned to lava fountaining at around 2140, with fountains rising 1-1.5 km high, and ash plumes rising to 12 km (39,400 ft) a.s.l. and drifting W. Two pyroclastic flows, visible at 2140 and 2219, traveled a few hundred meters SE towards the Valle del Bove. At 2226 a larger pyroclastic flow expanded 1.6 km S and SE and covered the northernmost 2002-2003 craters, reaching 2,750 m elevation, and damaging a hut along the way. Lava fountaining ceased at 2300. The ash plume slowly dispersed W over the next few hours and the lava flow continued to be fed, reaching 2,850 m elevation. A new deep scarp opening to the SSW was formed during the eruption, overprinting the smaller breach that was on the SW crater rim. The new scarp was about 500 m long and had variable widths of 100-190 m. Weak and sporadic explosive activity continued from the lower part of the scarp. Tephra fell in areas to the NW (particularly at Maletto, 15 km NW) and as far as Sant’Agata di Militello (50 km NW) and Capo d'Orlando (50 km NNW), along the Tyrrhenian coast. At 1125 on 11 February a small vent opened at the SE base of the SEC, emitted ash, and produced a short, thick lava flow that traveled a few tens of meters SE.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

2 February-8 February 2022 Cite this Report

INGV reported that sporadic explosive activity at Etna’s Southeast Crater (SEC) resumed at 0115 on 30 January, producing diffuse ash emissions that rapidly dispersed near the summit, and weak Strombolian activity was visible the next day. Webcam views were intermittent due to weather clouds the next day, but by the morning of 2 February all activity had definitely stopped. Minor and variable gas emissions rose from the Northeast Crater, Bocca Nuova, and Voragine Crater.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

8 December-14 December 2021 Cite this Report

INGV reported that during 6-12 December activity at Etna was characterized by gas emissions from all summit craters and ash emissions from Southeast Crater (SEC); weather conditions prevented views during most of the week. During 6-7 December Strombolian activity at SEC produced almost continuous ash emissions that dispersed ENE. On 8 December the ash emissions were diffuse and discontinuous, and dissipated near the summit. At 1805 on 13 December a new vent opened at the base of the W wall of the Valle del Bove, at 2,180 m elevation. A lava flow emerged from the vents and descended a few hundred meters.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

1 December-7 December 2021 Cite this Report

INGV reported that during 29 November-5 December eruptive activity at Etna was concentrated at the Northeast Crater (NEC) and the Southeast Crater (SEC), while only minor gas emissions rose from the Voragine and Bocca Nuova craters. Webcam images showed diffuse and discontinuous ash emissions from NEC on 1 December that quickly dissipated near the summit. On the morning of 4 December INGV staff working near the summit observed sporadic and diffuse ash emissions rising from SEC and quickly dissipating around the summit. During the afternoon and through the next day webcam images recorded Strombolian activity at SEC, in addition to the ash emissions.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

24 November-30 November 2021 Cite this Report

INGV reported that gas emissions from Etna’s summit craters were visible during 15-21 November, though weather clouds sometimes prevented webcam observations. At 1116 on 20 November an explosion at Northeast Crater (NEC) produced diffuse ash-and-gas plumes that quickly dissipated near the summit.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

20 October-26 October 2021 Cite this Report

Strombolian activity resumed at Etna’s Southeast Crater (SEC) beginning at 0447 on 20 October. Small ash-and-gas puffs drifted SW. Activity gradually increased and by 1920 on 21 October explosions were ejecting incandescent material out of the crater. Activity intensified during the evening of 22 October, and crater incandescence was visible in between weather clouds at night during 22-23 October. Ash plumes drifted NE.

Explosive Strombolian activity increased at 1000 on 23 October, producing ash plumes that then abruptly stopped at 1035. A series of strong explosions began a few minutes later, producing visible pressure waves and ash emissions. Lava fountaining began sometime before 1043 and dense ash-and-gas plumes rose several kilometers high and drifted ENE. A fracture opened on the SE side of the SEC cone and at 1048 a pyroclastic flow traveled 1.5 km SE toward the Valle del Bove. A second pyroclastic flow observed at 1100 also traveled 1.5 km SE. Several smaller pyroclastic flows were visible on the E flank of the cone. At 1158 a pyroclastic flow bifurcated and traveled a few hundred meters S and SE. Lava fountains rose as high as 800 m during the most intense period and a lava flow originating from the E side of the crater descended SE. The ash plumes rose more than 10 km (32,800 ft) a.s.l. and caused ash and lapilli to fall in many areas downwind, including Linguaglossa, Vena, Presa, Piedimonte Etneo, Taormina, and Mascali. Explosive activity began to decrease around 1200 and then ceased at 1220. Ash emissions continued to rise from the SEC and by 1932, the lava flows on the SE flank had stopped advancing.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

15 September-21 September 2021 Cite this Report

INGV reported that tremor amplitude at Etna began gradually increasing at 0420 on 21 September and then suddenly increased at 0440. Ash emissions rose from the Southeast Crater (SEC) at 0815 and by 0855 Strombolian activity was visible. An eruption plume rose 4.5 km above the summit and drifted ENE. Within an hour lava fountaining began and the plume rose 9 km and drifted ENE. Lava overflowed the crater and traveled SW. Lava fountaining had ceased by 1130, though Strombolian activity within the crater continued. Tremor amplitude decreased at 1250 and explosive activity ceased.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

25 August-31 August 2021 Cite this Report

INGV reported that activity at Etna was concentrated at the Southeast Crater (SEC) during 23-29 August. Gas emissions rose from Bocca Nuova crater. A series of explosions at SEC that began at 1530 on 27 August and continued through the next morning produced ash puffs. Strombolian activity began in the early afternoon of 29 August and within an hour, lava fountains were visible rising up to 400 m above the vent. Ash emissions rose a few hundred meters. The activity varied in intensity and during intense periods, ash plumes rose up to 10 km above the summit. Ash and lapilli fell in areas to the E, including in Fornazzo, Milo, San Alfio, and Giarre. Lava flows from the SEC traveled SW and one from the E base traveled E toward the Valle del Bove.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

4 August-10 August 2021 Cite this Report

INGV reported continuing activity at Etna’s summit craters during 2-8 August, mainly from the Northeast Crater (NEC) and the Southeast Crater (SEC). Gas emissions rose from Voragine Crater and from two active craters in Bocca Nuova. A series of discontinuous ash emissions from NEC began at 1350 on 4 August and lasted about two hours. An ash plume rose to 1.8 km (6,000 ft) a.s.l. and drifted NE. Similar but less intense ash emissions were visible on 5 August. The reddish mostly fine-grained material emitted from NEC was erupted when no thermal anomalies were present in the crater, suggesting that they were the result of landslides rather than eruptive activity. Strombolian activity began at SEC at 2057 on 7 August and was characterized by isolated explosions and the ejection of incandescent material beyond the crater rim; activity ceased during the night. An explosion at 2056 on 8 August was followed by the resumption of Strombolian activity at 0030 on 9 August. Incandescent material was again ejected beyond the crater rim and an ash plume drifted SE.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

7 July-13 July 2021 Cite this Report

INGV reported continuing Strombolian activity and two episodes of lava fountaining Etna’s Southeast Crater (SEC) during 5-11 July. The first episode began at 1130 on 6 July with Strombolian activity at SEC. The intensity and frequency of explosions progressively intensified and formed lava fountains. Ash plumes rose to 1.5 km (5,000 ft) a.s.l. and drifted S, causing ashfall in areas downwind. A small lava flow originated from the S side of the cone and traveled SW, stopping at 2,800 m elevation. During fieldwork on 7 July scientist observed deposits of bombs, 1 m in diameter, on the N flank and smaller bombs scattered farther away. A second episode began at 2100 on 8 July with Strombolian activity which again intensified and formed lava fountains. Ash plumes rose to 3.4 km (11,000 ft) a.s.l. and drifted SE, causing ashfall in downwind areas. Lava flowed SW to 2,350 m elevation.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

30 June-6 July 2021 Cite this Report

INGV reported three episodes of lava fountaining at Etna’s Southeast Crater (SEC) during 28 June-4 July, producing ash plumes that rose 5-10 km (16,400-32,800 ft) a.s.l. Occasional ash-and-gas emissions rose from Bocca Nuova Crater and Northeast Crater. The first episode at SEC began with Strombolian activity at 0040 on 2 July. Ash plumes drifted ESE and within an hour lava fountains were visible that sent flows SW; fountaining ceased at 0250. The second episode began at 1656 on 4 July, produced fountains at 1725, and ended at 1900. Lava flows traveled SW and ENE, and ash plumes drifted ESE. The last episode began at 2330 on 6 July and produced ash plumes that drifted SE. Explosive activity intensified at 0000 on 7 July; lava fountaining began 30 minutes later, rose as high as 1 km, and ended within two hours. Lapilli was reported in the S part of Tremestieri and ash fell in Nicolosi, as well as in many other areas downwind. According to news articles the Catania airport was closed during the night due to ashfall.

Sources: Sezione di Catania - Osservatorio Etneo (INGV); La Stampa; Il Mondo dei Terremoti

23 June-29 June 2021 Cite this Report

INGV reported that there were nine episodes of lava fountaining at Etna’s Southeast Crater (SEC) during 21-27 June. The episodes were recorded shortly after midnight on 21 June, at dawn on 22 June, at dawn and sunset on 23 June, in the late morning on 24 June, at dawn and sunset on 25 June, in the afternoon on 26 June, and during the late morning of 27 June. Explosive activity was concentrated in the W part of SEC at three of the four saddle vents; some weak explosions occurred at the E vents. The episodes produced ash plumes that rose 5-10 km (16,400-32,800 ft) a.s.l. and lava flows that traveled SW and SE. Lava also began to effuse on 23 June from the vent on the SE flank of the SEC cone. INGV noted that these continuing episodes have caused the SEC cone to grow significantly, especially compared to the previous year, changing not only it’s morphology but the whole profile of Etna as well.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

16 June-22 June 2021 Cite this Report

INGV reported that there were several episodes of lava fountaining at Etna’s Southeast Crater (SEC) during 14-23 June, and additional periods of Strombolian activity and ash emissions. The lava fountaining episodes were recorded during 1332-1450 on 16 June, 2220 on 18 June to 0210 on 19 June, 2040-2215 on 19 June, 1131 on 20 June to 0214 on 21 June, overnight during 21-22 June, and in the early hours of 22 and 23 June. Each episode began with Strombolian activity which was followed by lava fountaining and crater overflows sending lava down the flanks. Ash plumes that rose as high as 4.7 km above the summit and sometimes caused ashfall in areas downwind. Lava flows on 16 June descended the SW and SE flanks, and those produced on 21 June traveled about 1 km SW, towards Monte Frumento Supino, and stopped at 2,900 m elevation. The lava fountains on 21 June were notably tall.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

2 June-8 June 2021 Cite this Report

INGV reported a few eruptive episodes at Etna’s Southeast Crater (SEC) during 31 May-6 June, as well as minor and diffuse ash emissions at Bocca Nuova (BN) and ash emissions on 4 June at Northeast (NEC). Weak Strombolian activity at SEC began at 0850 on 2 June and produced minor and diffuse ash plumes. The activity intensified at 1000; within 30 minutes lava fountaining was observed and lasted for over two hours. Ash plumes rose 5-6 km (16,400-19,700 ft) a.s.l. and drifted E, causing ashfall in Petrulli, Santa Venerina, and in an areas N of Zafferana. Lava overflowed the S side of the crater and traveled W. Fountaining stopped at 1245. Weak Strombolian activity continued to be observed during the night hours of 3-4 June.

Activity increased at 1530 on 4 June and was characterized by discontinuous ash emissions and lava overflowing the S rim of SEC. Lava fountaining began at 1820 and an ash plume rose to 6.5 km (21,300 ft) a.s.l. Tephra fell in Aci Castello, Acitrezza, San Giovanni La Punta, Tremestieri, Catania, and Viagrande, and between Pedara, Fleri, and Siracusa. Fountaining began to decline at 1930. The lava flow continued to advance, and by 2300 had reached 2,800 m elevation. Occasional ash emissions were noted during 4-5 June, and the lava flow had ceased.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

26 May-1 June 2021 Cite this Report

INGV reported almost daily episodes of Strombolian activity at Etna’s Southeast Crater (SEC) during 24-30 May continued the recent pattern of Strombolian explosions followed by lava flows to the SW and occasional lava fountains. Ash plumes were visible most days, rising to a maximum of 7 km (23,000 ft) a.s.l. Tephra was collected in Milo (10 km E) on 26 May and in Petrulli (12 km SE) on 30 May.

The first episode of the week began at 2100 on 24 May, intensified during 2235-2345, and ended at 0010 on 25 May. Ash emissions at SEC began 1020 on 25 May, producing a plume that rose to 4 km (13,100 ft) a.s.l. and drifted ENE. Explosions were recorded at 1820 and within 30 minutes Strombolian activity was visible. Activity intensified during 2025-2100 and ended at 2215. Two eruptive episodes were recorded on 26 May, with peaks at 0350 and 1300. An eruptive episode on 27 May was not visually well-documented due to inclement weather, though it reportedly intensified at 1450. Tephra fell in Giarre (17 km ESE), Milo, and Fornazzo (10 km ESE). Another episode began around 0830 on 28 May, intensified around 0900, and then ended at 0930; ashfall was reported in Giarre. Two more eruptive events were recorded that day: during 1740-1815 and a more powerful one during 2115-2305. The last episode of the week began at 0545 on 30 May and lasted for two hours.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

19 May-25 May 2021 Cite this Report

INGV reported episodes of lava fountaining at Etna’s Southeast Crater (SEC) on 19 and 22 May that continued the recent pattern of Strombolian explosions followed by lava fountaining and lava flows. Strombolian activity began at 2340 on 19 May and produced ash plumes that drifted E. Activity intensified and lava fountains formed at 0234 on 20 May. At the same time lava overflowed the SEC and traveled SW, and within a few hours had reached 2,800 m elevation. The activity lasted about three and a half hours and then abruptly ended. The next episode during 0134-0454 on 22 May included Strombolian explosions and ash plumes that drifted SE; lava fountaining began at 0302 and flows traveled SW, overlapping the flows from 19 May. Explosions produced ash plumes that drifted SE around 0830 and 1014. Strombolian explosions intensified around 2031, producing dense ash plumes that drifted E. Lava fountains formed about two hours later, sending flows down the E and SW flanks; fountaining was over by 0038 on 23 May. A series of explosions were visible during 0351-0403, producing dense ash plumes that drifted E. Two ash plumes were observed rising from SEC’s E crater during the night and the day on 23 May. Intense explosive activity at SEC began at 1820 on 25 May, producing ash plumes that rose to 3.5 km (11,500 ft) a.s.l. and drifted E. Strombolian activity commenced at 1845 and lava fountains were visible around 2023. Lava flows were visible at 2244 and ash plumes drifted E at an altitude of 6 km (19,700 ft) a.s.l. Activity ceased by 0026 on 26 May.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

21 April-27 April 2021 Cite this Report

INGV reported that during 19-25 April activity at Etna was mainly characterized by gas emissions rising from the summit craters, though inclement weather conditions often prevented visual observations. Bocca Nuova in particular produced frequent steam puffs. A strong explosion at 0030 on 25 April from the E vent of Southeast Crater (SEC) ejected incandescent material up to 350 m above the crater rim. An ash plume dispersed to the S.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

31 March-6 April 2021 Cite this Report

INGV reported continuing episodes of lava fountaining, intra-crater explosive activity, and discontinuous ash emissions at Etna’s Southeast Crater (SEC) during the week of 29 March-4 April, though weather conditions often prevented visual observations. Gas emissions rose from the other summit craters and occasional explosive activity was visible; puffs of ash sometimes rose from Voragine Crater during 31 March-2 April.

At 0707 on 31 March a loud explosion was followed by several ash puffs, marking the beginning of the 17th lava-fountaining episode since they began on 16 February. At around 1100 a thermal anomaly at the S base of SEC was visible during an overflight and in thermal camera images. Explosive activity increased by late afternoon and several lava flows effused from the S-base vent. The main part of the flow traveled towards the Valle del Bove with other smaller flows traveled S and SW. Two other vents at the S base had opened by evening and one ejected spatter a few tens of meters high. Periods of lava fountaining began through the night, and the main lava flow descended the W wall of the Valle del Bove. Strombolian activity intensified at 1950, with an eruption plume that rose to 1.2 km (4,000 ft) a.s.l. and drifted SSW. Lava fountaining began at around 0100 on 1 April. At 0218 lava overflowed the E rim of SEC and headed towards the Valle del Bove, running parallel to the flows from the S base.

Lava fountains continued to be visible during the morning of 1 April and intense Strombolian activity produced dense ash plumes that drifted S. By 0940 the eruption plume had risen to 9 km (29,500 ft) a.s.l. and drifted SSW. Lava fountaining ceased around 1000 and the eruption plume rose to 5.5 km (18,000 ft) a.s.l. and drifted S. Ash fell in Milia, Nicolosi, and Catania and lapilli (1 cm in diameter) fell in Rifugio Sapienza. Lava effusion and flow advancement continued; lava from the S base of SEC spread out like a fan. A series of loud bangs were audible in the late morning and ash emissions continued until the afternoon. Lava overflowed the E rim of SEC at 1040, and a SSE flow entered the Valle del Bove at the SW wall. Explosive activity began to decline at 1320, and effusive activity waned overnight during 1-2 April.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

24 March-30 March 2021 Cite this Report

INGV reported continuing episodes of lava fountaining at Etna’s Southeast Crater (SEC) during the week of 22-28 March, though weather conditions often prevented visual observations. Weak Strombolian activity at SEC began at 2005 on 23 March and turned into lava fountaining at 0330 on 24 March. A lava flow from the SEC was observed at 0335 which split in two, one branch traveling toward the Valle del Bove and the other to the SE; the lava was followed by a pyroclastic flow at 0336 that traveled toward the Valle del Bove. The lava fountain produced an ash cloud that rose to 6-7 km (20,000-23,000 ft) a.s.l. and extended SSE, resulting in ashfall on the S slope and in Catania (29 km SSE). Lava fountaining gradually decreased at 0700, and by 0945 it had stopped. The lava flows continued to advance. Activity in Northeast (NEC), Bocca Nuova (BN), and Voragine (VOR) was characterized by variable intra-crater Strombolian activity, accompanied by sporadic and weak ash emissions that quickly dispersed.

On 24 March explosions at SEC continued after the lava fountaining had stopped, producing an ash plume that rose 4.5 km (15,000 ft) a.s.l. and drifted SE. At night, ashfall was reported in Milia and Trecastagni (16 km SE). Explosions stopped by 1347 that day. By 25 March the two active lava flows had ceased and began to cool. Weak Strombolian activity at SEC on 30 March resumed around 2030; intra-crater explosions continued in the NEC, BN, and VOR, the latter of which produced discontinuous ash emissions that rapidly dispersed in the summit area.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

17 March-23 March 2021 Cite this Report

INGV reported continuing episodes of lava fountaining at Etna’s Southeast Crater (SEC) on 15, 17, and 19 March, though weather conditions often prevented visual observations. Strombolian activity at SEC began at 2110 on 14 March and turned into lava fountaining at 0048 on 15 March. Lava traveled towards the Valle de Bove and an eruption plume drifted E. Lava fountaining ceased by 0343 and only weak Strombolian activity followed. The lava flows continued to advance.

Weak Strombolian activity at SEC on 17 March began to intensify at 0155 and changed into lava fountaining at 0319. An eruption plume drifted SE and lava flow advanced. Fountaining activity ceased at 0717 and was followed by explosive activity. By 1859 the lava flows had reached 2,200 m elevation. Explosions at SEC and the lava flow in the Valle de Bove were visible at 2142 on 18 March when the weather conditions allowed for partial visibility of the summit.

Explosive activity at SEC was visible at 0734 on 19 March. The activity intensified at 0915 and ash emissions were visible. Lava fountaining started at 0935 and an ash plume drifted ENE. Lava fountaining activity ceased at 1136 and changed to Strombolian activity which gradually decreased; by 1350 only sporadic explosions were visible along with minor ash emissions. Lava flows were noted late in the morning.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

10 March-16 March 2021 Cite this Report

INGV reported continuing episodes of lava fountaining at Etna’s Southeast Crater (SEC) on 9 and 12 March. The eleventh episode began with Strombolian activity at SEC observed at 1914 on 9 March. Just after midnight activity quickly intensified with lava fountaining and a large eruption plume that rose at least 9 km a.s.l. The plume drifted ENE and caused ash and lapilli to fall in Mascali (18 km E), Giarre (17 km ESE), and Fiumefreddo (19 km ENE). Lava reached an elevation of 1,800 m, also effusing from the flank of the S vent. Lava fountaining ceased at 0430 on 10 March and sporadic ash emissions continued until 0700.

The twelfth episode began at 0630 on 12 March with Strombolian activity at SEC and ash emissions. The activity intensified at 0754 and lava overflowed the E part of SEC, traveling towards the Valle de Bove. Lava fountaining began at 0841, with jets up to 500 m, and an eruption plume rose 6 km a.s.l. and drifted E. Lava advanced to 2,800 m elevation and within another hour had reached 2,000 m elevation. At 0939 the plume had risen 9-10 km and had caused ashfall in Milo and Fornazzo (10 km E), Giarre, Santa Venerina (15 km SE), and Torre Archirafi (20 km ESE). Lava fountaining ceased at 1050, though weak Strombolian activity and ash emissions continued until 1115. The lava flow advanced as far as 1,700 m elevation and a second lava flow expanded SE on the W slope of the Valle del Bove, stopping at 3,000 m a.s.l.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

3 March-9 March 2021 Cite this Report

INGV reported continuing episodes of lava fountaining at Etna’s Southeast Crater (SEC) on 2, 4, and 7 March. Weak Strombolian activity began at SEC at 1145 on 2 March, then intensified at 1234 and produced an ash plume. Lava fountaining began at 1324. Ash plumes rose to 9 km above the summit and drifted S, causing lapilli to fall in Nicolosi (16 km S), Aci San Antonio (18 km SE), Pedara (15 km SSE), and Catania (29 km SSE). Lava fountaining ceased at 1550, ending the eighth episode.

The ninth episode began at the SEC as weak Strombolian at 0120 on 4 March. Ash emissions were visible at 0200 but dispersed quickly. Strombolian activity at Voragine (VOR) was also visible with ejected material rising above the crater rim. Lava fountaining began at SEC at 0320, but by 0515 the activity had decreased. Lava flows that advanced towards the Valle de Bove were fed by spattering and a new vent that opened at the E base of the SEC. Strombolian activity at VOR changed to 300-m-tall lava fountaining at 0850. Ash plumes rose 11 km above the summit and caused lapilli to fall in Fiumefreddo (19 km ENE), Linguaglossa (17 km NE), and the area of Reggio Calabria.

The tenth episode began with Strombolian explosions at SEC and minor lava effusion at the new vent at the E base of SEC during the first hour on 7 March. Strombolian activity intensified at 0430; an eruption plume rose 5 km above the summit and drifted E. Lava overflowed the SEC onto the E flank and expanded into the Valle de Bove, reaching an elevation of 2,800 m by 0450. Strombolian activity again intensified beginning at 0520 and the lava flow advanced to 2,700 m elevation. Lava fountaining started at 0720 and ended at 0810. An eruption plume rose 10 km and drifted E. Ash and lapilli fell in Milo (11 km ESE), Fornazzo (10 km ESE), Trepunti (17 km ESE), Giarre (17 km ESE), Macchia di Giarre (16 km ESE), Mascali (18 km E), Riposto (19 km ESE), and Torre Archirafi (20 km ESE). Strombolian activity resumed at 1050 and was over by 1500.

Strombolian activity at SEC returned at 1914 on 9 March. Lava overflowed the crater at 2013 and advanced towards the Valle de Bove. Strombolian activity increased at 2100 and ash emissions drifted NE. The lava flow reached 2,900 m elevation.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

24 February-2 March 2021 Cite this Report

INGV reported continuing episodes of lava fountaining at Etna’s Southeast Crater (SEC) and 24 and 28 February. Strombolian activity at two vents in SEC increased during the late afternoon of 24 February. Lava overflowed the crater at 1820 and headed ESE towards the Valle de Bove. During 1900-2122 lava fountains rose as high as 500 m above the summit. A second lava flow traveled SW, and at 2100 a pyroclastic flow descended 1 km into the Valle de Bove. An eruption plume rose as high as 11 km a.s.l.

Weak Strombolian activity was visible at 0810 on 28 February. Lava fountaining began at 0839, feeding lava flows that traveled E, and abruptly intensified at 0902 with jets of lava rising 700 m above the crater rim. An eruption plume rose as high as 11 km a.s.l. and drifted ESE, causing ashfall in areas downwind. A small lava overflow at the S part of SEC began at 0909, followed by a pyroclastic flow at 0920. Lava fountaining ended at 0933, though the lava flow descending E remained active.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

17 February-23 February 2021 Cite this Report

INGV reported that a series of paroxysmal events separated by relative calm periods at Etna began on 16 February and continued at least through 23 February. The first episode began late on 16 February, characterized by gradually increasing Strombolian activity at the E vents of the Southeast Crater (SEC). Overflows of lava from the crater at 1805 caused a partial collapse of the cone and a pyroclastic flow that traveled 1.5 km along the W wall of the Valle de Bove. Lava fountains afterwards rose 500-600 m high. An eruptive plume rose several kilometers and drifted S, causing ashfall in areas as far as Syracuse, 60-80 km SSE. Lava flows advanced into the Valle de Bove and the Valle del Leone, and produced explosions in areas where they interacted with snow cover. Activity ended around 1900.

After a 30-hour pause the second paroxysmal episode began at 2330 on 17 February with overflows of lava from the eastern SEC vents. Lava fountaining began just after 0100 the next morning. Lava flows traveled towards the Valle de Bove, NE, SE, and SW. The eruption plume drifted SE, causing ashfall in Zafferana Etnea and Acireale. The lava fountains reached maximum heights of 600-700 m then ceased around 0140.

After another pause lasting about 32 hours, lava overflowed the SEC at around 0855 on 19 February. A rapid increase in explosive activity followed and lava fountaining began during 0945-0950. At 0953 lava fountains emerged from the S, or saddle, vent. At this time there were “fan-shaped” lava fountains rising from 4-5 vents orientated E-W. The eruption plume rose 10 km (32,800 ft) a.s.l. and drifted SE, again causing ashfall in downwind municipalities. Lava flowed S and towards the Valle de Bove causing explosions where they interacted with snow. Explosive activity ceased at 1110. Lab analysis of lava samples collected during 16-19 February eruptions showed that the magma was the most primitive over the past 20 years, meaning that the composition had changed little from its formation at depth and that it ascended quickly.

Weak Strombolian activity was visible in the late afternoon of 20 February. At 2230 a small lava flow descended a deep notch at the E end of the SEC and traveled towards the Valle de Bove. By 2300 the Strombolian activity had shifted to pulsating lava fountaining. Beginning at 0100 on 21 February more western vents became active and the E vents jetted lava 600-800 m high. Activity intensified at 0128 with jets of lava that rose more than 1 km high and were sustained for about 10 minutes. An eruption plume again rose to 10 km (32,800 ft) a.s.l. Beginning at 0200 the lava fountain became smaller, and at 0220 explosive activity ceased. Lava flowed SW and into the Valle de Bove.

Periodic ash emissions rose from both the S and E vents later than evening. Lava overflowed the SE crater just after 2230 and advanced 1 km towards the Valle de Bove. Lava fountains and Strombolian explosions occurred at multiple vents. Activity intensified at 0128 on 21 February and lava fountains rose 800-1,000 m above the SEC. Lava flowed from the S vent and an eruption plume rose several kilometers, but activity rapidly ceased at 0220. Lava flows continued to advance in the Valle de Bove; the longest flows were 3.5-4 km from the crater, between elevations of 1,700 and 1,800 m. During 0430-0515 very intense explosions from multiple SEC vents ejected incandescent bombs that fell as far as the base of the cone.

Weak Strombolian explosions at the SEC crater were visible late on 22 February. The frequency and intensity of the explosions increased and by 2210 material was ejected onto the flanks. By 2305 jets of lava were 300 m high, and by 2327 lava fountains rose from a second vent. Lava overflowed the crater at 2328 and headed towards the Valle de Bove. Within the first hour on 23 February lava fountains rose more than 1.5 km high and a sub-Plinian eruption plume had risen several kilometers above the summit, making this episode the most powerful and intense compared to the previous four. Lava overflowed the S vent and descended SW. Lava fountaining suddenly decreased at 0115 on 23 February, though lava flows continued to be fed. Strombolian activity again intensified at 0450, accompanied by ash emissions. Two lava flows formed and traveled SW and SE, the latter was longest and reached 1,700-1,800 m elevation. The activity ended at 1000.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

10 February-16 February 2021 Cite this Report

INGV reported that Strombolian activity from all four of Etna’s summit craters, the Southeast Crater (SEC), Northeast Crater (NEC), Bocca Nuova (BN), and Voragine (VOR), was visible during 8-14 February. The frequency and intensity of explosions at SEC were variable; almost continuous strong explosions originated from two vents in the E part of the top of the cone. Tephra accumulated near the top of the cone and rolled several tens of meters down the flanks. Minor ash emissions rapidly dispersed. Less-intense Strombolian activity occurred at the S vent (also called the saddle vent). Intra-crater Strombolian activity at NEC sometimes produced nighttime crater incandescence. The activity at BN sometimes ejected coarse material beyond the crater rim, and rare emissions that had diffuse ash content. The the VOR Strombolian explosions ejected material that sometimes rose above the crater rim and generated diffuse ash emissions.

During the morning of 15 February explosive activity at SEC gradually intensified. Activity originated from the E vents but sometimes intense explosions occurred at the saddle vent. A significant increase in tremor amplitude began at 1700. Tremor amplitude waned at 2100, the same time that explosive activity decreased. At 1700 on 16 February lava began advancing down the E flank of SEC. Part of the cone collapsed at 1705 and generated a pyroclastic flow that traveled 1.5 km along the W wall of the Valle de Bove. An ash plume rapidly dispersed to the S. Explosive activity at SEC increased and lava fountaining began at 1710. Ash clouds drifted S. Lava flows advanced into the Valle de Bove, reaching an elevation of 2,000 m by 1759 at the latest. Lapilli, 1 cm in diameter, was reported in Nicolosi (16 km S) and Mascalucia (19 km S), and ash and lapilli fell in Catania (29 km SSE). Ashfall was also reported in Syracuse, 60-80 km SSE. Another lava flow advanced N into the Valle del Leone. Lava fountains were about 500 m tall, possibly as tall as 600 m. Tremor amplitude began to decrease at 1750 and lava fountains ceased around 1800. Lava effusion from SEC gradually diminished; the flow in the Valle de Bove was a few kilometers long and smaller flows that had traveled N and S reached an elevation of 2,900. Strombolian activity persisted at SEC overnight during 16-17 February and ceased at 0715 on 17 February. Explosions at VOR were sporadic.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

3 February-9 February 2021 Cite this Report

INGV reported that Strombolian activity from all four of Etna’s summit craters, the Southeast Crater (SEC), the Northeast Crater (NEC), Bocca Nuova (BN), and Voragine (VOR), was visible during 1-7 February; the last time that had occurred was during 1998-1999. The strongest and almost continuous Strombolian explosions at SEC originated from two vents in the E part of the top of the cone. Tephra accumulated near the top of the cone and rolled down the flanks. Minor ash emissions rapidly dispersed. Less-intense Strombolian activity occurred at the S vent. Intra-crater Strombolian activity at NEC sometimes produced nighttime crater incandescence. Strombolian activity at BN sometimes ejected coarse material beyond the crater rim, and rare ash emissions that had diffuse ash content. On 5 February scientists observed explosions from three vents at the bottom of the crater that had formed cinder cones. Nearby was another cone that occasionally produced dense emissions that rapidly dispersed. Strombolian activity at VOR ejected material that sometimes rose above the crater rim and generated diffuse ash emissions. On 5 February lava flowed into BN, overlapping flows from the previous week.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

13 January-19 January 2021 Cite this Report

INGV reported that during 11-17 January activity at Etna was characterized by intra-crater Strombolian activity at Northeast Crater (NEC), occasional ash emissions from the Voragine (VOR) and Bocca Nuova (BN) craters, and Strombolian activity, lava effusion, and ash emissions at the Southeast Crater (SEC). In general, the activity was similar to the pervious week, though activity at SEC on 18 January was notable.

Lava effusion began around 0700 on 17 January but was confined to the SEC summit cone. At around 0740 the lava breached the crater and lava flowed down to the base of the cone. The effusion rate increased by 0819 and an ash emission was possibly visible; the lava flow lengthened and had reached an elevation of 3,000 m by 1000. Weather clouds moved in and prevented visual observations until 1830 on 18 January when the lava flow was visible again; it was no longer being fed and was cooling. Volcanic tremor amplitude increased and Strombolian activity intensified at 2000. A new lava flow emerged at 2015 and traveled towards the Valle del Bove, reaching an elevation of 2,900 m. Low lava fountains were visible at 2130 and an ash plume drifted ESE, causing ashfall on the downwind flank. Lava flows descended the SE, E, and NE flanks of the SEC. Explosive activity significantly decreased at 2200. Two distinct lava flows were visible, with one heading N and the other moving towards the Valle del Bove. Tremor and infrasound signals decreased to pre-episode levels by 2230. The the lava flows were stable and cooling on 19 January.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

16 December-22 December 2020 Cite this Report

INGV reported that strong activity at Etna’s Southeast Crater (SEC) included fountaining and lava flows on 21 December. Tremor amplitude had gradually increased on 20 December but weather conditions prevented visual observations. During the morning of the 21st Strombolian activity occurred at three vents. By 0800 tremor amplitude suddenly increased, and by 1000 lava fountaining from at least two vents was observed in thermal camera images, along with an eruption plume to 3 km (10,000 ft) a.s.l. [Correction: the eruption plume rose to 10 km (32,800 ft) a.s.l.] A lava flow emerged from the SW part of the cone, which had collapsed on 13 December, and traveled SW before branching W and E. A second flow from the NE side of the cone traveled E into the Valle del Bove. Lava fountaining ended around noon, with a simultaneous decrease in tremor amplitude. [Addition: An episode of lava fountaining occurred before sunrise on 22 December, producing lava flows that traveled SW, SE, and ENE.] During the morning of 22 December a few small phreatic explosions were visible in webcam images, likely generated from the interaction of snow and lava. The front of the active SW flow reached 2,500 m elevation. By 1741 both flows were cooling down and no longer advancing.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

9 December-15 December 2020 Cite this Report

INGV reported that during 7-12 December activity at Etna was similar to the previous week, characterized by intra-crater Strombolian activity at Northeast Crater (NEC), and Strombolian activity, lava effusion, and pyroclastic flows at the Southeast Crater (SEC). Additionally, infrequent ash emissions at the Bocca Nuova (BN) craters and some explosions and minor ash emissions at the Voragine (VOR) were also recorded. Webcam views of activity was limited due to weather conditions; a field visit was made on 14 December.

Strombolian activity originated from the E and central vents at SEC ejected lava onto the inner crater walls. Occasional ash emissions dispersed quickly near the summit. Activity intensified at 2020 on 13 December and lava fountains formed around 2300. Collapses of the SW part of the SEC cone spurred a series of pyroclastic flows. At 2315 a small pyroclastic flow traveled down the SSW flank. A second pyroclastic flow began at 2316 and traveled 2 km down the SSW flank and covered Monte Frumento Supino cone (SSW). At 2330 a third and minor pyroclastic flow traveled SSW. Around the same time as the generation of the first two pyroclastic flows, two fissures opened on the SW flank of the SEC and produced lava flows to the S and SW until about 2350. A period of lava fountaining was visible during 0050-0110 and 0210-0223 on 14 December.

During a field inspection on 14 December scientists confirmed the partial cone collapses and noted that the two lava flows (S and SW) were cooling. The S lava flow had widened at the near the base of SEC and formed four lobes. One of the lobes continued on and stopped just NW of cones that had formed in 2002-2003. The SW flow traveled SSW, branched, curved around the W part of Monte Frumento Supino, and then stopped. Explosive activity from central SEC vent continued, with roaring and sporadic ash emissions. An explosion at 1352 formed an ash plume that rose about 4 km and drifted S. Strombolian explosions deposited material outside of the crater.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

21 October-27 October 2020 Cite this Report

INGV reported that during 19-25 October activity at Etna was characterized by intra-crater Strombolian activity at Northeast Crater (NEC), Strombolian activity at the New Southeast Crater (NSEC) cone, and gas emissions at the Voragine (VOR) and Bocca Nuova (BN) craters. During a helicopter overflight along the W side on 23 October scientists observed Strombolian explosions at NSEC that produced ash emissions and ejected shreds of lava out of the crater. Both the frequency and intensity of explosions was variable. There were several thermal anomalies on the NEC crater floor, and some on the floor of the BN crater. An ash plume from NSEC rose to 4.5 km a.s.l. and drifted SSE. The report noted that, based on drone footage from the beginning of the month, the NSEC vent was 190 m long in the NW direction and 140 m wide in the NE direction.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

16 September-22 September 2020 Cite this Report

INGV reported that during 14-20 September activity at Etna’s New Southeast Crater (NSEC) was characterized by Strombolian activity and ash emissions. The ejection of incandescent material onto the crater rim and the S flank was occasionally visible during phases of increased activity. Minor ash emissions sporadically rose from Voragine Crater (VOR). Strombolian activity also occurred within Northeast Crater (NEC).

Source: Sezione di Catania - Osservatorio Etneo (INGV)

5 August-11 August 2020 Cite this Report

INGV reported that during 27 July-9 August activity at Etna was characterized by intra-crater Strombolian activity at Northeast Crater (NEC), sporadic Strombolian activity at Voragine Crater (VOR) with minor ash emissions that quickly dispersed, and both Strombolian activity and diffuse ash emissions at the New Southeast Crater (NSEC) cone. Explosive activity increased on 31 July; an ash cloud rose to 4.5 km (14,800 ft) a.s.l. On 2 August very minor ashfall was reported in Trecastagni and Acicastello, possibly from a slight increase in explosive activity that was not visually confirmed.

During 3-9 August Strombolian activity ejected material above the NSEC cone’s crater rim; the activity was almost continuous during the evening of 6 August and the next morning, and booming was heard several kilometers away. Ash emissions dispersed near the summit. A series of ash emissions were visible in the morning of 9 August.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

8 July-14 July 2020 Cite this Report

INGV reported that during 6-12 July Strombolian activity at Etna’s New Southeast Crater ejected incandescent material that was deposited near the crater rim. Gas emissions rose from the vent in the pit crater at the bottom of Bocca Nuova. Sporadic explosive activity at Voragine Crater ejected lithics and produced ash emissions. Gas emissions rose from Northeast Crater and were audible from the crater’s edge.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

6 May-12 May 2020 Cite this Report

INGV reported that on 5 May increasing and pulsating ash emissions at Etna’s New Southeast Crater (NSEC) formed a plume that drifted SSE. The activity may have concurrently occurred with the enlargement of vent number 3. Explosive activity at Voragine Crater (VOR), with minor ash emissions and occasional visible shreds of incandescent material, was relatively mild and discontinuous. During a field inspection on 8 May, volcanologists observed that the main cone was almost unchanged and produced modest ash emissions. Strong explosive activity at a cone located E of the main cone produced a lot of ash, and ejected coarse material that fell on the W edge of VOR as well as on the S terrace of Bocca Nuova Crater. Activity at NSEC again increased; on 10 May Strombolian explosions ejected material out of the crater and onto the flanks. Concurrently, increased activity in VOR was characterized by the ejection of ballistics beyond its crater rim. After a few hours Strombolian activity in NSEC significantly decreased and explosive activity in VOR was both less intense and less frequent.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

4 March-10 March 2020 Cite this Report

INGV reported continuing eruptive activity at Etna’s Voragine Crater (VOR), New Southeast Crater (NSEC), and Northeast Crater (NEC) during 24 February-1 March. Strombolian explosions from the vent at the top of the cone in VOR crater ejected pieces of lava sometimes 150-200 m above the vent. Ash plumes rose from the vent and rapidly dissipated. Strombolian activity from a vent at the base of the N flank of the cone was observed on 29 February. Lava continued to effuse from the vent on top of a building lava mound on the S flank of the cone and flow into the adjacent Bocca Nuova Crater. Activity at NEC was characterized by discontinuous Strombolian activity and periodic emissions of very diffuse ash plumes. During 24-25 February observers noted continuous diffuse ash emissions at NSEC, originating from a cone in the saddle area.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

22 January-28 January 2020 Cite this Report

INGV reported continuing eruptive activity at Etna’s Voragine Crater (VOR), New Southeast Crater (NSEC), and Northeast Crater (NEC) during 21-26 January. The cone in VOR produced Strombolian explosions which increased in frequency and resulted in rapid cone growth (especially the N part). Lava traveled down the S flank of the cone and into the adjacent Bocca Nuova Crater, filling the E crater (BN-2). Activity at NEC was characterized by discontinuous Strombolian activity and periodic emissions of very diffuse ash plumes. During 21-22 January there were several episodes of ash emissions at NSEC, originating from the vent that had opened on 11 December 2019 on the side of the saddle area. Ash emissions rarely rose form the E vent.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

25 December-31 December 2019 Cite this Report

INGV reported that Strombolian activity at Etna’s New Southeast Crater and North East Crater continued during 23-29 December, though had significantly decreased compared to previous weeks. Sporadic ash emissions from Voragine Crater rapidly dispersed into the atmosphere.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

27 November-3 December 2019 Cite this Report

INGV reported that eruptive activity at Etna’s summit craters continued during 25 November-1 December. Strombolian explosions at Voragine Crater (VOR) occurred at intervals of 5-10 minutes, and many incandescent jets rose above the crater rim. Some explosions created incandescent flashes in emissions rising above the crater rim. A cone which had started forming on the crater floor in mid-September had continued to grow according to observations by field guides. Sporadic ash emissions began at New Southeast Crater (NSEC) on the evening of 30 November, and a single Strombolian explosion was recorded on 1 December. Incandescence from Bocca Nuova Crater was intermittently visible at night.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

16 October-22 October 2019 Cite this Report

INGV reported that during 14-20 October diffuse ash plumes from Etna’s Northeast Crater (NEC) varied from quickly-dispersing puffs to emissions lasting several hours. Ash drifted S, producing ashfall in areas downwind including Pedara, Mascalucia, Nicolosi, San Giovanni La Punta, and Catania. Ash plumes also rose from Voragine Crater (VOR).

Source: Sezione di Catania - Osservatorio Etneo (INGV)

25 September-1 October 2019 Cite this Report

INGV reported that intense Strombolian activity from vents at the bottom of Etna’s Voragine Crater (VOR) continued during 23-29 September. Gas emissions from Northeast Crater (NEC) were intense and continuous, and ash plumes were occasionally visible and sometimes accompanied by incandescent flashes. A large ash emission rose from the crater on 27 September and drifted S.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

18 September-24 September 2019 Cite this Report

INGV reported that Strombolian activity from vents at the bottom of Etna’s Voragine Crater (VOR) continued during 16-22 September. On 18 September guides observed intensified explosive activity at VOR characterized by the ejection of scoria and ash from several vents to heights of tens of meters. A lava flow from the cone had descended the W flank of the cone to its base, and then flowed several hundred meters S and branched into the Bocca Nuova Crater. Similar activity was observed on 19 September, though by 22 September the lava flows were cooling and Strombolian activity from VOR vents had become less frequent. Gas emissions rose from Northeast Crater (NEC); an ash emission was noted on 22 September.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

11 September-17 September 2019 Cite this Report

INGV reported that Strombolian activity at Etna’s Northeast Crater (NEC) likely began on 8 September. Continuous Strombolian activity recorded between 2000 on 9 September and 0700 on 10 September produced diffuse ash emissions which quickly dissipated. The most intense part of the eruptive period occurred during 2000-2200. Minor ashfall was reported in Piedimonte Etneo, Giarre-Riposto, and Rifugio Citelli. Incandescence from the activity had significantly subsided by 0300 on 10 September, coincident with the ejection of lava fragments outside of the crater. Dilute ash puffs were continuously observed at dawn the next day. Strombolian activity ceased around 0540 and then resumed around 0800. Weather conditions hindered observations at times on 11 September but clear observations after 2000 allowed for the confirmation of continuing explosive activity at varying intensity at NEC.

Ash emission from Voragine Crater began during the morning of 12 September and gradually increased in frequency. Activity further intensified at 1200 as Strombolian activity commenced and tephra ejected out of the crater was deposited at the base of Bocca Nuova Crater. Strong Strombolian explosions were felt in Zafferana Etnea, Aci S. Antonio, Pedara, and neighboring areas.

Webcam and field observations on 13 September confirmed continuing activity at NEC and Voragine craters. Diffuse ash plumes rose from NEC and dispersed near the summit area. Strombolian activity at Voragine Crater ejected coarse tephra as high as 20 m above the crater rim and produced diffuse ash emissions. Impact craters from the ejected tephra were distributed mostly in the W part of the area between Bocca Nuova and Voragine craters down to 3,000 m elevation. Activity continued on 14 September. During an overflight on 15 September observers noted that a scoria cone had formed in Voragine Crater, and diffuse ash emissions continued to rise from NEC.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

4 September-10 September 2019 Cite this Report

INGV reported that the mean amplitude of volcanic tremor at Etna had been increasing. Notably, the increase since mid-August had reached significant values by 6 September and were comparable to those values recorded just before the December 2018 eruption, and higher than those observed before the eruptive episodes during May-July 2019. Inclement weather prevented visual observations of the summit craters, though mountain guides reported characteristic sounds of Strombolian activity at the Bocca Nuova crater on 6 September. A sudden increase in volcanic tremor amplitude was recorded at 0449 on 9 September, and by 0536 Strombolian activity at Northeast Crater (NEC) was visible. At 1050 volcanic tremor amplitude again increased, with signals localized beneath NEC. Diffuse ash plumes rose from the crater and dissipated near the summit.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

31 July-6 August 2019 Cite this Report

INGV reported that on 25 July Etna’s New Southeast Crater (NSEC) periodically emitted gas and ash. At 0630 on 27 July the seismic network detected a sudden increase in tremor amplitude, and at 0915 a new fissure opened on the S flank of NSEC. Explosive activity at the crater intensified at 1020 and a dense, ash-rich plume rose to 4.5-5 km a.s.l. and drifted E. A thin layer of ash was deposited in Giarre, Riposto and Torre Archirafi. Lava emerged from the S part of the new fissure and traveled SW and S; by 1235 the longest part of the flow had reached 2,850 m elevation and by 1330 it had reached 2,600 m elevation. Beginning at 1321 a sequence of particularly strong explosions generated ash plumes that rose as high as 7.5 km a.s.l. Explosive activity decreased around 0440 on 28 July, and lava effused from the vent at a lower rate. Starting at 0846 the Northeast Crater (NEC) occasionally emitted small plumes of red-brown ash. Explosive and effusive activity at NSEC ceased that evening. Activity during 29 July-4 August consisted of a few episodes of ash emissions at Bocca Nuova Crater and NEC.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

17 July-23 July 2019 Cite this Report

INGV reported that during 15-17 July sporadic explosions at Etna’s New Southeast Crater (NSEC) were accompanied by small ash puffs that quickly dissipated. Strombolian activity at NSEC increased during the morning of 18 July with explosions occurring at a rate of one every 1-2 minutes. In the following hours the rate of explosions increased, and by the evening Strombolian activity was almost continuous. The activity continued to intensify until 2300 when a sharp decrease occurred.

At 0009 on 19 July lava flowed from a new vent that opened on the lower NE flank of NSEC, and traveled towards the Valle del Leone. Within a few hours explosive activity again increased at NSEC; ash emissions occasionally rose from the Northeast Crater (NEC) and Bocca Nuova Crater. Explosive activity decreased and had ceased by noon. A sudden increase in explosive activity was recorded that afternoon and by the evening three vents within NSEC were producing Strombolian activity and sporadic ash emissions. Ashfall was reported in areas on the S flank. Explosive activity at NSEC again declined in the late evening. NEC produced abundant ash emissions until the morning of 20 July.

Just before 0800 on 20 July a new phase of explosive activity began at NSEC and lava effusion at the new vent on the NE flank increased. Later that morning explosive activity completely ceased; by evening the lava flow was only weakly fed.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

5 June-11 June 2019 Cite this Report

INGV reported that explosions at the fissure segment at 2,850 m elevation on the SE base of Etna’s New Southeast Crater (NSEC) declined in frequency and intensity during 3-4 June; explosions ceased on 5 June. The lava flow from the fissure was active only near the vent on 5 June and by the next day had ceased and began cooling. Sporadic ash emissions rose from Northeast Crater (NEC) and quickly dissipated on 6 June.

The report noted that the NE edge of the NSEC cone had dropped several meters, likely in conjunction with a period of ash emissions on 30 May. In addition, a hot zone high on the SE flank of the cone that was established prior to the recent eruption was extensively covered with colored fumarolic deposits by 6 June.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

29 May-4 June 2019 Cite this Report

INGV reported that at 0220 on 30 May a fissure opened at the N base of Etna’s NSEC at about 3,150 m elevation. The fissure produced Strombolian explosions and a lava flow that advanced towards the W wall of the Valle del Bove; by 0915 it had reached 2,050 m elevation near Monte Simone. The flow was 2 km in length. Two fissures opened a few hours later at the SE base of NSEC at an elevation of about 3,050 m, each producing lava flows that converged and traveled along the W wall of the Valle del Bove towards Serra Giannicola Grande, partially covering the 2018 lava flows. The flow reached 2,260 m elevation by 0915. The fissure activity was accompanied by ash emissions which were intense starting at 1150 but then decreased and almost stopped late in the evening. The lava flow reached the bottom of the valley in the early hours of 31 May and had a length of about 3 km.

INGV volcanologists confirmed that lava continued to effuse from both fissures during a visual inspection in the morning of 1 June and that vigorous spatter was occurring at a fissure on the SE base of NSEC. By 1930 the lava flow from the N base was no longer being fed and was cooling. During a visual inspection of the eruption site on 2 June volcanologists confirmed explosive activity at a fissure segment at 2,850 m and continuing lava effusion. The lava traveled along the W wall of the Valle del Bove, overlapping flows from previous days.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

22 May-28 May 2019 Cite this Report

INGV reported that gas emissions of variable intensity were observed rising from Etna’s summit craters during 20-26 May; weather conditions often prevented views. Weak and diffuse ash emissions occasionally rose from the New Southeast Crater (NSEC). An ash plume rose from Bocca Nuova Crater on 23 May.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

15 May-21 May 2019 Cite this Report

INGV reported that gas emissions of variable intensity were observed rising from Etna’s summit craters during 14 and 17-19 May; weather conditions prevented views on the other days during 13-19 May. Ash emissions periodically rose from vents in the S and E parts of New Southeast Crater (NSEC). Several Strombolian explosions at NSEC ejected incandescent pyroclastic material a few dozen meters above the crater rim during 17-18 May.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

1 May-7 May 2019 Cite this Report

INGV reported that during 22-28 April ash emissions rose from Etna’s Bocca Nuova Crater, Northeast Crater (NEC), and from the E vent in New Southeast Crater (NSEC). Pulsating incandescence from NSEC’s E vent was recorded at night by webcams. A new vent on the inner wall of Voragine Crater was noted on 30 April.

Strombolian activity from the BN-1 crater deep within the Bocca Nuova Crater was visible on 28 April and continued through 5 May; field inspections on 30 April revealed that two vents in BN-1 were active and producing explosions at a rate of one every 2-3 seconds. Bombs and lapilli were ejected above the crater rim but deposits remained mostly within the confines of the crater or near the rim.

Strombolian activity was visible at NSEC during 29 April-5 May. On 2 May, beginning at 0131, discontinuous explosions at the E vent produced emissions of fine tephra that rose as high as 1 km above the crater rim and quickly dissipated. During 5-6 May the frequency of explosions increased for brief periods in conjunction with a slight increases in volcanic tremor amplitude.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

10 April-16 April 2019 Cite this Report

INGV reported that during 8-14 April gas emissions of variable intensity rose from Etna’s summit craters. During each night webcams recorded pulsating flashes from the E vent in New Southeast Crater (NSEC) which became more intense towards the end of the week. A minor ash emission from Bocca Nuova Crater was visible at 0520 on 8 April.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

13 February-19 February 2019 Cite this Report

On 19 February INGV summarized Etna’s fissure eruption that occurred high on the SE flank during 24-27 December 2018, noting that 3-4 million cubic meters of lava erupted and covered an area of 1 square kilometer. After the event seismicity gradually decreased. The last significant event was a ML 4.1 recorded on 8 January 2019; afterwards seismicity was characterized as frequent events with modest magnitudes. Since the beginning of January ash emissions intermittently rose mainly from Northeast Crater (NEC) and more sporadically from Bocca Nuova. News sources noted that the Catania Airport (Aeroporto di Catania – Sicilia) was closed during 26-27 January. Preliminary assessments of some of the ash deposits showed they contained no juvenile material. During 11-17 February ash emissions of variable intensity rose from NEC and were notable on 14 and 18 February. Volcanic tremor amplitude did not significantly vary compared to the previous week, having average values overall. The Catania Airport announced the partial closure of airspace and flight delays during 17-18 February due to ash emissions.

Sources: Sezione di Catania - Osservatorio Etneo (INGV); Aeroporto di Catania

6 February-12 February 2019 Cite this Report

INGV reported that during 6-10 February webcams at Etna recorded gas emissions from New Southeast Crater (NSEC) and Voragine Crater, and occasional ash clouds from Northeast Crater (NEC); inclement weather prevented observations during 4-5 February. From the beginning of the afternoon on 6 February discrete ash emissions rose from NEC. The ash emissions were continuous from about 2215 on 7 February to 1015 on 8 February, producing relatively diffuse ash plumes that drifted S and then SE. Ash fell in Nicolosi (14 km S) and Pedara (15 km SSE). A diffuse ash plume drifted SW on 9 February.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

5 December-11 December 2018 Cite this Report

INGV reported that during 3-9 December activity at Etna was characterized by gas emissions at the summit craters, with periodic Strombolian activity from vents in Bocca Nuova, Northeast Crater (NEC), and New Southeast Crater (NSEC). Strombolian explosions at the cone in NSEC became more frequent on 4 December. In addition, lava effusion became continuous with small overlapping flows traveling about 500 m down the E flank of the cone. Incandescent blocks generated by the lava flows rolled to the base of the cone, and occasional small collapses produced minor ash plumes. Strombolian activity and occasional ash emissions were characteristic of vents in the W part of Bocca Nuova’s (BN-1) crater floor. Gas emissions at Voragine Crater continued from a vent on the E rim of the crater, and Strombolian explosions were evident at NEC.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

31 October-6 November 2018 Cite this Report

INGV reported that during 29 October-4 November activity at Etna was characterized by gas emissions at the summit craters, with periodic Strombolian activity from vents in Bocca Nuova, Northeast Crater (NEC), SE Crater (SEC), and New Southeast Crater (NSEC). Strombolian explosions at NSEC were interspersed with long pauses from a few minutes to a few hours. The explosions sometimes produced ash emissions that quickly dispersed; ashfall was deposited around the crater and in the Valle del Bove. Strombolian activity and gas emissions were characteristic of the N vent in the W part of Bocca Nuova’s (BN-1) crater floor. Spattering from the southernmost vent was also visible, as well as gas emissions. Gas emissions at Voragine Crater from a vent on the E rim of the crater were less intense compared to previous months. NEC activity was characterized by Strombolian explosions sometimes accompanied by minor ash emissions.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

17 October-23 October 2018 Cite this Report

INGV reported that during 15-21 October activity at Etna was characterized by gas emissions at the summit craters, with periodic Strombolian activity from vents in Bocca Nuova, Northeast Crater (NEC), Southeast Crater (SEC), and New Southeast Crater (NSEC). Strombolian activity at the N vent in the W part of Bocca Nuova’s (BN-1) crater floor ejected incandescent material higher that the crater rim. Spattering from the southernmost vent was also visible. Gas emissions increased at Voragine Crater from a vent that formed on 7 August 2016 on the E rim of the crater, and the crater continued to gradually widen and deepen. NEC activity was characterized by gas emissions and explosive activity of variable frequency and intensity. Fumarolic plumes rose from the rim and crater walls of NSEC and SEC. The E vent in NSEC produced Strombolian explosions and ash emissions which rapidly dispersed.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

26 September-2 October 2018 Cite this Report

INGV reported that during 24-30 September activity at Etna was characterized by gas emissions at the summit craters, with periodic Strombolian activity from vents in Bocca Nuova, Northeast Crater (NEC), and New Southeast Crater (NSEC). Strombolian activity at the N vent in Bocca Nuova (BN-1) ejected incandescent material almost as high as the W crater rim. No eruptive activity was observed at BN-2, though it produced explosions deep in the crater. A new high-temperature vent producing gas emissions was noted on 1 October in the same place a fumarole had been observed the previous week. Ash emissions from NSEC were sometimes accompanied by ejected incandescent material. Gas emissions increased at Voragine Crater from a vent that formed on 7 August 2016 on the E rim of the crater. NEC produced frequent brown-gray ash emissions, and ejected blocks and bombs, from a vent located in the W part of the crater floor.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

5 September-11 September 2018 Cite this Report

INGV reported that during 3-9 September activity at Etna was characterized by gas emissions at the summit craters, with periodic Strombolian activity from vents in Bocca Nuova, Northeast Crater (NEC), and New Southeast Crater (NSEC). A few Strombolian explosions at NSEC were recorded on 5 September; an explosion at 0536 generated an ash plume that produced local ashfall around the vent and in the Valle del Bove, and quickly dispersed. A similar but less intense event occurred earlier that day, at 0316. Similar Strombolian events continued during 6-9 September, at intervals of a few hours. Strombolian activity at the N vent (BN-1) in Bocca Nuova occurred at 3-5-minute intervals, ejecting incandescent material that fell within the crater confines. Gas emissions were sometimes punctuated with ash emissions. Intense degassing was characteristic of the second vent (BN-2). Strombolian activity occurred at NEC, and a few times explosions were accompanied by ash emissions.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

22 August-28 August 2018 Cite this Report

INGV reported that during 20-26 August activity at Etna was characterized by gas emissions at the summit craters, Strombolian activity, and ash emissions. Strombolian explosions continued from vents in Bocca Nuova (including from a vent that had opened on 16 August) and Northeast Crater (NEC). Activity at New Southeast Crater (NSEC) was characterized by modest and occasional explosions and Strombolian activity. Beginning at 1700 on 23 August Strombolian activity from the cone in the saddle between the Southeast Crater (SEC) and NSEC cone complex rapidly intensified; explosions ejected tephra 100-150 m above the vent rim. At 1730 Strombolian activity occurred at NSEC’s E vent, and a lava flow from the same vent traveled a few hundred meters towards the Valle del Bove. Just after 1730 lava overflowed the vent in the saddle cone and flowed N; Strombolian activity at that vent continued through the night and then stopped no later than 0620 on 24 August. At 0622 Strombolian activity from a vent on the S flank of NSEC produced a small lava flow that traveled a few dozen meters. During 25-26 August the activity at the saddle cone gradually decreased, and ash emissions were weak and occasional.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

8 August-14 August 2018 Cite this Report

INGV reported that during 6-12 August activity at Etna was similar to the previous week, characterized by gas emissions at the summit craters, Strombolian activity, and ash emissions. Strombolian explosions continued from vents in Bocca Nuova, and were particularly visible at night. Activity at Northeast Crater (NEC) consisted of frequent ash emissions and Strombolian explosions. Explosions at the E crater on the E flank of the New Southeast Crater (NSEC) generated gray-brown ash plumes that sometimes rose several hundred meters above Etna’s summit and quickly dissipated.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

1 August-7 August 2018 Cite this Report

Based on two field inspections and webcam data, INGV reported that during 30 July-5 August activity at Etna was characterized by gas emissions at the summit craters and Strombolian activity. Three vents at the bottom of the Bocca Nuova crater were active, with gas emissions rising from two vents and sporadic Strombolian activity occurring at a third. Three vents were also active at the bottom of Northeast Crater (NEC); one produced ash emissions, one steam emissions, and Strombolian explosions at the third ejected incandescent material as high as the crater rim. After several months of quiet conditions, explosive activity resumed at the E crater on the E flank of the New Southeast Crater (NSEC). The activity began at 0608 on 1 August with a brownish-gray ash emission that rose several hundred meters above the summit. The event was followed by more ash emissions and then Strombolian activity in the evening.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

18 July-24 July 2018 Cite this Report

INGV reported that during 16-22 July gas plumes rose from Etna’s summit crater; low-energy Strombolian activity also occurred from three vents at the bottom of Northeast Crater (NEC) and from two vents in Bocca Nuova. The activity was mostly confined to the craters, with material falling back into the craters, though occasionally incandescent lava was ejected about 100 m above the crater rim. The activity sometimes generated ash emissions that dissipated near the summit.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

11 July-17 July 2018 Cite this Report

INGV reported that during 9-15 July gas emissions continued to rise from Etna’s summit craters. Visibility of the fairly continuous, low-energy, Strombolian activity deep within the Northeast Crater (NEC) and Bocca Nuova was sometimes hindered by gas emissions. Ejected incandescent material fell back into the crater. Strong and prolonged roars (up to several tens of seconds) from NEC were sometimes accompanied by gray-brown and reddish ash emissions. Collapses of the crater’s inner walls widened the crater. Gas emissions from New Southeast Crater (NSEC) were weak and sometimes pulsating.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

24 January-30 January 2018 Cite this Report

INGV reported that activity at Etna during 22-28 January was relatively unchanged compared to the previous weeks and was mainly characterized by variable-intensity gas emissions from the summit craters. Weak and sporadic ash emissions rose from the New Southeast Crater (NSEC). On 22 January ash fell in areas on the S flank and also in Catania, though the crater which produced the ash emission was unknown due to poor visibility.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

29 November-5 December 2017 Cite this Report

INGV reported that, although weather conditions often prevented views of Etna during 27 November-3 December, gas emissions from the summit craters were visible along with ash emissions from a series of explosions from the vent in the saddle between the Southeast Crater (SEC) - New Southeast Crater (NSEC) cone complex.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

26 April-2 May 2017 Cite this Report

INGV reported that at 1820 on 26 April lava began effusing from a vent on the S side of Etna's New Southeast Crater (NSEC), traveling to the base of the cone. Around 2220 Strombolian activity ejected material from the vent and the lava flow headed towards the Valle del Bove. A lava flow on the N side of the cone began at 0220 on 27 April and traveled NE towards the Valle del Leone. Ash emissions were visible at 0320. Strombolian activity began to diminish around 1230 and eventually ceased. The lava flows advanced until around 1600; phreato-magmatic explosions occurred in areas where the NE flow interacted with snow.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

12 April-18 April 2017 Cite this Report

INGV reported that the effusive eruption from a vent in the saddle between Etna's Southeast Crater (SEC) - New Southeast Crater (NSEC) cone complex ended during 8-9 April. During 10-11 April lava effused from a vent located at the S base of the SEC. The lava flow traveled SE and flowed several hundred meters down the W wall of the Valle del Bove. In the evening of 13 April short-lived explosive activity occurred at a vent at the S flank of the SEC cone at about 3,200 m elevation. That vent and another at 3,150 m elevation produced lava flows for a few hours. Lava also effused from the vent at the S base of SEC, 3,010 m elevation, during 13-14 April, traveling SE and down the W wall of the Valle del Bove on top of the flows from 10-11 April.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

5 April-11 April 2017 Cite this Report

INGV reported that the eruptive episode that began on 15 March from a vent in the saddle between Etna's Southeast Crater (SEC) - New Southeast Crater (NSEC) cone complex was characterized by Strombolian activity and ash emissions. Lava had traveled down into the Valle del Bove from the W rim; by the afternoon of 18 March almost continuous collapses of parts of the lava flow produced several avalanches of incandescent material which reached the base of the wall. Explosive activity had greatly declined earlier that morning. The collapsing stopped by early the next evening, 19 March, and the lava reached the base of the valley. That lava flow stopped advancing on 20 March though a few lava flows closer to the vent remained active the next few days.

On 21 March a new lava flow expanded SSW, but then stopped in the last days of March at an elevation of 2,300 m. A few more lava flows had followed a similar path in early April and then also stopped at the same elevation. Around 28 March a new pit crater had formed on the S part of the pyroclastic cone which had formed around the SEC-NSEC saddle vent. Strong glow form the pit crater was observed at night.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

15 March-21 March 2017 Cite this Report

INGV reported that during the morning of 15 March lava began to flow down the S flank of Etna's Southeast Crater (SEC) - New Southeast Crater (NSEC) cone complex. Activity rapidly intensified at 0800, and by 1000 near-constant Strombolian explosions were generating ash plumes. The lava flow reached the base of the cone and traveled S. By late afternoon the lava was advancing on top of lava flows from the previous eruption. The intensity of the Strombolian activity reached a peak around 1840-1845, and by the evening both the eruptive activity and seismicity gradually diminished. Just before midnight a new lava flow began to effuse from a vent on the S flank of the cone. On 16 March at 1243 a phreato-magmatic explosion occurred at the front of a lava flow where it contacted an area covered with snow. An INGV-Osservatorio Etneo volcanologist was injured in the explosion, suffering minor bruises. A news article noted that about 10 people were injured during the event.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

1 March-7 March 2017 Cite this Report

INGV reported that Strombolian activity at Etna’s New Southeast Crater (NSEC) cone had gradually intensified beginning at 1700 on 27 February. Lava overflowed the vent, quickly traveled down the S flank, and then slowed after reaching the gently sloping terrain. The flow spread SSW, towards the old cone of Monte Frumento Supino. During 27-28 February frequent Strombolian explosions ejected incandescent lava fragments up to 200 m above the vent. During a field survey on 28 February INGV-Osservatorio Etneo staff observed sporadic emissions of vapor and brownish ash from several vents within the NSEC. A new pyroclastic cone around the vent had grown higher than the highest points on the SEC (Southeast Crater) or NSEC. The lava flow slowly advanced on top of the snow, and by 1 March was about 1.5 km from the vent. By the late evening, activity declined, and the volcanic tremor amplitude rapidly diminished.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

22 February-28 February 2017 Cite this Report

INGV reported that Strombolian activity at Etna’s New Southeast Crater (NSEC) cone that began on 23 January gradually began to intensify at 1700 on 27 February. A lava flow quickly reached the base of the cone and traveled SW towards Monte Frumento Supino. Ash plumes drifted E and caused ashfall in Zafferana and Linguaglossa.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

25 January-31 January 2017 Cite this Report

INGV reported that on the morning of 15 December 2016 minor emissions of brownish ash rose from the vent in the saddle between the newer cone and the old cone of Etna's Southeast Crater (SEC). That evening some of the emissions were more energetic, ejecting incandescent material out of the crater which landed on the steep S flank of the SEC cone. Analysis of samples of the ejected rock revealed no new material, only older material from the conduit walls. During the following five weeks weak ash emissions from the vent were observed, without being accompanied by incandescence.

During the early morning of 20 January the saddle vent was again active, with small black ash puffs and thermal anomalies identified by the surveillance camera. People on the SEC observed ejected incandescent material along with ash and blocks. Cloudy weather prevented visual observations for a few days; the evening of 23 January was cloud free and mild Strombolian activity was observed, accompanied by frequent emissions of small, black ash puffs. The activity gradually intensified through the night, with some explosions launching incandescent material as far as the base of the SEC cone. Fluctuating incandescence was also visible at the 7 August 2016 vent of the Voragine (VOR) crater. The frequency of explosions and ash emissions increased on 24 January but then slightly decreased the next morning.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

5 October-11 October 2016 Cite this Report

On 10 October INGV reported that during the past few weeks high-temperature degassing had continued from a vent that had opened on 7 August in the E portion of Etna's Voragine crater. In addition minor and infrequent ash emissions from old pulverized rock rose from a vent located on the upper E flank of the New Southeast Crater cone. In the early afternoon of 10 October an explosion occurred at the Bocca Nuova crater, in an area between the crater and the nearby Voragine crater. The explosion was recorded at 1526, and produced a distinct thermal anomaly and an ash puff that rose a few hundred meters. During the next few hours similar seismic events were detected although weather cloud cover prevented visual observations.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

3 August-9 August 2016 Cite this Report

INGV reported that during mid-July weak ash emissions rose from a vent located high on the E flank of Etna’s New Southeast Crater (NSEC) cone. The emissions continued periodically until early August. Pulsating glow from mild, intra-crater explosions in the Voragine (VOR) crater was recorded during 7-9 August.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

25 May-31 May 2016 Cite this Report

INGV reported that at around noon on 20 May Strombolian activity was visible at Etna's Voragine (VOR) crater and produced explosion noises audible across a large area on the S and E flanks. At night the activity intensified with explosions occurring at two or three vents, contemporaneous with renewed inflation of the summit area. Just after 0400 volcanic tremor amplitude rapidly increased and the Strombolian explosions turned into pulsating jets of lava, launching incandescent bombs 1 km S; an ash plume drifted SSE. A thermal camera also recorded activity from a vent in the S portion of Northeast Crater (NEC). Observers noted that a fracture had formed on the SE flank of the central cone. In addition, an effusive vent in the saddle between the cone and the old cone of the Southeast Crater produced a small lava flow that traveled towards the Valle del Leone. Activity decreased around 0500 and was over at about 0600.

On 22 May a vent on the upper E flank of New Southeast Crater cone produced a series of ash emissions which rose several hundred meters above the summit and dispersed. Some of the emissions had a thermal signature, indicating the presence of hot material. That evening Strombolian activity resumed at NEC; the rate and intensity of the activity fluctuated through the night. The strongest explosions ejected incandescent bombs up to a few hundred meters above the crater rim and onto the flanks. On 23 May sporadic ash emissions continued from the vent on the upper E flank of the New Southeast Crater cone.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

18 May-24 May 2016 Cite this Report

INGV reported that intense Strombolian activity began at Etna's Northeast Crater (NEC) during the evening of 17 May. Incandescent bombs were ejected above the crater rim and tephra was deposited on the flanks. During the morning of 18 May this activity was accompanied by ash emissions that drifted E and rapidly dispersed. Weak incandescence from the 25 November 2015 vent, on the upper E flank of the New Southeast Crater (NSEC) was visible, and an inclinometer about 1 km NW of NEC recorded rapid inflation of the summit area.

Just after 1250 on 18 May cameras recorded the onset of activity at Voragine (VOR) crater, which within a few minutes evolved into a pulsating lava fountain. At the same time Strombolian activity at NEC diminished and dark ash emissions formed briefly. Ash plumes from VOR rose as high as 3.5 km above the crater and drifted ESE. During the afternoon lava overflowed from the W rim of the Voragine-Bocca Nuova depression, and traveled W within the summit area. A second lava flow, emitted from a vent located at the E base of the Northeast Crater (NEC), expanded into the N portion of the Valle del Bove. The second lava flow remained active until the early morning hours of 19 May. Later that morning, the volcanic tremor amplitude sharply increased, and contemporaneously loud and virtually continuous bangs were heard in populated areas to the E and S of the volcano. A dense eruption plume drifted E at an altitude slightly higher than 1 km above the summit of Etna. Ash and lapilli fell onto the E flank of the volcano, near an area affected by the tephra fall on the previous day. A few hours later images revealed a new lava flow from VOR traveling W. Eruptive activity continued at least through 0900, though the volcanic tremor amplitude had diminished.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

30 March-5 April 2016 Cite this Report

Based on INGV webcam views, and VONA and SIGMET notices, the Toulouse VAAC reported a small eruption at Etna on 31 March which ended the next day.

Source: Toulouse Volcanic Ash Advisory Centre (VAAC)

17 February-23 February 2016 Cite this Report

INGV reported that during January eruptive activity at Etna was at low levels. During the last week of January and on 6 February ash emissions rose from a vent located high on the E flank of the New Southeast Crater (NSEC) cone. At 0422 on 23 February an explosion at Northeast Crater (NEC) ejected incandescent tephra several tens of meters above the crater rim, and produced a dark ash plume that drifted NE. A camera recorded lightning flashes in the plume. Weak ash emission rose from the crater during the rest of the morning.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

30 December-5 January 2016 Cite this Report

INGV reported that after intense activity at Etna's Voragine Crater, Bocca Nuova, and the New Southeast Crater (NSEC) during the first 10 days of December, activity shifted to the Northeast Crater (NEC). During 9-10 December Strombolian activity was detected at NEC, with a few ejected incandescence bombs falling onto the outer flank and abundant ash emissions. Activity gradually diminished over a few days. On 13 December ash emissions rose from NSEC and on 18 December the Voragine Crater produced two brief ash emissions. Ash emissions began at 1100 on 28 December from a vent located high on the E flank of the NSEC cone. The emissions ceased in the afternoon; very minor and sporadic explosions continued from the same vent during the following days.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

9 December-15 December 2015 Cite this Report

INGV reported that grayish-brown ash plumes rose from Etna's Northeast Crater on 9 December and drifted SE. Seismicity had significantly decreased.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

2 December-8 December 2015 Cite this Report

INGV reported that after a progressive intensification of activity during the evening of 2 December, an eruption at Etna's Voragine Crater peaked between 0330 and 0410 on 3 December. During the peak period sustained lava fountains rose over 1 km above the crater with some jets of hot material rising 3 km high. An ash plume rose several kilometers high and drifted NE, causing ashfall in Linguaglossa, Francavilla di Sicilia, Milazzo, Messina, and Reggio Calabria. Activity had almost ceased by dawn. This event was among the largest in the last 20 years, similar to large events occurring at the same crater on 22 July 1998 and 4 September 1999.

At about 1000 on 4 December renewed activity at Voragine Crater was characterized by tall lava fountains and an ash plume that rose 7-8 km high. The ash plume had a mushrooming top and produced deposits of coarse-grained pyroclastic material on the upper SW flank above 2 km elevation. Ashfall was reported in Giarre-Zafferana Etnea on the E flank. The activity was accompanied by frequent ash emissions from a new pit crater that had recently opened on the upper E flank of the New Southeast Crater (NSEC) cone. Two more events occurred at Voragine Crater during 4-5 December, between 2130 and 2215 on 4 December and 1555 and 1635 on 5 December, again producing tall lava fountains and many-kilometer-high ash plumes.

During the evening of 5 December activity at Voragine Crater progressively diminished. Between 0300 and 0400 on 6 December surveillance cameras recorded the onset of vigorous Strombolian activity from the vent on the E flank of the NSEC cone. Repeated collapses of both old and new material from the cone's flank generated hot avalanches that traveled a few hundred meters E towards the Valle del Bove. Ongoing effusive activity through the day produced two lava flows; one advanced NE for less than 1 km and the other advanced E. Strombolian activity continued through the evening. On 7 December a second vent on the E part of NSEC was also active, and the main lava flow had advanced 4 km. During the early morning hours of 8 December Strombolian activity progressively diminished and then ended. Later that afternoon weak Strombolian activity and ash emission were observed at the Northeast Crater.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

13 May-19 May 2015 Cite this Report

INGV reported that the new episode at Etna’s New Southeast Crater (NSEC) that began on 12 May continued the next day. At 0410 on 13 May a series of small collapses accompanied the opening of three vents, along a fracture oriented E-W, below the E rim of NSEC, one of which effused a small lava flow. At 0800 a fracture at the vent propagated 200 m from the rim down the cone within 10 minutes. This event was accompanied by collapses, along with reddish ash ejection onto the summit area and the high S flank. Strombolian activity increased that night and was characterized by almost continuous Strombolian explosions, sometimes accompanied by ash emissions. This activity continued during 14-15 May. Ash plumes rose a few hundred meters and dispersed with the wind; minor ashfall was reported in areas from the S to the NE. A single lava flow traveled NE towards Mt. Rittman, and then E towards Mt. Simone where it formed two branches. One branch approached the base of the N wall of the Valle del Bove while the other traveled W to a distance 5 km from NSEC. Activity decreased on 15 May and ceased on 16 May.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

6 May-12 May 2015 Cite this Report

INGV reported weak Strombolian activity inside Etna’s New Southeast Crater (NSEC) during 11-12 May, mainly from a depression on the E part of the crater and sometimes from a second vent in the middle of the crater. This activity was preceded by a sudden increase in tremor amplitude and intense degassing during 2-3 May; visible activity did not accompany the episode, and after a few days tremor returned to normal levels.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

8 April-14 April 2015 Cite this Report

INGV reported that on 12 April two explosions from the W part of Etna’s Bocca Nuova Crater were recorded within a 3-minute period beginning at 1505. Resulting ash puffs rose a few hundred meters above the crater and dispersed.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

28 January-3 February 2015 Cite this Report

INGV reported that a new eruptive episode at Etna began on 31 December and lasted through the morning of 2 February. Poor meteorological conditions prevented views of the summit area during the first 36 hours of the eruption. During improved viewing conditions on the evening of 1 February, volcanologists observed Strombolian activity from a single vent in the saddle between the cones of the Southeast Crater (SEC). Explosions occurred every few seconds and ejected incandescent bombs 200 m high. At the same time a vent at the base of the southern SEC cone issued a lava flow that traveled 2 km S, dividing into two branches. At dawn on 2 February the Strombolian activity produced a dense ash cloud that drifted E. At about 0550 emissions stopped and volcanic tremor suddenly decreased.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

14 January-20 January 2015 Cite this Report

INGV reported that in the evening 14 January weak Strombolian activity was recorded at Etna's Voragine Crater and Northeast Crater. The next day occasionally pulsating ash emissions rose from Northeast Crater and drifted SE. Ash emissions continued through 17 January; cloud cover prevented observations of the summit area on 18 January.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

7 January-13 January 2015 Cite this Report

INGV reported that at night during 6-7 January the frequency of Strombolian explosions at Etna's Voragine Crater decreased; however, some of the explosions ejected incandescent pyroclastic material outside of the crater and onto the W and SW flanks. On 7 January many of the small explosions generated brown ash plumes that rose a few hundred meters above Etna's summit and quickly dissipated. Strombolian activity increased on 8 January, possibly from two vents within the crater. Pyroclastic material continued to be ejected out of the crater. Early on 9 January Strombolian activity again decreased and gave way to ash emissions that rose several hundred meters. Ash emissions continued the next morning, decreased, and had almost completely ceased by late morning. Ash emissions resumed in the afternoon and were sometimes accompanied by Strombolian explosions. Ash emissions on 13 January were continuous in the morning but then decreased in frequency by the afternoon.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

31 December-6 January 2015 Cite this Report

INGV reported that on 29 December, a day after a short but intense eruption, cameras viewing Etna recorded small ash emissions from New Southeast Crater (NSEC) and persistent glow from the saddle between the old and new SEC cones at dusk. During the night on 1 and 2 January cameras recorded intermittent flashes from Voragine Crater (one of four summit craters), indicating Strombolian activity there for the first time in nearly two years. At 0530 on 2 January explosions at NSEC generated ash plumes that drifted SW. On the evening of 3 January explosions ejected incandescent material 150 m above the crater rim.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

24 December-30 December 2014 Cite this Report

INGV reported that starting at 1750 on 28 December Etna's New Southeast Crater (NSEC) produced a short but intense eruption characterized by lava fountains, lava flows, and an ash plume that drifted E and caused ash and lapilli fall in Milo, Fornazzo, South Alfio, and Giarre. Inclement weather prevented observations of the summit area so the erupting crater was not identifiable. Two lava flows traveled E and NE, towards the Valle del Bove. Tremor began to decrease at 1930, and indicated that the eruption was over at 2100.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

15 October-21 October 2014 Cite this Report

INGV reported that from the afternoon of 7 October through 16 October Etna's New Southeast Crater (NSEC) produced weak and intermittent explosive activity; small ash puffs were rapidly dispersed by the wind. During some nights small Strombolian explosions ejected incandescent material a few tens of meters above the crater rim.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

13 August-19 August 2014 Cite this Report

On 13 August INGV reported continued eruptive activity at New SE Crater of Etna, including Strombolian explosions accompanied by minor ash emissions. Lava continued to flow about 3 km NE towards Monte Simone. On 18 August INGV reported that the eruption at New SE Crater had ended on 15 August and lava flow activity had ceased as of 16 August.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

6 August-12 August 2014 Cite this Report

On 9 August INGV reported that volcanic tremor decreased and an ash plume rose to 1 km above the July 25 area of Etna and returned to strong Strombolian activity in the evening. Strombolian activity increased at New Southeast Crater that was accompanied by small emissions of black ash that remained within the crater. The Etna Volcanic Observatory raised the Aviation Color Code to Red on 9 August as an ash plume rose to 4 km (13,000 ft) a.s.l. returning to Orange on 10 August. The Aviation Color Code was raised to Red on 11 August with strong Strombolian activity at Etna accompanied by significant ash.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

9 July-15 July 2014 Cite this Report

INGV reported that a new, small fissure (tens of meters long) developed on the E flank of Etna during 5-6 July. The vent was located around 3,015-3,025 m elevation. Weak spattering from this vent fed a lava flow that extended ~100 m within the saddle of the NE and SE craters and cones. Weak and sporadic strombolian explosions and small ash emissions were observed during 6-7 July from New SE Crater, but by 11 July this activity had ceased.

Activity from the new fissure continued through 11 July with frequent strombolian explosions that were audible in nearby towns. The lava flow diverged, and the longest of the two branches extended ~1.5 km, reaching the bottom of Valle del Leone.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

18 June-24 June 2014 Cite this Report

INGV reported that weak Strombolian activity at Etna's New Southeast Crater (NSEC) continued through 10 June. Some explosions ejected incandescent pyroclastic material a few tens of meters above the crater rim that occasionally fell onto the outer flanks.

On 14 June a new eruptive episode began within the NSEC, beginning with near-continuous Strombolian explosions and lava fountaining. Fine ash emissions were concurrent with lava that began to overflow the edge of the SE crater, forming a flow that continued downhill on the W wall of Valle del Bove. During the morning of 15 June the overflowing lava followed the fissure that had been formed on 28 November 2013. A spatter cone also formed in the E sector of the cone. During 14-15 June volcanic tremor increased sharply and remained at a medium-high level until 18 June when it returned to normal levels.

INGV noted that this activity was similar to the episode of effusive lava emissions observed during 14-16 and 19-31 December 2013 in terms of duration and intensity.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

7 May-13 May 2014 Cite this Report

INGV reported that weak Strombolian activity at Etna's New Southeast Crater (NSEC) continued through 9 May. Some explosions ejected incandescent pyroclastic material a few tens of meters above the crater rim that rarely fell onto the outer flanks.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

30 April-6 May 2014 Cite this Report

INGV reported that during the morning of 22 April sporadic and weak Strombolian activity resumed at Etna's New Southeast Crater (NSEC) and continued for the next few days. Some explosions ejected incandescent pyroclastic material out of the crater and onto the upper S and SE flanks of the cone. A few small collapses occurred on the cone's unstable E flank. The frequency and intensity of Strombolian explosions slightly increased late in the evening on 30 April. Degassing at the Northeast Crater also increased and thermal anomalies were detected by a camera.

Weak Strombolian activity continued to be detected through 1 May. During the night of 2-3 May incandescence was caused by weak high-temperature gas emissions and/or Strombolian explosions. The activity intensified on 4 May and some of the explosions ejected incandescent pyroclastic material onto the high S and SE parts of the NSEC cone.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

2 April-8 April 2014 Cite this Report

INGV reported that during the night of 1-2 April emissions of minor lava flows from the NE base of Etna's New Southeast Crater (NSEC) cone decreased. Strombolian activity gradually intensified during the evening of 2 April and then decreased the next morning. Some collapses from the E flank of the cone were also observed that morning. Poor weather conditions prevented views of Etna for a few days, but by 7 April the lava flows had ceased and Strombolian activity had sharply declined. No activity was observed on 8 April.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

26 March-1 April 2014 Cite this Report

INGV reported that Strombolian activity from Etna's New Southeast Crater (NSEC) cone ceased during the night of 26-27 March, after 64 days of persistent activity. Lava emissions from the lower side of the NSEC significantly decreased; on the evening of 28 March a small lava flow continued to advance but had stopped and was cooling the next day.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

19 March-25 March 2014 Cite this Report

INGV reported on 24 March that during the previous week Strombolian activity with occasional diffuse ash emissions continued from one or two vents at the base of Etna's New Southeast Crater (NSEC) cone. Strombolian activity intensified during 18-22 March, producing more ash, and then decreased; no ash was emitted on 23 March. Lava flows originating from a vent on the upper wall traveled towards the upper part of the W wall of the Valle del Bove and also NE in the direction of Monte Simone.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

12 March-18 March 2014 Cite this Report

INGV reported on 17 March that during the previous week Strombolian activity with occasional diffuse ash emissions continued from one or two vents at the base of Etna's New Southeast Crater (NSEC) cone. Lava flows originating from a vent on the upper wall traveled towards the upper part of the W wall of the Valle del Bove. During 14-15 March lava also flowed NE in the direction of Monte Simone.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

5 March-11 March 2014 Cite this Report

INGV reported that during 6-10 March Strombolian activity and occasional diffuse ash emissions continued to rise from one or two vents at the base of Etna's New Southeast Crater (NSEC) cone. After several days of lava emissions from a vent on the lower part of the NSEC cone, during 5-6 March lava flows originated only from a higher vent and traveled 1.5 km towards the lower part of the W wall of the Valle del Bove. On 8 March sporadic emissions of hot material with small amounts of volcanic ash originated from Bocca Nuova.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

26 February-4 March 2014 Cite this Report

INGV reported that during 28 February-4 March Strombolian activity and diffuse ash emissions continued at Etna's New Southeast Crater (NSEC). An unstable part of the lower E flank of the cone that collapsed on 11 February continued to produce small collapses with reddish ash clouds. Lava continued to flow from a vent on the lower part of the NSEC cone to the W wall of the Valle del Bove, and during 2-3 March the flows reached the base of the wall.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

19 February-25 February 2014 Cite this Report

INGV reported that during 19-22 February Strombolian activity continued at Etna's New Southeast Crater (NSEC) and produced diffuse ash plumes. Lava continued to flow from a vent on the lower part of the NSEC cone to the W wall of the Valle del Bove. An unstable part of the lower E flank of the cone that collapsed on 11 February continued to produce small collapses with reddish ash clouds, and thermal anomalies.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

12 February-18 February 2014 Cite this Report

INGV reported that Strombolian activity continued at Etna's New Southeast Crater (NSEC) and slightly intensified on 12 February. An unstable part of the lower E flank of the cone that collapsed on 11 February continued to produce small collapses and reddish ash clouds. Lava continued to flow from the cone towards the Valle del Bove, and by nightfall had reached the base of the steep W wall of the valley, then advanced on the flat land to the N of Mount Centenarians. Strombolian activity continued during 14-15 February. Lava emissions declined, but produced lava flows a few hundred meters long. At 1208 on 15 February an explosion generated a vapor-and-ash plume, and was then followed by more explosions from the same area. During the afternoon a small lava flow emerged from a new vent at the N base of the NSEC cone. The flow traveled 100 m towards the W wall of the Valle del Bove, and remained active the next day. During 16-17 February Strombolian activity continued to produce small quantities of ash. Lava continued to flow from the vent at the base of the cone.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

5 February-11 February 2014 Cite this Report

INGV reported that during 4-5 February activity at Etna's New Southeast Crater (NSEC) was characterized by intermittent ash emissions accompanied by jets of incandescent pyroclastic material, and a constant emission of lava from one or two vents at the E base of the NSEC cone. The lava flows reached the base of the W slope of the Valle del Bove. On 6 February ash emissions ceased and small Strombolian explosions ejected incandescent pyroclastic material 100 m above the crater. On 7 February Strombolian explosions ejected material onto the flanks of the cone, and the next day ash puffs were observed. During 9-11 February activity continued to be characterized by Strombolian activity, periodic ash emissions, and advancing lava flows. At 0707 on 11 February a large quantity of reddish brown ash emitted from an area near the vents formed a very dense hot flow which quickly reached the base of the W wall of the Valle del Bove. Reddish brown ash emissions continued after the event.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

29 January-4 February 2014 Cite this Report

INGV reported that on 28 January there was a gradual but steady decrease of activity at Etna's New Southeast Crater (NSEC). Weak and sporadic Strombolian explosions were detected at night, but then the thermal cameras recorded no anomalies associated with Strombolian activity. Lava flows from two vents at the base of the NSEC cone continued to effuse at a very low rate. Weather conditions almost entirely prevented observations of Etna from the morning of 30 January until the evening of 3 February. Late on 3 February observers noted that the lava flow remained active and was several hundred meters long. Almost continuous ash emissions from NSEC began at about 1300 on 4 February and continued into the night; about 5-10 ash puffs were separated by steam emissions. Ash plumes drifted E. After sunset jets of hot material were observed rising 100 m above the crater rim. At 2000 the ash emissions and injection of incandescent material ceased, but the lava flow continued and reached 1 km long.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

22 January-28 January 2014 Cite this Report

INGV reported that during 4-13 January nearly continuous emissions of reddish ash from Etna's Northeast Crater were visible. Strong degassing continued at least through 22 January. Strombolian activity at New Southeast Crater (NSEC) began on the evening of 21 January, following 20 days of quiet. Some explosions generated very small ash emissions that barely rose above the crater rim. Late on 22 January a small lava flow from the vent on the high E flank of the NSEC cone traveled a few hundred meters in a few hours. Strombolian explosions ejected incandescent pyroclastic material onto the cone flanks. The frequency and intensity of the explosions decreased early on 23 January, and the lava flow stopped advancing. At 0105 a small puff of gas and/or ash from the E base of the cone heralded a new lava flow that traveled W towards the Valle del Bove. Weak Strombolian activity and the advancing lava flow continued during 24-28 January, although on 25 January the amount of ash produced by the Strombolian activity increased. On 26 January an ash plume drifted E. By evening the intensity of the Strombolian activity as well as the amount of ash in the emissions decreased. The lava flow was 4 km long.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

8 January-14 January 2014 Cite this Report

INGV reported that during 4-9 January 2014 pulsating and almost continuous ash emissions rose from Etna's Northeast Crater (NEC). Volcanic tremor amplitude remained at low levels.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

1 January-7 January 2014 Cite this Report

INGV reported that during 31 December 2013-1 January 2014 lava flows from a vent located on the NE flank of the cone of Etna's New Southeast Crater (NSEC) continued to travel towards the N part of the Valle de Bove; the lava flows had been active since activity resumed on 29 December. On 3 January staff doing field work noted that the effusive activity had stopped.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

25 December-31 December 2013 Cite this Report

INGV reported that on 28 December a helicopter overflight of Etna's New Southeast Crater (NSEC) revealed a crater floor partially covered with snow, and weak fumarolic activity on the N, W, and S crater rims. During the early morning hours on 29 December a camera recorded weak and sporadic incandescence from NSEC. Strong pulsating degassing also occurred at Northeast Crater. At 1115 NSEC produced a single Strombolian explosion, accompanied by an ash plume that rose 1 km and drifted E. After the explosion mild Strombolian activity continued and then progressively intensified in the evening. Frequent powerful explosions from two vents located within the crater were audible in a vast sector around the volcano. Diffuse ash plumes drifted NE. Contemporaneously, two lava flows are active, one from a vent on the E flank of the NSEC cone, and the second, fed directly from the crater, traveled down the NE flank of the cone.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

11 December-17 December 2013 Cite this Report

INGV reported on the 20th paroxysm in 2013 from Etna’s New Southeast Crater (NSEC) began with a strong explosion at 0925 on 14 December from a vent near the NE rim which generated an ash plume that rose 2 km. Intermittent ash emission gradually turned into Strombolian activity. After 1413 the activity intensified; small ash puffs were produced and Strombolian explosions ejected incandescent pyroclastics onto the flanks of the cone. Over the next few hours activity continued to intensify and a diffuse ash plume drifted ESE. At 2323 lava overflowed the SE crater rim and flowed towards the Valle del Bove. During the night explosive activity continued to intensify, and by 0330 on 15 December Strombolian activity was intense and virtually continuous. After 0500 explosive activity started to diminish, and at 0550 the volcanic tremor amplitude and the intensity and frequency of Strombolian explosions showed a sharp drop. Explosive activity continued to produce copious amounts of ash until about 0830. According to a news article, the ash emissions caused the cancellation of more than 20 flights in and out of the Catania airport.

At 0610 and 0633 two vents opened within the deep trench cutting the SE flank of the NSEC cone (where lava was still flowing from the crater since the previous evening), the first just a few tens of meters below the crater rim, the second about 100 m further downslope. Both vents initially produced lava fountains for a few minutes, with jets a few tens of meters high, and then produced lava flows that descended through the trench.

Between 0945 on 15 December and the morning of 16 December ash emission varied in frequency and intensity, related to variations in the intensity of the Strombolian activity at NSEC. During the afternoon and evening of 15 December explosive activity lasted a few to a few tens of minutes and Strombolian activity became significantly more intense or passed into pulsating, low lava fountains. The more intense periods produced greater amounts of ash leading to ashfall in populated areas on the E and SE flank, from the Milo-Zafferana area toward the Ionian coast. At night during 15-16 December lava flows continued to flow towards the Valle del Bove. A shift in wind direction caused ashfall in areas SE, S, and SW.

On 15 December small and periodic ash emissions also occurred from Northeast Crater. Small thermal anomalies detected with a thermal camera were detected during 15-16 December.

Strombolian activity at the NSEC continued through 16 December at a slowly decreasing rate and with numerous minor intensifications that generated diluted ash plumes. Lava effusion also gradually diminished, but at about 1430 on 16 December, a short fissure opened on the lower NE flank of the NSEC cone, producing a small lava flow which advanced a few hundred meters. Explosive activity finally ceased around midnight on 17 December. Very slow lava effusion continued, at a gradually decreasing rate, from the fissure on the NE flank of the NSEC cone, through the night of 17-18 December.

Sources: Sezione di Catania - Osservatorio Etneo (INGV); Agence France-Presse (AFP)

27 November-3 December 2013 Cite this Report

INGV reported on the 18th paroxysm occurred from Etna’s New Southeast Crater (NSEC) late in the afternoon on 28 November. Weather clouds prevented observations of the event. Vigorous Strombolian activity on 2 December produced a plume comprised mostly of gas drifting N. The activity intensified during the evening and evolved into a paroxysmal event that finished by 2330. The event was characterized by tall lava fountains, lava flows, and a plume laden with pyroclastic material that drifted NNW and deposited ash and lapilli in that area. The lava flows traveled SSE, SE, NE, and S. The next day sporadic explosions continued, inclement weather however prevented visual observations.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

20 November-26 November 2013 Cite this Report

INGV reported on the morning of 23 November the 17th paroxysm occurred from Etna’s New Southeast Crater (NSEC), five days after the previous one. The episode was characterized by a rapid evolution from Strombolian activity to lava fountains, an ash plume that rose several kilometers and drifted NE, and lava flows that were significantly less extensive than those emitted during the 16-17 November paroxysm.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

13 November-19 November 2013 Cite this Report

INGV reported that weak Strombolian explosions from Etna’s New Southeast Crater (NSEC) were visible on 13 November. INGV-Osservatorio Etneo staff visited the area the next day and noted that explosions were heard one to three times per minute, and during times of good visibility no pyroclastic material was ejected. Sporadic ejections of incandescent pyroclastics were observed after nightfall. Early on 16 November Strombolian activity gradually intensified; however, only pulsating puffs of vapor, but no ash, were produced.

On 17 November a new paroxysmal eruptive episode was characterized by violent Strombolian activity and pulsating lava fountains, emission of lava flows that traveled S, ESE, and NE, and the formation of an eruption column charged with pyroclastic material that drifted NE. The episode ended with a long series of powerful explosions and loud bangs heard tens of kilometers away. Strombolian activity continued until the late evening; after nightfall, a small lava flow issued from an effusive vent located on the lower E flank of the NSEC cone.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

6 November-12 November 2013 Cite this Report

INGV reported that ash emissions from Etna’s New Southeast Crater (NSEC) occurred at 1251 and 1254 on 6 November and were quickly dispersed by the wind. During 6-7 November several phases of frequent explosions produced ash puffs visible during the daytime and ejected incandescent material from Strombolian activity was visible at night. On 8 November the explosions occurred at intervals of several hours, producing small ash plumes that rose a few hundred meters above the summit and drifted ENE.

A culminating phase of lava fountains, ash emissions, and lava flows began at 0500 on 11 November, after about 10 hours of gradually intensifying Strombolian activity. Weather conditions prevented visual observations, but a strong increase in the volcanic tremor amplitude was detected. The phase of maximum intensity lasted about 7.5 hours, ending around 1130; the cessation of lava fountaining was followed by a long series of powerful explosions that generated loud bangs heard mostly in the N sector of the volcano. Ash and lapilli fell in areas E and NE. A voluminous lava flow expanded S from the NSEC, and two smaller lava flows traveled ESE and NE. Vigorous Strombolian activity continued, with explosions at intervals of 1-2 minutes, which launched incandescent material as high as 150 m above the crater rim. At night during 11-12 November Strombolian activity ceased and the lava flows were no longer active.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

30 October-5 November 2013 Cite this Report

INGV reported on 5 November that, after 10 days of relative quiescence, the New Southeast Crater (NSEC) showed signs of activity. A brief glow seen on surveillance cameras was followed by ash emissions. The event was accompanied by a strong seismic signal detected by summit seismic stations. Poor weather prevented additional observations.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

23 October-29 October 2013 Cite this Report

Sezione di Catania - Osservatorio Etneo reported that on 26 October Etna's New Southeast Crater (NSEC) produced a new episode of lava fountaining, six months after the previous paroxysm. A gas plume laden with pyroclastic material rose several kilometers above the summit and drifted SW, affecting population centers as far as the Caltanissetta area. According to a news article a representative from Catania airport noted that the eruption caused the closure of nearby airspace before dawn through the early morning.

Lava emitted from the saddle between the two cones of the Southeast Crater advanced S, destroying two wooden shacks at Torre del Filosofo. Another smaller lava flow descended the SE flank of the NSEC cone, partially filling the deep collapse scar formed during the 27 April 2013 paroxysm. At 1019 vigorous ash emissions from the Northeast Crater formed a dark brown plume that rose 1 km; ash emissions from that crater continued through late evening. Lava fountaining from NSEC continued through the late morning and was then followed by a long series of powerful explosions audible to many tens of kilometers away. Strombolian explosions occurred in the late evening. Lava flows continued to advance the next day.

Sources: Sezione di Catania - Osservatorio Etneo (INGV); Kasa

4 September-10 September 2013 Cite this Report

Sezione di Catania - Osservatorio Etneo reported that a series of small and sporadic ash emissions from Etna's New Southeast Crater (NSEC) began during the morning of 3 September, marking the end of four months of complete quiescence. Weak Strombolian activity from NSEC was observed during the early morning of 6 September. At daybreak small ash puffs were emitted once or twice per hour. The same morning intense incandescence emanated from Bocca Nuova. The report stated that since early May only degassing from the summit craters was noted, along with usual bangs and rumblings from deep within the conduit of the Northeast Crater (NEC), which during the past few weeks had become more continuous and louder.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

24 April-30 April 2013 Cite this Report

Sezione di Catania - Osservatorio Etneo reported that the thirteenth lava-fountaining episode of 2013 began at Etna's New Southeast Crater (NSEC) on 27 April. Activity increased on 21 April and was characterized by Strombolian explosions and frequent ash emissions. Eruptive activity and the volcanic tremor amplitude gradually increased in the evening of 26 April. Just after sunset on 27 April lava fountains rose 300-500 m, and lava flows from the SE and NE flanks of the NSEC cone and from the saddle between the two Southeast Crater (SEC) cones traveled S and N.

Sezione di Catania - Osservatorio Etneo reported that the thirteenth lava-fountaining episode of 2013 began at Etna's New Southeast Crater (NSEC) on 27 April. Activity increased on 21 April and was characterized by Strombolian explosions and frequent ash emissions. Eruptive activity and the volcanic tremor amplitude gradually increased in the evening of 26 April. Just after sunset on 27 April lava fountains rose 300-500 m, and lava flows from the SE and NE flanks of the NSEC cone and from the saddle between the two Southeast Crater (SEC) cones traveled S and N.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

17 April-23 April 2013 Cite this Report

Sezione di Catania - Osservatorio Etneo reported that the eleventh lava-fountaining episode of 2013 began at Etna's New Southeast Crater (NSEC) on 18 April. Activity increased on 16 April with ejected incandescent tephra and small ash puffs from a vent inside NSEC, followed by weak Strombolian explosions. Strombolian explosions became more frequent and intense on the morning of 18 April and then were almost continuous by 1300. During the next two hours lava fountains developed and a dense plume drifted SSW. Ash and lapilli fell in between the villages of Ragalna, Belper, and Paterno, as well as the tourist area "Etna Sud." Lapilli-fall was a few centimeters deep and clasts were at most 5 cm in diameter. Three lava flows were produced; the largest flowed through the deep notch in the SE rim of the crater and traveled 4 km towards the Valle del Bove. The interaction of the lava with snow led to rapid melting, generating small lahars. The two other lava flows originated in the saddle between the two SEC cones; one traveled N and the other S. After the lava fountains ceased, strong explosions were heard the rest of the day. On 19 April explosions produced little puffs of ash and ejected hot tephra.

The twelfth episode occurred two days later during the late afternoon of 20 April. Intermittent explosions ejected incandescent tephra and generated small ash puffs on 19 April. During the evening a large dark plume rose from NSEC, and sporadic Strombolian explosions were observed. The explosive activity ceased in the late evening, but shortly afterwards the lower of the two effusive vents at the base of the NSEC cone produced a lava flow that traveled 1.5 km towards the Valle del Bove. Around 1700 ash puffs rose from the crater, followed by incandescent tephra ejected at 1713. Within a few minutes sustained lava fountains were observed, along with a tall eruption plume that drifted E. Ash and lapilli fell over a wide area to the E, including along the Ionian coastline, just S of Guardia Mangano, up to Fiumefreddo, including the towns of Taormina, Ripon, and Mascali, and further upstream, including Santa Venerina, Zafferana, Milo, and Sant'Alfio.

On 20 April several lava flows on the W wall of the Valle del Bove interacted with the snow, generating explosions and lahars. Around 1815 lava-fountain activity decreased and turned into explosions and ash emissions. At 1840 the paroxysm was over. In the evening, the lava flow emitted from the effusive vent at the base of the SE part of the NSEC cone was still well-fed. Poor weather conditions prevented visual observations until the evening of 21 April, when surveillance videos showed sporadic Strombolian explosions accompanied by small ash puffs at the NSEC, and the emission of a small lava flow from the base of the cone.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

10 April-16 April 2013 Cite this Report

Sezione di Catania - Osservatorio Etneo reported that the tenth eruptive episode of 2013 began at Etna's New Southeast Crater (NSEC) on 8 April with sporadic ash emissions occasionally accompanied by incandescent material. A large explosion at 2252 was heard up to 15 km away. The ash emissions continued for about 48 hours. In the late afternoon on 10 April Strombolian activity began, producing minor ash emissions during some of the explosions. In the morning on 11 April Strombolian explosions occurred about every 2-5 seconds, ejecting incandescent pyroclastics several tens of meters above the crater rim. Strombolian activity increased slowly in intensity and frequency of explosions throughout the day; contemporaneously the volcanic tremor amplitude continued to show a gradual rise. Late in the afternoon frequent and very powerful Strombolian explosions occurred every 1-2 seconds and were widely audible around the volcano. Jets of incandescent pyroclastics often rose 200 m above the crater rim and generally contained minor amounts of ash. Around 1840, a small amount of lava flowed over the deep breach in the SE rim of the crater. In the late evening it stopped and showed evidence of cooling.

Around 0110 on 12 April another small lava flow traveled S then SE from the saddle between the two cones of the Southeast Crater (SEC). Throughout the night powerful explosions alternated with intermittent, low lava fountains. At daybreak on 12 April a dense eruption plume containing relatively minor amounts of pyroclastic material drifted ESE. Until about 1025 on 12 April, all eruptive activity occurred exclusively at one or two closely spaced vents within the NSEC, then lava was emitted from two vents at the NE base of the NSEC cone. At 1024 a flow of hot pyroclastic material from the same area traveled about 2 km NE in less than 1 minute.

In the meantime, eruptive activity continued at the NSEC with frequent, powerful Strombolian explosions and emission of modest quantities of volcanic ash, which was rapidly dispersed. Lava emission from the SSE rim of the NSEC, the saddle, and the NE base of the cone remained active. Shortly before 1200, the eruptive activity changed from low lava fountains to Strombolian explosions and intermittent ash emissions. Vigorous ash emissions resumed at 1214 both from the main vent of the NSEC and from the saddle vent. Expulsion of blocks, bombs and ash from the saddle vent continued until 1234, when the main vent of the NSEC reactivated, and for the next nearly 20 minutes both vents were the source intense ash emissions.

The activity shifted back entirely to NSEC, entering into the true paroxysmal phase of this episode at 1250 with sustained lava fountaining, accompanied by a return to high levels of the volcanic tremor amplitude. During the following 10 minutes, there was a considerable increase in the quantity of pyroclastic material in the plume, which drifted ESE. Tephra fall (ash and small lapilli) affected Fleri, Zafferana Etnea, Milo and S. Maria la Scala, although the quantity of fallout was much smaller compared to those of the previous paroxysms. Sustained lava fountaining continued for about one hour; a few minutes after 1400 the activity switched to sporadic Strombolian explosions and ash emissions, which gradually diminished in vigor. During 1400 and 1410, repeated collapses occurred on the SE flank of the NSEC cone, possibly from new vents at the base of the cone, from which a new lava flow traveled toward the Valle del Bove. The collapses generated avalanches and clouds ash. Explosive activity progressively diminished and completely ceased around 1700.

On the evening of 12 April, the lava flows emitted from the saddle and from the various vents on the flanks of the cone were incandescent and slowly moving; during the night, the surveillance cameras showed the cessation of all lava emission and the cooling of the flows. However, on the morning of 13 April, slow lava effusion resumed from the lower of the vents and a small flow advanced a few hundred meters. This flow ceased in the early morning hours the following day. Once more, on the evening of 14 April, there was a rather weak resumption of effusive activity from this vent, which ceased after a few hours.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

3 April-9 April 2013 Cite this Report

Sezione di Catania - Osservatorio Etneo reported that on 3 April, after almost 18 days of relative quiet, the New Southeast Crater (NSEC) of Etna produced its ninth episode of lava fountaining. Activity had increased on 2 April when small grayish-brown puffs rose from NSEC. Cloud cover prevented further visual observations through the following night; however, sporadic glow suggested Strombolian activity. On the morning of 3 April, the volcanic tremor amplitude slowly increased and was accompanied by numerous explosion signals. Field observations revealed that at 1330 vigorous Strombolian activity was occurring at one or two NSEC vents, with jets of pyroclastic material rising up to a few tens of meters above the crater rim. The activity progressively intensified between 1400 and 1430, with frequent, powerful Strombolian explosions often generating loud bangs and launching great quantities of incandescent bombs (with diameters of many meters) onto the flanks of the cone. Shortly after 1435, ash emission started from the saddle vent (SV), followed a few minutes later by Strombolian explosions from the same vent. At 1450, a continuous jet of incandescent lava fountained up to 100 m, whereas the vents within NSEC continued to produce powerful loud explosions. At around 1505 a lava flow moved through the deep breach in the SE rim of NSEC and then traveled over the W rim of the Valle del Bove. During the same time interval, lava emissions started from SV, feeding a flow that went S.

Since 1430 the eruptive plume drifted SE and contained modest amounts of volcanic ash. At around 1540 ash emissions progressively increased and the volcanic tremor amplitude showed a rapid rise. Between 1540 and 1615 low lava fountaining continued from SV, whereas the vents within NSEC emitted intermittent, pulsating lava fountains. The incandescent jets from the vents within NSEC rose up to 400 m above the crater rim. At 1615, lava fountaining at SV intensified, with jets rising 400-500 m high. Explosions from the vents within NSEC continued, producing loud detonations every 1-2 seconds.

Lava fountaining significantly decreased between 1625 and 1628 when a new eruptive vent (NV) opened a few tens of meters to the W of SV, on the E slope of the old SEC cone, and emitted grayish-brown ash. A dense cloud of pyroclastic material emitted by NSEC vents and SV rose about 2 km high and drifted SE. Fallout of pyroclastic material affected almost the same area that had already been subjected to the heavy shower of lapilli on 16 March: Zafferana Etnea and Santa Venerina on the SE flank, and the N part of Acireale plus a number of smaller villages to the N at the S margin of Giarre, in the Ionian area. The deposit was thinner than that of 16 March, and the dimensions of the lapilli were notably smaller.

Between 1630 and 1640, the eruptive activity reached a new peak of intensity with sustained lava fountains from SV and powerful explosions from the vents within the NSEC. At 1637 a thermal surveillance camera recorded a pyroclastic flow from the NE flank of the NSEC cone. Two lava flows emerged from the same area and traveled toward the Valle del Bove.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

13 March-19 March 2013 Cite this Report

Sezione di Catania - Osservatorio Etneo reported that Strombolian activity continued at Etna's Voragine Crater after the 5-6 March paroxysm at the New Southeast Crater (NSEC), but was rarely detected by 14 March. Sometime during the afternoon of 15 March, numerous explosion signals were detected, and the volcanic tremor amplitude increased through the evening. After nightfall, incandescence from the NSEC was visible, and nearby residents (on the SE flank) heard loud bangs coming from the crater. This activity continued during the night and through the following morning. At daybreak on 16 March, numerous gas rings formed by the more powerful explosions were recorded by the monitoring cameras and photographed by observers in the field.

During the early afternoon of 16 March, activity started to intensify more rapidly, and frequent jets of incandescent lava were launched up to150 m above the crater rim. At about 1800 lava started to flow through the deep breach in the SE rim of NSEC. Approximately 15 minutes later, explosions became progressively more energetic, ejecting incandescent bombs onto the outer flanks of the cone; contemporaneously, the quantity of pyroclastic material (ash and lapilli) in the eruptive plume increased. Ash plumes drifted SE.

Between 1830 and 1845, the eruptive activity changed from Strombolian explosions to lava fountaining, with the highest jets rising 600-800 m above the crater rim. The eruption column rose about 2 km above the summit of Etna before it was blown SE by the strong winds. Around 1900, several lightning flashes within the eruptive cloud were observed. Large, incandescent bombs and scoriae were deposited on the entire cone of the NSEC and the adjacent areas to the S and SE. Observations made after the end of the paroxysm revealed that a lava flow was emitted from the area of the saddle between the SEC cones. During the phase of most intense lava fountaining, numerous volcanic bombs fell onto the pyroclastic cones formed during the 2002-2003 eruption, up to 2 km from the NSEC. In this phase, the lava fountains were also spectacularly visible from the town of Randazzo, on the NNE flank, about 15 km from the NSEC.

Heavy tephra fall, mostly in the form of scoriaceous lapilli, affected the SE flank; on the W headwall of the Valle del Bove this material was still incandescent. Further downslope, in the towns of Zafferana Etnea, Santa Venerina, and a number of villages to the N of Acireale, the tephra fallout formed a continuous deposit of scoriaceous lapilli, which in the N portion of Zafferana Etnea locally was up to 10 cm thick. Many clasts in this area had diameters from 5 to 8 cm, and more rarely up to 10 cm. Numerous car windshields, skylights, and roof tiles were broken. Even on the Ionian coast, the deposit consisted largely of lapilli, with only a minor fraction of ash.

The activity started to decrease around 1904, and at 1910 the activity evolved into violent explosions that ejected broad fans of large, incandescent bombs, accompanied by loud bangs and detonations. These explosions ceased at 1920, but at 1927 two particularly powerful explosions ejected large incandescent rock fragments towards the SW at least 1.5 km from the crater. A few weaker Strombolian explosions occurred shortly after 1930. At 0449 on 17 March, a series of explosions started at Voragine, which continued for about 5 minutes, generating strong thermal anomalies that were recorded by the thermal surveillance camera, and probably produced small ash puffs. During the next few hours, weak glow coming from Voragine was recorded by a monitoring camera. There were also small collapses and slides of still hot material from unstable portions on the NSEC cone, which generated minor quantities of ash.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

6 March-12 March 2013 Cite this Report

Sezione di Catania - Osservatorio Etneo reported that during 5-6 March a new episode of lava fountaining occurred at Etna's New Southeast Crater (NSEC). On 5 March an explosion from the vent in the W part of NSEC was detected at 1854 and ejected incandescent bombs several tens of meters above the crater rim. This explosion was followed by similar ones, initially separated by intervals of 15-20 minutes, but then gradually became more frequent. As the evening went on, the activity at NSEC progressively intensified; likewise, the volcanic tremor amplitude started to rise. Around 0012 on 6 March, lava started to flow from the saddle between the two SEC cones; a few minutes later, an eruptive fissure with several vents opened in the lower portion of the saddle. Lava jets became continuous around 0017, forming a fountain that rose 200-300 m above the crater rim. Various vents were active within the NSEC, in the saddle area, and at the base of the saddle, from where a voluminous lava flow expanded S and SE. Around 0100 this lava flow had reached the area of Belvedere station. Lava also flowed through the breach in the SE rim of NSEC.

For the next 30 minutes, lava fountaining continued with jets rising 600 to 800 m above the crater. An eruption column heavily laden with pyroclastic material rose several kilometers above the summit and drifted NE. Deposition was intense on the upper NE flank of Etna, covering the area of the Valle del Leone, Pizzi Deneri, and Serra delle Concazze with incandescent bombs and scoriae. Further downslope, at Linguaglossa, scoria with diameters of several centimeters fell, and ash and lapilli fall was also observed at Piedimonte Etneo, Fiumefreddo, Taormina, and other towns along the Messinian Ionian coast.

Just after 0100, and within a few minutes, explosive activity nearly ceased, with only a few weak Strombolian explosions. During the same time, however, an eruptive vent opened on the lower E flank of the NSEC cone, which produced vigorous spattering and a well-fed lava flow that advanced SE. This activity continued at a slowly decreasing rate for a few days and ceased altogether on 9 March.

At the Voragine, Strombolian activity continued after the 5-6 March paroxysm at NSEC, but then alternated with short episodes of intense Strombolian activity and nearly totally quiet intervals. These oscillations were reflected in the volcanic tremor amplitude, which during the 24 hours following the paroxysmal episode at the NSEC showed about twenty small peaks.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

27 February-5 March 2013 Cite this Report

Sezione di Catania - Osservatorio Etneo reported that seismic activity at Etna's Bocca Nuova Crater (BN) gradually increased at night during 26-27 February. Copious, puffing emission of dense vapor from BN observed at sunrise slowly grew more energetic over the next few hours. Between 1030 and 1045, the volcanic tremor amplitude rapidly rose; at the same time an eruption column largely composed of vapor formed and hot material was ejected. The plume contained moderate amounts of reddish-brown volcanic ash, mostly during 1215-1220 and 1314-1316, which led to the fall of small quantities of very fine ash on the SE flank between Zafferana and Santa Venerina. These ash emissions likely resulted from collapse or sliding of unstable material on the steep inner crater wall; the eruptive vent, which lies in the SE part of the crater, is leaning against the wall and the rapid accumulation of pyroclastic deposits in that area might have facilitated collapses.

During the phase of most intense eruptive activity, INGV staff carrying out fieldwork in the summit area, noted that volcanic bombs fell outside the crater rim onto the SW flank of the central cone. Intense explosive activity was also observed within the Voragine (VOR), which since early October 1999 had not exhibited magmatic activity. The activity began to diminish around 1320, evident from a reduction in the volcanic tremor amplitude; at 1430, the episode was essentially over, even though strong degassing continued at both BN and VOR. During the evening of 27 February vigorous Strombolian activity in VOR was reported by observers on the W and E flanks. Minor and discontinuous Strombolian activity also occurred at BN which often launched incandescent volcanic bombs up to 150 m above the crater rim. The activity continued through the night, into at least early 28 February, when NSEC also started showing signs of renewed activity after more than four days of repose.

Weak explosive activity and sporadic weak ash emissions at New SE Crater (NSEC) were observed during the early morning hours of 28 February. Weak Strombolian activity in the W part of the NSEC appeared at 0917. Thirteen minutes later Strombolian activity was occurring at the main vent in the center of NSEC. Contemporaneously, the volcanic tremor amplitude started to rise. During the following hour, eruptive activity gradually increased, while the volcanic tremor amplitude increased rapidly; at 1030, at least three vents were erupting including the former "pittino" to the W, in the saddle between the old SEC cone and NSEC cone. This activity generated a dense gas plume containing modest quantities of ash. At 1040 lava flowed through the through the deep breach cutting the SE crater rim; 25 minutes later, explosive activity increased dramatically and lava fountains rose about 100 m above the crater rim. From 1115 on, frequent powerful explosions generated visible shock waves and heavily showered the NSEC cone with large volcanic bombs. The activity intensified further between 1117 and 1122, accompanied by a conspicuous cloud of vapor and brown ash issued from the saddle between the two SEC cones. This cloud marked the progressive collapse of a large portion of the saddle, which destroyed nearly all of the SW flank of the NSEC cone, and parts of the E flank of the old SEC cone. Voluminous amounts of lava flowed from the deep notch left by the collapse, expanding first S and then SE, in the direction of the Belvedere monitoring station. Lava was also emitted from the eruptive vents at the base of the NSEC cone; this lava mixed with the flow emitted directly from the NSEC toward SE.

Sustained lava fountaining, with intense pyroclastic fallout and the generation of a huge cloud of gas and ash, continued at maximum intensity for about 20 minutes. The ash cloud drifted E, leading to abundant ash and scoria fall in the Milo-Fornazzo and Giarre-Riposto areas. At 1142 the activity started to diminish, although dense clouds of vapor and grayish-brown ash were emitted from the collapsed saddle area. At about 1150, the activity at the "pittino" became phreatomagmatic; vapor and ash were emitted and hot, wet blocks that formed spectacular vapor trails were ejected. Shortly after 1200, explosive activity at the NSEC ceased, whereas lava emission continued from the collapsed saddle area as well as from the SE flank of the NSEC cone, at a slowly diminishing rate. The lava flows continued to advance during the night of 28 February-1 March, and ceased sometime during 1 March. Strombolian activity within the VOR continued without significant variations, and was observed by INGV staff during a field visit on the morning of 1 March, at least through 1500 on 3 March.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

20 February-26 February 2013 Cite this Report

Sezione di Catania - Osservatorio Etneo reported two episodes of lava fountaining from Etna's New Southeast Crater (NSEC) on 20 February. The first episode's most energetic phase occurred during 0150-0235, producing an ash plume that drifted ESE, small lahars, lava flows from the fissure cutting the SE crater rim, and lava flows from a new eruptive fissure which opened on the lower SW flank of the cone. After the cessation of lava fountaining, weak spattering and low-rate lava emission continued from two small fissures at the SE base of the cone. During the late morning, eruptive activity at NSEC re-intensified. The second episode began just after 1415 and ended at about 1450. An ash cloud drifted E, and new lava flows traveled towards the Valle del Bove, following the paths of previous flows. Slow-moving lava flows from the fissures at the SE base of the NSEC continued into the next day, accompanied by sporadic, weak Strombolian explosions at the NSEC.

At 0233 on 21 February a new vent opened high on the W slope of the Valle del Bove and produced a lava flow that melted snow, creating lahars and voluminous steam plumes. At about 0300 Strombolian activity resumed at the NSEC; the activity became virtually continuous by 0440 and produced jets of incandescent lava that rose at most 100 m above the crater rim. Cloud cover periodically prevented observations, but at 0540 the clouds were illuminated, and at 0545 a lava flow emerged from the cloud cover. An ash plume drifted N, causing ashfall in the area between Randazzo (15 km NNE) and Linguaglossa (7 km NE), at Patti on the Tyrrhenian (N coast of Sicily), and as far as Lipari (more than 80 km N). Scoria clasts up to 15 cm in diameter also fell in Linguaglossa. After the cessation of this fourth paroxysm in just over two days, effusive activity continued from the eruptive vents, feeding two lava flows that traveled 2.5 km down to the base of the steep W slope of the Valle del Bove. This activity, accompanied by sporadic small Strombolian explosions at the NSEC, continued into the morning of 22 February.

At about 0700 on 22 February, rising tremor amplitude signaled the onset of a new episode, but from Bocca Nuova. Between 0730 and 0815 many vapor puffs and thermal anomalies were observed. Cloud cover prevented clear views, but mild Strombolian activity was likely occurring within the crater. At about 0815 the volcanic tremor amplitude started decreasing and the gas emissions from Bocca Nuova became less conspicuous. Contemporaneously, the emission of lava from the two effusive vents at the SE base of the NSEC cone and below the Belvedere station decreased and completely ceased during the afternoon of 22 February.

At about 1625 on 23 February thermal anomalies were detected from NSEC and 15 minutes later lava was visible from the vent at the SE base of the NSEC cone. By nightfall the lava flow and Strombolian activity were visible from populated areas on the S and E flanks, although cloud cover hampered views. Activity intensified during 1900-1930; lava fountains rose at most 150 m above the crater rim and a well-fed lava flow spilled through the breach in the SE crater rim and traveled toward the W slope of the Valle del Bove. Within the next 10 minutes jets of lava rose 500-800 m above the rim. During that time, the emission of pyroclastic material increased dramatically, forming a dense plume that drifted NE; the entire NE flank, from the NSEC to Pizzi Deneri and beyond, was covered with a sheet of incandescent material. Eyewitnesses also reported the fall of large clasts, some incandescent, in the area of Monte Baracca, ~5 km NE of the NSEC. High lava fountaining continued for about 35 minutes. At 2014 the height of the lava fountains rapidly decreased, and two minutes later, the activity had changed to Strombolian explosions that ejected incandescent tephra up to 100 m above the crater rim. At 2030 all explosive activity was essentially over. During the morning of 24 February, the lava flow emitted from NSEC continued to be fed, probably by one or more vents near Belvedere.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

13 February-19 February 2013 Cite this Report

Sezione di Catania - Osservatorio Etneo reported that during the evenings of 13 and 14 February a camera recorded incandescence from Etna's New Southeast Crater (NSEC). In the early hours of 15 February incandescent bombs were ejected just higher than the crater rim. Strombolian activity gradually intensified on 17 February along with volcanic tremor amplitude. Small Strombolian explosions occurred every 1-2 seconds at daybreak, launching coarse-grained pyroclastic material a few tens of meters above the crater rim. After reaching a peak around 0700, activity started to diminish; a few hours later, the volcanic tremor amplitude returned to background levels, and by the evening there was no sign of eruptive activity.

Shortly before midnight on 18 February, the clouds dissipated from the summit area, revealing continuous weak Strombolian activity within NSEC. During 0000-0200 on 19 February the volcanic tremor amplitude rose gradually, then distinctly increased after 0200. Contemporaneously, the eruptive activity started to intensify from one vent in the center of the crater. About 10 minutes later, lava started to overflow through the deep notch in the SE crater rim, expanding slowly toward the steep W slope of the Valle del Bove. At 0457 the small pit crater that had formed on the SW rim of the NSEC on 27 August 2012 started to emit ash, and repeated rim collapses generated small landslides. Activity of the main vent within the crater rapidly increased, and at 0503 a lava fountain rose about 200 m above the summit of the cone.

During the interval from 0503 until 0507, several vents became active along a fracture from the pit crater to the notch in the SE crater rim. A dense cloud of ash rose and drifted E. Next, the entire NSEC cone was subjected to heavy fallout of coarse-grained pyroclastic material. The main lava flow advanced SE, and a small lava flow that developed on the flank below the pit crater traveled along the March 2012 fracture zone between the old and new SEC cones. At 0515 lava fountains rose 300-500 m above the crater rim and produced bombs and spatter that covered the S flank of the cone. Small avalanches of this incandescent material generated ash clouds. During 0516-0518 the S flank of the cone was veiled by a dense curtain of fallout from the lava fountains. At the same time, dense vapor clouds rose from the upper E flank of Etna, generated by the copious fallout of incandescent pyroclastic material onto the snow.

At 0519, a more substantial avalanche of fresh material detached from the S flank of the cone, generating a small pyroclastic flow that expanded a few hundred meters first S and then E. At 0536 a thermal monitoring camera recorded a lahar from near the Belvedere area, which was followed by a broad lava flow that descended the steep slope and reached the base after less than 20 minutes. During its descent, the lava continued to melt snow, producing numerous small lahars. At 0550 a second lava flow N of the first also generated lahars. Finally, at about 0600, a third lava flow, which generated a lahar, descended the W slope of the Valle del Bove to the S of the first flow.

Lava fountaining from the pit crater started to diminish around 0525, and at 0535 transitioned into ash emissions alternating with brief jets of incandescent lava. At 0545, one single vent, in the central portion of the NSEC, continued to produce lava fountains about 200 m high. A few minutes later, however, a new lava flow started to descend the lower SE flank of the cone, possibly after the opening of a new eruptive vent in the lower part of the notch cutting that sector of the cone. Surveillance cameras showed brief lava fountaining at that site, before all lava fountaining ceased shortly before 0600. During the interval between 0600 and 0615, the activity was characterized by emission of a dense ash plume with frequent jets of lava and powerful explosions, which launched large glowing bombs beyond the summit of the old Southeast Crater cone. After 0615 only ash emission persisted. At 0622 a puff of ash was emitted from the Bocca Nuova; shortly thereafter, ash emissions from the NSEC diminished notably and became discontinuous; the last, weak puffs of ash were observed around 0710. Slow lava emissions continued for a few more hours from the lowermost vent, which had opened shortly after 0547 on the SE flank of the cone. During the late afternoon of 19 February, small ash puffs were again emitted from the Bocca Nuova. Tephra fell in a narrow area extending from the NSEC towards the E, including Milo and Fornazzo (10 km E), Giarre (16 km E) and Riposto (18 km E).

Source: Sezione di Catania - Osservatorio Etneo (INGV)

6 February-12 February 2013 Cite this Report

Sezione di Catania - Osservatorio Etneo reported that during the days following the 2 February eruptive episode at Etna intermittent emissions of small quantities of ash were repeatedly observed from both the New Southeast Crater (NSEC) and Bocca Nuova Crater.

Volcanologists visited Etna on 5 February and observed the recent changes that had taken place at Bocca Nuova Crater, notably the growth of a pyroclastic cone surrounding the eruptive vent in the SE portion of the crater. This cone had grown at least 50-70 m, about halfway up the inner crater wall, and was leaning into the wall. The entire crater floor was covered with recent lava.

Later in the evening of 5 February a webcam recorded weak Strombolian activity at NSEC, which continued until daybreak the next day, and then became invisible due to deteriorating weather conditions. Seismic data showed an instantaneous increase of tremor at 1020; volcanic tremor amplitude rose to a peak within a few minutes after the start of the activity, and began to descend after less than one hour. People in the ski area on the NE flank of the volcano briefly saw a dense but ash-free gas plume rising from the summit.

After the episode on 6 February through most of 8 February sporadic ash emissions from NSEC were observed, although poor weather conditions often prevented observations. On the evening of 8 February weak glow from NSEC was intermittently visible. At 2100 a webcam recorded fluctuating glow from within Bocca Nuova which became more intense over the next 10 minutes. Around 2125 jets of incandescent lava were repeatedly seen rising above a thick blanket of clouds drifting over the summit area of Etna. Contemporaneously, the volcanic tremor amplitude rose sharply. After 2200 the volcanic tremor amplitude began to decrease, whereas the eruptive activity continued without showing signs of diminishing until about 30 minutes later. After 2230 on 8 February and during 9-10 cloud cover prevented observations. A brief ash emission was observed on 10 February.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

30 January-5 February 2013 Cite this Report

Sezione di Catania - Osservatorio Etneo reported that intense Strombolian activity at Etna's Bocca Nuova Crater began on the evening of 30 January and was the fifth episode of activity during a three-week interval that began on 10 January. Weak glow from a vent on the SE part of the crater floor was first observed at 1807. The glow became stronger and was visible to nearby residents; simultaneously volcanic tremor amplitude rapidly increased, and shifted from below the New Southeast Crater (NSEC) toward Bocca Nuova. Between 1900 and 1915 the activity intensified, and from 1920 onward jets of incandescent volcanic bombs and scoria nearly continuously rose higher than the crater rim. Some tephra was ejected 150 m above the rim.

During 1930-2000, lava fountains rose 100 m above the rim. Shortly after 2000, the fountain leaned SW and produced heavy fallout of incandescent bombs and scoria on the outer SW flank of the central summit cone, down to its base. At 2016 the fountain rose vertically and pyroclastic fallout outside the crater diminished.

Around 2030 the lava fountain started to wane; the incandescent jets became discontinuous and only rarely rose more than 100 m above the crater rim, except for one jet, at 2100, which rose 150 m above the rim. In addition, the volcanic tremor amplitude rapidly decreased and returned to normal levels in the late evening. After 2200, the incandescent pyroclastic jets no longer rose above the crater rim, and the glow became progressively less brilliant. During the night, however, weak eruptive activity continued on the crater floor, evident from a dull glow emanating from the crater. During the early morning hours of 31 January, the glow gradually faded away, and the episode ended with a series of sporadic, small ash emissions, the last of which was seen around 0641.

During 31 January-1 February ash emissions at New Southeast Crater (NSEC) were nearly continuous for intervals lasting from a few minutes to more than one hour. On 1 February small discrete "puffs" of ash rose from Bocca Nuova. At both craters ash plumes rose no higher than 100 m above the crater rims.

At 0300 on 2 February a camera recorded weak glow from NSEC then after 0330 sporadic small explosions ejected incandescent pyroclastic material up to a few tens of meters above the crater rim. The strongest explosions (at 0345, 0400, 0409, and 0411) ejected glowing bombs onto the flanks of the NSEC cone. Two minutes after the last of the explosions, weak glow appeared at Bocca Nuova that only lasted a short time; during the following 30 minutes, however, intermittent glow was recorded at both craters. At 0450 jets of lava rose above the rim of Bocca Nuova; at 0500 Strombolian activity became continuous, producing jest that rose many tens of meters above the rim. Small Strombolian explosions resumed in NSCE at 0512. Just after 0515 activity at Bocca Nuova started to increase rapidly; contemporaneously, the volcanic tremor amplitude showed a sharp rise. Lava fountains rose 120-150 m above the rim. Activity at NSEC started to decrease at 0530 then ceased just before 0600. Activity at Bocca Nuova decreased markedly between 0620 and 0630; weak intracrater activity continued for a few more hours and then by 0900 the episode was over.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

23 January-29 January 2013 Cite this Report

Sezione di Catania - Osservatorio Etneo reported that two episodes of Strombolian activity from Etna's Bocca Nuova Crater occurred during the evenings of 16 and 18 January. Both began with a sudden increase in volcanic tremor amplitude. Poor weather conditions prevented direct observations; the only visible evidence was a bright glow illuminating the clouds covering the summit. On 18 January some clasts were ejected onto the S outer slope of the central summit cone.

On the early morning of 20 January volcanic tremor amplitude again rose, and was much more pronounced at the EBEL station about 700 m from the New Southeast Crater (NSEC) than at the ECPN station much closer to Bocca Nuova. Contemporaneously, there were reports of glow illuminating the clouds over the summit of Etna. Seismic and infrasonic data analyses suggested that the activity occurred at NSEC and consisted of mild Strombolian explosions, which ceased a few hours later.

The next episode began at 22 January. Tremor rapidly rose at 1840 again producing a stronger signal at the EBEL station. Glow from Strombolian activity was first recorded by a camera at 1856; the activity then became more clearly visible and the Strombolian explosions became more frequent. Incandescent bombs were ejected as high as 100 m above the crater rim. The strongest explosions were followed by abundant fallout of coarse-grained tephra onto the flanks of the NSEC cone. Eruptive activity continued for nearly 12 hours with minor fluctuations. Noises produced by the explosions were audible to residents on the E flank. At about 0600 on 23 January the tremor amplitude decreased and the last explosion visible on camera footage was recorded at 0635. During the hour following, a few small, sporadic puffs of vapor mixed with volcanic ash rose from the crater and drifted E.

The two episodes of Strombolian activity at the New Southeast Crater during 20 and 22-23 January represented the first emission of new magmatic products after a quiet interval of nearly nine months. During the past few months, signs of a possible reactivation of the crater were observed, starting with a dull glow coming from within the crater on 22 November 2012 and a series of small vapor and ash emissions during 25-27 December 2012. A short-lived episode of intense glow occurred on the evening of 3 January 2013.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

9 January-15 January 2013 Cite this Report

Sezione di Catania - Osservatorio Etneo reported that during 22 November-early December 2012 weak glow emanated from Etna's New Southeast Crater (NSEC) caused by the emission of high-temperature gas. The glow was most intense during 1-2 December, then rapidly diminished and reappeared on 24 December. During 25-27 December sporadic and weak ash emissions from NSEC were accompanied by increased gas emissions. On the evening of 3 January a strong glow was briefly observed.

Vigorous Strombolian activity at Bocca Nuova Crater began at night during 9-10 January, three months after the last episode. At 0000 on 10 January a rapid rise in tremor amplitude was detected. Ten minutes later a video camera recorded the first incandescent burst in the E part of the crater, which progressively became stronger and more frequent. At 0350 jets of incandescent fragments rose significantly higher than the crater rim. In daylight the phenomenon was no longer visible via the surveillance cameras; the volcanic tremor amplitude remained elevated but started to decrease around 1200. In the early morning of 15 January volcanic tremor amplitude rapidly decreased, marking the cessation of Strombolian activity in the Bocca Nuova Crater.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

21 November-27 November 2012 Cite this Report

Sezione di Catania - Osservatorio Etneo reported that on the evening of 21 November, weak glow was observed coming from within Etna's New Southeast Crater, caused either by the emission of high-temperature gas and/or Strombolian activity. Incandescence was also visible during the following nights, but was weak and intermittent.

A seismic swarm, consisting of around seventy events, occurred below the NW flank on 22 November, with epicenters located in the area of Monte Maletto. During a field visit to the summit area on the morning of 23 November, scientists did not hear sounds typically associated with Strombolian activity. In addition, volcanic-tremor amplitude did not show any significant variations.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

10 October-16 October 2012 Cite this Report

Sezione di Catania - Osservatorio Etneo reported that on the evening of 2 October weak Strombolian activity resumed within Etna's Bocca Nuova crater, from the same vent on the SE part of the crater floor that was active in July and August 2012. On 3 October the activity was accompanied by a small inter-crater lava flow on the S part of the floor. Over the next few days the activity slowly intensified and a small new cone developed over the old cone formed during July-August, which had subsequently nearly completely collapsed. Volcanic tremor amplitude rapidly increased on the evening of 6 October at the same time eruptive activity intensified. Lava flowed towards the W part of the crater floor and lava fountains pulsated. The intensity of both the eruptive activity and the volcanic tremor amplitude peaked just after midnight on 7 October, and strong glow from the crater was observed from nearby populated areas. Some of the lava jets rose well above the crater rim. Activity decreased at 0430, and the next day dropped to the lowest levels recorded for many weeks.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

15 August-21 August 2012 Cite this Report

Sezione di Catania - Osservatorio Etneo reported that a new phase of activity at Etna's Bocca Nuova summit crater started on 2 July, was virtually continuous for three weeks until 24 July, then rapidly decreased. During the first 10 days explosions were separated by quiet intervals lasting several minutes, then later became more continuous. During periods of the strongest activity, some lava bombs were ejected beyond the crater rim, landing on a gently sloping area E of the crater. Lava was emitted during 4-24 July from vents on the flanks of the pyroclastic cone that had begun to grow around the explosive vent. Rarely, lava was emitted from the main explosive vent. The lava progressively covered the crater floor next to the pyroclastic cone, which had grown 30-40 m, before the activity ceased on 24 July. Frequent ash emissions observed the next day were mostly due to explosions, and possibly from minor collapses of the summit area of the new cone. Concurrent with the decrease in eruptive activity, volcanic tremor amplitude dropped to background levels.

Episodic activity occurred during 26 July-11 August. At daybreak on 26 July, strong incandescence marked the onset of the first episode of activity within Bocca Nuova, which had the same characteristics as the previous activity; frequent Strombolian explosions were accompanied by lava flow emissions from a vent located on the W flank of the cone. The next day, the lava had almost completely filled the central subsidence pit on the floor of Bocca Nuova, and the cone had grown in height. The activity then decreased, and essentially ceased by the evening. There were intermittent ash emissions on 28 July, and volcanic tremor amplitude decreased to background levels.

The second episode, during 29 July-1 August, was characterized by small Strombolian explosions and lava emission from a vent located on the S flank of the pyroclastic cone. Volcanic tremor amplitude showed strong oscillations, but never reached the same peak levels associated with the 26-27 July episode. Volcanic tremor amplitude dropped sharply on 1 August, marking the cessation of the activity; a few ash emissions were observed the next day.

The third episode began on 3 August with a rapid increase in the volcanic tremor amplitude and strong incandescence from Bocca Nuova, signaling the beginning of Strombolian activity and lava emissions onto the crater floor. Activity ceased the next day, and was followed by weak residual activity within Bocca Nuova, which generated small ash clouds. The fourth episode began on 6 August and ended the next day, and showed essentially the same characteristics as the previous episode.

The fifth episode began on 10 August and was again marked by a rapid increase in volcanic tremor amplitude; at nighl, bright glow illuminated the gas plume rising from the crater, which was visible up to tens of kilometers away. Some of the explosions ejected incandescent pyroclastic material well above the crater rim. The activity started to decrease just after midnight and then ended on 11 August. Subsequently, ash emissions resumed, which were particularly frequent on 13 August, and which produced small, brownish-gray clouds of fine-grained tephra. Some of the ash emissions later that evening were accompanied by ejected incandescent material; volcanic tremor amplitude, however, remained at background levels.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

11 July-17 July 2012 Cite this Report

Sezione di Catania - Osservatorio Etneo reported that on the evening of 2 July weak incandescence began to illuminate a gas plume rising from Bocca Nuova, marking the resumption of eruptive activity in this crater nearly one year after a short period of Strombolian and effusive activity. Observatory staff visited the crater the next day and observed Strombolian activity from a single vent, a few meters in diameter, at the base of the SE crater wall. Incandescent bombs and scoria ejected by the explosions fell back around the vent.

During the following days, the activity within Bocca Nuova continued with minor fluctuations; on 4 July, a few bombs fell outside the E crater rim, and on 8 July a small lava flow was observed on the flank of the pyroclastic cone growing around the active vent. Similar activity was also observed on 11 and 13 July. On 16 July, the amplitude of the volcanic tremor recorded by the summit seismic network showed a consistent increase, which was accompanied by an intensification of the activity within Bocca Nuova. During the night of 16-17 July, continuous, bright glow from the crater was visible from populated areas around the volcano.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

25 April-1 May 2012 Cite this Report

Sezione di Catania - Osservatorio Etneo reported that the twenty-fifth paroxysmal eruptive episode since January 2011 took place at New SE Crater (New SEC) of Etna during the morning of 24 April following about 11 days of quiescence. During 21-22 April a series of small ash emissions observed by web cameras drifted downslope to the E. On 22 April prolonged emissions of white vapor rose from an area in the upper portion of the fissure that cuts the SE flank of the cone. At night several incandescent spots were visible on the NE and S crater rims, where hot gas heated the surrounding rocks. On 23 April a small thermal anomaly in the area of New SE Crater was produced by a tiny lava flow, which issued from the same vent that had produced the prolonged vapor emissions on the previous day. The lava flow slowly advanced a few hundred meters toward the Valle del Bove, but stagnated on the W rim. Another lava flow was produced later that day.

At around 1800 the effusive vent started to vigorously spatter. A second vent became active a few tens of meters further upslope, which initially ejected spatter, but activity rapidly evolved into frequent Strombolian explosions accompanied by a slow rise in the volcanic tremor amplitude. During the following hours, sporadic explosions were also observed from a vent located within the New SEC; the activity remained more or less consistent, while the volcanic tremor amplitude fluctuated at only slightly elevated levels. At 0210 0n 24 April the Strombolian activity showed a marked increase and turned into sustained lava fountaining at 0230. A plume with a heavy load of ash and lapilli rose a few kilometers, drifted NE, and produced ashfall 15-17 km NE in Linguaglossa, Piedimonte, and Presa. The upper part of the plume drifted E and produced pea-sized lapilli fall in the area between Fornazzo (10 km E) and Giarre (17 km E). The phase of most intense lava fountaining lasted approximately 25 minutes, from 0240 until 0305 on 24 April, after which the intensity rapidly decreased and returned to Strombolian activity, before ceasing completely around 0340.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

18 April-24 April 2012 Cite this Report

Sezione di Catania - Osservatorio Etneo reported that the twenty-fifth paroxysmal eruptive episode since January 2011 took place at New SE Crater (New SEC) of Etna during the morning of 24 April following about 11 days of quiescence. The episode was characterized by lava fountains, emissions of ash and lapilli, and lava flows that descended the Valle del Bove.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

11 April-17 April 2012 Cite this Report

Sezione di Catania - Osservatorio Etneo reported that the twenty-fourth paroxysmal eruptive episode since January 2011 took place at New SE Crater (New SEC) of Etna during the morning of 12 April following about 10 days of quiescence. The episode was characterized by lava fountains, emissions of ash and lapilli, and lava flows that descended the Valle del Bove and explosively interacted with snow cover.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

28 March-3 April 2012 Cite this Report

Sezione di Catania - Osservatorio Etneo reported that the twenty-third paroxysmal eruptive episode since January 2011 took place at New SE Crater (New SEC) of Etna during the morning of 1 April following two weeks of quiescence. The episode was characterized by tall lava fountains from vents within the crater and on the SE flank of its cone, a gas-and-tephra plume, and lava flows descending toward the Valle del Bove. The paroxysmal phase lasted about 1.5 hours and ended just before daybreak. Ash and lapilli fell over the SE sector of the volcano, affecting mainly the area between Monterosso and Zafferana Etnea, but also the area between Acireale and Giarre, further downslope.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

14 March-20 March 2012 Cite this Report

Sezione di Catania - Osservatorio Etneo reported that the twenty-second paroxysmal eruptive episode since January 2011 took place at New SE Crater (New SEC) of Etna during the morning of 18 March following two weeks of quiescence. Roaring from high-pressure degassing was heard on 16 March. The next day there was incandescence and multiple vapor clouds with minor ash content that rose from New SE Crater. In the early hours of 18 March the incandescence intensified due to Strombolian activity on the crater floor, and volcanic tremor amplitude rapidly increased. Strombolian activity continued to intensify, and just before 0700 lava flowed through the deep breach in the SE crater rim. At about 0825 the ash content in the gas plume rising from the crater became more significant and pulsating lava fountains from a vent on the crater floor rose about 100 m high. Shortly before 0900 two vents were active within the crater and a jet of lava was emitted from another vent within the breach in the SE crater rim.

During 0900-0915 lava fountaining was essentially continuous from all three vents. An intense shower of coarse-grained pyroclastic material falling onto the N and NE flanks of the cone generated avalanches and clouds of rock and dust, which traveled to the base of the cone. A plume rose 4-5 km above Etna and drifted E. Ash and lapilli fell mainly in the area between the villages of Zafferana Etnea and Sant'Alfio, extending toward the Ionian Sea between Riposto and Pozzillo.

The main lava flow descended the steep W slope of the Valle del Bove. Several lava lobes, however, took a more northerly path to areas covered with thick snow. The interaction of the lava and snow led to rapid melting of the snow, generating small lahars, and strong explosions that produced ground-hugging vapor-and-ash clouds resembling pyroclastic flows, which repeatedly descended on the floor of the Valle del Bove. The vapor-and-ash clouds rose 1-1.5 km above the floor of the Valle del Bove. This phenomenon continued intermittently for some time after the cessation of the lava fountaining and ash emission, until about 1130.

Lava fountaining and strong ash emission continued without significant variations until about 1040; afterwards the activity rapidly diminished in intensity, and the last ash clouds were observed around 1110. Similar to the previous episodes, the lava that flowed through the breach in the SE crater rim advanced for several hours after the cessation of the paroxysmal activity into the upper part of the Valle del Bove. The lava reached a distance of about 4 km from the source, stagnating S of Monte Centenari. A small lava flow, emitted from a fracture on the N flank of the cone, followed the same path as a flow emitted from the same fracture during the 4 March paroxysm, and traveled a few hundred meters.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

29 February-6 March 2012 Cite this Report

Sezione di Catania - Osservatorio Etneo reported that the third episode of lava fountaining from Etna's New Southeast Crater (New SEC) occurred on the morning of 4 March and was more explosive than the preceding episode. The beginning of the eruption was characterized by a rapid increase in volcanic tremor amplitude coincident with Strombolian explosions that increased in intensity and frequency. Just after 0800 lava overflowed the deep breach in the SE rim of the crater and reached the SE base of the cone within 15 minutes, then advanced towards the W rim of the Valle del Bove. Explosive activity changed to continuous lava fountaining and an eruption plume developed at about 0830. Large pyroclasts fell on the steep flanks of the cone, causing avalanches.

At about 0850 small pyroclastic flows generated by the partial collapse of the eruption column mainly descended the NE flank, and somewhat down the S flank. A lava flow was emitted from a new eruptive vent on the upper SW flank of the New SEC cone and descended into the saddle between the old and new SEC cones. The lava interacted with snow, causing powerful explosions and small pyroclastic flows. These phreatic explosions generated jets of vapor and launched rock fragments to distances of several tens of meters. A lahar developed which traveled toward the "Belvedere" monitoring station, on the W rim of the Valle del Bove, and passed a few tens of meters to the N of the monitoring instruments.

A lava flow also issued from an eruptive fissure on the upper N flank of the cone and descended a few hundred meters to the NE, surrounding the N base of the cone. After descending the steep W slope of the Valle del Bove, the flow split into several branches on the more gently sloping terrain. These branches exceeded in length those of 9 February, reaching a total distance of about 3.5 km from the crater. Shortly after 1000, the activity started to diminish; lava fountaining ceased at 1032, two hours after the onset of the paroxysmal phase. The lava flow emitted from the fissure on the SW flank of the cone continued advancing for a few hours after the cessation of the activity.

The eruption column rose several kilometers above the summit of Etna. Ash and lapilli were carried NE by the wind, affecting the areas around Piedimonte, Etneo, and Taormina. Fine ash fell as far as the Messina area and southern Calabria. Again, the pyroclastic cone of the New SEC had grown in height, mainly on its N rim.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

8 February-14 February 2012 Cite this Report

Sezione di Catania - Osservatorio Etneo reported that on 8 February the New SE Crater (New SEC) of Etna entered another paroxysmal eruption episode after about 12 days of Strombolian activity. During the afternoon of 8 February, the Strombolian activity increased in both frequency and intensity of explosions from the vent on the W portion of the crater floor, and occasionally from a vent to the E. After about 1900, lava began to spill into the deep breach on the SE crater rim and then descended to the base of the cone. The lava flow expanded around 2100 and the Strombolian activity slowly increased, turning into a discontinuous lava fountain around 2330.

On 9 February the pulsating lava fountain rose 100-500 m above the crater before a continuous jet rising 300-400 m above the crater. A cloud with a small amount of tephra rose 6 km above the summit and then drifted W, producing some pyroclastic fallout that was on the upper portion of the volcano. Around 0200 and 0400, lava fountains from the two vents within the crater rose as high as 500 m above the crater. The fountain from the E vent caused abundant fallout on the crater rim and E flank. A third vent, located in the breach cutting the SE crater rim, produced sporadic violent explosions that ejected bombs many meters in diameter all over the E portion of the cone.

The lava flow reached the W rim around 0130, descended the flank, and branched into three different flows that reached a distance of 3 km from the New SEC. Lava fountaining started to diminish around 0530, and then around 0545 sporadic jets rose as high as 300 m above the crater. At the same time, the vent in the SE crater breach produced strong explosions that again ejected bombs many meters in diameter. These explosions generated loud bangs that were heard all over Etna and small ash emissions that were reported on the W portion of Bocca Nuova. Around 0900 activity started to diminish and ceased abruptly at 1000.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

1 February-7 February 2012 Cite this Report

Sezione di Catania - Osservatorio Etneo reported on 6 February that mild Strombolian activity and small ash emissions continued from Etna's New Southeast Crater (New SEC).

Source: Sezione di Catania - Osservatorio Etneo (INGV)

25 January-31 January 2012 Cite this Report

Sezione di Catania - Osservatorio Etneo reported that an explosion at the New Southeast Crater (New SEC) of Etna generated an ash plume at that rose 400 m above the crater at 1906 on 27 January. An explosive ash emission at 1124 from the vent on the W portion of the crater floor was followed by others that were less intense. At 2140 an explosion ejected incandescent material in a narrow vertical jet that rose a few tens of meters above the crater. A small Strombolian explosion occurred at 2231. On 28 January sporadic ash emissions continued from New SEC.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

4 January-10 January 2012 Cite this Report

Sezione di Catania - Osservatorio Etneo reported that on the night of 4 January the New SE Crater (New SEC) of Etna entered another paroxysmal eruption episode after about 50 days of quiescence. Several hours of Strombolian activity were observed on the SE and NE slopes starting at 2230 on 4 January. This activity continued into the early morning of 5 January when (around 0200) a small lava flow spread out into several branches at the SE base of the cone. Strombolian activity increased around 0400, generating lava fountains, from several vents within the crater that rose 100-150 m above the crater.

Significant ashfall and pyroclastic material fell onto the flanks at 0450 on 5 January. Around 0515 lava fountains generated a continuous eruption of ash-and-gas plumes that rose to an altitude of 2.1-2.4 km (7,000-8,000 ft) a.s.l. Small pyroclastic flows went a few hundred meters and lahars traveled down the NE, E, and S flanks of the cone. Around 0600 active vents along the N edge of the New SEC produced intermittent lava fountains. The most intense phase of the eruption occurred around 0620 when a strong explosion opened a vent on the top side of the SE cone, removed a portion of the SE crater rim, and generated ash plumes. The N slope of New SEC showed gravitational movement due to the amount of deposited pyroclastic material. Around 0630 activity started to diminish and ceased abruptly at 0730, but was followed by passive ash emissions that lasted until 0830.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

9 November-15 November 2011 Cite this Report

Sezione di Catania - Osservatorio Etneo reported that the eighteenth paroxysmal eruptive episode of 2011 took place at the New SE Crater (New SEC) of Etna during the morning of 15 November. Thermal monitoring cameras at the observatory in Catania and at Montagnola, about 3.5 km S of the summit craters, recorded a small thermal anomaly at the lower end of the eruptive fissure on the SE flank of the cone at about 0700. The anomaly slowly grew in size and temperature, caused by the emission and expansion of a small lava flow. Mild Strombolian activity commenced at 0900 from within the New SEC, and spattering began from several vents along the fissure on the SE flank of the cone. This activity continued for nearly three hours, while increasing very slowly, and the lava flow spread out into several branches at the SE base of the cone, advancing only a few hundred meters. At about 1155, the activity markedly and rapidly increased both within the crater and along the fissure, and just after 1200 lava fountains and ash emissions rose from the crater. Lava fountains then rose from vents along the SE flank fissure. Bombs and scoria fell into the cone.

At 1230 ash emissions significantly increased, especially from a vent located in the SE portion of the New SEC, and a plume of ash and gas rose several kilometers above the summit and drifted SE. The most intense phase of the eruption occurred between 1245 and 1315 when jets heavily laden with incandescent bombs rose as high as 800 m above the crater. Pyroclastic material fell onto the New SEC cone, areas well beyond the base, and the nearby old SEC cone. During this phase explosions occurred from a vent on the N flank of the New SEC cone, likely the same vent that emitted small lava flows on 28 September and 8 October. At about 1325 the activity started to diminish and ceased abruptly at 1329, but was followed by passive ash emissions that lasted until just after 1400. Weak and discontinuous spattering accompanied by slow lava effusion continued for a few hours from a single vent in the central portion of the eruptive fissure on the SE flank of the New SEC cone.

Lava flows from the eruption traveled less than 4 km toward the floor of the Valle del Bove, immediately to the N of the Serra Giannicola ridge, stagnating to the SW of Monte Centenari. The New SEC grew in height by 10 m on the S side, bringing the total height of the cone to about 180-200 m above its base. Ash and lapilli deposits affected the SE flank, including the towns of Zafferana Etnea (10 km SE) and Acireale (20 km SE).

Source: Sezione di Catania - Osservatorio Etneo (INGV)

19 October-25 October 2011 Cite this Report

Sezione di Catania - Osservatorio Etneo reported that the seventeenth paroxysmal eruptive episode of 2011 took place at the New SE Crater (New SEC) of Etna during the evening of 23 October. Weak explosive activity was recorded at 1913, and at about 1935 small anomalies appeared in images recorded by thermal cameras. Explosive activity rapidly intensified at 1940 and by 2007 that crater was completely filled with lava. The lava overflowed through a breach in the E crater rim and traveled towards the Valle del Bove.

At 2026, Strombolian activity transitioned to continuous lava fountains that rose a few tens of meters above the crater rim. At 2036, a vent opened on the SE flank of the cone, producing a second lava fountain, leading to a significant increase in the lava effusion rate. The height of the lava fountains significantly increased after 2100, reaching 300 m above the crater. At about 2130, a third vent became active within the New SEC, possibly near the N rim. Abundant amounts of tephra fell on the E flank of the cone, forming a dense curtain, while large incandescent blocks rolled to the base of the cone on more gently sloping terrain. At approximately 2229 two lightning flashes near the crater were observed. After 2230 both effusive and explosive activity showed a marked reduction, changing again into Strombolian activity around 2300, and ceasing altogether at 2315.

The lava flow continued to advance towards the Valle del Bove until about 0040 on 24 October and stagnated just upslope of Monte Centenari (at 1,900 m a.s.l.). The area most heavily affected by the tephra (ash and small scoriaceous lapilli) fall was the E flank of Etna, including the N portion of the towns of Zafferana (about 10 km to the E), Milo (about 11 km ESE), and Fornazzo (10 km E), downslope across Santa Venerina (SE flank) and Dagala del Re (14 km ESE) to Giarre (~17 km E) and Riposto (18 km E), as well as nearby villages.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

5 October-11 October 2011 Cite this Report

Sezione di Catania - Osservatorio Etneo reported that the sixteenth paroxysmal eruptive episode of 2011 took place at the New SE Crater (New SEC) of Etna during the afternoon of 8 October. A rapid increase in volcanic tremor amplitude was detected that morning, and at about 1300 weak and discontinuous Strombolian explosions were recorded by surveillance cameras. Two hours later, lava flowed from a deep notch in the SE rim of the crater.

At around 1545 vigorous Strombolian activity was observed from numerous vents along a short fissure on the SE flank of the cone, which had first been active during the 29 August paroxysm (the twelfth). Weather conditions deteriorated at about 1615, preventing direct observations of the Strombolian activity changing into sustained lava fountaining and ash emissions. However, this change was audible around 1630, and a dense ash-and-vapor plume rapidly rose above the weather clouds and drifted E. At the same time lava flows descended on the W slope of the Valle del Bove. Eruptive vents opened on the NE flank of the cone, approximately along the fracture that first opened during 8 September, and two small lava flows were emitted. The more voluminous lava flow traveled a few hundred meters downslope. The paroxysmal phase lasted a little longer than 20 minutes and ended around 1650. Ash emissions continued until 1945, when the volcanic tremor amplitude returned to levels similar to those preceding the paroxysmal episode, and the lava flow fronts appeared to stagnate. The ash cloud drifted ENE and produced ash- and lapilli-fall in a narrow sector from the Ripe della Naca area and the village of Puntalazzo (13 km E) to the town of Mascali (18 km E).

Source: Sezione di Catania - Osservatorio Etneo (INGV)

28 September-4 October 2011 Cite this Report

Sezione di Catania - Osservatorio Etneo reported that the fifteenth paroxysmal eruptive episode of 2011 took place at the New SE Crater of Etna during the evening of 28 September. That morning, noises originated from the New SE Crater. At 1600 volcanic tremor amplitude started to increase, and rhythmic ash emissions that rose from a vent located within the crater were occasionally accompanied by small Strombolian explosions. Starting at 1930 Strombolian activity progressively increased both in the intensity and frequency of explosions, and eventually became continuous. Bombs and scoria were ejected well beyond the crater rim. A small amount of lava flowed through the notch in the SE flank of the volcano at 2115 and was soon followed by explosions from a vent within the same area. The Strombolian activity waned for a few minutes then rapidly increased, forming a sustained lava fountain that rose as high as 800 m. At 2133 and 2134 two powerful explosions originating from a vent on the E rim of the crater created shock waves visible in the clouds above the crater and ejected large bombs hundreds of meters away. Lava fountains 100-150 m high commenced from a vent on the N base of the New SE Crater cone at 2136. The vent emitted a small lava flow soon after. At 2155 activity from all vents decreased, and between 2205 and 2210 all explosive activity ceased. Lava continued to flow until 2330.

The lava flow emitted from the SE flank of the cone reached the lower portion of the W slope of the Valle del Bove, somewhat SW of Monte Centenari. Ash plumes drifted SW and light ashfall occurred on the S flank of Etna, including in the towns of Nicolosi (14 km S) and Catania (27 km S).

Source: Sezione di Catania - Osservatorio Etneo (INGV)

14 September-20 September 2011 Cite this Report

Sezione di Catania - Osservatorio Etneo reported that the fourteenth eruption from Etna's New SE Crater in 2011 occurred during poor weather conditions on 19 September. Lava fountains rose from multiple vents within the crater and lava flows descended the W slope of the Valle del Bove. An ash plume drifted NE; ash and lapilli fell in an area to the N of Giarre (16 km E). The main phase of the event lasted from about 1020 until just after 1300. During the evening the lava flows were active and weak spattering continued from a vent at the SE base of the SE Crater cone.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

7 September-13 September 2011 Cite this Report

Sezione di Catania - Osservatorio Etneo reported that the thirteenth paroxysmal eruptive episode of 2011 took place at the New SE Crater of Etna on the morning of 8 September. Prior to the episode, a few emissions of ash from the New SE Crater occurred on 6 September. Sporadic, very weak Strombolian explosions from the crater started during the late evening on 7 September, and then continued in a subdued manner through the night.

On 8 September a series of ash emissions were followed by a rapid increase both in the intensity and frequency of Strombolian explosions. Loud detonations were audible across a vast sector of Etna's densely populated SE to E flanks. Simultaneously the volcanic tremor amplitude sharply increased and shifted from below the NE Crater toward the SE Crater. The Strombolian activity turned into a pulsating lava fountain, accompanied by increasing amounts of volcanic ash. Lava fountaining and ash emissions became more vigorous. Lava flowed through a deep breach in the E crater rim and along the fracture that had opened on the SE side of the cone during 29 August. The lava overflow was accompanied by repeated collapse and rockfalls from unstable portions of the cone in that area. Later brief periods of repeated emissions of brown ash mixed with white water vapor occurred from two or three vents on the N flank of the New SE Crater cone, in an area of the lava overflows from the N rim of the crater that had started shortly after the onset of the activity. The paroxysmal activity ceased in the evening and was followed by a series of progressively more passive ash emissions. Lava flows descended on the W slope of the Valle del Bove; expansion of the most advanced lava fronts continued for some time after feeding of the lava had ceased, mostly due to gravitational flow. Small active lava flows were observed for many hours after the cessation of the paroxysmal activity, remaining confined to the immediate vicinity of the crater.

The pyroclastic cone that grew around the New SE Crater during the recent series of eruptive episodes had undergone significant morphological changes. The S and N crater rims had further increased in height, whereas degradation and mass wasting on the SE flank had become more conspicuous. A large chunk of rock on the lower SE flank was rotated and uplifted, forming a steep-sided "spine" about 20-30 m tall, with locally vertical and sub-vertical flanks.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

24 August-30 August 2011 Cite this Report

Sezione di Catania - Osservatorio Etneo reported that nine days after the previous episode, the New SE Crater produced its twelfth paroxysmal eruptive episode of 2011 during the early morning of 29 August. The event was preceded by an explosion at 2252 on 27 August, and a series of ash emissions from the New SE Crater almost 15 hours later. Weak Strombolian activity visible during the evening on 28 August intensified during the night.

At 0115 on 29 August lava overflowed the rim through a breach in the E crater rim and traveled towards the Valle del Bove. Strombolian activity progressively intensified and two vents within the crater emitted pulsating lava fountains up to 100 m high. The lava fountains again increased in height and a dense plume rose a few kilometers above the summit before drifting toward the SSE. At the same time, a small lava flow issued from the area affected by the collapse of a portion of the cone's ESE flank during the 20 August paroxysm. At 0220 the SE flank of the cone fractured and exposed a line of new eruptive vents down to the base of the cone that produced lava fountains. A broad lava flow fed by the vents descended into the Valle del Bove, somewhat to the S of the lava flow emitted earlier during the episode. The lava fountaining from the vents within the crater turned into ash emission just after 0220, whereas the lowest vent on the new eruptive fracture continued to produce incandescent jets until 0250. Ash emission continued at a diminishing rate until about 0315.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

17 August-23 August 2011 Cite this Report

Sezione di Catania - Osservatorio Etneo reported that eight days after the preceding episode, Etna's New SE Crater was the site of another paroxysmal eruptive episode on the morning of 20 August, the eleventh event of this type since the beginning of 2011. The event began on 18 August with increased gas emissions from New SE Crater. On 19 August a powerful explosion ejected incandescent bombs and produced a small ash plume. The event was followed by a few more minor explosions, all accompanied by an increase in volcanic tremor amplitude and focal shift from the NE Crater toward the New SE Crater. Throughout the day small dilute ash was emitted. During the evening weak Strombolian activity commenced, with small explosions occurring about every 30 minutes.

On 20 August weak but continuous incandescence due to lava emissions appeared in the crater. Strombolian activity intensified, and lava overflowed the rim through a breach in the E crater rim traveling towards the Valle del Bove. Almost five hours later lava fountaining generated heavy fallout of large pyroclastics onto the flanks of the cone. Dense plumes of gas and tephra rose 5-6 km from the crater and drifted SW, causing ash- and lapilli-fall in areas such as Paternò (22 km SSW), Ragalna (13 km SSW), and Biancavilla (16 km SW). Closer to the crater, in the Torre del Filosofo area to the S, clasts up to several tens of centimeters in diameter landed on the ground.

Light brown dust clouds appeared in an area on the lower E flank of the cone, where a small depression had formed a few hours after the 12 August event. Shortly thereafter, the continuous, intense ejection of pyroclastics onto the flanks of the cone generated avalanches resembling pyroclastic flows, which descended a few hundred meters beyond the base of the cone, mainly towards the S. In the meantime, the lower portion of the E flank of the cone began to slide and collapse under the push of lava from within the channel. A new lava flow issued from the collapsed area, taking a more southerly path than the lava emitted until then, and divided into numerous branches. Lava fountaining slowed later in the evening and eventually ceased, followed by ash emissions from the crater for a few minutes. A series of ash explosions lasted for five minutes in the early morning on 21 August. The morphological changes affecting the pyroclastic cone surrounding the New SE Crater were significant. Besides the collapse on the lower E flank of the cone, the S and NE rims of the cone had grown in height.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

10 August-16 August 2011 Cite this Report

Sezione di Catania - Osservatorio Etneo reported that on 11 August sporadic ash emissions from Etna's New SE Crater produced small grayish-brown ash plumes. Thermal surveillance cameras revealed hot material in late-afternoon emissions. In the evening and throughout the night small Strombolian explosions were observed at intervals of a few tens of minutes. Early on 12 August, the day of the tenth paroxysmal eruptive episode of 2011, the Strombolian activity intensified and was accompanied by an increase in volcanic tremor amplitude. Strombolian explosions then produced dark ash clouds, and lava overflowed the E rim of the crater through a deep breach formed during previous eruptions. During the following 30 minutes or so Strombolian activity rapidly intensified, and formed a pulsating lava fountain about 100 m tall. Fifteen minutes later a dense column of ash rose above the lava fountain while large bombs and blocks fell onto the cone surrounding the New SE Crater.

During the most intense period three vents in the crater were active, two in the central portion and one close to the E-rim breach. Soon after, the two vents in the center of the crater emitted only ash, while the E vent continued to eject jets of incandescent lava. The activity completely ceased more than a half an hour later. The lava produced during the eruption descended the W slope of the Valle del Bove in numerous lobes; the most advanced lava fronts reached the base of the steep slope above Monte Centenari. Ash- and lapilli-fall affected a relatively narrow area between Zafferana (10 km SE), and the coastal area between Giarre and Acireale, on the SE flank.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

3 August-9 August 2011 Cite this Report

Sezione di Catania - Osservatorio Etneo reported that the ninth paroxysmal eruptive episode from Etna in 2011 took place at the New SE Crater (located on the E flank of the old SE Crater cone and previously called the "pit crater") during the night of 5-6 August. Weak Strombolian explosions occurred in the crater during the afternoon on 5 August and gradually increased over the next few hours. At 2215 lava flowed over the E rim of the crater and towards the W slope of the Valle del Bove. Strombolian activity rapidly increased and formed a lava fountain that rose 100 m above the crater rim. Activity again intensified and jets of lava rose several hundred meters high. An eruption plume laden with ash and lapilli rose a few kilometers above the crater and drifted SE. At the climax of the eruption lava fountains exceeded 500 m in height. Just after midnight the incandescent jets diminished in height, continued to pulsate for about an hour, then further diminished. By 0215 on 6 August the eruption was substantially over. Ash-and-lapilli fall were observed in the SE sector of the volcano, between Zafferana (10 km SE) and Viagrande (16 km SSE) and between Acitrezza (23 km SE) and Pozzillo (19 km SE) along the Ionian coast.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

27 July-2 August 2011 Cite this Report

Sezione di Catania - Osservatorio Etneo reported that in the evening of 28 July Strombolian explosions from the active vent on the E flank of Etna's SE Crater cone were weak and sporadic, then ceased during the night. Throughout 29 July the crater was quiet. In the early morning of 30 July intermittent incandescence from the crater gradually intensified and became more frequent, then was followed by intense Strombolian activity accompanied by loud detonations. Lava bombs ejected several tens of meters fell back into the crater or around the rim. A diffuse ash plume drifted E. A small lava flow on the E flank descended about 100 m then rapidly chilled. The activity was accompanied by a distinct increase in the mean amplitude of volcanic tremor that, along with the activity, abruptly decreased in the early afternoon.

Later that day the mean amplitude of volcanic tremor increased again along with Strombolian activity. A diffuse gas-and-ash plume again drifted E. Strombolian activity intensified and incandescent jets became continuous. At the same time lava flowed E and the effusion rate rapidly increased; lava flowed 3 km down the W slope of the Valle del Bove. The ash plume became more dense and ashfall was reported in the Ionian area (18 km E). During the most intense period, fragments of fluid lava were ejected 450-500 m above the crater and fell onto the flanks of the pyroclastic cone to distances of 200-300 m. Lava fountains jetted from at least two vents located within the crater and on the upper E flank, roughly aligned WNW and ESE. The activity ceased just after midnight. The event on 30 July was the eighth paroxysmal event in 2011.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

20 July-26 July 2011 Cite this Report

Sezione di Catania - Osservatorio Etneo reported that the seventh eruption of Etna in 2011 occurred from the active crater on the E flank of the SE Crater cone. On 24 July vigorous Strombolian activity started within the crater, gradually increased through the night, and culminated on 25 July. Strombolian activity gradually turned into a pulsating lava fountain, accompanied by increasingly voluminous ash emissions. The fountain fluctuated between 250 and 300 m above the crater with a few jets rising 350 m. Lava flowed through a breach on the E crater rim and divided into multiple parallel flows that reached the base of the steep W slope of the Valle del Bove near Monte Centenari. Plumes drifted E causing ashfall between the villages of Fornazzo and Milo on the flank (10 km E), and the Ionian coast near Riposto (18 km E). The final phase of the eruption was characterized by a series of violent explosions that produced loud detonations heard in the E and SE sectors of the volcano.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

13 July-19 July 2011 Cite this Report

Sezione di Catania - Osservatorio Etneo reported that on the evening of 11 July Strombolian activity began from Etna's Bocca Nuova crater, representing the first magmatic eruption since 2002. Incandescence was first recorded with a monitoring camera on the SE flank and was later visible from population centers in the SE sector of Etna. During the night of 12-13 July incandescence was more continuous and intense than during the previous night. At varying intervals, incandescent bombs that were ejected above the crater rim fell back into the crater. On 13 July volcanologists visited Bocca Nuova and observed a single large vent on the crater floor that was the source of the Strombolian activity. The strongest explosions ejected incandescent bombs several tens of meters above the crater rim. Most bombs fell back into the crater but some went over the rocky partition that divided Bocca Nuova from Voragine, and fell into the S portion of the latter.

In the evening of 15 July, volcanologists again visited Bocca Nuova and noted that the Strombolian activity had decreased slightly but within less than two hours had increased to levels greater than those observed on 13 July. Immediately to the W of the explosive vent, a lava flow was issuing from underneath a sheet of pyroclastic material deposited by the nearby Strombolian activity. The flow cascaded into a deeper depression in the W central portion of the crater floor.

On 16 July, a series of ash emissions from the pit crater located on the E flank of the SE Crater cone marked the resumption of explosive activity within the crater, and produced loud booming sounds that were widely heard in populated areas on Etna's flanks. On the evening on 18 July Strombolian activity increased and culminated into a new paroxysmal eruptive episode on 19 July. Lava flows traveled down the steep W slope of the Valle del Bove, following the same path as the lavas emitted during the preceding eruptive episodes, and stagnated at the base near Monte Centenari. Lava fountains rose 200-250 m and produced heavy fallout of fluid spatter, forming several lava flows. The largest lava flow descended the S flank of the cone reaching the base. A dense plume of gas and ash drifted E.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

6 July-12 July 2011 Cite this Report

Sezione di Catania - Osservatorio Etneo reported that explosions from the pit crater located on the E flank of Etna's SE Crater cone were heard on the morning of 4 July. Incandescence was observed later that evening. Small Strombolian eruptions were recorded by a camera during 5-6 July.

On 7 July Strombolian activity gradually increased along with volcanic tremor amplitude. Small pyroclastic cones began to grow on the crater floor. During the next morning, volcanic tremor amplitude clearly increased. Shortly thereafter it abruptly decreased and the Strombolian activity completely ceased. During the morning of 9 July, Strombolian activity resumed and volcanic tremor amplitude rose rapidly. Around noon lava overflowed the E rim of the crater and followed the path of lava flows from the previous eruption, into the upper W part of the Valle del Bove. Later that day Strombolian explosions turned into a continuous lava fountain. A dense eruptive plume rose several kilometers high and drifted S and SE, causing ash and lapilli fall in populated areas including Trecastagni, Viagrande, and Acireale towards the SE, and between Nicolosi and Catania towards the S, forcing the closure of the Fontanarossa international airport in Catania. A few hours later volcanic tremor amplitude dropped to very low levels and all eruptive activity ceased.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

15 June-21 June 2011 Cite this Report

Sezione di Catania - Osservatorio Etneo reported that on 13 June mountain guides heard loud hissing sounds coming from the interior of Etna's Bocca Nuova crater. After nearly six months of quiescence, ash emissions rose from Bocca Nuova the next morning. The emissions were composed of small ash clouds that seemingly originated from the central part of the crater and rose about 200-250 m above the crater rim, then drifted E. Thermal monitoring cameras showed no signs of incandescence in the emissions, which were observed for a few hours before meteorological clouds moved in and prevented further observations. During limited periods of good visibility from 15 to 17 June, sporadic small reddish-to-grayish-brown ash plumes were observed to occur every 5-15 minutes. Usual rhythmic emissions of gas and vapor from the Northeast Crater continued.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

11 May-17 May 2011 Cite this Report

Sezione di Catania - Osservatorio Etneo reported that on 8 May mild and discontinuous Strombolian activity resumed at the pit crater located on the E flank of Etna's SE Crater cone. On 11 May volcanic tremor amplitude progressively increased, and at about 2030 lava started to overflow the E crater rim. The activity intensified during the following hours and, shortly before 0400 on 12 May, culminated with lava fountaining which generated an ash cloud that drifted SSE. The lava fountaining lasted around 2 hours, showing a gradual diminution around 0545; an abrupt drop in the volcanic tremor amplitude at 0610 marked the end of the eruptive activity.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

4 May-10 May 2011 Cite this Report

Sezione di Catania - Osservatorio Etneo reported that on 8 May mild and discontinuous Strombolian activity resumed at the pit crater located on the E flank of Etna's SE Crater cone. Loud detonations were audible many kilometers away including in Monti Sartorius (NE flank) and in Zafferana Etnea (SW flank). After sunset, Strombolian explosions observed at intervals of 3-10 minutes ejected incandescent bombs up to a few tens of meters above the crater rim. During the night, some explosions ejected bombs well beyond the crater rim, down to the base of the cone that has grown around the crater during the recent events. Strombolian explosions continued without significant variations the next day.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

6 April-12 April 2011 Cite this Report

INGV-CT reported that from 29 March through the first few days of April, a series of gas-and-ash emissions, rarely with minor incandescent material, rose from the pit crater on the E flank of Etna's SE Crater cone. On 8 April small Strombolian explosions occurred from two vents located in the W portion of the crater floor; ejecta were confined to the crater depression. On 9 April seismicity from the Strombolian activity increased throughout the day. In the afternoon, explosive activity commenced from two vents before lava flows covered the crater floor. Later that evening incandescent blocks appeared within a breach in the E rim of the crater, followed by a small overflow of lava. The lava flow advanced from the base of the SE Crater cone toward the W headwall of the Valle del Bove, as far as 1 km. At the same time small but frequent Strombolian explosions continued within the crater.

During the night of 9-10 April, the Strombolian activity within the pit crater gradually increased, as well as volcanic tremor amplitude. The lava flow continued to advance. On 10 April, activity and tremor amplitude significantly increased and culminated with vigorous lava fountaining. An ash-and-gas plume drifted SE, causing ashfall in areas downwind. The lava-flow emission rate also increased dramatically. A second lava flow covered the first and traveled down into the Valle del Bove, essentially following the same path as the lava flows of 12-13 January and 18 February. The lava flow encountered thick snow cover, leading to violent explosive interactions that generated pyroclastic flows, and resulted in spectacular vapor-and-ash plumes. The eruption declined rapidly after about 1500; no activity was observed later than the afternoon.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

30 March-5 April 2011 Cite this Report

Based on a NOTAM, the Toulouse VAAC reported that on 3 April ash from Etna rose to an altitude between 2.4-3.4 km (8,000-11,000 ft) a.s.l. Ash was not identified in satellite imagery.

Source: Toulouse Volcanic Ash Advisory Centre (VAAC)

16 February-22 February 2011 Cite this Report

INGV-CT reported that on 16 February an explosive sequence, presumably from Etna's NE Crater, was detected on 16 February during the late evening. Cloud cover made direct observations difficult. On 18 February the thermal monitoring camera at Montagnola (EMOT) recorded anomalies from the pit crater located on the lower E flank of SE Crater cone. At the same time, the visible-light camera at Montagnola (EMOV) showed intermittent incandescence indicating Strombolian activity, and the seismic network recorded a rapid increase in the volcanic tremor amplitude. This eruptive episode lasted about 11 hours and produced pulsating lava fountains. Lava flows traveled E, following the same path as that of the 12-13 January event, in the direction of the Valle del Bove. Light ashfall occurred on the SW flank of the volcano.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

12 January-18 January 2011 Cite this Report

On the evening of 12 January Strombolian activity from a pit crater located on the lower E flank of Etna's Southeast Crater cone intensified and volcanic tremor amplitude increased. Just after 2100 lava breached the crater's E rim and formed a lava flow that traveled towards the W wall of the Valle del Bove. During the night of 12-13 January, the pit crater produced lava fountains, voluminous lava flows that descended to about 1,630 m elevation (about 4.2 km from the vent), and an ash plume that rose several kilometers. The ash plume drifted S and caused ashfall on Etna's S flank and in population centers such as Nicolosi. Scoria several centimeters in diameter fell in Rifugio Sapienza, at 1,910 m elevation. The lava fountains were sustained initially and rose 300-500 m high, then pulsated and became less vigorous, and eventually formed one single jet that rose less than 100 m. Fountaining ceased at 0055 on 13 January. Emissions of ash during 13 January were generated in part by collapses within the crater and also by sporadic explosions within the conduit. On 14 January small landslides within the pit crater produced grayish-brown plumes.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

5 January-11 January 2011 Cite this Report

After a few hours of quiescence on the evening of 3 January, very weak emissions of incandescent material (probably mostly hot gas with little or no solid material) resumed from the pit crater located on the lower E flank of Etna's Southeast Crater cone. Later that evening intense incandescence from the pit crater was reported by observers in the village of S. Alfio on the E flank of Etna. The emissions continued on 4 January at a rate of 4-6 events per hour, producing small plumes that appeared as thermal anomalies in thermal video footage. Activity ceased in the afternoon. Very weak emissions of incandescent material (probably again mostly hot gas) were observed on 5 January at the same rate as the previous day. A camera recorded white vapor plumes occasionally accompanied by some grayish-brown ash. Weak, intermittent incandescence from the pit crater was observed at night during 5-6 January. Emissions on 6 January occurred at a frequency of 3-4 events per hour, producing small plumes seen in thermal camera footage. That same day, intense degassing occurred from the W vent of Bocca Nuova (BN-1), and from the Northeast Crater, where pulsating emissions produced mushroom-shaped vapor plumes.

Starting in the late evening of 11 January, the seismic network recorded a slight increase in volcanic tremor amplitude. The amplitude peaked early on 12 January, and the source of the tremor shifted from a location N of the Northeast Crater towards the Southeast Crater. Weak Strombolian activity from the pit crater accompanied these changes on 11 January, and gradually became more intense on 12 January.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

29 December-4 January 2011 Cite this Report

INGV-CT reported that during the first few days of December gas emissions from a large pit crater on the lower E flank of Etna's Southeast Crater cone nearly ceased. On 22 December at 0446 a strong explosion occurred at the W vent of the Bocca Nuova (BN-1). This event generated an ash plume a few meters high, which then drifted NE, causing light ashfall in areas as far as the town of Linguaglossa (17 km NE). On 23 December bluish gas rose from a vent at the base of the W wall of the pit, at the base of the Southeast Crater cone. Bright incandescence was intermittently visible on video footage. Inclement weather prevented clear observations that day and during the next few days. On 29 December extremely small amounts of incandescent material emitted from the pit crater were observed using visible and thermal cameras. The brief emissions (2-6 second intervals) were jets of mainly hot gas that barely rose above the rim of the pit crater. Inclement weather again prevented observations of the crater during 30-31 December.

During the late afternoon on 2 January, strong incandescence at the pit crater evolved into vigorous Strombolian activity. Frequent Strombolian explosions (1-3 per minute) ejected coarse-grained incandescent material a few tens of meters above the rim of the pit. On a few occasions, incandescent bombs fell outside the pit's rim, mainly to the S and E. The activity continued into the early morning then decreased markedly. Negligible quantities of volcanic ash were produced.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

22 December-28 December 2010 Cite this Report

INGV-CT reported that a strong explosion from the W vent of Etna's Bocca Nuova crater at 0446 on 22 December produced an ash plume that rose a few hundred meters above the summit and drifted NE. The explosion of hot, though not incandescent, material and subsequent ash emission was observed and recorded by thermal cameras at Montagnola and Nicolosi (14 km S). Light ashfall was reported as far away as Linguaglossa (18 km NE). Small emissions of reddish-brown ash continued to occur before noon.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

10 November-16 November 2010 Cite this Report

Following several days of ash emissions from Etna's Northeast Crater, INGV-CT reported that on 14 November there was a significant increase in both the frequency and volume of ash emissions. The emissions were intermittent, alternating with periods of gas-and-steam. Ash plumes rose a few hundred meters high and drifted first SW on 14 November, then NE during 14-15 November, and finally E on 15 November.

INGV-CT staff visited the summit craters on 15 November and saw a few millimeters of brown ash on the ground mainly to the S of Northeast Crater. Ash deposits were 1 cm thick on the rim of the crater. Ash emissions were accompanied by nearly continuous deep rumblings. The vent on the crater floor was at least 75 m in diameter compared to about 25 m in October.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

1 September-7 September 2010 Cite this Report

INGV-CT reported that on 25 August a powerful explosion from Etna's Bocca Nuova crater initiated a series of ash emissions, which continued at decreasing strength for about 20 minutes. A thermal camera located at La Montagnola, 3 km S of the summit craters, showed ejected hot material and a cauliflower-shaped, dark gray ash plume that rose about 1 km and drifted E. Ashfall was reported in areas SE from Etna to Catania (27 km S). An inspection the next morning revealed that the W wall of the BN-1 crater of Bocca Nuova had collapsed. During 25-29 August a total of seven explosions were recorded.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

16 June-22 June 2010 Cite this Report

INGV-CT reported a series of landslides on 19 June from the NW rim of the pit crater located on the lower E side of Etna's Southeast Crater. The collapses generated small ash clouds that drifted NE, and changed the pit crater's morphology. Data from a thermal camera showed thermal anomalies over 180 degrees Celsius indicating that the landslide material was hot. Fumarolic activity was seen in the landslide area during an inspection the day before.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

7 April-13 April 2010 Cite this Report

INGV-CT reported that on 8 April a dozen low-frequency events located near the summit of Etna were detected by the seismic network. Concurrently, a dark-colored ash plume rose 1 km from a pit crater located at the E base of the Southeast Crater and drifted NE. Dark emissions from the central crater were also seen a short time later. Ashfall was reported from a few local areas. On 9 April intense gas emissions were noted at the pit crater.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

27 May-2 June 2009 Cite this Report

INGV-CT reported that during 25-31 May the NW-SE-trending fissure E of the Etna summit craters continued (since 13 May 2008) to produce active lava flows to the N of the SE end of the fissure, along the W wall of the Valle del Bove. At least three lava flows were active. Elsewhere on the volcano, activity was restricted to degassing from the Northeast Crater, from the NW and SE Bocca Nuova vents, from the E flank of the Southeast Crater, and along summit fumarolic fields. The activity was observed directly and by utilizing surveillance cameras in Milo (about 11 km ESE).

Source: Sezione di Catania - Osservatorio Etneo (INGV)

18 March-24 March 2009 Cite this Report

INGV-CT reported that after a week of Strombolian activity and ash emission from the top of Etna's 2008 eruptive fissure, activity from the summit craters during 16-22 March consisted of degassing from the Northeast Crater, the NW Bocca Nuova vent, from the E flank of the Southeast Crater, and along summit fumarolic fields. The activity was observed directly and by utilizing surveillance cameras situated in Milo (about 11 km ESE). The NW-SE-trending fissure E of the summit craters continued (since 13 May 2008) to produce active lava flows to the N of the SE end of the fissure, along the W wall of the Valle del Bove.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

7 January-13 January 2009 Cite this Report

INGV-CT reported that during 5-11 January activity from Etna's summit craters was observed utilizing surveillance cameras situated in Milo (about 11 km ESE); inclement weather prevented direct inspection of the summit area. Degassing was seen from the NW Bocca Nuova vent, from the walls and floor of Southeast Crater, and along summit fumarolic fields. The NW-SE-trending fissure E of the summit craters continued (since 13 May 2008) to produce active lava flows to the N of the SE end of the fissure, along the W wall of the Valle del Bove.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

19 November-25 November 2008 Cite this Report

INGV-CT reported that an inspection of Etna's summit craters on 19 November revealed degassing from the Northeast Crater and, to a lesser degree, from the Bocca Nuova BN-1 crater. A 100-m-long lava flow was active in mid-November; the lava flow field on the upper Valle del Bove has been active since 13 May.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

16 July-22 July 2008 Cite this Report

INGV-CT reported that an inspection of Etna's summit craters on 15 July revealed degassing from the Northeast Crater and to a lesser degree from the BN-1 crater of the Bocca Nuova. Explosive activity was restricted to Vent 2 of the active NW-SE-trending fissure E of the summit craters and characterized by weak Strombolian activity and diffuse ash emissions. During 15 and 17 July lava flows were active in the Valle del Bove. On 17 July, no explosive activity was seen along the fissure.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

14 May-20 May 2008 Cite this Report

INGV-CT reported continuous ash emission and periodic Strombolian activity from multiple vents, possibly along an E-trending fissure E of Etna's summit craters, during 10-19 May. Observations were limited due to cloud cover. Ash plumes rose to approximate attitudes of 3.5-7.3 km (11,500-24,000 ft) a.s.l. and sulfur dioxide emissions were elevated. Lava flows that issued from the fissure and another fissure to the N traveled about 6 km E into the Valle del Bove during 13-15 May. Ash-and-gas explosions were occasionally accompanied by roaring noises on 14 May. Explosions and roaring noises were audible on 20 May. [Correction: Ash plumes rose to an altitude of 4 km (13,100 ft) a.s.l.]

Source: Sezione di Catania - Osservatorio Etneo (INGV)

7 May-13 May 2008 Cite this Report

Based on observations using the summit web camera, INGV-CT reported that a week of Strombolian activity from a depression on the E flank of the South East Crater at the summit of Etna ceased on 28 April. On 1 May, a seismic swarm was detected along the NE rift and degassing from the South East Crater and the North East Crater was noted. On 10 May, an eruption produced ash plumes that drifted N; observations were hindered due to cloud cover, but the ash cloud was detected on satellite imagery. Lava flows advanced about 6.4 km E and covered the W wall of the Valle del Bove. Ashfall was reported in multiple areas during 10-11 May.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

29 August-4 September 2007 Cite this Report

Based on information from the Istituto Nazionale di Geofisica e Vulcanologia and observations using satellite imagery, the Toulouse VAAC reported that a diffuse eruption plume from Etna rose to an altitude of 4.6 km (15,000 ft) a.s.l. during 4-5 September and drifted E.

According to news reports, a Strombolian eruption on 4 September produced lava flows that descended down the flanks. Ashfall was reported in several villages and the airport in Catania closed through the night.

Sources: Reuters; Toulouse Volcanic Ash Advisory Centre (VAAC)

22 August-28 August 2007 Cite this Report

On 15 August, the South East Crater at the summit of Etna produced ash emissions from a depression on the E flank. A resultant ash plume rose a few tens of meters and quickly dispersed. Ashfall formed a red deposit on the flanks of the South East Crater cone. Based on observations using the summit web camera, incandescent blocks associated with energetic emissions of ash were propelled out of the depression on 21 August. A field assessment on 22 August revealed that the ash emissions were associated with collapses within the depression. During 23-24 August, the ash emissions increased in frequency and erupted incandescent blocks were again observed.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

4 July-10 July 2007 Cite this Report

The Toulouse VAAC reported that minor activity from Etna was detected on satellite imagery on 7 July.

Source: Toulouse Volcanic Ash Advisory Centre (VAAC)

2 May-8 May 2007 Cite this Report

A summit eruption that occurred at Etna on 29 April began with an increase in volcanic tremor and was followed by lava fountaining and a vertical ash plume. Lava flows traveled E within the Valle del Bove. The INGV-CT monitoring web cameras showed that the eruption lasted about 8-9 hours.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

11 April-17 April 2007 Cite this Report

A summit eruption that occurred at Etna on 11 April began with an increase in volcanic tremor and was followed by lava fountaining. A resultant ash plume drifted E; ashfall was reported as far as Zafferana, about 10 km to the E. Two lava flows were observed at the summit of Etna, one towards the E within the Valle del Bove, and the second to the S. The E lava flow stopped 3 km away at the base of the Serra Giannicola Grande, within the W Valle del Bove. The second flow stopped near Mt. Frumento Supino (less than 1 km S of the summit). The INGV-CT monitoring web cameras showed that the eruption lasted about 5 hours.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

4 April-10 April 2007 Cite this Report

In the morning of 29 March, an increase in volcanic tremor at Etna was accompanied by lava fountaining and an ash plume that drifted NE. Three fissures opened and produced lava flows. The first two fissures produced lava flows from vents located on the SE flank of Bocca Nuova and in the saddle between Bocca Nuova and Southeast Crater (SEC), in the same location of the October-November 2006 events. The two flows merged down slope and traveled less than 1 km S, halting at the rim of Cratere del Piano. The third fissure opened at the E base of SEC, and the lava flow spread within the upper Valle del Bove. The flows stopped by early afternoon. Ash and lapilli fallout occurred in a narrow zone between SEC, Rifugio Citelli and Giardini Naxos, on the NE flank of the volcano.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

13 December-19 December 2006 Cite this Report

Based on increased volcanic tremor, INGV reported that weak Strombolian activity and emissions of lava and ash from the SE Crater of Etna occurred on 6 December. Later that day, seismicity dropped and explosive activity stopped. On 11 December, INGV monitoring cameras recorded Strombolian activity that resumed from a pit on the SE Crater, following a weak increase of seismicity. Lava was emitted continuously from the E flank of the SE Crater since 13 October. Lava also flowed from a vent at 2800 m elevation on the W headwall of the Valle del Bove. The eruption and lava flows from the 2800-m vent finished on 15 December. The Toulouse VAAC reported that a diffuse plume possibly containing ash was intermittently visible from a webcam on 13 December, drifting E.

Sources: Sezione di Catania - Osservatorio Etneo (INGV); Toulouse Volcanic Ash Advisory Centre (VAAC)

29 November-5 December 2006 Cite this Report

Based on a pilot report and satellite imagery, the Toulouse VAAC reported that an ash plume from Etna was visible during 4-5 December.

Source: Toulouse Volcanic Ash Advisory Centre (VAAC)

22 November-28 November 2006 Cite this Report

INGV reported that a black ash plume from Etna rose above cloud cover to an altitude of 4.8 km (15,700 ft) a.s.l. on 21 November at about 1500. Light ashfall was reported from areas E and NE, including Rifugio Citelli (6 km NE of the SE Crater). After 1900, the cloud cover dissipated and the SE Crater came into view. Strombolian activity generated jets of material greater than 300 m high. Lava flowed down the SSE flanks and continued into 23 November. According to the Toulouse VAAC, mild eruption plumes were visible on an INGV webcam on 24 November. Due to the possible presence of ash plumes, the Fontanarossa airport in E Sicily closed from the evening of 24 November until early 28 November.

Sources: Sezione di Catania - Osservatorio Etneo (INGV); Toulouse Volcanic Ash Advisory Centre (VAAC); AGI News - Agenzia Giornalistica Italia

8 November-14 November 2006 Cite this Report

An English-language report on Etna's activity during 31 August-5 November that was recently prepared and distributed by scientists from the Instituto Nazionale di Geofisica e Volcanologia (INGV) is summarized this week.

Strombolian activity and lava flows from SE Crater that began on 31 August continued until 15 September. During 22-27 September, 3-6 October, and 10-11 October, new but similar eruptive episodes with Strombolian explosions produced lava flows.

On 12 October, a short fissure opened on the ESE flank at the base of SE Crater. Lava spread in the upper Valle del Bove and advanced a few hundred meters downslope. On 17 October, mild spattering led to the growth of three hornitos on the fissure. Vigorous Strombolian activity from a vent in the SE Crater and large explosions occurred on 20 October. Lava flowed less than 1 km SE and a new cone grew at the summit.

On 23 October, vigorous Strombolian activity and lava fountaining from SE Crater marked a new eruptive episode. Lava flowed down the ESE flank and the summit cone rapidly grew. The explosive activity ceased the next day and was followed by ash emissions. Field observations revealed that a 50 m wide collapse pit opened on the SE flank and the new cone at the summit of the SE Crater had collapsed.

On 25 October ash emissions and weak Strombolian activity were observed from the summit of the SE Crater. Lava flows were emitted from fissures on the SSE flank and the S base of the central summit cone. On 27 October, ash emissions were followed by lava flows from the SSE flank fissure. Ash emissions on 29 and 30 October produced ashfall in inhabited areas including Catania, 27 km S of the summit cone. Lava continued to flow from the 25 October fissure and from the 12 October fissure at least until 5 November, when field observers reported actively flowing lava in the uppermost portions of the flow fields.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

6 September-12 September 2006 Cite this Report

On 14 July, a fissure opened on the E flank of the SE Crater of Etna and produced a lava flow that traveled E to the Valle del Bove. Moderate Strombolian activity from the E flank of the SE Crater produced a small amount of ashfall on Catania (~25 km SSE of the volcano). The lava flow reached a maximum distance of 3 km within the Valle del Bove and ceased on 24 July. On 26 July, strong explosions were heard from the rim of the NE crater.

On 31 August, Strombolian activity from the summit of the SE Crater produced lapilli and bombs that fell mainly in the crater. The ejecta filled the crater and overflowed on the E side on 5 September, forming lava falls that accumulated in a steep-sided circular depression on the middle part of the E flank. On 7 September, the sluggish a'a' flow breached the E rim and spread out on the E flank of the SE Crater and towards the Valle del Bove rim. Explosive activity at the SE Crater summit produced lava blocks that fell to the base of the cone.

On 10 September, a rockfall from a wall that divided the SE Crater and the depression on the middle part of the E flank produced an ash plume that drifted W. Lava flows and Strombolian activity from the summit of the SE Crater continued on 11 September.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

2 February-8 February 2005 Cite this Report

INGV-CT reported that the effusive eruption that began at Etna on 7 September 2004 continued through 27 January 2005. On 18 January the INGV-CT web camera recorded a dense, pulsating gas plume emanating from the summit of Northeast Crater for a few minutes. During the afternoon of the 18th, a new lava flow formed upslope along the 2,620-m eruptive fissure at about 2,450 m elevation. The lava flow spread about 200 m SE along the middle wall of the western Valle del Bove. The flow moved slowly, stopping after about 24 hours. Lava emission stopped from the ephemeral vents below 2,000 m elevation. The lower ephemeral vents started to emit lava again on 19 January. During the afternoon of 22 January, two new lava flows traveled from 2,400 m elevation, along the same lava-tube system fed by the 2,620-m-elevation vent. Two parallel, fast-moving flows spread E. They were still visible on images recorded on 27 January by the INGV-CT web camera at Milo. In addition, a number of ephemeral vents and small flows at the lower end of the lava tube were visible.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

5 January-11 January 2005 Cite this Report

On 8 January, Etna erupted plumes of black ash from its SE Crater. Following the eruption, a reddish glow emanated from the crater. Toulouse VAAC reported that the ash was barely discernable by satellite imagery.

Sources: Toulouse Volcanic Ash Advisory Centre (VAAC); Etna Volcan Sicilien (Charles Rivière)

6 October-12 October 2004 Cite this Report

According the Etna Volcan Sicilen website, lava emission continued at Etna during 6-11 October from vents around 2,620 m and 2,350 m elevations. Lava emission from the 2,620-m-elevation vent flowed in several arms down Valle del Bove. At the 2,350-m-elevation vent, lava flowed in tunnels for tens of meters.

Source: Etna Volcan Sicilien (Charles Rivière)

15 September-21 September 2004 Cite this Report

News reports indicated that INGV scientists, during a helicopter survey on 15 September, noted that both of the effusive openings on the western side of the Valle del Bove had decreased in activity. The lava flow from the vent at 2,620 m a.s.l. had reached a maximum length of 1,450 m but had almost stopped, like the smaller one near Monti Centenari at 1,900 m a.s.l.

Source: AGI News - Agenzia Giornalistica Italia

8 September-14 September 2004 Cite this Report

INGV-CT reported that at about 1030 on 7 September an effusive eruption began at Etna's summit. An approximately 230-m-long fissure opened at the base of Southeast Crater without any significant accompanying seismicity. Lava flowed from the base of the fissure, spreading SE towards the Valle del Bove. After 2 days of slow expansion of the field of fractures, between 0600 and 0700 on 10 September a new effusive vent opened at 2,650-m elevation on the upper western flank of the Valle del Bove. A lava flow poured out from this vent towards the E, spreading on the upper wall of the Valle del Bove. No explosive activity accompanied the emission of lava, but some phreatic explosions were triggered by lava flowing on a thick layer of snow. By 0930 the longest branch of the lava flow was 300 m long and 50 m wide. On the afternoon of 13 September, another effusive vent opened within the Valle del Bove, at about 2,200-m elevation, about 500 m SE of the previous vent. A lava flow from this vent spread in the valley at low output rate, while the previous flow from the vent at 2,650 m continued to feed a 1-km long lava flow. No lava flows threatened villages; the closest lava flow was at least 10 km from the nearest village.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

1 September-7 September 2004 Cite this Report

According to news articles, on 7 September a fracture opened at the base of Etna's Southeast Crater between cones created by eruptions in 1999 and 2001.

Sources: AGI News - Agenzia Giornalistica Italia; Reuters

10 March-16 March 2004 Cite this Report

INGV-CT reported that, following the last eruption of Etna on 28 January 2003, no further eruptive activity had been observed as of 8 March 2004. Summit activity was limited to pulsating gas emissions from Northeast Crater and from one of the two vents within Bocca Nuova crater. The other central crater vents and Southeast Crater were essentially blocked, producing only extremely weak gas emissions. The first significant variation from this very low level of activity occurred between 12 and 14 February 2004, when a weak ash emission was observed within the summit crater plume. The high amount of juvenile components within the ash suggested an uprise of magma into the summit feeder conduit of the volcano, the first to occur since the end of the 2002-2003 flank eruption. Since January, several shallow earthquakes have been recorded at Pernicana fault on the volcano's NE flank.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

11 February-17 February 2004 Cite this Report

On 10 February, video footage showed ash emissions from Etna's Bocca Nuova and Northeast craters. Gas was emitted from Southeast and Voragine craters.

Source: Etna Volcan Sicilien (Charles Rivière)

5 November-11 November 2003 Cite this Report

On 9 November aviation sources and web camera observations detected a small ash and steam plume at Etna. The plume rose to ~4 km a.s.l.

Sources: Sezione di Catania - Osservatorio Etneo (INGV); US Air Force Weather Agency

24 September-30 September 2003 Cite this Report

On 25 September an ash-and-steam plume was recorded by the Etna video camera reaching a height less than 4.5 km a.s.l. and drifting W.

Source: Toulouse Volcanic Ash Advisory Centre (VAAC)

10 September-16 September 2003 Cite this Report

Volcanic activity remained at low levels at Etna's summit craters. Abundant SO2 and steam emissions occurred at Northeast and Bocca Nuova craters. An M 3.3 earthquake occurred near Etna beneath the Ionian Sea.

Source: Etna Volcan Sicilien (Charles Rivière)

20 August-26 August 2003 Cite this Report

INGV-CT reported that on 11 August at 1715 an increase in volcanic tremor at the summit seismic stations on Etna lasted about 15 minutes. The tremor was followed by about 30 minutes of strong explosion earthquakes that were recorded at all INGV-CT seismic stations. This was the first such event recorded since the end of the flank eruption on 28 January 2003. A red puff of ash from Northeast Crater was visible on a INGV-CT web camera located at Milo, about 11 km from the summit. Red glow from the crater was seen during the night. No explosive activity or loud sounds occurred during a field survey on 14 August, and no explosion earthquakes or tremor were recorded during 11-16 August. Periodic measurements of the gas plume at the volcano's summit revealed that gas emissions had generally decreased since the end of the flank eruption.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

13 August-19 August 2003 Cite this Report

As of 16 August, the mild volcanic activity that was seen at Etna's Northeast Crater on 11 August was no longer observed. No incandescence was visible during the evening. Gas emission continued from the summit craters.

Sources: Italy's Volcanoes; Etna Volcan Sicilien (Charles Rivière)

6 August-12 August 2003 Cite this Report

According to the Etna Volcan Sicilian website, loud noises emanated from Etna's Northeast Crater on 5 and 6 August, but only strong degassing was seen. The Italy's Volcanoes website reported that on the 11th, weak, fluctuating glow was observed at the base of a dense gas column emitted from Northeast Crater. The gas column has been emitted from the crater for several months.

Sources: Italy's Volcanoes; Etna Volcan Sicilien (Charles Rivière)

30 July-5 August 2003 Cite this Report

During the end of July, heightened seismicity occurred in the eastern area of Etna. Also, vigorous degassing continued at Northeast crater, and less intense degassing occurred at Bocca Nuova crater. Four small earthquakes with magnitudes up to 2.6 occurred on 30 July between the villages of Milo and Zafferana on the volcano's E flank.

Sources: Italy's Volcanoes; Etna Volcan Sicilien (Charles Rivière)

25 June-1 July 2003 Cite this Report

As of 30 June strong degassing continued at Etna's Northeast Crater, and there were minor emissions at Bocca Nuova crater. A series of small, shallow earthquakes occurred on 26 June under Etna's E flank near the village of Fornazzo. These earthquakes are thought to be associated with an unstable section of the volcano that is slowly sliding eastward.

Source: Italy's Volcanoes

11 June-17 June 2003 Cite this Report

The Toulouse VAAC reported that the Etna web video camera showed an ash plume below ~4 km a.s.l. drifting SE on 7 June. According to the Italy's Volcanoes website, in early June intense gas emissions took place from Northeast Crater, often feeding a plume that extended tens of kilometers. At Bocca Nuova crater strong gas emissions and occasional strong explosions occurred, but no fresh volcanic material was ejected beyond the pit. Gas was emitted from two pits in Voragine crater. There was a progressive increase in the number and activity of fumaroles near Southeast Crater's summit and the S flank.

Sources: Italy's Volcanoes; Toulouse Volcanic Ash Advisory Centre (VAAC)

12 February-18 February 2003 Cite this Report

According to the Italy's Volcanoes website, on 12 February a series of ten earthquakes occurred on Etna's NE flank in the same area that was affected by vigorous seismicity and ground deformation before and during the initial phase of the 27 October 2002 to 28 January 2003 eruption. The largest earthquake occurred on 13 February at 0632, with a magnitude of 3.8 and a focal depth of 1.65 km.

Source: Italy's Volcanoes

5 February-11 February 2003 Cite this Report

INGV-CT reported that the Etna flank eruption that began on 27 October 2002 ended on 28 January 2003 after 3 months of activity. In January, lava flows and Strombolian explosions were confined to Etna's S flank at a 2,750-m-elevation vent. Lava flows emitted from this vent formed a fan, covering the previous lava-flow field. Strombolian activity from the 2,750-m-cinder cone significantly declined on 27 January and ended on 29 January. In addition, lava flows slowed down on the 27th and by the 29th were no longer fed and were cooling down. At the same time there was a significant decrease in SO2 emission to a minimum of 2,000 tons/day on 29 January. Volcanic-tremor amplitude also showed a marked decrease on 27 January. The end of the eruption was interpreted to occur on 28 January at 2240 when volcanic tremor decreased to background levels.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

29 January-4 February 2003 Cite this Report

According to the Italy's Volcanoes website, the eruption that began at Etna on 26-27 October 2002 ended during 28-29 January 2003. During the previous week, volcanic activity decreased at the pyroclastic cone on Etna's upper S flank and by the evening of the 28th seismic and volcanic activity had ceased.

Sources: Italy's Volcanoes; Toulouse Volcanic Ash Advisory Centre (VAAC)

22 January-28 January 2003 Cite this Report

According to the Etna Volcan Sicilien website, during 22-27 January low-to-moderate activity continued at the 2,750-m-elevation pyroclastic cone on Etna's upper S flank. Occasional strong explosions, and gas-and-ash emissions occurred. Lava flows were observed traveling to the S and W.

Sources: Etna Volcan Sicilien (Charles Rivière); Toulouse Volcanic Ash Advisory Centre (VAAC)

15 January-21 January 2003 Cite this Report

According to the Etna Volcan Sicilien website, on 15 January ash emission increased at the 2,750-m-elevation pyroclastic cone on the volcano's upper S flank. There was also an associated increase in lava emission towards the S. On the 16th explosive activity continued at the 2,750-m-elevation cone, with occasional explosions ejecting volcanic material onto an area within 300 m in the crater. On the 20th a reduction in activity occurred at the pyroclastic cone in comparison to the previous day, with ten explosions occurring in 8 hours. According to the Toulouse VAAC, low-level steam-and-ash clouds were occasionally visible on the Etna web camera.

Sources: Etna Volcan Sicilien (Charles Rivière); Toulouse Volcanic Ash Advisory Centre (VAAC)

8 January-14 January 2003 Cite this Report

According to the Etna Volcan Sicilien website, a reduction in explosive activity at the 2,750-m pyroclastic cone on the upper S flank of the volcano occurred for about a week until 10 January. On the 10th explosions occurred every few seconds, sending volcanic material several meters high that fell within the cone. Lava flows from the cone traveled towards the S.

Sources: Etna Volcan Sicilien (Charles Rivière); Italy's Volcanoes; Toulouse Volcanic Ash Advisory Centre (VAAC)

31 December-6 January 2003 Cite this Report

According to the Etna Volcan Sicilian website Strombolian activity continued at the crater at 2,750 m elevation during 31 December to 4 January. Explosive activity was accompanied by weak, sporadic ash emission. During 3-4 January the level of activity at the crater seemed to be lower than during the previous days. Lava was emitted from a fissure at the base of the 2,750-m crater that split into two arms, with both traveling S.

Sources: Etna Volcan Sicilien (Charles Rivière); Toulouse Volcanic Ash Advisory Centre (VAAC)

24 December-30 December 2002 Cite this Report

INGV-CT reported that the eruption that began at Etna on 27 October continued through 23 December. Lava flows and Strombolian activity occurred at the volcano's S flank at the 2,750 m vent. During 9-10 December, two vents opened at the SE base of the 2,750-m cinder cone that fed four major lava flows which spread between the S and SE. On the 17th a strong explosion occurred at a building in the Rifugio Sapienza tourist area. The explosion was not directly caused by the eruption, but by the vaporization of oil or water, still contained inside the building, when the lava flow contacted it.

The effusion rate from the two vents gradually decreased, eventually causing the closure of the western vent and then the lack of supply to the lava flows spreading SW towards Monte Nero. A new vent opened on 17 December at the S base of the 2,750 m cinder cone, a few meters W of the previous vents. A lava flow soon started from this vent, spreading SW towards Monte Nero. Lava flows from the 17 December vent slowed down and crusted over on 22 December, when a new vent opened at the SW base of the 2,750 m cinder cone. Again, a flow traveled SW towards Monte Nero. As of 23 December the lava flow continued to flow in this direction. SO2 emission rates remained relatively low, around 7,000 tons per day. Updated maps of the lava flows, and reports of the eruptive activity, gas emission, and ash composition can be found on the INGV-CT web page (in Italian).

Source: Sezione di Catania - Osservatorio Etneo (INGV)

18 December-24 December 2002 Cite this Report

Eruptive activity continued during 16-21 December at Etna. According to the Italy's Volcanoes website, during the evening of 16-17 December explosive activity changed from lava-and-ash fountaining to discrete, ash-poor Strombolian explosions. Lava continued to flow from two vents at the S base of the active pyroclastic cone at 2,750-m elevation. During 19-21 December there were frequent shifts from lava fountaining and ash emissions to Strombolian explosions, and vice versa. Lava was no longer traveling towards the Rifugio Sapienza tourist complex. Ash had not fallen at the Catania airport since 8 December, so the airport returned to full service.

Sources: Italy's Volcanoes; Toulouse Volcanic Ash Advisory Centre (VAAC); Etna Volcan Sicilien (Charles Rivière)

11 December-17 December 2002 Cite this Report

According to an INGV-CT report, the eruption that began at Etna on 27 October continued through 13 December. On 8 December there was a sudden change in eruptive style. Strong Strombolian explosions from the 2,800-m vent replaced previous fire fountaining, signaling the end of ash emissions for about 24 hours. On 9 December fire fountaining resumed at this vent, but on the10th activity changed to Strombolian explosions. This alternating activity culminated on 10 December with the opening of two vents on the SSE base of the cone and the emission of two lava flows. These flows spread SW towards Monte Nero, and S towards the cinder cone that formed at 2,550-m elevation during the 2001 eruption (also called Laghetto cone).

The S flow expanded on the 11th and 12th, and as of the 13th it had reached 300 m from the road leading to the Rifugio Sapienza tourist area, about 3.3 km from the vent. Civil Protection authorities, for the second time during this eruption, built an earth dam to divert the lava away from Rifugio Sapienza structures. SO2 emission rates significantly decreased on 1 December, dropping from previous estimates of ~20,000 to ~7,000 tons/day.

According to a Reuters news article, a lava flow that reached the Rifugio Sapienza tourist area on the evening of 16 December caused an explosion that destroyed a building and injured 32 people. The article stated that the exact cause of the explosion was unknown.

Sources: Sezione di Catania - Osservatorio Etneo (INGV); Reuters

4 December-10 December 2002 Cite this Report

According to the Italy's Volcanoes website, as of 5 December explosive activity continued at one of Etna's vents in the northernmost portion of the fissure that opened on Etna's upper S flank on 27 October. Ash emission and lava fountaining were vigorous, with continuous tephra fall affecting areas NE and E of Etna during several days before 5 December. Lava emission seemed to temporarily cease after about 3 weeks of near-continuous activity from vents on the flanks of the new pyroclastic-cone complex. Intermittent seismicity occurred at and around Etna. The largest reported damage occurred at a vacated school building near Giarre that partially collapsed. On 8 December ash emission and lava fountaining at the 2,800-m vent changed to violent Strombolian explosions. The following day ash emission recommenced, and on 10 December explosive activity shifted to the main pyroclastic cone, while the 2,800-m cone became less active, and lava was emitted that fed a flow to the S. By the 11th the lava flow had divided into several branches, with one slowly advancing toward the Rifugio Sapienza tourist area.

Sources: Italy's Volcanoes; Toulouse Volcanic Ash Advisory Centre (VAAC); Etna Volcan Sicilien (Charles Rivière)

27 November-3 December 2002 Cite this Report

Etna continued to erupt through 2 December. According to the Italy's Volcanoes website, during the afternoon on 1 December ash fell in Catania and surrounding areas, leading to the closure of Fontanarossa Airport. On the 2nd, explosive activity continued at two vents on Etna's upper S flank and lava was emitted from a third vent at the SW base of the large pyroclastic cone that formed during the first 5 weeks of activity. In addition, the most advanced part of the most recently active lava flow that burned part of a forest on the SW flank seemed to have stopped. According to the Toulouse VAAC, since the eruption began on 27 October there has been unsteady activity at the volcano with periods of stronger activity leading to temporary ash emission.

Sources: Italy's Volcanoes; Toulouse Volcanic Ash Advisory Centre (VAAC); Etna Volcan Sicilien (Charles Rivière)

20 November-26 November 2002 Cite this Report

The 2002 Mt. Etna flank eruption that began on 27th October is continuing, after almost a month of activity. During this period several distinct phases of eruptive style have been observed. The first phase of the eruption ended on 5th November, when lava flows from the northern fissure stopped. Strombolian and fire-fountaining activity continued at the southern fissure, localised within the 2750 m elevation cinder cone that formed during early November. Lava jets reached heights of over 300 m above the crater, forming an ash column that spread mostly N, due to the strong wind, and reached an elevation of 4.7 km a.s.l..

The second phase of activity started on 12th November, when strong jets and continuous emission of ash gave way suddenly to mild Strombolian activity. Lava flows began to spread SW from the 2750 m vent on the 13th November. These flows ran parallel to the October flows towards Monte Nero and achieved a maximum length of 4 km on 19th November, stopping just 300 m before Casa Santa Barbara, at 1770 m a.s.l.. Lava output from the main vent then declined, and overflows covered the previous flow channel. As of 25th November the most advanced active flow fronts were located within 1 km from the vent.

Between 20 and 21st November another new vent opened on the SSE base of the 2750 m cinder cone. This vent produced a new lava flow that spread south towards Rifugio Sapienza. The flow length reached 1.9 km on the 22nd, and 2.7 km on the 23rd, covering the Rifugio K. The Rifugio Sapienza was threatened by the flow, and Civil Protection soon built up two earth barriers to divert the lava towards the east of buildings, as in the 2001 eruption. This diversion was once again successful, and the flow eventually stopped on 24th, a few metres before reaching the SP92 road connecting Zafferana to Rifugio Sapienza, after having traveled 3.6 km from the main vent.

Early on the 25th November, two new explosive vents opened to the N and SSE of the 2750 m cinder cone. This caused a shift in explosive activity from the crater of the previous cone to the newly formed vents, which produced fire fountaining activity and an ash plume rising to 4.7 km elevation and spreading north. Immediately afterwards the effusion rate of the south lava flow (towards Rifugio Sapienza) significantly decreased, and slightly increased in the southwest flow (towards Casa Santa Barbara). This caused new overflows above the previous flow channel on the lava flows directed to Casa Santa Barbara. The low effusion rate did not allow these flows to reach previous flow lengths, and they were less than 1 km long when last observed on 25th November. Observation of the flow field was impossible on the 26 November due to poor weather conditions.

SO2 emission from the volcano is still very high and fluctuating, keeping within the range of 20,000 to 7,000 tons per day. Taken together, the high amount of gas released by the volcano, the still high volcanic tremor, and the explosive activity still ongoing at the south vent, rather suggest that the eruption may continue for some time.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

13 November-19 November 2002 Cite this Report

The eruption that began at Etna on 27 October continued through 12 November. INGV-CT reported that on 12 November at 1340 volcanic tremor recorded by their seismic network gradually increased, reaching an amplitude two times higher than before. This seismicity increase occurred when fire fountaining and ash emission from the vent at 2,750 m elevation on the volcano's S flank suddenly stopped and were substituted by Strombolian activity. This change marked an increase in the magma level within the conduit, and on the 13th at 1600 a lava flow was emitted from the S base of the upper cinder cone that formed around the 2,750-m vent. The lava flow spread S, filling up the intermediate and lower cinder cones along the same eruptive fissure. It expanded SW towards Monte Nero, running parallel to the lava flow that had stopped on 31 October. By 14 November at 0930 the lava-flow front had reached 1.2 km in length, was at an elevation of 2,450 m a.s.l., and traveled at a velocity of about 2-3 m per minute. Strombolian activity was substituted by fire fountaining and the emission of ash that reached 3.5 km a.s.l. and drifted N and E. SO2 emission from Etna remained very high and fluctuated around 20,000 tons per day. According to a news article, Fontanarossa Airport in Catania, which had been closed since 10 November, reopened on the 13th. The Toulouse VAAC reported that moderate-to-severe ash emissions had occurred at Etna since the eruption began, but had become weaker since the afternoon of 12 November.

Sources: Sezione di Catania - Osservatorio Etneo (INGV); Toulouse Volcanic Ash Advisory Centre (VAAC)

6 November-12 November 2002 Cite this Report

An eruption began at Etna on 27 October. According to a report from INGV-CT, the lava supply from Etna's main vents ended by 3 November. At that time lava flows were no longer emitted from the volcano's S and N flanks. As of the 11th, fire fountaining continued from the S vent at 2,750 m elevation, near Torre del Filosofo. All data (gas emission, volcanic tremor, composition of the ash) suggest a steady state at this vent. Ash fallout caused intermittent disruption at the Catania airport and damage to buildings. The Toulouse VAAC reported that moderate-to-severe ash emissions had occurred since the eruption began. During 6-12 November ash clouds rose to a maximum height of ~6.1 km a.s.l.

Sources: Sezione di Catania - Osservatorio Etneo (INGV); Toulouse Volcanic Ash Advisory Centre (VAAC)

30 October-5 November 2002 Cite this Report

Volcanic and seismic activity continued at Etna during 29 October to 4 November after a new eruption commenced on 27 October. The eruption consisted of fissures opening on the volcano's S and N flanks, lava emission from these fissures, and fire fountains rising several hundreds of meters. Significant ash emissions led to the closure of Fontanarossa airport and produced ash clouds that drifted as far as Libya. According to an INGV-CT report, two major lava flows were emitted from the lower end of the northern fissure and spread toward the NE and E. The NE flow stopped on 31 October after traveling 2 km, when a decline in effusion rate was observed. As of 1 November the E flow had slowed down, but it was still moving and crusting over in the middle portion of the flow field. A few sectors of solid crust were detected during a survey with the helicopter of the Civil Protection using a thermal camera. This suggests that a lava tube is forming on this lava flow. The lava flow from the S fissure started about 12 hours after the N one, spread SW, and split in two branches around Monte Nero, following the same path as one of the 2001 eruption's lava branches. The S flows stopped on 31 October, reaching a total length of about 1 km. Fire fountains and phreatomagmatic activity decreased in intensity with time at both the N and S fissures. As of 1 November the effusion rate from the N fissure was declining, which increased the possibility of lava-tube formation along the E flow.

According to the Toulouse VAAC, ash was emitted from Etna during the report period and was occasionally visible on satellite imagery rising to 6.1 km a.s.l. On 1 November ash was visible on satellite imagery extending ENE from Etna's summit, reaching the coast of Greece. On several occasions meteorological clouds in the vicinity of Etna prohibited satellite views, but the Etna web video camera located in Catania showed continuous ash emission on 4 November.

Sources: Sezione di Catania - Osservatorio Etneo (INGV); Toulouse Volcanic Ash Advisory Centre (VAAC)

23 October-29 October 2002 Cite this Report

A relatively large eruption began at Etna on 27 October, following a series of ~200 small earthquakes the previous evening. The eruption began with fissures opening on the volcano's S and NE slopes around 2,700 m elevation, between Southeast Crater and Montagnola cone. Lava fountains rose 100-200 m, lava flows were emitted from the fissures, and significant ash plumes were produced. On the 28th seismicity continued, with a M 3.8 earthquake occurring beneath the volcano. Lava flows cut across the road connecting the towns of Linguaglossa and Piano Provenzana and lava ignited several forest fires near Piano Provenzana. The lava flows were estimated to be 365 m wide and 6.1 m high.

Ditches were dug in an effort to control lava flows, but by the 29th they were completely covered by lava. Authorities also tried to control the flows by having planes douse the lava with water, causing the flows to cool and stagnate, but they continued to travel down the volcano's flanks. Authorities stressed that the popular ski town of Linguaglossa (6,000 residents), located ~15 km NE of Etna's summit, was not in danger of being engulfed by lava flows. As a precautionary measure ~50 residents were evacuated and schools were closed. By the 28th lava flows had destroyed several hotels, restaurants, a ski school, ski lift pylons, and power lines on the volcano's flanks. Ash fell in towns at the base of the volcano. Some streets in the town of Nicolosi, ~15 km S of the summit, were covered with a 5-cm-thick layer of ash.

During 27 to at least 29 October ash clouds were visible on satellite imagery and the Etna volcano video camera, reaching a maximum height of ~6.4 km a.s.l. The clouds drifted towards the SE and on the 27th one had reached ~350 km S to Libya. From the beginning of the eruption, Catania's Fontanarossa airport was closed. Ash emissions continued on the 29th and a M 4.4 earthquake occurred around 1100, damaging hundreds of buildings in the town of Santa Venerina on the volcano's SE flank.

Sources: Reuters; Associated Press; Etna Volcan Sicilien (Charles Rivière); Toulouse Volcanic Ash Advisory Centre (VAAC)

16 October-22 October 2002 Cite this Report

On 17 October around 1530, a significant amount of brown ash was emitted from Etna's Northeast Crater. No activity was visible during the night from cities at the base of the volcano. Earthquakes with magnitudes between 2.3 and 2.7 occurred on the morning of the 18th during 0427-0500. Approximately 30 minutes later the Northeast Crater expelled plumes of brown ash.

Source: Etna Volcan Sicilien (Charles Rivière)

2 October-8 October 2002 Cite this Report

When weather conditions were favorable on 22 and 27 September, black ash was seen rising from Etna's Northeast Crater. On the 27th ash was also emitted from Bocca Nuova crater. On 1 October degassing was seen at Bocca Nuova every 5-10 minutes, lasting ~30 seconds. No ash was emitted. Poor weather conditions prevented observations at the other craters.

Source: Etna Volcan Sicilien (Charles Rivière)

11 September-17 September 2002 Cite this Report

During 9-14 September, Strombolian activity continued at Etna's Northeast Crater, with ash and incandescent material being ejected from it. Volcanic bombs ejected vertically to heights of 100-150 m fell within the crater. Low-level ash clouds were visible on satellite imagery.

Sources: Etna Volcan Sicilien (Charles Rivière); Toulouse Volcanic Ash Advisory Centre (VAAC)

4 September-10 September 2002 Cite this Report

On 4 September the strong ash emissions that occurred at Etna's Northeast Crater the previous week were no longer observed, and only degassing occurred. Ash was emitted from Bocca Nuova crater once every 5-10 minutes and gas was emitted from Voragine and Southeast craters. On the night of 6 September, a M 5.6 earthquake, centered near the town of Palermo (~145 km NW of Etna) produced aftershocks that were felt in Catania (25 km SSE of Etna). On 8 September, strong Strombolian activity was observed at Northeast Crater. Explosions occurred every 1-3 minutes and incandescent material was ejected outside of the crater.

Source: Etna Volcan Sicilien (Charles Rivière)

14 August-20 August 2002 Cite this Report

The Toulouse VAAC reported that beginning on 18 August around 1030, a web camera revealed that ash was near Etna's summit. Ash was also visible on satellite imagery. The Etna Volcan Sicilian website reported that during a visit to Etna on 18 August, ash was emitted from Northeast Crater, and gas, ash, and blocks were emitted from Bocca Nuova crater. Only gas was emitted from Voragine and Southeast craters.

Sources: Etna Volcan Sicilien (Charles Rivière); Toulouse Volcanic Ash Advisory Centre (VAAC)

7 August-13 August 2002 Cite this Report

The Toulouse VAAC reported that beginning on 9 August at 0630 ash was visible at Etna on a web cam. The ash was around summit level and was not visible on satellite imagery. According to the Etna Volcan Sicilian website, during a visit to the summit on 8 August brown ash was emitted from Bocca Nuova crater. By the 9th only gas was released from Bocca Nuova.

Sources: Etna Volcan Sicilien (Charles Rivière); Toulouse Volcanic Ash Advisory Centre (VAAC)

31 July-6 August 2002 Cite this Report

Activity continued at Etna during 31 July-6 August with brown ash explosions from Bocca Nuova crater. SO2 emissions were detected from Voragine crater on 4 August. Strong explosions originating in Northeast Crater were felt during the afternoon of 6 August. The area near Northeast Crater contained numerous bombs, some more than 70 cm in size weighing more than 30 kg.

Source: Etna Volcan Sicilien (Charles Rivière)

24 July-30 July 2002 Cite this Report

During a visit to Etna on 26 July it was revealed that Strombolian activity had continued at Northeast Crater. Activity consisted of volcanic bombs being thrown beyond the rim of the crater. There was very little activity at Voragine and Southeast craters. According to the Toulouse VAAC, ash was observed on 29 July at 0855, possibly around summit level.

Sources: Etna Volcan Sicilien (Charles Rivière); Toulouse Volcanic Ash Advisory Centre (VAAC)

17 July-23 July 2002 Cite this Report

During 19-21 July, explosions at Etna's Northeast Crater emitted gas and ash, and ejected volcanic bombs and fresh lava that landed within the crater. At Bocca Nuova crater, gas-and-ash emissions and explosions also occurred. At Voragine crater, degassing was less intense than it had been during previous observations on 22 June 2002. According to the Air Force Weather Agency, surface observations revealed that on 22 July a low-level ash cloud was visible. Ash was not visible on satellite imagery.

Sources: Etna Volcan Sicilien (Charles Rivière); US Air Force Weather Agency

19 June-25 June 2002 Cite this Report

During 17-23 June, ash continued to be emitted from Etna's Northeast Crater and to a lesser extent from Bocca Nuova crater. Ash plumes from Northeast Crater rose several hundred meters. Quiet degassing occurred at Voragine and Southeast craters. Seismicity was at low levels during the week.

Sources: Italy's Volcanoes; Etna Volcan Sicilien (Charles Rivière)

12 June-18 June 2002 Cite this Report

On 13 June ash emissions, which began several days earlier, intensified at Etna's Northeast Crater. A slight increase in seismicity occurred at the same time, with a few events being felt by residents on the volcano's S and SE flanks. The Toulouse VAAC reported that volcanic ash was observed on satellite imagery on 14 June at 0450 drifting SSW at heights of ~2.4-4.6 km a.s.l. Beginning on 16 June ash was emitted from Bocca Nuova crater as well. No incandescence was visible at the volcano during the night.

Sources: Italy's Volcanoes; Toulouse Volcanic Ash Advisory Centre (VAAC); Etna Volcan Sicilien (Charles Rivière)

29 May-4 June 2002 Cite this Report

During late May, volcanic and seismic activity were low at Etna. Volcanism consisted of gas emissions from Northeast, Voragine, and Bocca Nuova craters. Also, several small new fumaroles formed on the lower SE flank of Southeast Crater during about 26 May to 2 June. According to Italy's Volcanoes website, a visit to the summit craters on 30 May revealed that few changes had occurred there since the previous visit on 28 January.

Sources: Italy's Volcanoes; Etna Volcan Sicilien (Charles Rivière)

8 May-14 May 2002 Cite this Report

During early May, degassing continued at Etna. It was most pronounced at Bocca Nuova and Northeast craters.

Sources: Italy's Volcanoes; Etna Volcan Sicilien (Charles Rivière)

24 April-30 April 2002 Cite this Report

Ash emissions that had been occurring at Bocca Nuova crater for several weeks seemed to diminish during 23-25 April. During the 24th-25th, only ash-free gas emissions were observed, mostly from Bocca Nuova and Northeast craters. On the 28th a brief emission of brown ash was seen coming from the W side of Bocca Nuova. No felt earthquakes occurred after the 15th.

Sources: Italy's Volcanoes; Etna Volcan Sicilien (Charles Rivière)

17 April-23 April 2002 Cite this Report

During 14-18 April, a dense ash plume persisted at the SE vent of Etna's Bocca Nuova crater. Dense ash-free plumes rose above Voragine and Northeast craters. Earthquakes continued on Etna's SE flank, and there were reports of seismicity on the NE flank.

Sources: Italy's Volcanoes; Etna Volcan Sicilien (Charles Rivière)

10 April-16 April 2002 Cite this Report

Signs of unrest persisted at Etna during 6-14 April. On 13 April two earthquakes, with magnitudes 2.7-3, were felt by the local population. They occurred on the SE flank between the towns of Zafferana and Santa Venerina. During the report period, ash emissions were nearly continuous at Bocca Nuova crater, rising to several hundreds of meters. No incandescence was visible in the crater.

Source: Italy's Volcanoes

3 April-9 April 2002 Cite this Report

Ash emissions during 29 March-6 April at Etna's Bocca Nuova crater deposited ash as far as the town of Catania ~25 km SSE of the volcano. Ash emissions apparently stopped at Northeast Crater by 2 April; only steam was visible rising above the crater. During 4 and 5 April, earthquakes occurred at or near Etna with magnitudes up to 4.2.

Sources: Italy's Volcanoes; Etna Volcan Sicilien (Charles Rivière)

27 March-2 April 2002 Cite this Report

Following almost 3 weeks of ash emissions from Etna's Bocca Nuova crater, around 25 March ash emissions began at Northeast Crater. The emissions appeared to coincide with a series of small earthquakes under the volcano's SE flank the night of 24-25 March. On the 27th and 28th ash from both craters rose in distinct puffs several hundreds of meters above the summit. On 28 March a small amount of ash fell on Etna's S flank, reaching as far as the town of Catania. The following day dark ash rose nearly continuously to several hundreds of meters above the summit. The Toulouse VAAC reported that no ash was visible on satellite imagery.

Sources: Italy's Volcanoes; Toulouse Volcanic Ash Advisory Centre (VAAC)

20 March-26 March 2002 Cite this Report

The emission of pink, lithic ash from Bocca Nuova crater that reportedly began on 9 March continued through 21 March. In addition, voluminous degassing occurred at Northeast Crater and there was minor fumarolic activity at Voragine and Southeast craters. No incandescence was visible at night.

Source: Italy's Volcanoes

13 March-19 March 2002 Cite this Report

Beginning around 9 March, near continuous, pulsating emissions of lithic ash were erupted from the NW vent of Bocca Nuova crater and an ash plume drifted dozens of km. The source vent of this activity was also the site of deep-seated explosions during the past 6 months. According to the Italy's Volcanoes website, the emissions might be caused by collapses within the conduit, which are thought to have occurred repeatedly following the July-August 2001 eruption.

Source: Italy's Volcanoes

6 March-12 March 2002 Cite this Report

As of 7 March there had been no new eruptive activity at Etna for several months. Numerous small earthquakes were recorded beneath the volcano's S flank, where the largest of the July-August 2001 lava flows vented. Some of the earthquakes were felt by the population near the volcano.

Source: Italy's Volcanoes

30 January-5 February 2002 Cite this Report

On 30 January low levels of activity were observed at Etna. Loud explosions occurred approximately every 5-30 minutes in the NW pit of Bocca Nuova crater, but no solid material was ejected. Degassing occurred at Bocca Nuova, Voragine, Northeast, and Southeast craters.

Source: Italy's Volcanoes

16 January-22 January 2002 Cite this Report

In mid-January, increased gas emissions occurred at Southeast Crater, and increased gas-and-ash emissions occurred at Bocca Nuova crater. Very small amounts of ash fell on the E side of the volcano, as far as the town of Acireale, ~20 km SE of the volcano. No incandescent ejections were visible at night.

Source: Italy's Volcanoes

2 January-8 January 2002 Cite this Report

Volcanic activity has been low at Etna since the voluminous lava outburst during the July-August 2001 eruptive event. On 6 January low-level fumarolic activity occurred from the western rim of Southeast Crater at intervals of a few minutes. In addition, a dense gas plume was emitted from Bocca Nuova crater. The activity at both craters continued through at least 7 January.

Source: Italy's Volcanoes

17 October-23 October 2001 Cite this Report

As of 16 October moderate amounts of degassing took place at Etna's summit craters, with most occurring at Northeast Crater. A portion of the western crater rim of the scoria cone that formed during the July-August 2000 eruption at 2,100 m elevation collapsed into the vent.

Source: Italy's Volcanoes

3 October-9 October 2001 Cite this Report

During 4 and 5 October a large amount of degassing occurred at Northeast Crater. Degassing at Bocca Nuova crater was occasionally accompanied by ash emissions generated by the crumbling of the crater walls. Gas and "smoke" were continuously emitted from the edges of the new crater located at 2.55 km elevation.

Source: Etna Volcan Sicilien (Charles Rivière)

26 September-2 October 2001 Cite this Report

According to reports on 28 September, gas emissions from Bocca Nuova crater had been vigorous at times during the previous few weeks. In addition, a dense gas plume was visible rising above Northeast Crater. The cones that formed during the July-August 2001 eruption on the S flank continued to emit heat and minor amounts of gas.

Source: Italy's Volcanoes

12 September-18 September 2001 Cite this Report

Volcanic activity resumed at Etna's summit on 11 September. Loud explosions emanated from the NW vent of Bocca Nuova crater at 5- to 10-minute intervals. The explosions were followed by dense gas clouds, but no volcanic fragments were ejected.

Source: Italy's Volcanoes

5 September-11 September 2001 Cite this Report

No new eruptive activity has occurred at Etna since 10 August. During the week strong degassing was observed at Bocca Nuova and Southeast craters.

Sources: Etna Volcan Sicilien (Charles Rivière); Italy's Volcanoes

22 August-28 August 2001 Cite this Report

Volcanic activity was relatively low at Etna during the week. Degassing and seismic activity continued at Etna's summit craters.

Source: Etna Volcan Sicilien (Charles Rivière)

15 August-21 August 2001 Cite this Report

During the week volcanic activity was relatively low at Etna, with no explosions or lava flows. There were several small earthquakes, and slight degassing at fissures on the volcano's flanks. Vapor was emitted from the summit craters, and was accompanied by occasional plumes of brown ash at Bocca Nuova crater.

Source: Etna Volcan Sicilien (Charles Rivière)

8 August-14 August 2001 Cite this Report

As of 13 August lava flows appeared to cease advancing down the slopes of Etna. Slight degassing occurred from many of the fissures and the rate of SO2 emission was low in comparison to average values for the season.

Sources: Etna Volcan Sicilien (Charles Rivière); BBC News

1 August-7 August 2001 Cite this Report

News articles stated that around 1 August lava stopped advancing towards the Rifugio Sapienza tourist area, although lava in other parts of the volcano slowly continued to advance. According to the Toulouse VAAC, narrow ash clouds that rose to below 5.5 km a.s.l. were occasionally visible in satellite imagery and on Sistema Poseidon's web cam. The international Fontanarossa airport in Catania was closed, for the fourth time since the eruptive period began, during 2-5 August due to ash clouds in the area. The amount of ash emitted from the volcano decreased on 5 August and only steam with small amounts of ash located close to the ground was visible on the web cam.

Sources: Sezione di Catania - Osservatorio Etneo (INGV); Associated Press; Toulouse Volcanic Ash Advisory Centre (VAAC); Etna Volcan Sicilien (Charles Rivière)

25 July-31 July 2001 Cite this Report

During 25-31 July the eruption that began on 17 July at Etna's Southeast Crater continued at the same five eruptive fissures as the previous week. One of the fissures was located on the NE flank and the other four on the S flank at elevations of 2,950, 2,700, 2,500, and 2,100 m. During 24-26 July eruptive activity declined at the 2,100 m fissure, but then intensified on 27 July to reach the original level of Strombolian activity on the evening of 28 July. On 26 July modest lava emission occurred at the NE-flank fissure. At the 2,500 m fissure, where the strongest explosive activity occurred, a change was noted from the mostly phreatomagmatic eruptions that were prominent during the previous week to more violent Strombolian explosions and lava effusion. After lava began to flow from the 2,500 m fissure on 25 July, a pyroclastic cone began to grow around three of the vents and by 30 July the cone was ~100 m high. At the 2,950 m fissure (near the base of Southeast Crater) and 2,700 m fissure lava emission and mild explosive activity continued.

On 26 July lava from the 2,500 m elevation fissure continued to flow towards Rifugio Sapienza tourist complex, and as of 31 July a cable car base station and a small tourist shop had been destroyed by lava that surpassed constructed earth barriers. Lava continued to flow from the lower vents of the 2,100 m fissure in the direction of the town of Nicolosi (~15 km SSE of the volcano), but it was no longer considered a significant threat to the town. Near-continuous ashfall occurred S of the volcano, including in the town of Catania, ~25 km SSE of the volcano. The international Fontanarossa airport in Catania was closed repeatedly on 29 and 30 July due to ash on the runways. The Toulouse VAAC reported that ash clouds were occasionally visible on the Sistema Poseidon web cam and satellite imagery, with the highest cloud rising ~5.5 km above the volcano.

Sources: Italy's Volcanoes; Reuters; Associated Press; Etna Volcan Sicilien (Charles Rivière); Toulouse Volcanic Ash Advisory Centre (VAAC)

18 July-24 July 2001 Cite this Report

A large flank eruption began on 17 July at Etna and produced several lava flows that were emitted from four new fissures and strong explosive activity at a fifth. Four of the fissures were on the SE flank, and the fifth was on the NE flank. There were fears that lava flows from two of the fissures would reach the town of Nicolosi (~15 km SSE of the volcano) and a nearby popular tourist area. According to the Italy's Volcanoes website, the 17th eruptive episode in 2001 began on the morning of 17 July and a few hours later a new eruptive fissure opened at the S base of the Southeast Crater cone (see map of fissure locations). Mild Strombolian activity occurred from the fissure and a lava flow extended SSE. During the evening of the 17th a second eruptive fissure emitted an extensive lava flow that spread SE toward the Valle del Bove rim. On 18 July at about 0200 a seismic swarm was accompanied by the opening of a third eruptive fissure at about 2,100 m elevation. Mild Strombolian activity and a sluggish lava flow traveled toward the S. Later in the day the lava flow crossed the main access road to the S flank of Etna and headed towards Nicolosi. A spectator was seriously injured when he fell while trying to avoid projectiles.

On the evening of 18 July the fourth eruptive vent since the episode began opened near 2,700 m elevation on the SE flank. The main explosive activity occurred at this vent, including powerful Strombolian blasts that sent incandescent volcanic bombs as high as 200 m and produced ash columns that rose several kilometers. Lava from this vent progressed towards the tourist complex around the Rifugio Sapienza. On 20 July around 1100 a fifth eruptive fissure became active, but unlike the other fissures it was on the NE flank in the Valle de Leone. Lava emitted from this fissure flowed SE.

By 22 July the lava flow from the third fissure was 4 km away from Nicolosi, but it was advancing very slowly over nearly flat terrain and appeared to have stopped by the next day. Earth barriers were created in an attempt to divert lava from the tourist complex that had already been damaged by volcanic bombs. Continuous ashfall occurred near the explosive fourth vent. The entire area between the towns of Giarre (~17 km E of the volcano) and Catania (~25 km SSE of the volcano) was covered by a thin layer of ash; there was an especially large amount of ash in Catania. The Fontanarossa International Airport of Catania was closed on 22 July and again the next day due to ashfall.

The Toulouse VAAC reported that the new Etna Sistema Poseidon webcam showed ash emission starting on 20 July. The previous webcam had been damaged by earthquakes near the start of the eruption. SE-drifting ash clouds were detected several times on satellite imagery. An ash cloud was reported to have reached a maximum height of ~5.2 km on 22 July. According to news reports, a state of emergency was declared for the area near Etna on 20 July. As of 24 July the eruption was continuing.

Sources: Italy's Volcanoes; NASA Earth Observatory; Reuters; Etna Volcan Sicilien (Charles Rivière); Toulouse Volcanic Ash Advisory Centre (VAAC)

11 July-17 July 2001 Cite this Report

On 13 July the 16th eruptive episode in 2001 took place at the NNE vent of Etna's Southeast Crater. During the 4-hour-long episode, lava flows, Strombolian activity, and several earthquakes occurred. The largest two earthquakes had magnitudes of 3.9 and were felt 15 km away in the town of Nicolosi. The Toulouse VAAC reported that a small ash cloud was visible on the Sistema Poseidon Etna webcam and on satellite imagery. It did not rise above 3.7 km a.s.l.

Sources: Etna Volcan Sicilien (Charles Rivière); Associated Press; Sezione di Catania - Osservatorio Etneo (INGV); Toulouse Volcanic Ash Advisory Centre (VAAC)

4 July-10 July 2001 Cite this Report

After 4.5 days of low-level activity at Etna, an eruption occurred at Southeast Crater on 4 July that lasted for approximately 5 hours. The episode began with lava flowing from the NNE vent towards the NE and SSE and was followed by modest Strombolian activity. At the summit vent powerful explosions sent an incandescent fountain up to 400-500 m high and several large magma bubbles burst sending fragments to the base of the Southeast Crater cone. A dense tephra column rose from the summit vent and deposited ash on Etna's SE flank. Fine ash and 3- to 5-mm-long Pele's hair fell as far as the town of Acireale, ~20 km SE of the volcano. On 7 July another eruptive episode lasted for approximately 1 hour at Southeast Crater. The episode consisted of lava flows and the eruption of black ash and small volcanic blocks that reached a height of ~1 km above the volcano and drifted to the E.

Sources: Italy's Volcanoes; Etna Volcan Sicilien (Charles Rivière)

27 June-3 July 2001 Cite this Report

An eruptive episode began on the evening of 27 June at the NNE vent on Southeast Crater. The episode began with lava flowing from the NNE vent and was followed by Strombolian activity at the NNE vent and the summit. Volcanic material was ejected to a maximum height of 400 m. No sustained lava fountains developed. The Toulouse VAAC reported that Sistema Poseidon's Etna webcam recorded renewed volcanic activity on 28 June at 0030 and associated steam and ash that did not rise far above the summit. The eleventh eruptive episode in one month began on 30 June. Inclement weather inhibited visual observations, but during a break in cloud cover around 0400 mild Strombolian activity was observed. Seismic data revealed that the episode ended around 1600. On 3 July increased degassing was observed at Northeast Crater.

Sources: Italy's Volcanoes; Sezione di Catania - Osservatorio Etneo (INGV); Toulouse Volcanic Ash Advisory Centre (VAAC)

20 June-26 June 2001 Cite this Report

During the week two eruptive episodes occurred at Etna's Southeast Crater. On 22 June an eruption began after 3 days of low activity. The eruption was similar to the previous episodes, with lava flowing down the flanks of the volcano prior to Strombolian activity. Volcanic bombs were thrown 300-400 m above the crater and lava fountains reached a maximum height of 150 m. An ash plume rose up to 3 km above the crater. The Toulouse VAAC reported that the ash plume was visible on Sistema Poseidon's Etna webcam for ~2 hours, but not on satellite imagery. The same day very strong degassing was observed at Bocca Nuova crater. On 24 June another eruptive episode lasted more than 2 hours.

Sources: Sezione di Catania - Osservatorio Etneo (INGV); Toulouse Volcanic Ash Advisory Centre (VAAC); Etna Volcan Sicilien (Charles Rivière)

13 June-19 June 2001 Cite this Report

The Italy's Volcanoes website reported that on 13 June, after ~44 hours of low activity, the fourth eruptive episode within in a week began at Southeast Crater. The episode lasted longer and was more intense than the previous three episodes. Lava flowed from a vent on the NNE flank of Southeast Crater cone. During the most intense phase of the eruption lava fountains rose 150-200 m above the NNE flank vent. Strombolian bursts occurred so frequently that they eventually blended into one continuous pulsating fountain that rose up to 400 m. Also bursts periodically sent bombs up to 500 m above the crater rim. A small amount of ash was emitted with many of the stronger bursts. On 15 June another eruptive episode occurred with activity similar to the 13 June episode.

Source: Italy's Volcanoes

6 June-12 June 2001 Cite this Report

According the Italy's Volcanoes website, Etna's Southeast Crater was inactive on 6 June, but the following day volcanic activity commenced with lava flowing from the NNE side of the Southeast Crater cone and Strombolian bursts from the crater's summit vent. By 8 June volcanic activity decreased. A new eruptive episode began at Southeast Crater on 9 June that consisted of lava flows and Hawaiian-style lava fountaining from the NNE flank vent, and Strombolian bursts from the summit vent. Volcanic activity decreased until 11 June when Southeast Crater erupted again with more intense Strombolian activity at the summit vent than in the previous episode, and mild Strombolian activity at the NNE flank vent. A dark, tephra-laden cloud was observed rising from the summit vent, while lava fountains rose ~150 m above the NNE flank vent. The Toulouse VAAC reported that weak volcanic activity was visible on Etna WebCam imagery during 0445-0515. By 12 June no volcanic activity was observed at Southeast Crater.

Sources: Italy's Volcanoes; Reuters; Toulouse Volcanic Ash Advisory Centre (VAAC); Etna Volcan Sicilien (Charles Rivière)

30 May-5 June 2001 Cite this Report

According to the Italy's Volcanoes website, volcanic activity was at similar levels as it has been during the previous few weeks. Lava continued to travel from a vent on the NNE flank of the Southeast Crater cone, and mild, discontinuous Strombolian activity continued at the Southeast Crater's summit vent. Scientists determined that the lava effusion rate was approximately 5-10 cubic meters per second, which is high for Etna. On 31 May mountain guides reported that pressure waves, which were caused by explosions, were observed approximately every 10 minutes and that volcanic bombs were thrown ~100 m above the crater rim. Degassing was observed at Southeast Crater and occurred to a lesser extent at Bocca Nuova crater, but increased at Northeast Crater.

Source: Italy's Volcanoes

23 May-29 May 2001 Cite this Report

According to the Italy's Volcanoes website, through 25 May at Southeast Crater lava continued to flow from a small cone on its NNE flank and mild Strombolian activity continued at its summit vent. Volcanic activity had been relatively regular since a strong eruptive episode began on 9 May.

Source: Italy's Volcanoes

16 May-22 May 2001 Cite this Report

According to the Italy's Volcanoes website, mild eruptive activity continued at Southeast Crater, with persistent lava outflow from a vent on the NNE flank of its cone. Very weak Strombolian bursts occurred at the summit vent of the cone that occasionally sent incandescent bombs up to 100 m above the crater rim.

A Spanish tourist who visited the volcano alone has been missing since 14 May and is presumed dead. The remains of her tent were found on 18 May near the rim of Bocca Nuova crater. Local press sources reported that a rescue team found footprints leading from the tent to the rim of one of the two active pits within the crater, but no prints were found leading back from the pit. It is possible that the tourist was standing on the rim of the pit when a portion of it broke loose.

Source: Italy's Volcanoes

9 May-15 May 2001 Cite this Report

The Italy's Volcanoes website reported that after more than 8 months of minor activity (slow lava flows, degassing, light ash emission, and low-level Strombolian activity), a new episode of vigorous volcanic activity began at Southeast Crater on 9 May. On 6 May active lava flows and explosions were observed launching pyroclasts and lithics onto the volcano's S flank every 7-10 seconds. On 9 May an obvious increase in activity occurred, with Strombolian bursts occurring every few seconds. By 1745 activity further increased and lava fountains rose up to 100 m above the NNE flank fissure while a dense eruption cloud simultaneously rose above the summit vent. Local press sources reported that air traffic was rerouted during the activity. The high level of activity continued at Southeast Crater through at least 14 May and strong degassing occurred at Bocca Nuova crater.

Sources: Italy's Volcanoes; Etna Volcan Sicilien (Charles Rivière)

2 May-8 May 2001 Cite this Report

Sistema Poseidon reported that during 30 April to 6 May degassing occurred at Bocca Nuova, Southeast, and Voragine craters. In addition to degassing, ash was emitted from Bocca Nuova crater, although after 3 May the emissions became more sporadic. Lava continued to flow from the northern vent on Southeast Crater and hornitos were formed in the area.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

25 April-1 May 2001 Cite this Report

According to the Italy's Volcanoes website, activity at Etna's summit craters progressively increased beginning on about 20 April. Lava effusion from a vent on the lower NNE flank of Southeast Crater cone continued, with an increase in the effusion rate on 26 April. Ash vented from Bocca Nuova and light gas was emitted from a vent on the NNE flank of Southeast Crater.

Source: Italy's Volcanoes

18 April-24 April 2001 Cite this Report

Sistema Poseidon reported that during 9-15 April volcanic activity at Etna was similar to the previous week. Strombolian activity continued at Bocca Nuova crater, although by the end of the report period activity decreased in comparison to previous weeks. Lava also continued to flow down the NE flank of Southeast Crater, and degassing continued at Voragine and Northeast craters. The Australian Broadcasting Corporation reported that on about 22 April thirty small earthquakes occurred near Etna, but did not cause any injuries or property damage.

Sources: Sezione di Catania - Osservatorio Etneo (INGV); ABC News - Australian Broadcasting Corporation

11 April-17 April 2001 Cite this Report

Sistema Poseidon reported that during 2-8 April Strombolian activity continued at Bucca Nuova crater. In addition, degassing of the crater was accompanied by ash emissions. Lava continued to flow from a fissure on the NE flank of Southeast Crater. Lava also flowed from a 6-m-high tumulus that formed on the N flank of the volcano at an elevation of approximately 3,095 m. Voragine and Northeast craters continued degassing at low levels.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

4 April-10 April 2001 Cite this Report

According to the Italy's Volcanoes website, volcanic activity at Etna decreased slightly during the week ending on 6 April. The Bocca Nuova crater produced sporadic ash emissions, rather than the Strombolian activity that was observed in March 2001. Lava continued to flow from a vent low on the NNE flank of the Southeast Crater cone, as it has since approximately 20 January 2001.

Source: Italy's Volcanoes

28 March-3 April 2001 Cite this Report

According to the Italy's Volcanoes website, volcanic activity continued at Etna through the end of March. Continuous Strombolian activity was observed at a pit in Bocca Nuova Crater. Lava continued to slowly flow from the NNE flank of the Southeast Crater.

Source: Italy's Volcanoes

7 March-13 March 2001 Cite this Report

According to the Italy's Volcanoes website, during the first half of March mild, but occasionally vigorous eruptive activity continued at Etna's summit craters much like it has since mid January. Near-continuous Strombolian activity continued at two vents in Bocca Nuova Crater and Strombolian activity intermittently occurred within the central pit of the Northeast Crater. Short lobes of lava continued to form after slowly emerging from a vent on the NNE flank of the Southeast Crater cone.

Source: Italy's Volcanoes

28 February-6 March 2001 Cite this Report

According to the Italy's Volcanoes website, during late February fluctuating eruptive activity continued at Etna's summit craters. Strombolian activity continued at two vents in Bocca Nuova Crater and within the central pit of Northeast Crater. In addition, lava continued to slowly flow from the NNE flank of the Southeast Crater.

Source: Italy's Volcanoes

21 February-27 February 2001 Cite this Report

According to the Italy's Volcanoes website, on 20 February slow lava extrusion continued from a vent on the NNE flank of the Southeast Crater cone. Mild eruptive activity continued from the Bocca Nuova Crater, with Strombolian bursts from two vents on the NW and E parts of the crater. During 18-20 February, a slight increase in activity was observed at the Bocca Nuova Crater.

Source: Italy's Volcanoes

14 February-20 February 2001 Cite this Report

According to the Stromboli On-Line website, on 12 February a Stromboli On-Line research group observed lava flowing from the Southeast Crater's NE fissure as it has since late January. Lava and gas were emitted from a small tumulus in strong pulses and flowed several hundred meters into Valle Leone. On 14 February Voragine and Northeast craters were observed emitting steam and Strombolian activity occurred at both of Bocca Nuova Crater's vents. The Strombolian activity at the Bocca Nuova's NW vent was irregular and occasionally reached at least the height of the crater rim. Strombolian activity at the Bocca Nuova's SE vent was more vigorous with eruptions every few seconds. The explosions were directed roughly vertically and volcanic bombs reached up to several hundred meters above the crater rim.

Source: Stromboli On-Line

31 January-6 February 2001 Cite this Report

According to the Italy's Volcanoes website, since 20 January lava has continuously issued at a low but persistent rate from a vent on the NNE flank of the Southeast Crater. The lava formed a small field of overlapping and adjacent flows that extend a few hundred meters. At Bocca Nuova Crater Strombolian activity increased, with ejecta being thrown above the crater rim.

Source: Italy's Volcanoes

24 January-30 January 2001 Cite this Report

Sistema Poseidon reported that during 22-28 January, eruptive activity at Etna was dominated by modest, intermittent lava flows that were emitted from the radial fracture on the N flank of the Southeast Crater. The Bocca Nuova Crater mostly produced ash-and-gas emissions during the beginning of the report period, but they decreased near the end of the period. At night, weak Strombolian activity was observed inside the crater. Limited gas emissions were released from the Northeast and Voragine craters.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

17 January-23 January 2001 Cite this Report

According to Italy's Volcanoes website, volcanic activity increased at Etna. On 15 January intense degassing occurred at the Bocca Nuova and SE craters. On 16 January, weak Strombolian bursts occurred at 5- to 10-minute intervals at the summit vent of the SE Crater and strong gas emissions with occasional ash were released from Bocca Nuova Crater. On 21 and 22 January an active lava flow was visible extending from a fissure on the N flank of SE Crater, but no explosive activity was observed.

Sources: Italy's Volcanoes; Sezione di Catania - Osservatorio Etneo (INGV)

10 January-16 January 2001 Cite this Report

There has been no new eruptive activity at the summit craters of Etna since early December. Beginning on 7 January 2001, degassing from Bocca Nuova became more rhythmic, indicating some deep explosive activity. On 11 January gas emissions from the Bocca Nuova became more intense and came in distinct puffs. Southeast Crater continued to emit heat; an incandescent fumarole remained high on its SE flank, and snow rapidly melted on the S and E flanks of the cone. During the early morning of 9 January 2001, significant seismicity affected the SE flank, shaking villages and towns including Catania. Tens of thousands of people were woken by the strongest event (M 3.5, MM V). The seismic crisis ended that same day after more than 50 shocks had been registered by the monitoring network. At least three of the earthquakes measured M 3.0 or more, and several were felt by the population of a large area between Nicolosi, Fornazzo, and Catania. Cracks opened in the walls of numerous buildings, but only one uninhabited building in Zafferana partially collapsed.

Source: Italy's Volcanoes

20 December-26 December 2000 Cite this Report

Volcanic activity at Etna was low during December, with low gas emission at the SE Crater throughout the month and a few isolated Strombolian events at the Bocca Nuova crater in mid-December.

Sources: Italy's Volcanoes; Sezione di Catania - Osservatorio Etneo (INGV)

29 November-5 December 2000 Cite this Report

According to Italy's Volcanoes website, lava emission continued from both vents in the Bocca Nuova Crater with variable intensity. On 30 November observations revealed that after 3 months of low activity a small lava flow issued from the NNE fissure in the SE Crater. Lava extrusion was accompanied by strong degassing, but there was no explosive activity.

Sources: Italy's Volcanoes; Sezione di Catania - Osservatorio Etneo (INGV)

22 November-28 November 2000 Cite this Report

According to the Italy's Volcanoes website, Italian press sources reported that a new burst of seismic activity occurred near Etna's NNW flank on 19-21 November. The earthquakes were thought to be of tectonic origin. During the week mild eruptive activity continued at the Bocca Nuova crater as it has for several weeks, and incandescence was noted at the NE and SE Craters.

Sources: Italy's Volcanoes; Sezione di Catania - Osservatorio Etneo (INGV); Stromboli On-Line

8 November-14 November 2000 Cite this Report

According to the Italy's Volcanoes website, during the week mild Strombolian activity continued at the Bocca Nuova Crater. The overall level of activity appeared to be generally lower than the previous week.

Sources: Italy's Volcanoes; Sezione di Catania - Osservatorio Etneo (INGV); Stromboli On-Line

1 November-7 November 2000 Cite this Report

According to the Italy's Volcanoes website, volcanic activity continued to fluctuate at Bocca Nuova Crater, varying from explosions to effusive lava flows as it has for several weeks. The Bocca Nuova Crater is Etna's southwestern-most crater and explosive activity was observed at its NW and E vents. In addition, incandescence was visible on the upper SE flank of the Southeast Crater cone. In related news, at 1826 on 5 November a M 3.6 earthquake occurred in eastern Sicily. The earthquake's epicenter was located near Monte Vetore, a prehistoric pyroclastic cone on Etna's S flank. In press reports Poseidon scientists interpreted the earthquake as being purely tectonic.

Sources: Italy's Volcanoes; Stromboli On-Line; Sezione di Catania - Osservatorio Etneo (INGV); La Sicilia

Bulletin Reports - Index

Reports are organized chronologically and indexed below by Month/Year (Publication Volume:Number), and include a one-line summary. Click on the index link or scroll down to read the reports.

06/1968 (CSLP 11-68) Explosive activity on 16 June follows two months of lava flows

07/1968 (CSLP 11-68) New lava flow and crater explosions; 16 June activity was a tectonic earthquake, not an explosion

07/1969 (CSLP 11-68) Report of activity during a week of fieldwork at Bocca Nuova

10/1969 (CSLP 11-68) Review of typical activity; diagram of Northeast Crater

04/1971 (CSLP 33-71) New craters, cones, and lava flows; lava surrounds observatory

05/1971 (CSLP 33-71) Additional vents and fissures open; very active lava flows

06/1971 (CSLP 33-71) Crater enlargements; corrections to previous reports

09/1971 (CSLP 33-71) Activity starts again after 100 days of quiescence

12/1971 (CSLP 33-71) Periodic explosions from La Voragine crater

02/1974 (CSLP 20-74) W-flank eruption rapidly builds cone; explosions and lava flows

03/1974 (CSLP 20-74) New vent SW of the 1974 cinder cone opens on 10-11 March

10/1974 (CSLP 20-74) Lava lake drains and lava flows about 1 km

02/1975 (CSLP 10-75) Eruption on NW flank produces spatter cones and lava flows

03/1975 (CSLP 10-75) New eruptive center on the North Rift zone

11/1975 (NSEB 01:02) Continuous activity for most of 1975; new lava vent

05/1976 (NSEB 01:08) Lava eruption stops in mid-May

06/1976 (NSEB 01:09) Explosions from Bocca Nuova and The Chasm; lava flows on N-flank

07/1977 (NSEB 02:07) Lava effusion and explosive activity from a new vent

08/1977 (NSEB 02:08) Two eruptions in August generate fountaining and lava flows

11/1977 (NSEB 02:11) Eruption from the NE crater, the fourth since mid-July

12/1977 (NSEB 02:12) Frequent eruptions from Northeast Crater continued into January

03/1978 (SEAN 03:03) New lava flow and ash on 25 March

04/1978 (SEAN 03:04) First SE flank activity since 1971

05/1978 (SEAN 03:05) SE-flank eruption continues through May

06/1978 (SEAN 03:06) SE-flank eruption ended by 14 June

07/1978 (SEAN 03:07) Persistent SE flank activity resumes 26 May-5 June

08/1978 (SEAN 03:08) New SE flank eruption

09/1978 (SEAN 03:09) SE flank eruption ends; occasional central crater explosions continue

11/1978 (SEAN 03:11) New SE-flank eruption

07/1979 (SEAN 04:07) Eruption from summit and SE flank

08/1979 (SEAN 04:08) Lava extrusion from several SE flank vents; ashfall to 70 km away

09/1979 (SEAN 04:09) Nine killed and 23 injured by explosion

10/1979 (SEAN 04:10) Thermal anomaly on SE flank

01/1980 (SEAN 05:01) Reduced thermal anomaly; small ash eruption

02/1980 (SEAN 05:02) Red glow in SE crater

04/1980 (SEAN 05:04) Explosions from summit and SE craters; thermal anomaly on S flank

05/1980 (SEAN 05:05) Incandescent tephra ejected; temperature anomaly on S flank

07/1980 (SEAN 05:07) Incandescent tephra ejection; decreased gravity readings

08/1980 (SEAN 05:08) Two one-day eruptions

09/1980 (SEAN 05:09) Ashfall to coast; lava flow; bombs

02/1981 (SEAN 06:02) Explosions and lava flow from Northeast Crater

03/1981 (SEAN 06:03) Large lava flows cause severe damage

04/1981 (GV11 81:04) Photograph from Space Shuttle

07/1981 (SEAN 06:07) Ash ejection, probably caused by central crater collapse

09/1981 (SEAN 06:09) Collapse in the central crater; ash ejection

10/1981 (SEAN 06:10) Small plumes on satellite images

12/1981 (SEAN 06:12) Collapse continues in central crater; ash plumes

05/1982 (SEAN 07:05) Small central crater explosions follow earthquakes and higher ground temperatures

07/1982 (SEAN 07:07) Eruption cloud; lava in main crater

09/1982 (SEAN 07:09) Strombolian activity on central crater floor

11/1982 (SEAN 07:11) Small explosions, but tephra to 12 km

12/1982 (SEAN 07:12) Incandescent tephra from central crater

03/1983 (SEAN 08:03) Lava from S-flank fissure; central crater enlarged

04/1983 (SEAN 08:04) Lava effusion continues; central crater explosions; deformation, temperature and self-potential data

05/1983 (SEAN 08:05) Lava production slows; lava partially diverted; central crater explosions continue; self-potential data

06/1983 (SEAN 08:06) Lava production continues but at lower rate; central crater explosions; lava temperatures

07/1983 (SEAN 08:07) Eruption ends after four months of lava extrusion

08/1983 (SEAN 08:08) No new activity

01/1984 (SEAN 09:01) Incandescent tephra from central crater; seismicity

04/1984 (SEAN 09:04) Strombolian activity and small lava flows from Southeast Crater

05/1984 (SEAN 09:05) Continued lava production; Strombolian activity

06/1984 (SEAN 09:06) Explosions and lava production continue from Southeast Crater; central crater explosions

07/1984 (SEAN 09:07) Lava production and Strombolian activity continue from Southeast Crater; strong explosions from Central and Northeast craters

08/1984 (SEAN 09:08) Lava production and ash emission continue

09/1984 (SEAN 09:09) Lava flows, Strombolian activity and ash emission

10/1984 (SEAN 09:10) Earthquake swarm starts as lava production ends

11/1984 (SEAN 09:11) Occasional ash emission; flank seismicity continues

02/1985 (SEAN 10:02) Seismicity, then Strombolian activity and lava flows from Southeast Crater; ashfall on coast towns

03/1985 (SEAN 10:03) S-flank fissure eruption preceded by seismicity and tilt

04/1985 (SEAN 10:04) South-flank lava production continues; tremor energy increases

05/1985 (SEAN 10:05) Lava flows toward SW and SE; strong gas and vapor emissions

06/1985 (SEAN 10:06) Continued S-flank lava production

07/1985 (SEAN 10:07) Four-month eruption ends in mid-July

12/1985 (SEAN 10:12) SE-flank fissure eruption follows seismic swarm and deformation

01/1986 (SEAN 11:01) Strong flank seismicity

02/1986 (SEAN 11:02) Ash and bombs from Northeast Crater

05/1986 (SEAN 11:05) Strombolian activity and gas emission

09/1986 (SEAN 11:09) Strombolian activity and lava flow, then strong explosion

10/1986 (SEAN 11:10) Lava flows and Strombolian activity from SE fissures and crater

11/1986 (SEAN 11:11) Fissure eruption continues

12/1986 (SEAN 11:12) Lava flows; Strombolian activity; ash emission

01/1987 (SEAN 12:01) Lava flows in tubes; Strombolian activity and seismicity decline

02/1987 (SEAN 12:02) 120-day eruption ends

04/1987 (SEAN 12:04) Phreatic explosions from Southeast Crater kills two, injures seven

03/1988 (SEAN 13:03) Inflation and seismicity

01/1989 (SEAN 14:01) Strombolian activity from summit craters: inflation

05/1989 (SEAN 14:05) Explosions from summit craters; small lava flow; high SO₂

06/1989 (SEAN 14:06) Summit explosive activity

07/1989 (SEAN 14:07) Summit Strombolian activity; little deformation in past year

08/1989 (SEAN 14:08) Explosions and lava flows; tephra reaches the coast

09/1989 (SEAN 14:09) Strong tephra emission; lava fountains >1 km; lava flows

10/1989 (SEAN 14:10) Details of September-October eruption

11/1989 (SEAN 14:11) Summit tephra emission; strong, fluctuating SO₂ emission

12/1989 (SEAN 14:12) Southeast Crater explosive activity drops tephra on nearby towns

01/1990 (BGVN 15:01) Renewed Southeast Crater Strombolian activity; flank tephra fall and small lava flows; increased seismicity and SO₂

03/1990 (BGVN 15:03) Lava fountains and flow then strong block ejection from Southeast Crater

10/1990 (BGVN 15:10) Strombolian activity and lava fountaining from central craters; earthquakes and tremor; deformation

03/1991 (BGVN 16:03) Periodic summit explosions; brief earthquake swarms; deformation

05/1991 (BGVN 16:05) Strong degassing

07/1991 (BGVN 16:07) Strombolian activity and continued strong degassing

09/1991 (BGVN 16:09) Summit-area Strombolian activity apparently ends; continued degassing

10/1991 (BGVN 16:10) Minor Strombolian activity from several summit-area vents; little deformation

11/1991 (BGVN 16:11) Brief SE-flank fissure eruption

12/1991 (BGVN 16:12) Lava from SE-flank fissures covers about 5 km²; barrier constructed

01/1992 (BGVN 17:01) Lava production continues from SE-flank fissure but explosive activity declines

02/1992 (BGVN 17:02) Continued flank lava production

03/1992 (BGVN 17:03) Lava production continues from SE-flank vent; town threatened by lava flow

04/1992 (BGVN 17:04) SE-flank fissure eruption continues; lava diversion attempted

05/1992 (BGVN 17:05) Fissure eruption continues; lava diverted; lava field described

06/1992 (BGVN 17:06) Continued flank lava production

07/1992 (BGVN 17:07) Continued lava production from SE-flank fissure; lava diversion summarized

08/1992 (BGVN 17:08) Increased lava emission from break in main tube

09/1992 (BGVN 17:09) Lava flows from tube system remain within 1991-92 lava field

10/1992 (BGVN 17:10) More vigorous lava production and gas emission

11/1992 (BGVN 17:11) Lava emerges from tubes onto 1991-92 lava field; small summit ash ejections

12/1992 (BGVN 17:12) Continued lava production; summit degassing

01/1993 (BGVN 18:01) Continued lava production extends lava field; summit degassing; low seismicity

02/1993 (BGVN 18:02) Lava flows continue; volume estimates reported

03/1993 (BGVN 18:03) 1991-93 eruption ends

04/1993 (BGVN 18:04) Steady degassing; seismicity low

05/1993 (BGVN 18:05) Steady degassing continues; seismic swarm

03/1994 (BGVN 19:03) Summary of activity since the end of the 1991-1993 eruption

07/1994 (BGVN 19:07) Explosive degassing from La Voragine; fumarole temperatures reported

10/1994 (BGVN 19:10) Minor explosive degassing and higher fumarole temperatures

06/1995 (BGVN 20:06) Small explosions in May followed by larger ash plumes in June

07/1995 (BGVN 20:07) Gas-and-ash explosions followed by sustained Strombolian activity in late July

08/1995 (BGVN 20:08) Magmatic activity resumes in Bocca Nuova and Northeast craters

09/1995 (BGVN 20:09) Ash emissions and another episode of Strombolian activity from the summit craters

10/1995 (BGVN 20:10) Frequent Strombolian explosions and ash emissions from Northeast Crater and Bocca Nuova

12/1995 (BGVN 20:11) Six lava fountaining episodes from Northeast Crater

02/1996 (BGVN 21:02) Two additional significant eruptive episodes during January-February

03/1996 (BGVN 21:03) Intermittent ash emissions and Strombolian activity from two summit craters

06/1996 (BGVN 21:06) Crater glow, gas emissions, and mild Strombolian eruptions

07/1996 (BGVN 21:07) Crater glows, Strombolian eruptions, and two fire fountaining episodes

10/1996 (BGVN 21:10) Southeast Crater resumes activity after five-years

02/1997 (BGVN 22:02) Summary of activity since November 1996

05/1997 (BGVN 22:05) New map of the craters Voragine and Bocca Nuova

06/1997 (BGVN 22:06) Summary of April-June 1997 activity

07/1997 (BGVN 22:07) Continued activity from three craters through mid-July; crater descriptions

08/1997 (BGVN 22:08) Strombolian activity and lava overflows; all four summit craters active

09/1998 (BGVN 23:09) Summary of summit eruptive activity during August 1997-January 1998

10/1998 (BGVN 23:10) Summary of eruptive activity from summit craters during January-May 1998

11/1998 (BGVN 23:11) Summary of eruptive activity from summit craters during June-September 1998

12/1998 (BGVN 23:12) Episodic eruptions from Southeast Crater during October-December

02/1999 (BGVN 24:02) Extensive lava flows discharging from a 4 February fissure on the SE flank

03/1999 (BGVN 24:03) Additional details of mid-October 1998 activity at Southeast Crater

05/1999 (BGVN 24:05) Lava emission continues through May from Southeast Crater into the Valle del Bove

06/1999 (BGVN 24:06) Lava-flow temperature measurements

09/1999 (BGVN 24:09) Summary of June-September activity; powerful eruption from the Voragine on 4 September

11/1999 (BGVN 24:11) Vigorous eruptions at Bocca Nuova send lava flows 5 km down the W flank

03/2000 (BGVN 25:03) Frequent eruptions in early 2000 discharging lava flows at new vents and fissures

06/2000 (BGVN 25:06) Frequent Strombolian eruptions and high gas emissions March-June 2000

09/2000 (BGVN 25:09) Additional descriptions of April-May eruptions and an aircraft damaged by tephra-fall

12/2000 (BGVN 25:12) Summary of July to November 2000 notes small lava flows, Strombolian eruptions

05/2001 (BGVN 26:05) Strombolian activity and lava flows during January-April 2001

06/2001 (BGVN 26:06) 9 April-13 May activity punctuated by Strombolian eruption on 9 May

08/2001 (BGVN 26:08) Strombolian activity during May and June 2001

09/2001 (BGVN 26:09) Strong June eruptions, a M 3.9 earthquake, copious July-August flank lavas, and a new cone

10/2001 (BGVN 26:10) Amphibole megacrysts from the 2001 S-flank eruption

03/2002 (BGVN 27:03) Overview of Etna's much-photographed July-August 2001 flank eruption

04/2002 (BGVN 27:04) Nine months of relative quiet follow mid-2001 flank eruption

08/2002 (BGVN 27:08) Generally weak activity at summit craters during mid-May through July 2002

10/2002 (BGVN 27:10) A flank eruption started on 27 October; lava vented at N- and S-flank fissures

11/2002 (BGVN 27:11) Witnesses saw N- and S-flank eruptions begin at around 0200 on 27 October

12/2002 (BGVN 27:12) Late October 2002 earthquake swarm signals start of new flank eruption

01/2003 (BGVN 28:01) Flank eruption that began in October ends on 28 January

02/2003 (BGVN 28:02) Petrographic and geochemical comparison of 2001 and 2002 lavas

08/2003 (BGVN 28:08) Ash emissions during April from Bocca Nuova; volcanic seismicity and ash puff on 11 August

12/2003 (BGVN 28:12) September-November 2003 volcanism low; web camera and satellites depict small plumes

01/2004 (BGVN 29:01) Additional details and interpretation of the 2002-03 eruption; space-based photographs

03/2004 (BGVN 29:03) Ashfall with juvenile components, emitted gases, and seismic patterns imply magma ascent

09/2004 (BGVN 29:09) New effusive eruption begins on 7 September and spreads to several fissure vents

01/2005 (BGVN 30:01) 7 September eruption continues on W wall of Valle del Bove, includes lava tubes, multiple vents

12/2005 (BGVN 30:12) Late degassing, summit explosion and ash release in December 2005

07/2006 (BGVN 31:07) An upper E-flank fissure eruption lasting from 14 to 24 July 2006

08/2006 (BGVN 31:08) Changes in morphology of SE Crater and the emission of lava flows to the SSE

10/2006 (BGVN 31:10) Lava flows from multiple vents during 22 September to 4 November

12/2006 (BGVN 31:12) Changing lava chemistry after 24 October 2006

02/2007 (BGVN 32:02) Episodes of eruptions continue between 4 November and 14 December 2006

03/2007 (BGVN 32:03) Eruptions continue in April 2007

07/2007 (BGVN 32:07) Ash emissions started 15 August and built a small cinder cone on SEC's E flank

08/2007 (BGVN 32:08) Explosive activity and lava fountains during 4-5 September 2007

09/2007 (BGVN 32:09) 4-5 September eruption emitted long-duration fountains; lava flows extend 4.6 km

01/2008 (BGVN 33:01) Tall sustained lava fountains, lava flows, and tephra blanket on 22-24 November 2007

05/2008 (BGVN 33:05) 6-km-long lava flow; ash emissions; 13 May 2008 opening of a new eruptive fissure

05/2011 (BGVN 36:05) Ongoing effusive fissure eruption that began on 13 May 2008 ends on 4 July 2009

02/2012 (BGVN 37:02) Sporadic summit activity and pit crater collapse in late-2009 and 2010

09/2013 (BGVN 38:09) 46 paroxysms and birth of the New Southeast Crater (NSEC)

11/2014 (BGVN 39:11) January–13 June 2014: NSEC emits lava and 11 Feb landslide with ground-hugging reddish cloud

02/2015 (BGVN 40:02) Strombolian eruptions, ash emissions, and new effusive vents through February 2015

05/2017 (BGVN 42:05) Major eruptions with lava fountains, ash plumes, and lava flows during January-February, May, and December 2015

09/2017 (BGVN 42:09) Lava flows during May 2016 followed by new fracture zones and major subsidence at the summit craters

10/2017 (BGVN 42:10) Extensive lava flows during February-May 2017; new summit crater emerges

04/2018 (BGVN 43:04) Persistent degassing from multiple vents; minor ash emissions and pyroclastic ejecta, September 2017-March 2018

08/2018 (BGVN 43:08) Degassing continues, accompanied by intermittent ash emissions and small Strombolian explosions in June and July 2018

12/2018 (BGVN 43:12) Lava flows emerge from NSEC in late August and late November 2018; Strombolian activity continues from multiple vents

04/2019 (BGVN 44:04) Lava flows from NSEC scoria cone and SE flank fissure in December 2018; ash emissions through March 2019

10/2019 (BGVN 44:10) Five lava flows and numerous ash plumes and Strombolian explosions, April-September 2019

04/2020 (BGVN 45:04) Strombolian explosions and ash emissions continue, October 2019-March 2020

09/2020 (BGVN 45:09) Effusive activity in early April; frequent Strombolian explosions and ash emissions during April-July 2020

12/2020 (BGVN 45:12) Strombolian explosions and ash plumes persist from multiple craters during August-November 2020

04/2021 (BGVN 46:04) Frequent explosions, ash plumes, fountaining, and lava flows during December 2020-March 2021

08/2021 (BGVN 46:08) Strombolian explosions, ash plumes, lava fountaining, and flows during April-July 2021

03/2022 (BGVN 47:03) Strombolian activity, ash emissions to 10 km altitude, and lava flows at SEC through January 2022

07/2022 (BGVN 47:07) Lava flows, pyroclastic flows, Strombolian explosions, and ash plumes during February-June 2022

03/2023 (BGVN 48:03) New vents and lava flows during November 2022-February 2023

08/2023 (BGVN 48:08) Intermittent Strombolian activity, lava flows, and ash plumes during March-June 2023

Information is preliminary and subject to change. All times are local (unless otherwise noted)

June 1968 (CSLP 11-68)

Explosive activity on 16 June follows two months of lava flows

Notification Report (16 June 1968) Explosive eruption follows two months of lava flows

Eruption accompanied by two sharp earth tremors, clouds of dense black smoke. Additional information obtained from UPI dispatch, 1948 EST: Streams of red-hot lava on Etna for last two months. Today's tremors registered II on XII-point Mercalli scale (with IV registered in some villages) and second tremor, less than two hours later, registered between VI and VII. Eruption location undetermined because of heavy clouds.

Information Report 1 (18 June 1968) Explosions and lava flow from Northeast Crater

"Current Etna activity scarce. Medium explosive activity from Northeast Crater. Seven-hundred-meter-long lava tongue from new opened vent below Northeast Crater."

Information Contacts:
Notification Report (16 June 1968) BBC (via Paul Mohr); UPI.
Information Report 1 (18 June 1968) F. Cugusi, Rome, Italy.

July 1968 (CSLP 11-68)

New lava flow and crater explosions; 16 June activity was a tectonic earthquake, not an explosion

Information Report 2 (17 July 1968) "A new lava flow, accompanied by crater explosions every three seconds, is creeping down the slopes of Mount Etna, but there is no danger to villages on the mountain."

Information Report 3 (24 July 1968) The following report, clarifying the activities of Mt. Etna during the last months, has been received from Dr. Rittman. Seismic activity, reported to have taken place at Mt. Etna on 16 June 1968, actually was an earthquake of tectonic origin and was not related to Etna's activity.

"Since January 1968 Mt. Etna is in persistent activity with the usual fluctuations, due to oscillations of the dynamic equilibrium between the gas tension of the magma and the hydrostatic pressure of the magma column in th eopen vent. The NE-Crater ejects at intervals clots of glowing lava up to 250 m above the crater rim. Sporadically small flows of gas-poor lava issue from small sub-terminal boccas and may reach ont or two km of length. These more or less spectacular events can continue for months and years without reaching any paroxysmal climax.

"In contrast with such persistent activity, real eruptions are short lived violent events followed by a period of exhaustion... On 16th June 1968 there was no eruption at Mt. Etna... (but) a weak precursory shock was registered at 3 o'clock 54 minutes. A second, stronger one at 14h 10m. At 15 o'clock 3 minutes 34 seconds happened the third, very important shock (followed after two seconds by a similar one). The magnitude of this 3rd shock was M = 5.7 to 5.8. Epicenter: at 37.75°N Lat. 14.5°E Long. Hypocenter: at a depth between 50 and 60 kilometers. This earthquake is surely of tectonic origin and has nothing to do with the activity of Mt. Etna which lies more than 40 km to the E from the epicenter. Th islies on the southern slope of the Mts. Nebrodi, about 65 km from Catania and 100 km from Messina.

"Also Mt. Etna was shaken to such a degree that loose material on the inner slope of the crater have glided down into the vent, causing a cloud of dust which has been mistaken for an eruptive ash cloud."

Information Contacts:
Information Report 2 (17 July 1968) A. Rittman, Geophysical Institute of Catania, Sicily, Italy.
Information Report 3 (24 July 1968) A. Rittman, Geophysical Institute of Catania, Sicily, Italy.

July 1969 (CSLP 11-68)

Report of activity during a week of fieldwork at Bocca Nuova

Card 0656 (10 July 1969) Report of activity during a week of fieldwork at Bocca Nuova

Our mission of nine scientists and a 12-man support team, spent 7 days at the Bocca Nuova experimenting new devices to continuously measure and record the values of temperature, pressure and speed of the gases; chemical determinations, closely grouped (separated by the order of 10 seconds from one another), provided curves of the variations of the different constituents of the gas phase. Some figures can be given a indicative of the very rare phenomenon presented by this blow-hole: temperatures varied from ~800 to 1,100°C, speed from zero to ~20% in weight, CO₂ content from 4 to 60%. The permanently eruptive state of Mt. Etna is presently characterized by: 1) lava fountaining in the NE crater with "bombs" hurled up to 250 m above the crater rim from any of the three vents opened in the bottom. 2) lava flows being poured out from a fissure opened on the W side of the NE cone; lava supplies vary up to 10 or 12 m³/s the flows do not exceed 1 km in length. 3) lava fountaining in the bottom of the deep (>400 m) main crater pit (so-called "la voragina"). 4) hot (>800°C) gas rhythmic activity at the June 1969 born blow-hole (so-called Bocca Nuova) on the west side of the cone containing "la voragina."

Information Contacts: Haroun Tazieff, Paris, France; Centre National de la Recherche Scientique, France; Commissariat a L'Energie Atomique, France; Office National d'Etudes et Recherches Aerospatiales, France.

October 1969 (CSLP 11-68)

Review of typical activity; diagram of Northeast Crater

Card 0777 (06 October 1969) Review of typical activity; diagram of Northeast Crater

Since January 1967, Mt. Etna (figure 1) is in persistent activity. This activity can be observed if the vent of the volcano is open (the NE Crater of Mt. Etna) and the column of the fluid magma stands high in it. The gases escape through the crater producing intermittent explosions by which spatters and lumps of liquid lava are thrown in the ai sometimes as high as about 200 m. This explosive activity undergoes strong fluctuations in intensity. The intervals between consecutive explosions vary between a few seconds to many hours and even some days. It happens that during a long interval the scories lying on the inner slopes of the funnel glide down and cover the surface of the lava lake within the vent. For a while, only "smoke" issues quietly from the crater, till a new, somewhat stronger explosion throws the detritus our in the form of an "ash clouds" (crumbled scories but no real "ash"), and the usual persistent activity begins again, presenting often impressing spectacle, particularly at night.

Figure 1. Sketch showing the Northeast Crater at Etna. 1) Magma column with 2-phase convection; 2) Intermittent explosive activity; 3) Intrusion of epimagma into the cone; 4) Subterminal effusive bocca; 5) Partly consolidated lava cake; 6) Secondary effusive bocca (ephemeric); 7) Small subterminal lava flow (ephemeric). Courtesy of S. Rittman.

It seems that some tourists observed the opening of a new "bocca" on the lower slopes of the NE Crater and believed that they were seeing the beginning of a new eruption, not knowing that during the normal persistent activity such ephemeral secondary boccas form very often – if the magma column stand high in the vent – and die out in a few days. In this case the degassing takes place at the surface of the magma column where trains of rising bubbles explode at intervals, throwing spatters out of the crater. The degassed epimagma descends along the wall of the vent while the foaming pyromagma rises in its central part. During the 2-phase-convection, the hydrostatic pressure may cause an intrusion of the epimagma between the strata of the more or less welded spatter and cinder cone of the NE Crater. At a certain distance form the vent, the increasing hydrostatic pressure in the downwards tended intruding epimagma becomes higher than the load and the resistence of the overlaying strata which are then uplifted giving way to the epimagma to the surface. A bocca forms without any explosive activity and the lava flows out quietly. Such a subterminal effusion is a common feature of the persistent activity of Mt. Etna. These small lava flows cool down rapidly and are covered by a slightly socriasceous glassy crust, under which the liquid lava continues to flow in a tunnel.

Fluctuations in the supply of epimagma, due to oscillations of the magma level in the vent, cause the formation of new lava channels and the ceasing of the former ones. In time, a great lava cake will form, covered by a consolidated crust. Here and there through this crust new secondary boccas are formed, from which ephemeral small lava flows are poured out. Such an activity may last for months and even for years without any paroxismal climax, i.e., without a true eruption, characterized by its violent character and by a following period of exhaustion with almost only fumarolic activity.

The only particular aspect of the actual activity of Mt. Etna is the existence of a large blow hole at the western part of the central crater from which, at short intervals, roaring gases escape violently. My friend and collaborator, Tazieff, with a team of specialists are studying this event carefully using new equipment which permits measurement of temperature, pressure and the speed and composition of the gases. All the qualities very widely within very short time intervals. The maximum temperature measured was 1070°C. During the night, large flames of burning gases are seen. Tazieff and his team will come to Catania within a few days to continue their research."

Information Contacts: S. Rittman, Institut Internazionale Ricerche Vulcanologiche, Italy.

April 1971 (CSLP 33-71)

New craters, cones, and lava flows; lava surrounds observatory

Card 1167 (06 April 1971) Lava flows from fissure approach observatory

"A fissure opened a little above and halfway between the Volcano Observatory and the water condensation fumaroles. Lava flows, comparatively wide and swift, have almost reached the Observatory. Two points of emission and strong degassing craters on these fissures are delivering huge quantities of scoria and cinders with thunderous noise. The altitude of the activity is approximately 3,000 m. A party of six volcanologists will be there for field investigations on 7 April."

Card 1169 (08 April 1971) Activity from two radial fractures; three new cones built

Mount Etna thundered in new activity on 8 April 1971. Half a million persons watched to see whether it would threaten them. "For now it is not possible to determine whether the phenomenon will pose a threat to the countryside and the cities", said Swiss volcanologist A. Rittman, chief of the Volcanological Institute Center. The University of Catania Volcanological Institute said each of two radial fractures of the volcano's surface opened since 6 April near the 9,700-foot [(2,950-m)] level had 10 or 12 explosive centers hurling burning rock, ash, and steam into the air, and pushing molten lava down the mountainside. A report on 7 April said the more westerly of the two centers of activity already had thrown up three volcanic cones which were about 65 feet high. "It is the center of a violent uninterrupted explosive activity throwing hunks of lava and incandescent rock mor that 650 feet into the air accompanied by thunderous explosive noises." Lava flow from that eruption has surrounded three sides of the Volcanological Observatory, perched a half mile from Etna's main crater at 9,679 feet. The Etna cableway was halted because lava surrounded several of its supporting pillars. Etna's upper slopes are bare or snow-covered, but the rich soil of the lower elevations yields bountiful fruit and vegetable crops and has one of the highest population densities. The triangle between Catania, Nicolosi, and Acierale on Etna's southern flank supports more than 3,200 persons per square mile.

Card 1170 (12 April 1971) Very active lava flows almost surround observatory

Two apparently radial fractures ~200 m apart; the W one 100 m long from 3,000 m elevation, the E one 100 m long from ~3,100 m elevation (figure 2). Presently two lava flows issuing from E fissure proceed ~3 km down W slope of Valle del Bove. One lava flow is presently flowing out lower end W fissure. It is fed by a small fountaining breached spattercone; its speed ~2 m/s, width 10-12 m, thickness up to our knees. One offshoot of western flow is leaning against north, east, and western walls of University of Catania Observatory. Other lava offshoots seriously threaten cableway. Length evening 8 April about 2 km with lava thickness 2-10 m, heights reached by observable molten lumps up to 300 m, speeds up to 200 m/s. Central crater big chasm and usually actively erupting; bocca nordest presently quiet and filled by whitish sulphur oxide smelling fumes.

Figure 2. Photograph of the eastern fracture and lava fountains at Etna, 7 April 1971. Courtesy of Haroun Tazieff. [Originally published in the CSLP 1971 Annual Report].

Card 1171 (12 April 1971) About 150,000 m² were covered by noon on 6 April

Maximum temperature estimated ~1,030°C. volume emitted lava about 10-20 m³/s. Area covered at noon 6 April about 150,000 m². Prevailing winds were ~100 km/hour in strength from northwest direction carrying volcanic gases plus steam from snow and condensed atmospheric water plus ash from both volcanic and phreatic explosions. 10 April: Activity continues, heavy fog prevents observations.

Card 1173-1174 (19 April 1971) Lava covers 1 km² by 17 April; observatory and cableway damaged

"This is a report of the eruption between 15 April and 17 April. The two radial fractures are covered by lava flows. On the place of the E fracture, there is a single volcanic cone now 70 m high. There were violent explosions about every 20 minutes. At the foot of the active center there is a small cone delivering hot steam. Some ten meters below there is a vent with a lava flow which was going toward the Valle del Bove with a speed of 1 m/hour. This lava flow stopped Friday morning 16 April. The water condensation fumarole is preserved by the lava. The activity has momentarily stopped on the eastern sector fracture zone.

"On the place of the W fracture there are now two big cones, 40 m high on a N-S direction throwing incandescent rocks more than 200 m high. The southern one has on it flank a vent emitting 1 m³ of lava per second. This lava flow, after having entirely destroyed the observatory, has surrounded four pylons of the cableway, and the cable was broken by the lava Thursday morning, 15 April. The lava flow is still following its way at about 1 meter per hours. It is a typical block lava. Between Thursday evening, 15th and Saturday morning, 17th, the lava has moved about 50 m towards the intermediate station of the cableway which is now about 150 m from the lava. The northern cone stopped activity Thursday morning. According to the local guides it was during the night between 15 and 17 April that the explosive activity was the biggest since the beginning of the eruption. The observatory is surrounded on its four sides by four-meters-high lava products. The lava is threatening the north wall of the observatory and penetrated inside the observatory. The area covered by lava Saturday noon is about 1 square kilometer, and the damage is estimated to be about 1 million dollars."

Card 1183 (30 April 1971) Three new craters formed; lava flows advancing on the S flanks

"Etna activity which commenced 5 April continues. Three craters have formed S of the central crater. Two are currently active with frequency of 25-30 explosions per minute per crater, with ejecta being hurled up to 300 m. Lava flows were advancing to the SE (Valle del Bove - 3 km) and continue to advance to the S (cable car lines - 4 km), and SW (Frumento - 2 km).

"The first chemical analysis of lava indicates a phonolitic tephrite. Gas from active craters shows an excess of CO₂ over SO₂; gas from lava flows shows an excess of SO₂ over CO₂. N-S fractures have been observed on the E side of Monte Frumento and between Central Crater and Northeast Crater. Central Crater continues to smoke, mostly white, occasionally brownish-black. Northeast Crater shows no activity. Presently no danger exists for populated area."

Card 1184 (30 April 1971) Observatory surrounded, but not destroyed, by lava flows as of 25 April

The following corrects statements made on cards 1173 and 1174: "The observatory was not 'entirely destroyed' nor lava penetrated neither on April nor ... 25 April, when we last reached it (but to reach it, one has to cross the thick and still hot lava flows which do completely surround the building); the outpour of lava is an average of 25,000 m³ per hour presently emitted, at speeds varying from 0.5 to 4 m/s.; it is not a 'typical block-lava' but a quite typical aa flow with accessory pahoehoe streams."

Card 1185-1186 (30 April 1971) Two new explosive vents on the E fissure; cone growth continues

"The [E] fissure, which was the most active from the start, stopped all explosive and apparently effusive activity (although there are still some small and slow lava flows progressing on the big one which has flowed into the Valle del Bove. On the other hand, the [W] fissure extended upwards (northwards) for about 250 m with two new explosive vents starting on 19 April; they were still very active yesterday when we eventually reached them to collect gases (F. Le Guern). This fissure is now approximately 2.5 km long, extending en echelons from the very base of the central cone (alt. ca 3,050 m) down to the NW foot of Mt. Frumento Supino. Only its upper half km is active. The direction of this open fracture is N10-15°W. It is also the direction of the fault which worked last week (earthquake intensity 6-7 on the Mercalli scale) in the Giarre region, on the E foot of Mt. Etna. Exceptionally, some sort of relationship between an eruption and a tectonic earthquake could perhaps be considered as existing here.

"Presently, explosive degassing is continuously going on at the three lower and two upper main vents left open in the fissure. The lava lumps do not reach higher than about 200 m above crater rims. The cones are steadily growing up. The effusive activity decreased during the third week of the eruption and is more awkwardly estimated, the major part of the lava being now emitted through tunnels within the body of the main flow. This allows the lava keeping its heat content almost intact until its exit point, this meaning it being able to flow further down than the preceding ones in spite of decreased output and temperatures, as compared with the bigger flows of the first week of the eruption.

"R. Romano, assistant to A. Rittmann's I.I.V. magmatological laboratory, Catania, is carrying on daily analyses of emitted lavas. S. Cuccuzza-Silvestri, from the University of Catania, together with C. Sturiale and Riuscetti, also do watch the developments of the eruption. The two physicists of our eruptive gas-investigating group, P. Zettwoog and C. Vavasseur, will join F. Le Guern on 3 May. The violent degassing with related lava bombing, together with the strenuous access over fresh lava-flows, make it somewhat difficult to carry on P, T, and V measurements of the erupting gases as well as chemical analyses. The probes and protecting suits developed so far are suitable for the comparatively mild permanent eruptive activity of Mt. Etna (or Stromboli as well), but do not suffice for more violent eruptions."

[Corrections of fissure locations by H. Tazieff, Card 1229].

Information Contacts:
Card 1167 (06 April 1971) Haroun Tazieff, Paris, France; Sr. Antonio Nicoloso.
Card 1169 (08 April 1971) A. Rittman, Instituto Internationale di Volcanologia, Catania, Italy; David Haskell, UPI.
Card 1170 (12 April 1971) A. Rittman and H. Tazieff, Instituto Internationale di Volcanologia, Catania, Italy.
Card 1171 (12 April 1971) H. Tazieff and R. Romano, Instituto Internationale di Volcanologia, Catania, Italy.
Card 1173-1174 (19 April 1971) M. Krafft, Centre Vulcain, Mulhouse, France; Roland Haas.
Card 1183 (30 April 1971) T. Casadevall, F. LeGuern, and R. Romano, Instituto Internazionale di Vulcanologia, Catania, Italy; CNRS, France.
Card 1184 (30 April 1971) H. Tazieff, Instituto Internazionale di Vulcanologia, Catania, Italy.
Card 1185-1186 (30 April 1971) H. Tazieff, Instituo Internazionale di Vulcanologia, Catania, Italy.

May 1971 (CSLP 33-71)

Additional vents and fissures open; very active lava flows

Card 1195 (06 May 1971) Activity continuing in early May at high levels

"The activity of Etna has shown some increase during the past few days. A new fracture opened ... 4 May at the eastern base of the terminal cone between about 2,870 and 2,840 m above sea level and about 1 km from the crater's rim. Scoria cones were formed. An effusive bocca produced lava flowing with a velocity of about 20 m an hour at 1500 (local time) the 5th of May, along the W slopes off Valle del Bove. Explosive activity at the main focus of the eruption continues with somewhat reduced intensity, but the lava flows continue to be well supplied, the fresh material spewed through units on top of the old lava or sometimes running alongside. The lava is advancing in three main branches. The first south to southwest joined by the second moving south toward the central part of Piano del Lago about 2,880 m above sea level, while the third moving SSE flanks the main flow reaching down to 2,270 m above sea level by 1600 hours, travelling with an average velocity of 150 m an hour. Small lava flows running S or SSW continue to be emitted from the bocca above the principal eruptive focus at the higher level of 3,020 to 3,040 m above sea level."

Card 1198 (10 May 1971) Eruption stops at some locations, but opens new vents and emits more lava flows

"Early on the morning of 7 May activity suddenly ceased at the two eruptive centers above the former observatory, and at the four small bocche situated on a fissure to the E which had opened on 4 May. Towards the evening of 7 May, two new bocche opened to the NNE of the center of 4 May, one at a height of 2,700 m above sea level and the other a little to the N, and ca. 2,580 m. A little later, a third fissure with four orifices opened at ca. 2,540 m. All are emitting lava flows directed toward the Valle del Bove. In contrast to the earlier centers, the rather less explosive activity leads to the formation of hornitos rather than cinder cones."

Card 1200-1201 (13 May 1971) Details of lava-flow activity during early May

"Present volumetric output of lava was estimated this past week as follows: 5 May, ~140,000 m³/hour; 6 May, ~90,000 m³/hour; 9 and 10 May,3/hour. A new fracture system did open on 4 May about 2200 on the E foot of the central main cone of Mt. Etna along a trend perpendicular to the initial N-S one at an altitude of 2,890 m above sea level. High pressure gases without lava fountaining fumed at the upper part of the main new fracture. Intense fountaining, a big spatter cone approximately 30 m high about 100 m downslope, and a lava flow averaging 10 m in width and [a speed of about 9 km/hour] around was discovered on the down slope end of the fountaining crater. These eruptive fissures, perpendicularly opened during one [same] eruption and exactly one month apart, constitute a rather exceptional phenomenon. It is in fact really quite interesting. On 6 May former activity . . . located on the N-S fissure completely stopped and the big chasm in the central crater started emitting big ash-laden puffs. On 7, 8, and 9 May the new easterly trending fissure extended downward towards Pizzi Deneri across the Valle del Leone which is the upper part of the Valle del Bove.

"[Henceforward, explosive activity is concentrated in the new collapse-chasm formed in the E foot of Mt. etna's central cone, at the upper end of the fracture zone. Effusive activity] of 4-6 May stopped at the upper part of this fissure as similar although much lighter activity resumed at altitudes several hundreds of meters lower down.

"We were able to simultaneously make recorded measurements of speed by way of special speedometers, temperature by way of a thermocouple gage, and pressure by way of a special Pitot tube, and make a large series of gas samplings for chemical analyses which are being (analyzed) now. The temperatures were usually about 1,000°C and the speed (it is not yet exactly calculated) was about 400 km an hour. These gas samplings and measurements were made on maybe the best possible place just at the head of the erupting fissure where the degassing of the magma is optimum."

[Corrections of fissure locations by H. Tazieff, Card 1229].

Card 1202 (13 May 1971) Two additional eruptive vents open on 11-12 May

"Two new eruptive vents opened at an altitude of only 1,800 m above sea level S from [Rifugio] Cetelli. The first vent opened ... 11 May at 1137 exactly, and the second vent opened at 0400 [on] 12 May. These two vents have very slight explosive activity and the molten lava lumps are hurled only about 20 m high. The lava flows had already entirely crossed the forest zone and had reached the cultivated areas after having [crossed the road leading to Rifugio] Citelli. So, it's only an effusive . . . type of activity. All other activity stopped several days ago on the volcano, [but for the strong explosive degassing, without any fresh lava but with old ash- and rock-laden puffs at the new chasm, at an altitude of circa 3,000 m on the E foot of Etna's central cone.]

"The fissures system on the upper part of the volcano is always moving, and the fissures are extending, widening, and steam and hot gasses escape from an altitude of 2,670 m up to the very top of Etna at 3,300 m."

[Corrections of fissure locations by H. Tazieff, Card 1229].

Card 1208 (17 May 1971) Lava flow from 11-12 May centers cuts highway

"During the night 11-12 May two new effusive centers opened on a fissure directed NW-SE on the E slope of Mt. Etna at about 1,800 m elevation outside of Valle del Bove. The lower bocca is emitting a big lava flow which in 30 hours reached 1,100 m elevation cutting the highway Fornazza-Cabancitelli (Mare Niri). The effusive centers of 7 May on the inner slope of Valle del Bove are still very active. Up to now, no danger for inhabited places."

Card 1211 (18 May 1971) New fissure on the S flank emits lapilli and fumes

The following report was telephoned to the Center by H. Tazieff. "The fissure system with a trend N63°E is extending on about all the upper part of the E flank of Mt. Etna and at an altitude of 1,800 m above sea level it presently delivers two lava flows: the first one is approximately . . . . . . speed about 4 km/hour and an estimated output of 10,000 m³/hour; the second flow is approximately 8 m wide with a speed of 15 km/hour and an output of 10,000-15,000 m³/hour. Both flows coalesce lower down and proceed with decreasing speed down to 20-40 m/hour . . . . . the town of Formazzo which is still 5 km away from the lava front. Trees are burning and the menace becomes really important now.

"On the other hand, a new fissure opened today at an altitude of 3,000 m above sea level on the S flank just N from the new mountain hut called 'Il Torre del Filosofora' and this fissure starts throwing lapilli and fumes up into the air."

Card 1213 (19 May 1971) Farm houses destroyed by lava flow; strong explosions on 18 May

The following was telephoned to the Center by A. Rittman. "Emission of lava from the bocche near Cabancitelli is continuing and supplying copiously the great lava flow which advances slowly on a front about 700 m large towards the road Fornazzo-Lingualossa. Some farm houses and a vast area of cultivated land have been destroyed. In the early morning of 18 May strong explosions started to open a new sub-terminal crater which at 1000 was already more than 150 m wide and violently emitting dark clouds charged with ashes and white vapor. The new crater is situated at the place where on 4 May a small eruption center had opened on the E slope of Mt. Etna at about 2,900 m altitude. The activity of the bocche in the Valle del Bove continues much reduced; the Central Crater and the Northeast Crater quietly emit white vapor."

Card 1215 (21 May 1971) Summary of activity during 4-12 May

"A flank eruption has occurred on the E slope of Mount Etna, after 30 days of strong effusive and explosive activity located on the upper S zone of the volcano. The eruption started in the evening of 4 May by the opening of a new fissure at the E foot of the Central Crater about 2,900 m above sea level. The discharge of highly fluid lava increased during the night, and the strong and almost continuous degassing throwing lava lumps and incandescent scoriae 250 m began to build an elongated, sharp-shaped cone 30-35 m high. This cone was open toward the E, where a big lava flow was flowing with an initial speed of 10-15 km/hour. in a few hours the new lava reached a zone S of Monti Centenari in Valle del Bove near the 2,000-m level.

"This new activity apparently does not affect the S vents (figure 3), which remained active until 6 May. on this day, however, the explosive and effusive activity was somewhat decreasing. At midnight, the activity of the E vent began to decrease considerably and completely ceased on the 7th of May at 0200. In the morning of 7 May all was quiet on the volcano, excepting small cooling lava flows toward the S and some increased emission of gas from the Central Crater accompanied by rumblings and occasionally throwing brown cinder clouds.

Figure 3. Explosive craters at the south vents of Etna (elevations 3,000 and 3,100 m), at 1900 on 4 May 1971. Courtesy of J.C. Tanguy. [Not previously published.]

"By the 8th of May at 0100 we were able to observe a large red glow toward the E on the Valle del Bove, where a flank eruption was starting on the slope between Valle del Leone and Vale del Bove (level 2,700 to 2,400), near the 1950 eruption vents. Six or seven lava flows were vigorously active, but explosive activity was almost negligible. In the 9 May morning at 1100, our team reached the vents. There was a continuous cracking of ground between the now inactive upper E vent and the location of the flank eruption. This flank eruption had broken by two en echelon fissures, the upper being between 2,680 and 2,650 m, and the lower near 2,500 m. Several lava flows were moving at an initial speed of 1-2 m/s, while continuous degassing (but without violent explosions) was building small eruptive conelets (hornitos).

"In the morning of 12 May, the magma erupted at a more lower point by the aperture of a new vent near Rifugio Citelli, around 2,000 m level, and the lavas from this new outbreak could be dangerous for the inhabitants of the Etnean E zone. This flank eruption is of the 1928 eruption type, and is even located approximately on the same fracture line as the 1928 eruption was. The maximum lava temperature recorded by both thermocouple and optical pyrometers is between 1,100 and 1,130°C. The viscosity, as estimated by Jeffreys' formula, appears very low, from 1,000 to 10,000 poises only."

Information Contacts:
Card 1195 (06 May 1971) A. Rittmann and R. Romano, Instituto Internazionale di Vulcanologia, Catania, Italy.
Card 1198 (10 May 1971) A. Rittmann, R. Romano, and F. LeGuern, Instituto Internazionale di Vulcanologia, Catania, Italy.
Card 1200-1201 (13 May 1971) F. LeGuern, P. Zettwoog, C. Vavasseur, and H. Tazieff, Paris, France.
Card 1202 (13 May 1971) F. LeGuern, French Atomic Energy Commission; T. Huntington, Reading University, England; H. Tazieff, Paris, France.
Card 1208 (17 May 1971) R. Romano, C. Sturiale, and A. Rittmann, Instituto Internazionale di Vulcanologia, Catania, Italy.
Card 1211 (18 May 1971) F. Le Guern and H. Tazieff, Paris, France.
Card 1213 (19 May 1971) R. Romano, E. Lo Giudice, and A. Rittman, IIV, Catania, Italy.
Card 1215 (21 May 1971) C. Archambault, F. Gauthier, A. Nicoloso, and O. Nicoloso, Instituto Internazionale di Vulcanologia, Catania, Italy; J.C. Tanguy, Laboratoire de Geomagnetisme du Parc Saint-Maur 94, Saint-Maur-des-Fosses, France.

June 1971 (CSLP 33-71)

Crater enlargements; corrections to previous reports

Card 1229 (03 June 1971) Crater enlargements; corrections to previous reports

"Important developments are the engulfments which recently did enlarge both the central crater's big chasm (la Voragine) and the new eastern chasm, as well as the extent, in length, width, and throw, of the fracture zone which is responsible for the second phase of the present eruption."

[H. Tazieff also submitted a number of corrections to his previous reports and comments about other reported aspects of the eruption. The corrections have been made to cards 1185, 1200, 1201, and 1202, above. Additional comments regarding card 1195 are included below. Comments disputing the interpretation and information presented by A. Rittman in a 3 May 1971 report not published by SI, included on the original card, are not reproduced here.]

Regarding Card 1195 (06 May 1971): "The velocity of the lava flow escaping through the newly opened N63°E fracture was approximately 9 km/hour (see Card 1200) and the mentioned speed of 20 km/hour can only be that of some flow-front."

Information Contacts: H. Tazieff, Paris, France.

September 1971 (CSLP 33-71)

Activity starts again after 100 days of quiescence

Card 1294 (23 September 1971) Activity starts again after 100 days of quiescence

"[After] 100 days [of} complete quiescence, Mt. Etna volcanic activity started again. Lava column raised up to 200 m from Main Crater's rim. Two explosive boccas are located at the bottom of the crater."

Information Contacts: A. Rittman, Istituto Internazionale di Vulcanologia, Catania, Sicily, Italy.

December 1971 (CSLP 33-71)

Periodic explosions from La Voragine crater

Card 1332 (21 December 1971) Periodic explosions from La Voragine crater

"After a few months of complete quiescence -- last activity occurred around the end of September -- Mt. etna activity started again. Two explosive boccas are located at the bottom of the main summit crater named La Voragine. They emit periodically volcanic sands and ashes mixed with fragments of molten lava that reach about 400 m elevation falling into a surrounding area of about 300 m radius."

Information Contacts: R. Romano and L. Villari, Istituto Internazionale di Vulcanologia, Catania, Sicily, Italy.

February 1974 (CSLP 20-74)

W-flank eruption rapidly builds cone; explosions and lava flows

Card 1791 (06 February 1974) First W-flank eruption of this century rapidly builds cone

"The eruption started [on 30 January] at an altitude of 1,800 m on the W flank of Mt. Etna. A new fissure was observed. The activity is essentially explosive. Only very short and thick tongues of lava seep slowly (less than 0.1-2 m/hour) to the E foot of a new rapidly built-up cinder cone about 50 m across the base and 100 m high. After initial, almost continuous lava fountaining which lasted throughout the first day, explosions occurred at the rate of 30-50 per minute. Lumps of a few kilograms were hurled 300-500 m high. Blocks weighing several tons have been observed reaching about 100 m above the crater rim. The lava temperature is estimated to be over 1,100°C in the crater and under 1,000°C in the lava flows. The viscosity is exceptionally high and probably due to a high degree of crystallization. The excepotionally high proportion of pyroxene accounts for the impoverishment of the lava in several magnesium elements and its relative enrichment in alumina and silica.

"Geophysical teams from the IIV in Catania, from the Observatorio Vesuviano, and from the Polytechnical School, Milano, started measurements on 4 February. It is totally impossible to reach the crater due to dense and continuous bombardment. I am presently sampling the eruptive gas phase. No eruption has occurred on the W flank of Mt. Etna this century. Local people called the quickly built-up new cone 'Mt. Rapido.' The latest report states that the 'explosions are stronger but still no lava flow.'"

Card 1795 (12 February 1974) Vigorous and frequent explosive activity from the new crater

The eruption that began on 30 January 1974 on the W slope of Mt. Etna was visited by J.C. Tanguy from 2 to 8 February.

According to Rittmann's classification, this should be an eccentric eruption with little or no relation to the main vent. It is mostly characterized by a highly explosive crater situated at an elevation of 1,680 m, which quickly built a cone over 100 m high. During the first days of activity, a restricted lava flow very slowly traveled about half a kilometer westward.

On 3 February, a very small lava tongue seemed to progress towards the SE, but next morning all effusive activity had stopped. The explosive crater, however, was vigorously active with continuous ejections (40-50 per minute) of big lava lumps and scoriae 400-600 m high. From time to time, the vent was blocked for a few seconds and the successive outbreak was accompanied by a strong air-shock percussion. Impressive also were the numerous earth tremors, especially E of the crater where the cone is partly open. Optical temperature at the vent is about 1,020-1,030°C, but measurements are probably too low as the top of the magma column cannot be observed. Another typical feature of this kind of eruption is the intense seismic activity the preceded the opening of the vent. Numerous earth tremors were felt from 14 January even at Rifugio Sapienza, 1,900 m high on the S flank of the volcano.

On 7 February the eruption was still continuing with some fluctuations. Explosions were 15-30 per minute, somwhat irregular in power and frequency. A new small but thick lava flow issued the day before from the N foot of the cone and is progressing as slowly as the former towards the NW. Earth tremors are persistent E of the crater.

Card 1807 (25 February 1974) Eruption ended on 17 February

"The eccentric eruption on the W slope of Mt. Etna ended on the 17th of February. On 8 February, the explosive activity began to decrease, although exceptionally strong recrudescences occurred from time to time. The outpouring of lava, however, was more important than at the beginning of the eruption. Nevertheless, it was still restricted in area and characterized by the sluggishness of the effusions. A flow starting on 9 February slowly reached a maximum length of about 2 km over the next few days. On the morning of 16 February, the explosions stopped at the vent and all outflow of lava ceased on 17 February.

"A run of lava temperature measurements was made using two chromel alumel thermocouples and a Schneider digital voltmeter. Although the eruption was coming to an end, temperatures as high as 1,075-1,085°C were recorded in both thermocouples. The optical surface temperature was 1,015-1,020°C. It can be compared to the measurements made at the explosive vent during the first phase of strong activity.

"The viscosity was high, but not measured (10⁵ poises?), However, this high value can be partially understood with respect to superficial cooling connected with the slow rate of lava discharge."

Information Contacts:
Card 1791 (06 February 1974) H. Tazieff, Chairman, Science Council, IIV, Catania, Italy.
Card 1795 (12 February 1974) J.C. Tanguy, Laboratoire de Geomagnetisme du Parc Saint-Maur, France.
Card 1807 (25 February 1974) J.C. Tanguy, Laboratoire de Geomagnetisme du Parc Saint-Maur, France; Guy Kieffer, Institute de Geographie, Clermont-Ferrand, France.

March 1974 (CSLP 20-74)

New vent SW of the 1974 cinder cone opens on 10-11 March

Card 1814 (14 March 1974) New vent SW of the 1974 cinder cone opens on 10-11 March

"After 22 days of quiescence, eruptive activities started again on the W flank of Mt. Etna during the night of 10-11 March 1974. A new volcanic vent opened about 200 m SW from the cinder cone built up during the period of the earlier 1974 activity. The area is located about 8 km W of the summit crater. The vent is characterized by highly explosive activity which brought about the formation, during the first two days, of an 18-19-m-high cinder cone. A viscous lava tongue is flowing out [of] the vent very slowly, proceeding westward. The length of the lava flow was about 700 m after 14 hours from the opening of the vent. From an approximate examination of the erupted material the rate of emission during the first 14 hours approached 10-12 m³/s."

Information Contacts: CNR, Instituto Internazionale di Vulcanologia (IIV), Catania, Italy.

October 1974 (CSLP 20-74)

Lava lake drains and lava flows about 1 km

Card 1954 (10 October 1974) Lava lake drains and lava flows about 1 km

"The NE side of the terminal crater that stopped its activity at the beginning of the April 1971 eruption was opened again during the night of 28-29 September 1974 with strong explosive activity. During the night of 9-10 October 1974, following the collapse of the ring on the SW side, the lava lake that had formed in the base began to flow out. After 20 m, the flow changed its direction to the NNW for about 1 km. At the present time the activity is of irregular explosions and a slow flow of lava going for about 2,000 m."

Information Contacts: E. Lo Giudice and D. Condarelli, IIV.

February 1975 (CSLP 10-75)

Eruption on NW flank produces spatter cones and lava flows

Card 2092 (26 February 1975) Eruption on NW flank produces spatter cones and lava flows

An eruption began on the NW flank of Mt. Etna during the night of 23-24 February 1975, 24 hours after normal summit activity stopped. The eruption continues at the present time. Several spatter cones with fountaining activity have formed along the fissure which opened at an altitude of 2,500 m above sea level on the NW slope of Mt. Etna. A lava flow fed by the lowest vent has already reached a length of about 1 km. The front of this lava flow is presently about 10 km from the village of Maletto, to which it seems to be directed at the moment. The NE crater has stopped its activity, while the central crater is erupting dense clouds of ashes and sand.

Information Contacts: D. Condarelli, IIV.

March 1975 (CSLP 10-75)

New eruptive center on the North Rift zone

Card 2124 (19 March 1975) New eruptive center on the North Rift zone

On 24 February 1975, the persistent activity of the NE summit crater (altitude about 3,300 m) shifted towards the North Rift zone of Mt. Etna. Thus, a moderate outpouring of lava occurred at the 2,600-m level, accompanied by weak explosive activity that formed small so-called "hornitos." This new eruptive center was visited again on 13 March. The upper, sharp-shaped hornito (altitude 2,590 m) was continuously emitting white vapors and tiny pieces of scoriae only a few meters above the magma level. The lower hornito was inactive, being partly buried by early lava flows. The liquid lava itself poured out slowly 100-150 m downward from beneath a consolidated crust, forming several short-lived flows that did not exceed a few hundred meters in length. Emanations of gas were occurring also from a fissure near the 2,550-m level on the right edge of the lava field.

A maximum temperature of 1,065°C was recorded on chromel-alumel thermocouples inserted to 60 cm into the lava of the uppermost source. This temperature was nearly the same as those (1,075°C) measured in the lavas of the NE crater before 1971.

At the summit craters system there was on this day a strong continuous emission of dense white vapors from the NE crater and heavy clouds of brown ashes from the "Voragine" (chasm) of the central crater.

Information Contacts: G. Kieffer, Department of Geology, University of Clermont-Ferrand, France; A. Nicoloso, Capo Guida dell'Etna, C.A.I., Catania, Italy; J.C. Tanguy, Laboratoire de Geomagnetisme du Parc Saint-Maur, University of Paris VI, France.

November 1975 (NSEB 01:02) Cite this Report

Continuous activity for most of 1975; new lava vent

Continually active throughout most of 1975, lava began flowing from a new opening on the NW side of the volcano on 29 November [originally reported as 21 November].

Further Reference. Pinkerton, H., and Sparks, R.S.J., 1976, Formation of the 1975 subterminal compound lava flow, Mount Etna: JVGR, v. 1, p. 167-182.

Information Contacts: G. Nappi, IIV.

May 1976 (NSEB 01:08) Cite this Report

Lava eruption stops in mid-May

In mid-May, Etna [temporarily] ceased erupting lava. For several days prior to 15 May, the volcano's two lateral craters were inactive, and only a thin column of vapor rose from the central crater. A team of scientists, led by Haroun Tazieff, was on the scene conducting investigations.

Information Contacts: IIV, Catania.

June 1976 (NSEB 01:09) Cite this Report

Explosions from Bocca Nuova and The Chasm; lava flows on N-flank

Observations were made by the University College group and R. Romano of the IIV, 16 May-4 June 1976. Until this time weather conditions had been very bad on the volcano and reports of activity were sporadic. In the summit region, Bocca Nuova was fuming strongly and had a depth estimated to be in excess of 200 m. This pit was exploding throughout the period of observation, at rates varying from one explosion per 3 minutes up to 2 or 3 explosions/minute. Incandescent material was occasionally thrown above the level of the crater rim and vesicular scoria and Pele's hair fell close to the crater down-wind. The Chasm was also fuming strongly, and although its bottom was not seen, it had a depth of several hundred meters. During the afternoon of 25 May the Chasm started deep violent explosions at a rate of 20-25/minute. No bombs were seen from these explosions, and the activity died down over the next few days. The new pit on the W side of Northeast Crater was fuming quietly but not exploding. The area around this new pit contained large amounts of sublimates and its total depth was around 50 m. The Northeast Crater itself is now inactive, the vent being plugged by scree; but there is still heavy fumarolic activity high on the W inside wall.

The effusive activity during the period was occurring from new vents on the N side of the mountain (near Punta Lucia). A 40-m-high cone formed at about the 2,900 m level. Inside this cone was a conelet from which mild strombolian explosions of fresh gassy lavas were occurring on 26 May, though it was quiet on 31 May. Lava emissions were taking place farther downslope in the new lava field, from a number of boccas with positions that changed from day to day in an area above the 2,500 m contour. The rate of emission from one bocca was measured to be 0.4 m³/sec. and the total emission for the whole field was 2 m³/s.

Information Contacts: J. Guest, J. Murray, S. Scott, and W. O'Donnell, Univ. of London; R. Romano, IIV.

July 1977 (NSEB 02:07) Cite this Report

Lava effusion and explosive activity from a new vent

Lava effusion and explosive activity, from a new vent at 3,200 m elevation just N of the Northeast Crater, began during the early morning of 16 July. A small lava lake, first observed at 0400, occupied the new vent, which was the source of two lava flows. The larger moved E into the Valle del Leone, and the smaller to the N. By 18 July, the flows had reached 2 km and 800 m length respectively. Strombolian activity began at 0515 on 16 July and rapidly increased in frequency and power. Ejecta reached 600 m in height and fell over an area ~1 km in diameter. The explosions had ended by 20 July and lava extrusion ended on 23 or 24 July.

Precision leveling two weeks before the eruption by John Guest and co-workers showed a 1-cm inflation of the S flank since September 1976, but strong deflation under aa fields on the N flank.

Information Contacts: J. Guest, Univ. of London; R. Romano, and G. Frazzetta, IIV.

August 1977 (NSEB 02:08) Cite this Report

Two eruptions in August generate fountaining and lava flows

"After a period of quiescence since the beginning of this year, Etna erupted again on 16 July. New explosive and effusive boccas opened on the lower flank of the Northeast Crater cone at an altitude of 3,200-3,270 m. The first signs of eruption occurred in early July when a small pit opened on the N edge of the Northeast Crater Cone. Initially this pit emitted high-temperature gas which during the night was seen to be incandescent.

"The first sign of lava emission was seen by a guide at 0400 on 16 July when he observed a small 'lake' of lava in the bottom of the pit. An hour later weak explosive activity started and increased to become stable at about 15 explosions/minute by 1000. Incandescent material was thrown 300 m above the vent, with a maximum height of 500 m. The maximum range of the bombs was 400-500 m. During this early period of explosive activity, a fracture opened at about 3,240 m on the lower slopes of the cone and flows were emitted from the end of the fracture (at 3,220 m), first towards the NE and later to the E. At the same time ephemeral boccas (3,200 m) opened below the main fracture and fed a small flow in a northerly direction. Explosive activity reached its peak during the night of 17 July. During the early hours of 18 July collapse occurred in the Northeast Crater itself, causing great clouds of dust and ash. The explosive activity at the new vent then diminished both in frequency and intensity, becoming extreme1y variable.

"On 18 July the flows had reached a length of 800 m to the N and 2 km to the E. From then onwards the explosive activity continued to diminish, as did the effusion of lava to the N flow. The E flow reached the edge of Valle del Leone and continued as the principal flow, reaching a total length of 4 km by the end of the eruption. The N flow stopped with a total length of 1 km. Explosive activity ended at 1000 on 22 July and the lava flows stopped in the late afternoon.

"The area covered by lava was 0.16 km², the volume of lava was 4.8 x 10⁵ m³ and volume of pyroclastic material 500 m³. Microseismic activity was noted before and during the eruption.

"The Northeast Crater started erupting again on 5 August at 1430. The activity began with strong explosions from the July vent, with lava fountains being thrown to 400 m in the early stages. One lava flow formed, advancing N from a fracture on the N slope of the Northeast Crater Cone. The fracture was oriented approximately NNE. The lava was fluid and traveled about 3 km. Seismic activity was observed just before and during the eruption, which ended at 0630 on 6 August."

UPI reported that a third eruption began early 14 August and lasted only 14 hours. Fountains or strombolian ejecta rose 200 m above the vent, and two lava flows, each about 200 m wide, moved about 4 km down the volcano.

Information Contacts: R. Romano, G. Frazzetta, and D. Condarelli, IIV; J. Guest, Univ. of London; UPI.

November 1977 (NSEB 02:11) Cite this Report

Eruption from the NE crater, the fourth since mid-July

Etna's fourth eruption since mid-July began during the night of 2 November from the Northeast Crater Cone, site of the three previous events. Two lava flows were extruded, but (in contrast to the earlier events) explosive activity was very weak. The larger flow traveled 2.5 km NW from the vent and the smaller 1 km to the N, before the eruption ended about noon on 4 November.

Information Contacts: R. Romano, IIV; J. Guest, Univ. of London.

December 1977 (NSEB 02:12) Cite this Report

Frequent eruptions from Northeast Crater continued into January

Frequent eruptions from Etna's Northeast Crater continued through early January (table 1). Since the 2-4 November activity, progressively briefer 1-day eruptions occurred on 7, 22, and 25 November. On 6 December, extrusion of a single lava flow began at about 1100 from a NNE-trending fissure on the N side of the Northeast Crater. The flow traveled 4.5 km down the E flank before the eruption ended at 2200. On 24 December, tephra was thrown 1,000 m above the vent, and renewed activity 5 days later, accompanied by small earthquakes felt in nearby villages, projected tephra several hundred m above the vent. Lava extrusion resumed 2 January and the flow had advanced 1 km on a 150-m-wide front by evening. The eruption was continuing as of the morning of 4 January.

Table 1. Summary of Northeast Crater activity since November 1977. Courtesy of R. Romano.

Month	Dates of Eruption
Nov 1977	2-4, 7-8, 22 (10 hrs), 25 (7-8 hrs), 27 (10 hrs)
Dec 1977	6 (8 hrs), 10-(?)13, 18, 24-25, 29
Jan 1978	2-3, 4, 5, 7
Mar 1978	25-26, 27-28

Information Contacts: R. Romano and L. Villari, IIV; J. Guest, Univ. of London; New York Times; UPI.

March 1978 (SEAN 03:03) Cite this Report

New lava flow and ash on 25 March

Etna erupted for the first time since January on 25 March [originally reported as 26 March], extruding a lava flow, destroying trees on the flank, and emitting ash, that was blown S towards Catania (25 km from the summit) by a strong wind.

Information Contacts: UPI.

April 1978 (SEAN 03:04) Cite this Report

First SE flank activity since 1971

An eruption began 29 April and continued as of 3 May. Lava was extruded from four new vents, on the SE flank, and had reached the 1700 m level near Monti Centenari, the 1852 cone by the morning of the 3rd. Explosive activity ejected bombs to 300 m above the largest of the vents (near the 1819 crater; figure 4) and built a 50-m cone. Explosions had declined by early 3 May, but vigorous lava effusion continued.

Figure 4. Map of Mt. Etna, showing 1971 lava flows in black and earlier flows in other patterns. Contour interval, 100 m. From Rittman and others, 1971.

Frequent brief eruptions from Etna have occurred since July 1977, but all have originated from vents on the Northeast Crater cone. The last SE flank eruption occurred 5 April-12 June, 1971, destroying the Etna Observatory.

Reference. Rittman, A., Romano, R., and Sturiale, C., 1971, L'Eruzione Etnea dell'Aprile-Giugno 1971: Atti della Accademia Gioenia di Scienze Naturali in Catania, Serie Sestima, v.3.

Information Contacts: J. Guest, Univ. of London; R. Romano, IIV.

May 1978 (SEAN 03:05) Cite this Report

SE-flank eruption continues through May

R. Romano reported the eruption started on 29 April at about 2000-2030 from bocca 1 (figure 5). Explosive activity built a cone that was 50 m high by 2 May. Lava flowed from the E side of the cone into the Valle del Bovee. Fissures opened, extending into the 1819 crater, where they intersected another fissure set which runs along the wall of the Valle del Bove.

Figure 5. Map showing locations of vents, fissure systems and lava flows of the April-May 1978 eruption. Bocca Nuova is W of the Chasm in the Central Crater; other boccas are identified by number. Prepared by J. Guest and J.B. Murray.

"During the afternoon of 1 May new boccas 2 and 3 opened on the existing fissures, then early the next afternoon bocca 4 opened, emitting a small lava flow that stopped the same day. Activity at bocca 1 also ended on 2 May, but the main flow front advanced at 100 m/hour. Bocca 3's activity diminished 6 May and ended by 7 May."

John Guest and J.B. Murray arrived at the volcano on 10 May and reported: "Lava effusion was limited to bocca 2, marked by a hornito 10 m high. The rate of eruption was 10 m³/s through midday 13 May when bomb ejection began at a rate that increased to 40-50 m³/s, but decreased to 20-30 m³/s by the next day and had returned to 10 m³/s by 15 May.

"Although bocca 1 was not emitting lava during this period, there were several collapses in the vent, producing billowing brown smoke. Occasional big explosions began 14 May, throwing bombs as much as 100 m above the vent. Explosions intensified on 27 May, but activity quickly returned to the 15 May level, and the eruption was continuing on 31 May.

"These eruptions have completely changed the Northeast Crater and surrounding area; the highest point on the volcano is now the Northeast Crater. Strong explosive activity during several eruptions has covered much of the summit area with ash, and during the Easter eruptions (March 25-28) there was a light ashfall as far away as Catania (25 km SE). Lava flows were extensive, one reaching as far down as 1,700 m elevation of the NW flank."

Information Contacts: R. Romano, IIV; J. Guest, Univ. of London.

June 1978 (SEAN 03:06) Cite this Report

SE-flank eruption ended by 14 June

The eruption of Etna, which began 29 April, had ended by 14 June. [This date was later corrected to 5 June, and the report was removed completely from GV 75-85.]

Information Contacts: J. Guest, Univ. of London.

July 1978 (SEAN 03:07) Cite this Report

Persistent SE flank activity resumes 26 May-5 June

Etna's SE-flank eruption, which began on 29 April, stopped for about 12 hours on 26 May, then resumed and continued until the evening of 5 June. When visited by John Guest and others in late July, the main SE flank vents contained glowing red fissures and emitted jets of gas at high pressure. Occasional deep explosions could be heard inside Bocca Nuova (the W vent of the central crater), accompanied by rumbling and frequent collapse activity. The Chasm (the larger E vent of the central crater), normally continuously active, was largely filled with ash and snow, and showed no signs of activity. Steam emission continued from the Northeast Crater, site of a series of brief eruptions between July 1977 and March 1978.

Information Contacts: J. Guest, Univ. of London.

August 1978 (SEAN 03:08) Cite this Report

New SE flank eruption

Activity resumed on Etna's SE flank during the night of 24-25 August. The initial activity consisted of ejection of spatter bombs and ash from one of the 1971 eruption craters, at 3,000 m altitude on the SE flank of the summit cone. Lava extrusion from this crater began the night of 25-26 August and had ended by the next morning. Lava flowed eastward into the Valle del Bove, traveling 2.5 km to 2,000-2,100 m elevation. During the afternoon of the 26th, a second vent opened at 2,725 m altitude, on the wall of the Valle del Bove. Its flow moved 3 km in 12 hours, reaching 1,650 m altitude.

The explosive activity that started 24-25 August began to decrease on 27 August, but 7 more vents opened that afternoon on the walls of the Valle del Bove, between 2,800 m and 2,500 m. By 29 August, the number of active vents had decreased to four with a notable diminution of lava effusion, and explosions had ended.

Information Contacts: R. Romano, IIV.

September 1978 (SEAN 03:09) Cite this Report

SE flank eruption ends; occasional central crater explosions continue

The SE flank eruption ended on the morning of 30 August. Activity since then has been confined to occasional explosions from Bocca Nuova. Two distinct sets of fissures formed during the eruption. The active vents trended NE-SW, parallel to the 1971 vents. No lava was extruded from the second set, which trended N-S. Fault throws of up to 3 m were observed.

Further Reference. Mackey, M., and Scott, S.C., 1980, The eruption of Mt. Etna in August 1978, in Huntingdon, E.T., and others, eds., 1980, U.K. Research on Mt. Etna; Royal Society of London, p. 43-44.

Information Contacts: J. Guest, Univ. of London.

November 1978 (SEAN 03:11) Cite this Report

New SE-flank eruption

A new SE flank eruption began on 18 November. Initial activity consisted of ejection of ash and wallrock from one of the spatterspatter cone cones formed in the August eruption. Ejection of incandescent ash and larger tephra from this cone started during the morning of 23 November, and was accompanied by minor lava effusion on the crater floor. Lava fountains rose 500 m above the August cone during the afternoon of 25 November and lava began to flow eastward into the Valle del Bove. That night, two new vents opened on the wall of the Valle del Bove at about 2,600 m altitude, extruding flows that traveled 4 km E, to an altitude of 1,500 m. Strong ash emission from the August cone was visible from 40 km away on 26 November.

Two more vents opened in the Valle del Bove on 27 November at 1700 m above sea level, and another vent opened nearby the next day, at 1,800 m altitude. Lava flows from these vents had traveled 4 km into the Valle Calanna, a steep valley extending SE from the E end of the Valle del Bove, by the evening of the 27th. A sixth vent opened that night at 1,650 m altitude, extruding lava that advanced slowly toward the town of Zafferana Etna (population 7,000), a few km S of Milo. The eruption ended during the night of 29-30 November.

Information Contacts: R. Romano, IIV; UPI; AP.

July 1979 (SEAN 04:07) Cite this Report

Eruption from summit and SE flank

By early July, activity had resumed at the Chasm in Etna's central crater. The Chasm had been continuously active for many years but had become quiescent and largely filled with ash during the 1978 eruptions. John Guest and coworkers arrived at the volcano 11 July and observed small, sharp, strombolian explosions from a small pit that had formed in the floor of the Chasm. When visited again on 27 July, the pit was filled with lava, covered by a thin crust that swelled prior to frequent Strombolian explosions. The lava lake had grown further by the next day. Large blisters formed in the lake, then burst, throwing bombs 200 m or more high. Some fell 50-60 m outside the rim of the Chasm.

Bocca Nuova, adjacent to the Chasm, was quiet on 11 July. However, collapse activity deep in this crater could be heard 27 July, and billowing clouds of dust were emitted.

Guest and coworkers observed the beginning of activity at a third site during the morning of 16 July, when strong gas emission started from a vent at the bottom of one of the 1978 craters on the upper SE flank (figure 5). Ejection of lithic blocks and a little fresh magma soon commenced, with the proportion of juvenile material increasing steadily. By afternoon, strong strombolian activity was occurring from the vent. The next day, bombs from many of the spasmodic explosions rose 200-300 m above the rim of the (100-m deep) 1978 crater. Most bombs fell back inside the crater, but a few landed as much as 50 m outside the rim. Another vent, on the side of the 1978 crater, emitted ash, building a small conecone. Similar activity continued until the night of 22-23 July, when the explosions became stronger and more frequent. The stronger activity continued through the morning of the 23rd, then declined to the more moderate levels of 17-22 July. Six vents were active at various times, two of which were dominant. This activity persisted, with some fluctuations in intensity, through 28 July, when Guest and coworkers left the volcano.

After a series of felt earthquakes 29-30 July, strong explosions from the Chasm began during the night of 3-4 August. Heavy ashfall took place in Catania, closing the airport, and ash fell as far away as Syracusa, about 80 km to the SSE. Unusual lightning accompanied the explosions, which were visible from the mainland, 75 km from Etna. Two fissures opened early 4 August near crater l, at 2950 m and 2875 m altitude. By afternoon, fluid lava from these fissures had traveled 13 km down the E flank, threatening the village of Fornazzo and forcing its evacuation. However, about 300 m from Fornazzo the lava changed direction, and damage was limited to about 1,000 acres of fruit and nut orchards. By late 4 August, summit explosions had apparently ceased.

Several new fissures opened the next day. The first was 1 km long, located at 1,800 m altitude in the Valle del Bove, on the SE flank. Others opened later on the NE flank, producing lava that flowed down two valleys. Lava effusion from some of these vents was continuing as of the morning of 7 August.

Information Contacts: J. Guest, J. Murray, Univ. of London; R. Romano, IIV; UPI; Reuters.

August 1979 (SEAN 04:08) Cite this Report

Lava extrusion from several SE flank vents; ashfall to 70 km away

The following report was prepared by John Guest and Romolo Romano from observations by E. LoGiudice, D. Condarelli, and A. Pellegrino.

"In the afternoon of 3 August, lava fountaining up to a height of 300 m started in the 1978 crater, which we are now calling the Southeast Crater. This crater has been active since the middle of July. Ash from this explosive activity fell over the E flank of the volcano, then later that day fell over the SW flank as far as Syracusa, some 80 km away. During the evening of 3 August, an eruptive fissure opened near the 1819 Crater. Lava erupted that night reached Monte Centenari, some 2 km away. Fifty-four earthquakes were recorded with magnitudes up to 3.5-4.

"At 0545 on 4 August, another fissure opened in the Valle del Bove, SE of Monte Simone from 1,800 m to about 1,700 m elevation, 1 km long. Two flows were erupted quietly from the fissure. The flow from the top of the fissure moved SE (towards Rocca Musar-ra). The second, from the lower part of the fissure, traveled along the N wall of the Valle del Bove past Rocca Caora and reached the Torrente Fontanelle by midday. At 1430 the flow front was advancing at 100 m/hour and cut the Rifugio Citelli-Fornazzo road. The flow continued to advance, stopping in the evening 50 m from the N-S road through Fornazzo, just N of the town at 870 m above sea level.

"In the central crater area, large explosions had occurred from the Chasm during the end of July. At 1000 on 4 August, the magma level in the Chasm dropped, and in the Southeast Crater explosive activity was greatly diminished. At 1130 on 5 August there were again large explosions from the Southeast Crater and fountaining resumed at 1345 with heights of up to 400 m.

"At 1615 on 5 August, a new fissure opened just NW of the 1819 Crater, with fountaining. A lava flow from this fissure reached the foot of the wall of the Valle del Bove. At 1715, another eruptive fissure opened SE of the 1819 Crater, again with fountaining, and a flow moved into the Valle del Bove. Ash from this eruption also fell in the region of Catania and Syracusa. At 1730, a fissure with a NE trend opened at 2,500 m above sea level in the Valle del Leone. During the night of 5-6 August, lava from this fissure traveled 3 km.

"Early in the morning of 6 August, many earthquakes of up to M 3.5-4 were recorded until about 1218. In the afternoon, activity increased from the fissure near Monte Simone, which had been active on 4 August, and lava flows overlapped the earlier ones from this vent. The 6 August flow traveled some 1.5 km. At 2030, yet another fissure opened, with an ENE trend, at an altitude of 2,150 m, coinciding almost exactly with the 1928 fissure on the outer flank of the Valle del Bove. A sluggish flow followed the path of the 1928 lava, stopping on 8 August, 50 m from the Rifugio Citelli road, having traveled 1 km. Flows from vents in the Valle del Bove stopped on 9 August."

Information Contacts: J. Guest, Univ. of London; R. Romano, IIV.

September 1979 (SEAN 04:09) Cite this Report

Nine killed and 23 injured by explosion

Activity resumed during the night of 1-2 September, with a collapse of part of the wall of Bocca Nuova and small explosions from the neighboring summit crater, the Chasm, the following day. The volcano then remained quiet until a 30-second explosion from Bocca Nuova killed nine persons and injured 23 at 1747 on 12 September. Some of the 150 tourists in the area at the time of the explosion were on the crater rim, and others were at a parking lot 400 m to the NW, where a large number of blocks about 25 cm in diameter fell. The explosion was apparently somewhat directed, because the distribution of blocks was dominantly to the NW of Bocca Nuova and no blocks traveled as far as 200 m in directions other than NW. No fresh magma was ejected by the explosion. The next day, considerable quantities of fine ash were emitted from Bocca Nuova and one or two small deep explosions were heard, but activity since then has been limited to weak emission of vapor containing SO₂.

Further Reference. Kieffer, G., 1981, Les explosions phreatiques et phreatomagmatiques terminales a l'Etna: BV, v. 44, p. 655-660.

Information Contacts: J. Guest, Univ. of London; UPI.

October 1979 (SEAN 04:10) Cite this Report

Thermal anomaly on SE flank

The following thermal anomaly report is from C. Archambault, J. Stoschek, and J. C. Tanguy.

"The existence of a N-S elongated thermal anomaly about 10 km has been determined on the upper half of Mount Etna, both by field measurements and infrared satellite imagery. It is believed that this high temperature anomaly is symptomatic of storage of magma at shallow depth within the rift zones of Etna. However, the magnitude of the thermal anomaly is expected to change with respect to volcanic activity (four flank eruptions have occurred from this zone during the past 2 years). Since 26 June, ground temperatures have been continuously recorded at the end of the thermal anomaly (figure 6). The results in this part of the volcano are considered the most significant because no volcanic activity has occurred in this zone for 70 years, therefore, the abnormal temperature cannot be due to cooling of residual magma. In order to eliminate the climatic effect, the data are presented (figure 7) as the difference between recordings of the central part of the thermal anomaly (Monte Calcarazzi Station) and those of a "reference station" (Sapienza) located at the same altitude about 1 km outside the anomalous zone.

Figure 6. Infrared image taken 16 September 1978 by the NOAA 5 weather satellite. The thermal anomaly is shown by the dark area around Monte Calcarazzi.

Figure 7. Graph showing the variation between temperatures recorded at Monte Calcarazzi and Sapienza, September 1978-9 August 1979.

"There had been considerable temperature increase (3°C) at the Monte Calcarazzi station during the month that preceded the flank eruption of 3 August. On 10 August the temperature at 120 cm depth, checked by direct measurements, was 9°C higher than the normal (Sapienza). Such a variation may be either a transient response to the August eruptive phenomena on the SE, E, and NE flanks, or the indication of magma motion southward - a problem that should be solved in the months to come.

References. Mise en évidence de zones thermiquement anormales sur le massif de l'Etna. 7éme R. ann. Sci. Terre, Lyon, Avril 1979, p. 15.

Mise en évidence d'anomalies thermiques dans la basse zone du secteur Sud de l'Etna, Note technique CNET 110/79.

Etablissement d'une carte thermique du massif de l'Etna à partir des données transmises par le satellite météorologique NOAA V...: Note technique CNET 111/79.

Further Reference. Guest, J.E., and Murray, J.B., 1980, Summary of volcanic activity on Etna, 1977-1979, in Huntingdon, E.T., et al., eds., 1980, U.K. Research on Mt. Etna: Royal Society of London, p. 50-52.

Information Contacts: C. Archambault and J. Stoschek, CNET, France; J. Tanguy, Univ. de Paris VI; PIRPSEF, CNRS-INAG.

January 1980 (SEAN 05:01) Cite this Report

Reduced thermal anomaly; small ash eruption

[Some elements of this report were excised at the authors' request.] "Since the August flank eruption, no major volcanic event has occurred on Mount Etna, although on 12 September a moderate phreatic explosion resulted in nine casualties near the W vent Bocca Nuova. On 11 January 1980, ashes were emitted from both Bocca Nuova and the Southeast Crater, where activity has preceded all the flank eruptions for the past two years.

"However, ground temperature measurements made on 21 January in the S part of Etna (Sapienza, Monte Silvestri, Monte Calcarazzi) show that the thermal anomaly has been reduced to a very low level (1-2°C, in contrast to 9°C in August 1979). This is the lowest temperature recorded in this zone since temperature measurements were initiated in September 1978.

Information Contacts: C. Archambault and J. Stoschek, CNET, France; J. Tanguy, Univ. de Paris VI; PIRPSEF, CNRS-INAG.

February 1980 (SEAN 05:02) Cite this Report

Red glow in SE crater

During the night of 29 February-1 March, red glow was visible in the Southeast Crater. No glow was reported the next two nights, but cloud cover may have obscured the crater.

Information Contacts: J. Guest, Univ. of London; R. Romano, IIV.

April 1980 (SEAN 05:04) Cite this Report

Explosions from summit and SE craters; thermal anomaly on S flank

During the evening of 14 April, explosions began from Etna's summit area and red-hot gases were emitted from the Southeast Crater. Explosions continued for the next several days. Residents of Zafferana, 11 km SE of the summit, saw large explosions on 16 and 17 April that were especially spectacular at night because of incandescence or perhaps lightning. Poor weather prevented observations from the IIV in Catania.

Etna guides who climbed the volcano, probably on 17 April, saw large fresh bombs near the Chasm and Bocca Nuova craters. Bombs were particularly prominent on the N and W sides of the central crater area. On 27 April at 1705, a large summit explosion produced a 3-km-high ash cloud. Renewed explosions began during the afternoon of 29 April and continued through the night from the Southeast Crater.

Information Contacts: R. Romano and L. Villari, IIV; J. Guest, Univ. of London; C. Archambault and J. Stoschek, CNET, France; J. Tanguy, Univ. de Paris VI; G. Scarpinati, Acireale.

May 1980 (SEAN 05:05) Cite this Report

Incandescent tephra ejected; temperature anomaly on S flank

"After a 3-month period of stabilization, ground temperatures in Etna's S-flank fissure zones (6 km S of the summit) began to increase again in March (figure 8). However, station 3, only 25 m from station 2, continued to show a nearly constant temperature. Variations in temperature are calculated by comparison with Sapienza reference station 1, located outside the fissure zones, 0.5 km WNW of stations 2 and 3, and 1.25 km from station 5.

Figure 8. Differences between ground temperature measured at 120 cm depth at stations 2, 3, and 5, and reference station 1 (T₂-T₁, T₃-T₁, and T₅-T₁) on Etna's S-flank, 21 January-2 June 1980.

"The increase in temperature preceded renewed activity from the summit crater system. On 14 April, red-hot gases were emitted from the Southeast Crater and on the following days fresh lava lumps were ejected from the Chasm.

"On 20 April, S flank temperatures were stationary or even slightly lower. Between 20 April and 1 May, temperatures strongly increased again. A large explosion on 27 April (probably at Bocca Nuova) and strong lava fountaining on 29 April at the Southeast Crater were followed by moderate magmatic activity until at least 3 May. After a short period of stabilization (1-4 May), temperatures were still increasing, although more slowly.

[Archambault, Stoschek, and Tanguy added the following paragraph to replace explanatory material excised from 5:1]. "It was initially believed that the thermal anomaly fluctuations were related to the reopening of cracks caused by increases in volcanic pressure. Further investigations showed this hypothesis to be incorrect, with the systematic seasonal increase of surficial temperatures being mainly the consequence of a microclimate (Bourlet and Bourlet, 1982). A volcanic effect does occur, but its influence cannot be simple and is probably linked to the circulation of hot waters through the S flank. From this standpoint, a striking example is the rapid temperature increase measured in November 1982 at 6 m depth (figure 8, 08:04), where a climatic effect cannot be invoked. Such a variation was not observed the following years (November 1983 and 1984). It may have resulted from the heating of meteoric waters by an intrusion of magma into the S flank a few months before the March 1983 eruption.

"The Southeast Crater was intermittently active throughout May. On 31 May, two vents were observed inside the crater with moderate ejections of incandescent magmatic material up to 50 or 100 m, with some bursts occasionally reaching 200 m. As of 3 June, activity had increased noticeably, and explosions were stronger and more frequent. The number of explosions per hour reached 165 and the ejecta reached heights of 200-300 m."

References. Bourlet, Y. and Bourlet, F., 1982, Etude microclimatique de 5 stations sur le versant sud de l'Etna: Bull. PIRPSEV, no. 63.

Bourlet, Y. and Bourlet, F., 1983, Etude des anomalies thermiques et hydriques sur le versant NE à Citelli et sur le versant sud à la Montagnola: Bull. PIRPSEV, no. 73.

Information Contacts: J. Tanguy, Univ. de Paris VI; C. Archambault and J. Stoschek, CNET, Lannion, France; G. Scarpinati, Acireale (direct measurements and observations); PIRPSEV, CNRS/INAG, France.

July 1980 (SEAN 05:07) Cite this Report

Incandescent tephra ejection; decreased gravity readings

Activity increased gradually between 13 and 20 July in the Southeast Crater, site of lava fountaining in late April, intermittent eruptions in May, and stronger explosions in early June. No information was available on activity between 4 June and 12 July [but explosive activity was persistent from the SE Crater and Bocca Nuova]. In mid-July, many small explosions were observed on some days, while other days were characterized by fewer but larger explosions. After a period of poor weather, renewed observations of the Southeast Crater on 31 July revealed four active vents, located 25 m below the lowest portion of the crater rim. The two larger vents steamed continuously, and exploded about every 2 seconds, ejecting incandescent tephra to heights of 25 m. At approximately 2-minute intervals, stronger explosions sent tephra upward 100 m. A small spatter cone surrounded the vents. The two smaller vents ejected juvenile material only occasionally.

Explosions from deep within Bocca Nuova were heard about every 2 seconds on 31 July. No tephra reached the rim. Since last September, Bocca Nuova's diameter [corrected from radius] has increased by as much as 80 m, bisecting a small crater formed in 1964. Most of the increase occurred during the winter, but further crater growth took place in June.

The Chasm, E of Bocca Nuova, was filled with solidified lava to within 25 m of its rim on 31 July. Large amounts of spatter and many bombs surrounded the crater as a result of activity in April (05:04).

Gravimeter readings made in late July by Tim Sanderson on the S flank yielded values that were significantly lower than in September 1979, indicating a loss of mass on that flank. July 1980 N flank gravity values were very similar to those of the previous September.

Information Contacts: J. Guest, J. Murray, C. Kilburn, and R. Lopes, Univ. of London; T. Sanderson, Imperial College.

August 1980 (SEAN 05:08) Cite this Report

Two one-day eruptions

Relatively weak activity similar to that of late July continued through August at Etna. A 1-day eruption on 1 September deposited ash on the E flank and extruded two lava flows.

John Guest climbed the volcano on 18 August. As on 31 July, explosions occurred deep within Bocca Nuova. The Chasm remained quiet. Mild strombolian activity continued from the Southeast Crater, but reportedly weakened the following week. Romolo Romano reported that a swarm of local seismic events began on 21 August.

At 0957 on 1 September, a pale brown plume was seen rising from the Northeast Crater, which last erupted in March 1978 (03:05). By 1130, explosions were ejecting large bombs or blocks every 10-15 minutes. An increase in seismicity at about 1700 was followed at 1730 by stronger explosions that were audible in Fornazzo, 10 km E of the crater. A large black eruption column rose to 6 km above the crater. By 1800, ash was falling on Fornazzo and the entire E flank. Geologists reached the eruption area by about 2000 and saw nearly continuous strombolian explosions from two vents in the Northeast Crater ejecting tephra to 500-600 m above the rim. Lava from the Northeast Crater flowed to the N and NW. By the next morning, the eruption had stopped. Heavy fog made mapping of the two lava flows difficult, but the NW flow had moved past Punta Lucia, about 3/4 km from the Northeast Crater.

A second brief eruption from the Northeast Crater began early 6 September, ending at about 1500 the same day, after an estimated 10 hours of activity. A small lava flow was extruded. No further information was available at press time.

Information Contacts: J. Guest and C. Kilburn, Univ. of London; T. Sanderson, Imperial College; R. Romano, IIV; G. Kieffer, Univ. de Clermont-Ferrand.

September 1980 (SEAN 05:09) Cite this Report

Ashfall to coast; lava flow; bombs

The 6 September eruption began at about 0500. Vigorous strombolian activity continued for 10 hours, ejecting bombs to 500 m above the same Northeast Crater vent that had erupted 1 September. Bombs 20 cm in diameter or larger fell as far as 750 m away. A lava flow, extruded from the same vent at a rate of 10-20 m³/s, traveled 2 km to the N, directly over the main lobe of the bifurcated 1 September flow, which extended about 1/2 km farther to the N. Ash fell on the coastal towns of Acireale and Taormina, 20 km SE and 30 km NE of Etna. Observations after the eruption showed the vent completely filled by lava and slumped debris. As of 3 October, no further eruptions had been reported.

Rumbling and deep explosions continued in September from Bocca Nuova. The Chasm remained inactive. Mild strombolian activity at the Southeast Crater stopped in September, with only infrequent gas emission and small collapse events reported.

Tim Sanderson collected gravity data before the 1 September eruption and after the 6 September one. Frequent ground temperature measurements by J. C. Tanguy and associates continue (05:05).

Information Contacts: C. Kilburn, Univ. of London; T. Sanderson, Imperial College.

February 1981 (SEAN 06:02) Cite this Report

Explosions and lava flow from Northeast Crater

The IIV reported explosions and extrusion of lava from the Northeast Crater. After a period of ash emission at the end of January and the beginning of February, stronger activity began with intense explosions the evening of 5 February. Lava flowed through a breach in the W-to-NW side of the Northeast Crater cone, forming three lobes that moved W, NW and N, covering the upper NW slope of the volcano. The N lobe, the largest, traveled ~2 km to 2,600 m elevation where it had a 1.2 km front. The eruptive activity stopped the evening of 7 February.

Information Contacts: R. Romano, IIV; J. Guest, Univ. of London.

March 1981 (SEAN 06:03) Cite this Report

Large lava flows cause severe damage

An eruption 17-23 March extruded lava from several fissures on the NNW flank. Initial estimates indicate that the main flow reached 7.5 km in length, lava flows covered an area of 6 km², and 30-35 x 10⁶ m³ of lava were extruded [but later calculations from topographic measurements by Murray (1982) yield 18 x 10⁶ m³] at a rate of 58-70 m³/s. Damage was estimated at about $10 million. Of the 90 historic eruptions of Etna for which location data are available, only three (1614, 1764, and 1918) occurred on the NW or NNW flanks.

Etna began to erupt on 17 March after a 2-day swarm of about 500 earthquakes, including a M 4-5 event during the morning of 16 March. On 17 March at 1337 an eruption fissure opened at about 2,550 m [corrected from 2,250 m] above sea level on the NW flank, trending approximately NW-SE. Lava fountains rose 100-200 m from this fissure and lava flowed rapidly westward. In the next 4 hours, three more fissures opened, the first and third also trending NW, the second WNW. All showed strong lava fountaining and were the source of lava flows. As fissures formed at lower altitudes, those higher on the volcano ceased to be active.

At 1855 on 17 March, another fissure opened at 1800 m elevation on the NNW flank, trending NW at its upper end, but after a short distance changed direction to more directly downslope. A large lava flow that originated from this fissure traveled 5 km within 4 hours, cut a railroad and highway (at 730 m altitude) during the night, and crossed another railway line and road (at 680 m altitude) early on 18 March. The lava destroyed orchards and farm buildings, and passed very close to the village of Montelaguardia, forcing the evacuation of its 250 residents. The fissure propagated downslope to 1,300 m altitude at 1130 on 18 March. The lower section extruded a small lava flow that briefly threatened Randazzo (population 15,000) but did not force its evacuation. By 1630, the center of the main flow was more than 1 km wide and its front had reached 650 m altitude, 100 m from the bed of the Alcantara River.

At 2200, another fissure opened between 1,235 and 1,140 m altitude extruding flows that moved toward Randazzo. By this time, the system of eruptive fissures had a total length of about 7.5 km. The main flow reached the Alcantara River bed (600 m above sea level) on 19 March at 1100, while the flows extruded from the fissure between 1,235 and 1,140 m altitude continued to advance slowly. By noon on 20 March, this fissure was characterized by mild spatter ejection that continued to feed slow-moving lava flows. However, the main flow had nearly halted. Sporadic activity between 1235 and 1140 m continued 21-22 March, finally ending during the evening of the 23rd. The longest flow from this fissure stopped at 900 m elevation, 2 km from Randazzo. More than 25 small earthquakes were recorded on 23 March, centered around the eruption fissures.

Throughout the period of lava extrusion, more or less intense emission of sand-size tephra occurred from Bocca Nuova, enlarging it to the W. Strong winds caused flank ashfalls on 22 March [as the Northeast Crater briefly ejected juvenile cinders; Tanguy and Patané, 1984].

Further References. Murray, J.B., 1982, Les Déformations de l'Etna à la suite de l'eruption de Mars 1981: Bull. PIRPSEV, no. 57.

Sanderson, T.J.O., Berrino, G., Corrado, G., and Grimaldi, M., 1983, Ground deformation and gravity accompanying the March 1981 eruption of Mount Etna: JVGR v. 16, p. 299-316.

Guest, J.E., Kilburn, C.R.J., Pinkerton, H., and Duncan, J.M., 1987, The evolution of lava flow-fields: Observations of the 1981 and 1983 eruptions of Mt. Etna, Sicily: BV v. 49, p. 527-540.

Information Contacts: R. Romano, IIV; UPI; AP.

April 1981 (GV11 81:04)

Photograph from Space Shuttle

The fissures and lava flows on the NNW flank resulting from the March 1981 activity (figure 9) were visible to astronauts aboard the Space Shuttle in April 1981.

Figure 9. Photograph of Mt. Etna and vicinity taken from the Space Shuttle in April 1981. North is towards the top of the photo; Catania is SE of the volcano on the eastern coast of Sicily. Photo no. STS 1-13-444, courtesy of Charles A. Wood.

Information Contacts: Charles A. Wood, NASA Johnson Space Center.

July 1981 (SEAN 06:07) Cite this Report

Ash ejection, probably caused by central crater collapse

On 29 July, a dense ash cloud was ejected for more than 30 minutes from Bocca Nuova. The ash emission may have been produced by collapse within the crater; no significant explosions were associated with the activity. Similar events have occurred on several occasions since the March eruption.

Information Contacts: J. Guest, Univ. of London; R. Romano, IIV.

September 1981 (SEAN 06:09) Cite this Report

Collapse in the central crater; ash ejection

Collapse activity deep within Bocca Nuova has been frequent since the 17-23 March fissure eruption. No fissuring or other evidence of surface collapse has been observed around Bocca Nuova. Explosions associated with the collapse activity ejected fine ash, caused strong ground vibrations 300 m from the crater, and could be heard as much as 10 km away. Plumes produced by this activity could sometimes be seen on the satellite images returned once daily by the NOAA 7 polar orbiter. Images returned shortly after noon on 3 and 4 October showed narrow, well-defined plumes extending ~75 km downwind from Etna. A smaller, less dense plume extending outward only about 20 km was present on the 6 October image.

Information Contacts: J. Guest, Univ. of London; M. Matson, NOAA.

October 1981 (SEAN 06:10) Cite this Report

Small plumes on satellite images

Images returned by the NOAA 7 polar orbiting satellite continued to show occasional plume emission: on 9 October at 1442 plume roughly 75 km long, drifting to the SE, and on 1 November at 1329 a much smaller plume, roughly 20 km long was moving to the SW. No other activity was seen on the almost daily imagery between those dates.

Information Contacts: M. Matson, NOAA.

December 1981 (SEAN 06:12) Cite this Report

Collapse continues in central crater; ash plumes

As of mid-January, collapse on Bocca Nuova's inner walls was almost continuous, producing plumes that contained fine ash but no fresh magma. At times of little or no wind, the plumes rose 3-4 km above the crater. There was no evidence of collapse beyond the crater rim. No changes have occurred in seismicity or tilt.

Images from the NOAA 7 satellite showed plumes emerging from the summit area on 4 and 6 January. A plume observed on 4 January at 1431 extended ~80 km to the SE, beyond the coast. Infrared data showed that the plume's apparent temperature was comparable to that of the sea water beneath it, and thus it probably remained at a relatively low altitude. The next image of the area, at 1408 on 6 January, showed a fairly diffuse linear plume ~55 km long, drifting SE. A plume from Etna had last been observed on satellite imagery (available most days for the Etna area) on 1 November.

Information Contacts: L. Villari, IIV; M. Matson, NOAA.

May 1982 (SEAN 07:05) Cite this Report

Small central crater explosions follow earthquakes and higher ground temperatures

[Some elements of this report were excised at the authors' request.] Since the fissure eruption of 17-23 March 1981, explosions associated with collapse activity deep within Bocca Nuova have produced small to moderate ash plumes. Magma was observed in the bottom of Bocca Nuova in mid-May, mid-July, and early September 1981, and incandescence was seen there in February 1982. All activity from Bocca Nuova stopped 8 May, but resumed about a week later at around a time of unusual seismic and thermal activity on the NE flank. Incandescent scoria rose above the crater rim 20-22 May.

Seismicity increased during the third week of May and culminated with an explosion, possibly at 1515 on 27 May, when the summit seismometer operated by the Univ of Catania detected a M 3.5 earthquake that was felt by local residents. The next day, geologists found blocks of old lava that had been ejected more than 300 m from the Chasm. Blocks up to 1.5 m across were found in small impact craters at the rim. Many blocks larger than 10 cm occupied elongated depressions, implying relatively oblique impact, oriented radially to the crater. The greatest concentration of blocks was immediately N of the crater, although the pattern of smaller blocks suggested a NW orientation. The depth of the Chasm had increased from ~50 m in March to ~100 m after the explosion, by removal of material that had filled it since 26 May 1980 [explosive activity had begun in mid April], and vents in its walls were steaming. However, activity 28 May was concentrated in Bocca Nuova, where occasional detonations could be heard and the crater floor was obscured by sulfurous steam. On 29 May, Bocca Nuova ejected black ash, containing fresh magma, every 2-3 minutes. Ash clouds rose 200-300 m above the crater rim and were blown a few hundred m to the south. Only fumarolic activity was observed in the Northeast and Southeast craters.

Information Contacts: R. Romano, IIV; M. Malin and M. Sheridan, Arizona State Univ.; J. Sheridan, Tempe, AZ; C. Archambault and J. Stoschek, CNET, France; J. Tanguy, Univ. de Paris VI; R. Basile, S. Scalia, and G. Scarpinati, Gruppo Ricerca Speleologica; M. Cosentino, S. Gresta, G. Lombardo, and G. Patane, Ist. di Scienze della Terra, Catania.

July 1982 (SEAN 07:07) Cite this Report

Eruption cloud; lava in main crater

Etna erupted on 8 August, when a black tephra column was emitted from Bocca Nuova and lava rose to 150-200 m below the crater rim. The activity was accompanied by a marked increase in minor earth tremors. Sicilian authorities have restricted tourist access to the volcano.

Information Contacts: J. Guest, Univ. of London; Reuters.

September 1982 (SEAN 07:09) Cite this Report

Strombolian activity on central crater floor

Strombolian activity on the floor of Bocca Nuova was observed in September. Fine ash fell on the crater rim. Since summer 1981, continuing collapse activity at Bocca Nuova has widened the crater by nearly 100 m, to 250 m in SW-NE dimension. Poor visibility prevented determination of the crater's depth. Just to the E, vapor emission was continuous from the Chasm, site of an explosion in late May that removed ~50 m of debris that had choked this vent for 2 years (07:05).

Information Contacts: J. Guest, Univ. of London.

November 1982 (SEAN 07:11) Cite this Report

Small explosions, but tephra to 12 km

A C-141 cargo plane pilot observed tephra from Etna at ~12 km altitude on 6 December at 1800. Romolo Romano reported there had been many small explosions from Bocca Nuova throughout the day. No eruption plume was visible on the only satellite image of Etna that was available on 6 December, from a NOAA polar orbiter at 1530. Poor weather and heavy snow make access to Etna's summit area difficult during the winter.

Information Contacts: R. Romano, IIV; M. Matson, NOAA.

December 1982 (SEAN 07:12) Cite this Report

Incandescent tephra from central crater

Explosive activity of varying intensity continued through early January from the floor of Bocca Nuova. Large ash emissions were sometimes observed. During the night of 24-25 December, intense explosions ejected incandescent tephra. Most of the tephra fell back within the crater, but some was deposited outside the crater rim.

Press sources reported emission of large quantities of gray and white "smoke" from the Northeast Crater but Romolo Romano noted that the Northeast Crater activity was fumarolic and no ash was ejected. The Northeast Crater last erupted in February 1981, producing a lava flow and ash (06:02).

Further Reference. Scarpa, R., Patane, G., and Lombardo, G., 1983, Space-time evolution of seismic activity at Mt. Etna during 1974-1982: Ann. Geophysicae, v. 1, no. 6, p. 451-462.

Information Contacts: R. Romano, IIV; UPI.

March 1983 (SEAN 08:03) Cite this Report

Lava from S-flank fissure; central crater enlarged

A destructive S-flank fissure eruption began on 28 March, preceded by a series of strong earthquakes first felt during the night of 26-27 March. At about noon on the 27th, a strong smell of H₂S was noted from an old cone (Monte Silvestri) roughly 2 km S of the initial eruption, although H₂S is not normally present in that area. Seismicity continued through the following night. At about 0845 on 28 March a NNE-SSW-trending eruptive fissure opened from about 2,450 to 2,250 m altitude, roughly 4 km S (bearing ~170°) of the central crater (between the eruption fissure of 1910 and La Montagnola). The base and E side of this fissure fed several lava flows that initially moved to the SSE and SSW then turned S. Weak explosive activity along the entire fissure ejected modest quantities of lava fragments. By evening, the main flow had cut a road and overrun several buildings.

During the morning of 1 April, vigorous emission of gas, ash, and old lava, accompanied by occasional phreatic explosions, began from two explosion craters upslope at 2,700 m altitude. At the end of the day, explosions from the southern vent ejected lava fragments. On 2 April, nearly constant lava production fed numerous superposed flows that formed a 500-m-wide lava field extending to 1,900 m altitude. As of 3 April, the lava had not advanced below 1,450 m altitude, 3.5 km from the fissure. At least four principal effusive vents were active along the 750-m fissure, and from its upper part strong gas emission with sporadic explosions occurred at about 30 hornitos.

Bands of open fractures, oriented about N-S, extended from the central crater area to the eruptive fissure. A substantial widening was noted at the S rim of Bocca Nuova, site of frequent collapse activity since Etna's last eruption (from N flank fissures in March 1981). Strong vapor emissions from Bocca Nuova sometimes included abundant ash. There was no activity from the Northeast and Southeast craters.

The temperature of the lava was less than 1,100°C and its chemistry (alkali basalt) [corrected from phonolitic tephrite] was similar to that from some of the more recent eruptions. An area of more than 1 km² was covered by lava and the volume emitted was estimated at about 8-10 x 10⁶ m³. The IIV considered the eruption to be a typical slow subterminal type. The last activity of this type on the S flank was in 1780. As of 8 April, effusive activity had diminished, but the eruption had not yet ended.

The lava destroyed ski lifts [the cable car system originally reported destroyed survived until March 1985] and destroyed or seriously damaged nine privately-owned huts and 11 small buildings owned by local authorities, including restaurants, chalets, mountain refuges, and a first aid station. Lava remained 8 km from the village of Nicolosi, its closest approach to a village or town.

Information Contacts: R. Romano, IIV; M. Krafft, Cernay, France; UPI.

April 1983 (SEAN 08:04) Cite this Report

Lava effusion continues; central crater explosions; deformation, temperature and self-potential data

The eruption was continuing as of 6 May. J. C. Tanguy noted that temperature station cables in the S part of the summit zone broke on 27 March between 0530 and 0946, probably because of the opening of the eruption fracture. Fissures extended S from 2,700 m (where two explosion vents formed on 31 March) to 2,450 m, then turned SSW along the trend of the 1910 eruption. Small hornitos and spatter cones formed between 2,450 and 2,350 m. The main effusive vent was at 2,280 m altitude. On 31 March, the temperature of lava at this vent was 1,067°C at 60 cm depth, and the same value was measured in the main flow 30-40 m downslope on 4 April. F. Mousnier-Lompre and G. Scarpinati recorded a lava temperature of 1,078°C on 1 May. J.B. Murray and A. Pullen reported that lava flow surface velocities measured 17-30 April were in the 1.17-3.41 m/s range. Using surface velocities, Murray and Pullen calculated an average effusion rate of 22 m³/s if flow thickness was 3 m and 44 m³/s if the thickness was 5 m.

Romolo Romano reported that lava flowed S and SW, forming a wide, complex field as much as 1 km across and 40 m thick. On the E side of the field, the fronts of the longest flows were about 6 km from the vent and reached 1,150 m altitude before stopping. On 23 April, the principal flow shifted to the W side of the field, and advanced to about 6.5 km from the vent, stopping at 1,100 m altitude only 30 m from a road. On 4 May the primary flow was again moving down the E side of the lava field and had reached 1,450 m altitude as of early 6 May. Lava flowed from the vent at about 2 m/s, a rate of about 10 m³/s, and had a temperature of about 1,030°C [but note 1,067° and 1,078° above]. The rate of advance of the flow fronts was quite variable and dependent on the gradient; estimated velocities ranged from a very few meters per hour to ~60 m/hour. The area covered by the lava was about 4 km² on 6 May and the volume of lava emitted was ~40 x 10⁶ m³.

Earlier in the eruption, small hornitos and spatter cones had formed above the main effusive vent and small quantities of lava fragments were ejected. Vapor emission continued from this portion of the eruption fissure but no lava fragment ejection has been noted since 10 April. Two explosion vents [not one as originally reported] at 2,700 m altitude ejected ash during the morning of 1 April [not 28 March as originally reported; Tanguy and Patané (1984), Frazzetta and Romano (1984)], but only vapor emission has been observed at this vent since then.

Throughout the eruption, ash was ejected at varying intensity from Bocca Nuova. More vigorous ash ejection 2-5 May sent plumes to 2 km above the crater and caused ashfalls on the mainland (Calabria coast) at least 60 km from the volcano. On 4 May, a polar orbiting satellite image showed the beginning of an ash emission episode at 0453. By the next image at 0606, a narrow plume extended nearly 1,000 km SE from Etna at an altitude of about 7.5 km. Venting was continuing at 0945 but the plume was smaller; at 1603, it was 100-150 km long. Another image, at 0705 on 6 May, showed a plume ~100 km long. From the Chasm, weak emission of gas that sometimes contained reddish ash has been observed during the eruption. In the Northeast and Southeast craters, eruptive activity was limited to weak fumarolic emissions, but new concentrations of large fractures were seen in these craters as well as small internal collapses.

Murray and Pullen reported that vertical ground deformation during 1981-82 was characterized by summit deflation and S flank inflation. Reoccupation of a precise leveling network 20-22 April 1983 showed large changes on the upper S flank (near Piccolo Rifugio) since September 1982: 42 cm of uplift W of the eruption fissure, 12 cm of uplift E of the fissure, and a drop of 126 cm on the fissure itself. Large and complex movements had occurred elsewhere, including deflation of 76 cm above the eruption fissure at about 2,900 m altitude (near Torre del Filosofo). Horizontal measurements across the fissure showed an E-W extension of 1.3 to 2 m since August 1981, with contraction of 17 cm and 6 cm at 500 m and 1 km W of the fissure. A network of 25 dry-tilt stations occupied 24-29 April 1983 showed no general inflation or deflation of the edifice since 1982.

Ground temperature measurements at 6 m depth on the S flank at 1,900 m altitude showed a strong increase in November 1982 (figure 10). In the summit zone, ground self-potential increased at roughly the same time and again in mid-January. A very steep rise occurred in early April, after the start of the eruption (figure 11). Immediately before the eruption a geophone in the S summit zone registered strong seismic activity, up to 134 events/hour during the morning of 27 March.

Figure 10. Ground temperatures measured July 1982-March 1983 at 6 m depth, Silvestri station (closed circles) and Calcarazzi station (open circles), Etna's south rift zone, 1,900 m altitude.

Figure 11. Ground self-potential (top), and temperature (bottom), at 120 cm depth, recorded at Vulcarolo station, south summit zone, 2,965 m altitude. Note that the very steep rise in self-potential occurred in early April, after the start of the eruption. Telemeasurements by ARGOS system.

Further References. Frazzetta, G., and Romano, R., 1984, The 1983 Etna eruption: event chronology and morphological evolution of the lava flow: BV, v. 47, p. 1079-1096.

Tanguy, J., and Patané, G., 1984, Activity of Mount Etna, 1977-1983: volcanic phenomena and accompanying seismic tremor: BV, v. 47, p. 965-976. (both in Barberi and Villari, eds., 1984, cited after 8:07)

Information Contacts: R. Romano, L. Villari, S. Gresta, and O. Consoli, IIV; J. Tanguy and J. Murray, PIRPSEV; A. Pullen, Imperial College; M. Matson, NOAA; C. Archambault and J. Stoschek, CNET, France; S. Scalia and G. Scarpinati, Acireale; J.Bartaire J. and N. Bartaire, St. Maur des Fossés; R. Cristofolini, M. Cosentino, G. Lombardo, G. Patanè, A. Viglianisi, and P. Villari, Ist. di Scienze della Terra, Catania; P. Mousnier-Lompré, Servizio Sismico Regionale.

May 1983 (SEAN 08:05) Cite this Report

Lava production slows; lava partially diverted; central crater explosions continue; self-potential data

The continuing eruption showed signs of a progressive decline on some days. The velocity of the lava flow from the vent at about 2,280 m altitude decreased from ~1.7 m/s on 28 May to <0.5 m/s in early June, with a reduction in the rate of outflow to ~3 m³/s. In early May, the velocity at the vent had been about 2 m/s and the effusion rate was about 10 m³/s. New flows, most of which moved S and SW, continued to add to the S flank lava field that has accumulated during the eruption. On 25 May a flow advanced beyond the edge of the lava field, reaching 1,240 m altitude by the 27th, ~5.5 km from the vent. From 28 May, all of the lava flowed toward the interior of the lava field or approached its W side. In early June, frequent and impressive overflows occurred from both sides of the main lava channel at about 2,200 m altitude. Within the lava field, effusive pseudo-vents at around 1,800-1,980 m altitude have remained numerous. As of 8 June the area covered by lava was estimated at 6 km² and the volume of lava produced by the eruption was ~75-80 x 10⁶ m³.

Explosions of varying intensity continued, particularly from Bocca Nuova and primarily ejected reddish ash. On 15 May and 1-4 June the explosions were quite large. A NOAA 7 satellite image at 1529 on 15 May showed a strong plume (as large or larger than the 4 May plume; 8:04) that extended 100-150 km to the SE. Pilots reported that the plume had emerged from the summit area at about 1100. on 1 June at 0800, pilots estimated the height of a plume at about 5 km and reported that it was drifting SSE. In May and early June, only vapor emission was observed from an explosion crater at 2,700 m altitude and a fissure between 2,450 and 2,300 m altitude that were active early in the eruption. On 3 June, deep felt shocks (M 3.3) occurred near the active vent; these events continued the next day.

Because the advancing lava flows threatened additional property damage, efforts were made to divert the lava. Explosive charges were detonated at 0409 on 14 May to blast a passage from the W side of the main lava flow at 2,100 m altitude into a previously prepared artificial channel. Initially 20% of the total lava flux was diverted into the artificial channel, but by 16 May lava had ceased to flow in this channel after reaching 700 m length. After the explosions, however, there were numerous substantial overflows from the main natural channel, particularly from the W side, and these slowed the advance of the most distant flow. Artificial embankments have also been constructed E and W of the main natural channel, allowing control of the overflows from this channel that were moving over earlier flows.

Pham Van Ngoc and D. Boyer obtained self potential data during a PIRPSEV mission to Etna 27 April to 3 May. The following is a report from Pham Van Ngoc.

"Five self potential (SP) profiles were carried out from 2,350 to 2,700 m elevation. These profiles straddled the open fissure that trends NNE-SSW below Piccolo Rifugio (at 2,500 m altitude on the S flank) and the N-S fractures above it. The profiles were located upstream from the lava emerging at 2,320 m altitude. Figure 12 shows the results of the SP profiles.

Figure 12. Results of self potential profiles obtained 27 April-3 May across open fractures that trended N-S above 2,500 m altitude (Piccolo Rifugio) and NNE-SSW (about 200° azimuth) below 2,500 m. The topographic profile (vertical exaggeration 2:01) parallels the fissure trends, changing strike at Piccolo Rifugio. Arrows pointing left show positions of self-potential profiles. Arrows pointing right diagrammatically show the inferred subsurface flow of magma, its emergence from the vent at 2,320 m altitude, and continuation downslope as flowing lava. The inset at lower left details profile III, indicating that the axis of the subsurface flow was under the ski lift building, 40 m W of the open fissure. Here arrows show local stress field and fault movement. Courtesy of Pham Van Ngoc.

"The shape of the SP anomalies was very different S and N of Piccolo Rifugio. To the S, profiles I, II, and III show huge (more than 50 mV) and sharp anomalies suggestive of superficial origin. it is notable that the maxima of these anomalies were not located just above the open fissure, but 40-50 m westward. The detail of profile III, just below Piccolo Rifugio, indicated clearly that the axis of the underground flow lies 40 m W of the active fissure (under the ski lift building W of Piccolo Rifugio). These results confirm that the pressure exerted by underground flow induced an E-W extension, creating a small graben clearly visible in the area of Piccolo Rifugio. The open fissure corresponds to a normal fault on the E edge of the graben and caused the collapse of the W part of Piccolo Rifugio.

"Above Piccolo Rifugio, profiles IV and V show much smaller Sp anomalies (~250 mV). Furthermore, these anomalies widen, thus indicating a deeper origin. It is notable that the shape of the SP anomalies changed completely from profile III to profile IV in a distance of ~300 m.

"SP results suggest that: 1) above Piccolo Rifugio, the magma flowed deeply in a N-S direction; and 2) level with Piccolo Rifugio (2,500 m altitude), the magma suddenly approached the surface and followed a shallow underground NNE-SSW channel that ran some 50 m W of the open fissure, then came to the surface at about 2,320 m altitude. Arrows in figure 12 indicate the path inferred from the lava."

Information Contacts: R. Romano, IIV; Pham Van Ngoc, Ecole Nationale Supérieure de Géologie; M. Matson, NOAA.

June 1983 (SEAN 08:06) Cite this Report

Lava production continues but at lower rate; central crater explosions; lava temperatures

Romolo Romano reported that the velocity of the lava flow from the main vent, at about 2,280 m altitude on the S flank, continued to decrease in early July, from somewhat less than 0.5 m/s in early June, to an estimated 0.1 m/s on 7 July. The rate of outflow, ~3 m³/s in early June, had dropped to ~0.5 m³/s by 7 July. Lava flowed SE, S, and SW onto the S flank lava field that has accumulated since the eruption began, but the flows were smaller than in previous months and reached a maximum length of 1 km. Between 1,800 and 1,950 m altitude, some flows approached the E edge of the lava field and effusive pseudo-vents remained numerous. Moving lava was visible through many small windows. Between the main vent and the lava field, numerous overflows occurred from the E and W sides of the main lava channel from 2,270 to 2,100 m altitude. As of 8 July, the volume of lava erupted since 28 March was estimated at 100-110 x 10⁶ m³.

J.C. Tanguy reported that on 14 June, the temperature of a slow (~0.15 m/s) lava outflow at 2,280 m altitude was determined to be 1,071-1,073°C using both Cr-Al and Pt-Rh thermocouples inserted at 40 cm depth. This temperature was identical to that measured in the main lava flow 12 May by P. Mousnier-Lompre. Lava velocity at the vent began to increase 14 June and reached almost 4 m/s 18-21 June. Gas pressure increased during the same period and new hornitos were built just below the main vent between 2,280 and 2,260 m altitude. Lava overflows occurred in this zone 18 and 20 June. On 21 June, gas pressure decreased and the lava velocity at the vent decreased to <1 m/s. The level of lava in the main channel dropped again, leaving impressive grottoes where gas combustion produced temperatures as high as 1,137°C (thermocouple) - 1,165°C (infrared measurements) on 21 June.

Moderate to violent explosions have continued to occur from Bocca Nuova. Explosions on 20, 24, and 26 June, and 8 July were especially strong. On 24 June, emission of white vapor had been increasing since at least 0700, culminating in an explosion at 1015 that ejected old material, including reddish cinders and large blocks, that fell as much as 250 m from the vent, primarily to the W. A polar orbiting satellite image 26 June at 0606 showed a low-altitude plume that extended ~100 km ESE, and a similar plume, ~150 km long, trended SSE on 4 July at 0640. Larger plumes were seen on satellite images 8 July at 1427 and 1609 (more than 500 km long, to the ESE), 10 July at 0615 (500 km, to the SSE) and 2036 (150 km, to the SE), and 11 July at 0554 (300-500 km, to the SSE). On 12 July at 1415, the U.S. Navy reported a cloud extending 250 km to the SE with a base at 1 km altitude and a top at ~5 km altitude. Only weak vapor emission has been observed from the Chasm, and from vents at 2,700 m on the S flank active earlier in the eruption.

Information Contacts: R. Romano, IIV; J. Tanguy, PIRPSEV; R. Clocchiatti, CEN, Saclay, France; F. De Larouziere, CNRS; R. Cristofolini, M. Cosentino, G. Patane, A. Viglianisi, and P. Villari, Ist. di Scienze della Terra, Catania; M. Matson, NOAA.

July 1983 (SEAN 08:07) Cite this Report

Eruption ends after four months of lava extrusion

After 131 days of activity, the eruption stopped during the morning of 6 August. The July activity was similar to that of the second half of June. The main lava channel was almost completely roofed over, but moving lava was visible through four "windows" in the channel roof. Numerous overflows from the upper "windows" produced modest lava flows of short duration during the first 10 days of July. Through the end of the month, lava emerged from scattered short-lived pseudo-vents at about 1,860-1,800 m above sea level and flowed onto the S flank lava field that has accumulated during the eruption (figure 13). These small superposed flows approached the E and W edges of the lava field; one advanced beyond the field's W margin on 13 July but stopped quickly. Efforts to contain the lava flows continued with the construction of new small embankments. None of the July flows moved below 1,600 m altitude.

Figure 13. Summit at S flank of Etna, showing the active vents and lava field of the 1983 eruption. Fractures are shown diagrammatically by short N-S lines. Contour interval 200 m. Large arrow on the upper W side of the lava field indicates the site of the partially successful attempt to divert lava into an artificial channel 14 May (08:05). Embankments constructed to limit the lava's spread are shown by x's. Several roads and villages in the area are shown (Sapienza is an inn, and Mt. Mazzo is an old vent). Nicolosi, Regalna, and Rocca cover larger areas than indicated. Courtesy of Romolo Romano.

Ash emissions occurred at irregular intervals from Bocca Nuova, but were not as strong as in the previous month. High-altitude winds carried ash to Catania (~30 km to the SSE) on 9, 10, and 11 July. No significant activity stoccurred from other vents.

Preliminary estimates suggest that the 131-day eruption extruded ~100 x 10⁶ m³ of lava, at a rate of 10 m³/s. Lava flowed a maximum of 7 km from the vent, reaching 1,100 m altitude (E of Mt. Mazzo), and covered an area of ~6 km².

Further References. Kieffer, G., 1983, L'Eruption de l'Etna commencée le 28 Mars, 1983: sa place dans l'exceptionnel cycle eruptif en cours (1971-1983): Comptes Rendus Acad. Sci. Paris, Ser. II, v. 296, p. 1689-1692.

Barberi, F., and Villari, L., eds., 1984, Special issue on Mt. Etna and its 1983 eruption: BV, v. 47, no. 2, p. 877-1177 (22 papers).

Lockwood, J.P., and Romano, R., 1985, Diversion of lava during the 1983 eruption of Mount Etna: Earthquake Information Bull., v. 17, no. 4, p. 124-133.

Information Contacts: R. Romano, IIV.

August 1983 (SEAN 08:08) Cite this Report

No new activity

No additional activity has been reported since 4 months of lava extrusion ended 6 August. [Corrections were made to the figure caption from the previous issue; this report was removed for GV 75-85.]

Information Contacts:

January 1984 (SEAN 09:01) Cite this Report

Incandescent tephra from central crater; seismicity

"Beginning in December, numerous seismic crises were recorded, mainly connected to the degassing of the magma column through the central vents. In the same period, ejections of reddish ash (old material) or dark ash (fresh material) occurred from the central crater. At times (14, 16, and 28 January) these have been rather significant, depositing thin layers of ash on the E flank. Some nights, pulsating flashes, due to the ejection of incandescent material from Bocca Nuova were observed. Tiltmeter variations were also recorded."

Information Contacts: R. Romano, IIV.

April 1984 (SEAN 09:04) Cite this Report

Strombolian activity and small lava flows from Southeast Crater

"During the night of 27-28 April, an eruptive fissure oriented approximately NW-SE opened inside the Southeast Crater, near its NE margin. This crater, which is at ~3,000 m elevation behind the SE side of the central crater, formed in May 1971 and had numerous eruptive episodes in 1978 (April-July, August, November), 1979 (July-August), and 1980 (January-September, explosive activity only).

"Initially, moderate activity was observed from three explosive vents along the fissure, which ejected lava fragments. At the same time, small lava flows emerged from the fissure, remaining inside the Southeast Crater. During the next few days, strombolian activity increased with the ejection of lava fragments to 250 m or slightly more in height. During the morning of 1 May, lava flowed over the NE rim of the crater then turned SE, covering the E side of the Valle del Bove and quickly reaching a length of 2 km. Feeding of this flow was continuous but of variable volume, resulting in numerous superposed and parallel subflows but little advance of the flow front after its initial rapid movement. On 6 May, lava overflowed the SE rim of the crater, advancing NE and later E. This flow, which was fed until the morning of 8 May, reached a length of about 1 km. As of 10 May, both the strombolian activity (which formed a scoria conescoria cone inside the Southeast Crater) and the effusive activity appeared to be decreasing.

"Starting 5 May, strong ash ejections from the Chasm were observed, while from Bocca Nuova only emission of gas under pressure was detected. In the past months, a lava lake 150 m from the rim of Bocca Nuova has been noted."

Information Contacts: R. Romano, IIV.

May 1984 (SEAN 09:05) Cite this Report

Continued lava production; Strombolian activity

"The Southeast Crater eruption was continuing in early June. The explosive strombolian activity from the small new cone within the Southeast Crater had been diminishing, and stopped almost completely 13 May. Starting that day, ash ejections have been observed at more or less regular intervals, while slow emission of gas and vapor usually occurred. The strombolian activity started again in late May; at times (25 May and 4 June) it was particularly violent.

"The effusive activity has been continuous, with alternating phases of greater or lesser vigor. The lava field has grown noticeably toward the S (reaching a maximum dimension of more than 500 m) and by early June had in its interior, many ephemeral effusive vents, which generated small lava flows that advanced over earlier ones. The main flows (generally one to the S and another to the N), which originated from convergence of the small flows, barely got below 2,700 m elevation.

"At irregular intervals, more or less violent ejections of reddish ash from the Chasm have been noted, while from Bocca Nuova there have only been gas emissions."

Information Contacts: R. Romano, IIV.

June 1984 (SEAN 09:06) Cite this Report

Explosions and lava production continue from Southeast Crater; central crater explosions

Tanguy and Clocchiatti reported that in late May and early June explosions, usually 10-30/minute, ejected lava fragments and scoria to 50-200 m above the inner cone that had formed inside the Southeast Crater. Explosive activity sometimes declined to weak puffs of gas without much tephra, but at other times the ejecta were rich in large fragments of magmatic material. During periods of more vigorous activity, occasional bursts hurled the smallest tephra to 500-600 m height. In contrast, lava effusion occurred at a steady rate of a few (perhaps 2-5) cubic meters per second, significantly lower than in paroxysmal eruptions (>10 m³/s) but probably higher than in typical subterminal persistent activity (1 m³/s). The maximum temperature measured at small effusive vents on 31 May and 5 June was 1,075-1,076°C (at 60 cm depth).

Romolo Romano reported that explosive activity at the Southeast Crater in June and early July was limited to ejection of incandescent tephra at varying intervals, occasionally accompanied by ejection of dark ash. Effusive activity continued, resulting in further enlargement of the lava field, especially to the N. Lava flows did not extend much below the 2,800 m level. During the last 10 days of June, lava overflows occurred from the SE side of the Southeast Crater, but did not flow over the edge of the Valle del Bove. On 4 July, an overflow of very thin (0.5 m thick) fast-moving lava occurred from the still-active SE side of the Southeast Crater. Tanguy and Clocchiatti reported Bocca Nuova was filled with lava to within ~100 m of its rim in April, but by early June the lava column was again very deep (> 300 m) and activity was limited to quiet emission of large amounts of SO₂. Romano reported that violent ejection of reddish ash from Bocca Nuova was observed beginning in the second half of June. Recently, the ash has been gray (indicating presence of new material). On 3 and 9 July, violent explosions ejected lava fragments that fell outside the crater rim, especially on the SW flank. During this period, strong emission of gas under pressure was noted at the Chasm.

Tanguy reported that in late April seismicity recorded by Christian Archambault from a geophone about 1 km SSE of the Southeast Crater increased from less than 500 to more than 2,200 events/day (figure 14). A seismic crisis was also recorded January-March, accompanied by lava filling and strombolian activity at Bocca Nuova. The temperature at 3 cm depth at the station about 400 m SSE of the Southeast Crater decreased before the 1983 flank eruption but increased before the current eruption began in April 1984.

Figure 14. Number of seismic events recorded per day (averaged over a 10-day period) at the TDF geophone about 1 km SSE of the Southeast Crater (top) and plot of the difference in subsurface temperature (measured at 3 cm depth) between the CC1 (~400 km SSE of the Southeast Crater) and TDF stations (bottom). Arrows indicated periods of eruptive activity. Courtesy of J.C. Tanguy.

Information Contacts: R. Romano, IIV; J. Tanguy, Univ. de Paris VI; R. Clocchiatti, CEN, Saclay, France; C. Archambault, CNET, France.

July 1984 (SEAN 09:07) Cite this Report

Lava production and Strombolian activity continue from Southeast Crater; strong explosions from Central and Northeast craters

"The Southeast Crater eruption was continuing in early August with more or less intense strombolian activity, accompanied at irregular intervals by violent expulsions of dark ash. This activity produced a scoria cone (~50 m high) higher than the rim of the Southeast Crater. The effusive activity took place from vents around 3,000 m above sea level that changed their positions continuously. On 6 August, two effusive vents were active along the old rim of the Southeast Crater, one on the NE edge, the other on the S edge. Some rather well-fed flows originated from these vents. The final flow direction was always E, toward the Valle del Bove. During this period, the lava flows never advanced below 2,600 m. The lava field that formed from this continuous and variable (in terms of intensity and position) effusive activity was larger than 1 km in extent. The volume of lava emitted can be estimated at around 8-10 x 10⁶ m³.

"An increase in central crater eruptive activity was recorded in July. From Bocca Nuova, violent expulsions of gray ash continued at irregular intervals, while on the vent floor, violent and continuous strombolian activity continued. At times, incandescent lava rose higher than the crater rim. The Chasm, after showing activity similar to that at Bocca Nuova in mid-July, was the source of violent activity on 19 July between 1300 and 1700. Very violent strombolian activity ejected incandescent lava fragments about 1 m in diameter to 500 m from the crater rim. The S and N flanks of the central crater were most often impacted by the lava fragments (their average diameter was ~30 m, they fell within an average radius of 300 m)."

The pilot of an aircraft flying near Etna at 1542 on 19 July observed an eruption cloud that reached ~6.5 km altitude. At 1613, the NOAA 7 polar orbiting satellite showed a plume extending 100 km E from Etna.

"After this, the Chasm remained obstructed until 1 August, when it reopened (at 1900) with the expulsion of old material that fell outside the crater rim. On 6 August, this vent was once again obstructed (around 1300) as the result of internal landslides."

"The Northeast Crater, inactive since February 1981, had a violent explosion that ejected old material on 20 July at 1715. Since then, strong emissions of gases occurred from the small vent that formed near the summit."

Information Contacts: R. Romano, IIV; M. Matson, NOAA.

August 1984 (SEAN 09:08) Cite this Report

Lava production and ash emission continue

"The Southeast Crater strombolian activity was intense at times (23 August, 1 and 6 September) and almost absent at other times (afternoon of 7 September). Violent expulsions of dark ash still occurred, at irregular intervals. The effusive activity took place through various vents along the edge of the Southeast Crater (around 3,000 m elevation). In August the effusive activity occurred mainly on the SE side producing lava flows variable in number, position, and rate of feeding. At first they were directed toward the S; later they turned E, rarely (on 23 August) advancing below the edge of the Valle del Bove (about 2,700 m elevation). On 31 August, one of these flows advanced to ~200 m from the rifugio Torre del Filosofo at 2,910 m elevation. The flow then turned E and stopped 1 September at 2,780 m elevation.

"August activity from Bocca Nuova was similar to that of the previous month, mainly showing emission of gas and steam. The Chasm remained obstructed by landslides within the conduit. During the first few days of September, isolated expulsions of reddish ash from the Northeast Crater were noted, always in the afternoon. The last one was observed on 5 September. Usually, strong emissions of gas occur from this crater."

On 16 August at 0606, a weather satellite image showed a plume extending ~200 km SE from Etna at about 5.5 km altitude. The next morning at 0726, a similar plume was present on the imagery. Low sun angles in the early morning improve the visibility of eruption plumes.

Information Contacts: R. Romano, IIV; M. Matson and J. Paquette, NOAA.

September 1984 (SEAN 09:09) Cite this Report

Lava flows, Strombolian activity and ash emission

Continuing strombolian activity, particularly intense at times (on the 14th and 20th) and very irregular in intensity and duration, marked the activity in September. Beginning 27 September, this activity was nearly replaced by expulsions of reddish ash at irregular intervals, rarely accompanied by the ejection of incandescent material (bombs and incandescent lava fragments). Lava flows, rarely thick (20 September), usually emerged from effusive vents on the S rim of the Southeast Crater at 3,050 m elevation, and were directed mainly SE, E, S, and ENE. A lava flow advanced S to about 100 m from the rifugio Torre del Filosofo. The flows moved across the lava field, rarely advancing below 2,700 m elevation, within the Valle del Bove.

"Strombolian activity occurred at the bottom of Bocca Nuova. The activity was particularly violent at times with ejection of incandescent lava fragments above the level of the crater rim (24 and 27 September). Generally, only gas emissions were observed. The Chasm usually remained obstructed. Rarely (11 and 24 September), incandescent gas under pressure was observed emerging from a small vent. From the Northeast Crater, isolated expulsions of reddish ash continued, but activity was usually limited to quiet gas and vapor emissions."

Michael Matson reported that a weather satellite image on 14 September at 0740 showed a plume at 4.5 km elevation or higher extending SE from Etna. Ejection of the plume was estimated to have begun 1-2 hours earlier. No plume was evident on an image at 0946.

The following report by Christopher Kilburn, is based on observations 25 August-1 October.

"Since the eruption began in late April, a cone has developed inside the upper E rim of the Southeast Crater, roughly coincident with the position of the most northerly vent active in 1979 (figure 15). On 1 October the cone was ~120 x 100 m at its base (the longer axis oriented roughly NNW) and some 30-40 m high. Until 20 September, the strombolian activity consisted of intermittent violent explosions, with peak frequencies of 14/minute and bomb trajectories ranging from subvertical to directed. Lower-angle ejections were mainly to the E and S, but occasionally to the N and W. Bombs of the order of 0.04 m³ had maximum ranges of ~300-400 m. After 20 September, the violence of the explosions markedly decreased. Weak ejections every few minutes or hours were interspersed with periods of inferred internal collapse that generated small convection columns of pale brown ash and dust. This change in explosive behaviour followed a brief period of rapid lava discharge to the E on 20 September as well as a period of heavy precipitation. Enlargement of the vent at the top of the new cone, which occurred sometime between 13 and 24 September, may have been associated with the 20 September lava discharge.

Figure 15. Morphology of Southeast Crater before the 1984 eruption (left); contours are approximate, in meters above sea level. Morphology of Southeast Crater 11 September 1084 (center) and 1 October 1984 (right); dashed line indicates the approximate extent of ponded lava, arrows the direction of lava discharge. After Murray, J. B., 1982, Sommit del Mt. Etna, Settembre 1981, 1:5000 scale map, Ordnance Survey, Southampton, U.K. Courtesy of Christopher Kilburn.

"Lava discharge was virtually continuous from ephemeral vents S and E of the base of the new cone. Lava flowed S, SE, and E over low points in the Southeast Crater rim. Activity typically alternated between the S and E vents at intervals of one to several days. The successive aa flows, few of which were longer than 1.5 km with frontal thicknesses rarely exceeding 5 m, created a compound flow field with an estimated area that approached 1.5 km² by 1 October (figure 16). By 23 September, ponding inside the Southeast Crater had reached a maximum accumulated thickness of more than 45 m, raising the level of its bottom to ~3,065 m above sea level. Assuming a conservative average thickness of 5 m, and including the material within the Southeast Crater, a provisional estimate of the minimum volume of the flow field on 1 October is 8.5 x 10⁶ m³, yielding a minimum average effusion rate of ~0.64 m³/s. Estimates of the eruption rate, made near the vent 17-28 September, were 0.5-1.0 m³/s for lava discharged toward the S. The chief uncertainties in these discharge rates are the velocity profiles across the flow surface and with depth, and the thickness of the flow; for the minimum value, parabolic velocity profiles and a flow depth of 3-4 m have been assumed, the maximum (central) surface velocity and lava channel width being estimated in the field.

Figure 16. Provisional sketch map of 1984 lava flows as of 1 October. Courtesy of Christopher Kilburn.

"The Strombolian activity at Bocca Nuova was accompanied by the emission of large quantities of SO₂-rich fumes. Until at least 24 September, magma was probably roughly 100-200 m below the W rim; observations were obscured by fumes. An apparently fresh bomb was found ~20-30 m from the NW rim 24 September, while others, up to 70 cm across, were seen being expelled toward the N and NW 28-29 September to a maximum estimated range of ~100-120 m. It is not known whether ejection of material outside the crater indicated a rise in level of magma within Bocca Nuova or an increase in explosive vigour due to changes in the physical state of the magma, notably in its vesicle content."

Information Contacts: R. Romano, IIV; C. Kilburn, Univ. of London; J. Murray, D. Decobecq, and C. Delmotte, Univ. Paris Sud; P. Briole, PIRPSEV; M. Matson, NOAA.

October 1984 (SEAN 09:10) Cite this Report

Earthquake swarm starts as lava production ends

After 172 days of activity, the eruption in the Southeast Crater stopped during the evening of 16 October, although activity continued at the Northeast and central craters. On 17-18 October, only violent ejections of ash at rather long intervals occurred from the small cone that had formed inside the Southeast Crater. The ash ejections stopped completely the morning of 18 October. During the last week of activity from the Southeast Crater, there was a gradual decrease in lava effusion, which was limited to vents along the S rim, and ash ejection from the small cone inside the crater. The lava flows were directed mainly toward the SE, generally stopping after only a few hundred meters.

"During the late morning of 16 October, strombolian activity began from a vent at the bottom of The Chasm. Activity was extremely violent during the evening. At times, lava fragments were ejected above the crater rim, falling back within a 100-m radius. The strombolian activity diminished during the night but continued, with alternating phases, through 17 October. During the morning of 18 October, the crater was obstructed by consolidated lava. It reopened 25 October with the ejection of old lava and ash, and more or less intense emission of gas has continued since then. Bocca Nuova alternated phases of slow emission of gas with periods of intense emission of vapor mixed, at times, with mainly reddish ash.

"Ejections of vapor mixed with reddish ash that had started at the beginning of September from the Northeast Crater intensified during the final phase of the Southeast Crater eruption. During the night of 19 October, weak strombolian activity from the Northeast Crater was recorded at irregular intervals. This activity was succeeded by almost continuous ejection of dark ash, followed during the night of 21 October by the collapse of the crater's summit area. This enlarged the central part of the crater and ejected old lava to a distance of about 500 m, mainly toward the W. Discontinuous and more or less intense emission of vapor mixed with reddish ash started 21 October from this crater, while continuous emission of dense white vapor occurred from a small vent to the N.

"During the afternoon of 16 October a seismic crisis began, with earthquakes mainly occurring in the middle and upper parts of the E flank. The strongest shocks (M ~3.5-4.5), which were felt, were all shallow (around a few kilometers)."

A few of the largest earthquakes in the swarm are described below. Date, time, epicenter, and some casualty and damage data are from Romolo Romano; intensity values and the remaining casualty/damage information are from press sources.

18 October, 1258: centered near Piano Pernicana (15.5 km NE of the summit): Intensity reached MM V-VII, causing ground fracturing and some cracking of roofs and walls.

19 October, 1843: centered near Zafferana Etnea (11.5 km SE of the summit): 1 person was killed and others injured. Intensity reached MM VII-VIII. More than 400 buildings were damaged, including 50% of the historic district, and about 500 people were left homeless. Damage also occurred in Milo (11 km ESE of the summit), Fornazzo (10.5 km E), Santa Venerina (14 km SE), and Giarre (16.5 km ESE).

25 October, 0211: centered near Fleri (14 km SE of the summit), where it reached MM VIII, injured 12-15 people, destroyed 80% of the houses, and left 900 homeless. Ground cracking was observed in the area. Mt. Ilice, a 350-m-high prehistoric cone roughly 1.5 km upslope from Fleri, lost about 20 m of height during the earthquake. The shock was also felt in Catania.

7 November, 0956, centered near Pedara (15.5 km SE of the summit), where a few buildings were damaged.

Information Contacts: R. Romano, IIV; La Stampa, Torino; Corriere della Sera, Milano.

November 1984 (SEAN 09:11) Cite this Report

Occasional ash emission; flank seismicity continues

No major eruptive activity has occurred since the Southeast Crater eruption ended in mid-October. From the Northeast Crater, emission of white vapor was more or less continuous and consistent. Sporadic expulsions of reddish ash were observed 27 November and 3 December. Ejection of mainly reddish ash observed at Bocca Nuova was particularly violent 22-24 November. Ash ejected 23 November was mainly dark in color, but on succeeding days was mostly reddish older material that had fallen into the conduit. Ash fell on the lower SE flank. Only weak emission of gas and vapor occurred from The Chasm.

Flank seismicity began as the Southeast Crater eruption ended in mid-October (09:10). Isolated tremors continued in November. Both felt and located events were mainly on the N and NE flanks. No additional damage was reported.

Information Contacts: R. Romano, IIV.

February 1985 (SEAN 10:02) Cite this Report

Seismicity, then Strombolian activity and lava flows from Southeast Crater; ashfall on coast towns

Weak strombolian activity started 8-9 March in the Southeast Crater. Lava began to flow from the Southeast Crater the morning of 10 March and advanced E (toward the Valle del Bove), stopping that night as feeding ended. Mudflows were also observed in the Valle del Bove; heavy rains had caused flooding in Sicily during the previous week. On 11 March, fissures opened on the upper S flank (in Piano del Lago Alto). The press reported that temperatures in some of the fissures were high enough to melt plastic at nearby cable car stations. Ash fell on the towns of Acireale and Fiumefreddo (~20 km SE and 20 km ENE of the central crater). During the morning of 12 March, lava emerged from vents that opened at progressively lower elevations (from 2,620 to 2,500 m above sea level) and flowed S and SSW, reaching 2,250 m elevation by the next morning. Numerous mudflows preceded the lava flows.

An 11 March newspaper article citing the National Institute of Geophysics reported that microtremors with epicenters in the W part of the Valle del Bove had been recorded for the past few days. A M 3.4 event near the central crater occurred 9 March at 1523, and a shock with a focus at 5 km depth was felt 10 March at 1101 in the towns of Linguaglossa, Milo, and Sant Alfio (16 km NE, 11 km ESE, and 13 km E of the central crater). No magnitude was reported for the 10 March earthquake but both events were said to reach MM IV-V intensity.

Information Contacts: R. Romano, IIV; Il Progresso, New York; Corriere della Sera, Milano, UPI.

March 1985 (SEAN 10:03) Cite this Report

S-flank fissure eruption preceded by seismicity and tilt

The following is a report from Romolo Romano. Additional information about the eruptive activity from French volcanologists has been inserted in parentheses in this section. Their report of seismicity and tilt associated with the eruption is presented below.

"Explosive and effusive activity occurred 8-10 March from the Southeast Crater (French volcanologists noted that a strong but short-lived phase of the Southeast Crater activity started 10 March at 1100, with vigorous lava fountaining and overflow of lava toward the Valle del Bove). After numerous fractures formed 11 March on the upper S flank between 3,000 and 2,600 m above sea level, an exclusively effusive vent opened 12 March at 2,620 m elevation, with no recorded seismic activity. The same day, three more effusive vents opened at lower elevations (2,600, 2,510, and 2,490 m); only the last two (near Piccolo Rifugio) remained active. The lava flows that originated from these vents moved mainly toward the S and SW, giving rise to numerous individual lobes. Near the vent at 2,510 m elevation, weak explosive activity occurred, soon creating several small spatter cones and hornitos.

"On 14 March, the lava flows moving S destroyed two Etna cableway pylons; the cable broke the next day. The longest flow stopped 15 March at 2,080 m elevation. Along this trend, superposing lava flows were noted during the following days, until the effusive activity from the vent at 2,490 m ceased on 23 March.

"The lava flows that moved SW created an extensive lava field (maximum width 500 m). At 2,100 m elevation the lava field split into at least five lobes. The longest (and easternmost) flow had descended to 1,850 m elevation by 4 April, covering a distance of ~3 km.

"As of early April, the main lava channel had become a lava tubelava tube between 2,450 and 2,300 m above sea level. Short-lived effusive vents opened near the lower end of the tubelava tube, with lava flows approaching the E side of the lava field or flowing over it. The velocity of the lava flows varied from a few meters per hour to ~30 m/hour. The surface covered by the lava can be estimated at around 2.5 km² and the volume of lava at ~12 x 10⁶ m³. The temperature of lava at the vents was around 1,050°C.

"Particularly during the first few days of the eruption, because of the snow cover, several mudflows formed ahead of the lava flows. Phreatic explosions, violent at times (25 March) were also observed. During the eruption, more or less vigorous emission of vapor, gas, and rarely ash occurred from the central crater vents. (French volcanologists reported a strong explosion from the Chasm on 1 April at about 1625). Isolated expulsions of dark ash from Northeast Crater were observed.

"Collection of information on the eruptive activity was possible thanks to the cooperation of the following Italian Alpine Club rescue team guides and volunteers: G. Baglio, A. Cariola, A. Cristaudo, C. Ferlito, A. Nicotra, G. Puglisi, and F. Zipper."

Later newspaper reports described a swarm of about 30 earthquakes, some reaching intensities of MM IV-V, that started 7 April and continued until early on the 9th. The events were felt most strongly in the towns of Santa Venerina, Acireale, and Giarre (14.5 km SE, 20 km SE, and 17 km ESE of the central craters). After the swarm, the rate of lava production increased by a factor of about 1/3.

The following report, on activity monitored through the ARGOS system, is from PIRPSEV, CNRS-INAG, in the context of French-Italian cooperation.

"Two geophones and a Blum pendulum inclinometer, connected with ARGOS for telerecording of the data, operate near the summit (TDF) and on the south flank (SLN) (figure 17). The geophones record both earthquakes and pulses of volcanic tremor as seismic events, and appear to be good indicators of seismic activity linked to volcanism. The eruption was preceded by an increase in seismic activity (mainly tremor energy) as indicated by the two geophones (TDF and SLN, figure 18). However, after the Southeast Crater eruption, the tremor energy returned to very low levels (figure 19), although effusive vents subsequently opened on the S flank.

Figure 17. Sketch map of the summit and south flank of Etna, showing locations of geophones at Torre del Filosofo (TDF) and Serra la Nave (SLN), and orientation of the tiltmeter at SLN.

Figure 18. Seismicity (number of events per day), top, and tilt, bottom, preceding the 10 March eruption, recorded by the geophones at TDF and SLN, and the SLN tiltmeter. The TDF geophone detection level is 6µm/sec, the three SLN levels are 1.8, 9, and 45 µm/s.

Figure 19. Number of events per hour recorded by TDF geophone, 7-12 March 1985, showing a strong increase during the Southeast Crater eruption. Arrows at top indicated that eruption and the production of flank lava flows.

"The SLN inclinometer showed continuous tilt toward the WSW during early February, consistent with inflation on the site of the 1983 (and March 1985) eruptions (figure 18). Since mid-February, however, tilt has been mainly westward (figures 20 and 21), thus indicating inflation lower on the S rift zone. This change appears almost synchronous with the appearance of new frequencies of volcanic tremor (personal communication by S. Gresta)."

Figure 20. Tangential vs. radial component of the SLN tiltmeter, 25 January- 11 March 1985 (S rift zone inflation westward, summit inflation southward).

Figure 21. Small changes in tilt accompanying the Southeast Crater eruption, as recorded by the SLN tiltmeter, 7-11 March.

Information Contacts: R. Romano, IIV; C. Archambault and C. Pambrun, CNET/PIRPSEV; P. Blum, IPG/PIRPSEV; P. Briole, IIV/IPG/PIRPSEV; G. Kieffer, Centre de Recherches Volcanologiques, Clermont-Ferrand/PIRPSEV; J. Tanguy, PIRPSEV; La Stampa, Torino.

April 1985 (SEAN 10:04) Cite this Report

South-flank lava production continues; tremor energy increases

"The S flank activity that began 12 March was continuing in early May. During April, the main lava channel was transformed to a continuous lava tube (with at least three 'windows') from 2,510-2,320 m elevation. Around 2,300 m elevation numerous ephemeral effusive vents formed, variable in number and location, from which several lava flows originated and advanced over the lava field or along its E edge.

"The lava flows, directed mainly SE, S, and SSW, have not advanced much, generally stopping at 2,150-2,050 m above sea level. The lowest elevation reached during this period was 1,950 m (20 April). At times (19 and 21 April and 6 May), because of an increase in the production rate, lava overflows occurred following roof collapses in the upper parts (2,510 and 2,485 m elevation) of the lava tube, giving rise to small lava flows of short duration.

"No gas emission was noted from the mid-April hornitos. More or less intense emission of gas and vapor continued from both of the central crater vents; ash emission was very rare. The Northeast Crater generally emitted vapor and rarely (10 April and 9 May) ejected reddish ash.

"The surface covered by lava can be estimated at around 3 km² and the volume at ~20 x 10⁶ m³. In this period there has been almost a total absence of earthquakes. However, during the week of 8-14 April, 20 shocks with magnitudes less than 3 were recorded. Afterwards, a variation in the main spectral peaks of the tremor was observed. A gradual increase in the tremor energy was observed during the entire month of April (S. Gresta, personal communication).

"The Etna Guides and volunteers from the Italian Alpine Club rescue team cooperated in the collection of information about eruptive activity."

Information Contacts: R. Romano, IIV.

May 1985 (SEAN 10:05) Cite this Report

Lava flows toward SW and SE; strong gas and vapor emissions

"The eruption continued through May without significant changes from last month. The main lava channel has been transformed into a lava tube, between 2,510 and 2,320 m elevation, that has at least four windows through which it was possible to see the lava flow. The lava has maintained a constant velocity during the last few weeks. On 23 May another lava overflow occurred as a result of roof collapse along the upper portions of the lava tube (2,485 m elevation), generating small lava flows of brief duration.

"The numerous short-lived vents inside the lava field (from 2,320 to 2,150 m elevation) were variable, as usual, in number and position. The lava flows that originated from these short-lived vents have increased the size of the lava field on both the W and E sides to a maximum width of ~1.5 km.

"Beginning 10 May the lava moved mainly toward the SW (Monte Rinatura and Monte Nero). Around the beginning of June there were numerous lava flows toward the SE (1910 craters area). Lava continued to flow toward the south (Monte Castellazzi area), but these flows were not strongly fed. None of the lava flows descended below 2,000 m elevation.

"The more or less intense emission of gas and vapor from both vents of the central crater and from the Northeast Crater continue. Emissions of ash are rare and inconsistent. Gas under pressure emerged from a small opening at the southern base of the 1984 cone inside the Southeast Crater (P. Briole, personal communication). R. Clocchiatti conducted temperature measurements with a thermocouple; the temperature ranged between 1053°C and 1,088°C (CEN-SACLAY).

"M. Cosentino and G. Lombardo reported that no particular seismic activity was recorded. Instead, an increase in the average amplitude of harmonic tremor was noticed, probably connected to the degassing of the central and Northeast craters.

"The Etna guides and rescue volunteers from the Italian Alpine Club (A. Cristaudo and A. Nicotra) helped with information on the activity."

Information Contacts: R. Romano, IIV.

June 1985 (SEAN 10:06) Cite this Report

Continued S-flank lava production

"After a brief period of quiescence from 11-13 June, the eruption continued. Only one effusive vent remained active (2,485 m elevation) with major lava flows originating from it. From 9 to 11 July, following a brief increase in activity, four effusive vents were present at high elevation (2,490-2,480 m). The velocity of the lava produced in this period ranged from 20 to 7 cm/s, volume 2.5 to 0.5 m³ /s.

"The directions of the lava flows were mainly toward the S, SSE, and SE. In the last few weeks, lava flows of significant size were also present, and were directed toward the SSW, S, and SW. The short-lived vents were still present and numerous, scattered on the lava field from 2,350 to 2,250 m elevation. As usual, they varied in number and location. Recently, the lava field enlarged on the E side, but the lava flows have not descended below 2100 m elevation. The emission of gas continued and was sustained from the central craters, and the Southeast Crater. At times, expulsion of generally reddish ash from Bocca Nuova was noted. From the Northeast Crater, violent expulsions of old material (28 June), and emission of reddish ash (10 July) were observed.

"The temperature of the lava flow at the main effusive vent was around 1,080°C (P. Briole). During this period seismicity remained at low levels. On 12 June at 1848, a seismic event (M 2.5) with an epicenter in the lower E flank (14 km depth) was recorded. On 7 July, three events of low magnitude (<2.8) with epicenters on both the E and W flanks were also recorded.

"On 9 July at 0430, the amplitude of harmonic tremor increased abruptly, coinciding with the increase in effusive activity. During the following 24 hours, the amplitude of the harmonic tremor returned to normal levels (communications with M. Cosentino and G. Lombardo). The Etna guides and rescue volunteers from the Italian Alpine Club have cooperated in the collection of information."

Information Contacts: R. Romano, IIV.

July 1985 (SEAN 10:07) Cite this Report

Four-month eruption ends in mid-July

"The eruption ended 13 July. The first phase (12 March-11 June) lasted 92 days, the second phase (13 June-13 July) lasted 31 days.

"The effusive activity that had shown new strength during the last days of the eruption greatly diminished on 12 July. Only one main effusive vent at 2,490 m elevation and two short-lived effusive vents in the lava field (at 2,300 and 2,600 m) remained active. The flows from the upper vent never descended below 2,400 m elevation and those from the lava field vents never below 2,100 m. From preliminary estimates, the area covered by lava was ~2.2 km² and volume of lava produced was ~30 x 10⁶ m³. The maximum width of the lava field is 1.5 km, the maximum length of flows, 1,830 m (figure 22).

Figure 22. Preliminary map of 1985 lava field and its relation to the 1984 lavas. Data, provided by Romolo Romano, is provisional and subject to revision. "Bocca Nuova had a relatively sustained gas emission. Inconsistent expulsions of reddish ash were also observed. This activity was related to explosive activity on the floor of the vent (~300 m below the rim), and was limited to the collapse of the vent's internal walls. The Chasm produced only weak gas emission. Collapses of the walls of the Northeast Crater were observed, and starting 22 July, this crater was partially obstructed, with emission of gas under pressure. Except for the isolated seismic events felt in the upper part of volcanic on 19 and 20 July (M 2.8) and 22 July (M 3), the seismicity remained at low levels. [Originally published in SEAN 10:08, without accompanying text.]

Information Contacts: R. Romano, IIV.

December 1985 (SEAN 10:12) Cite this Report

SE-flank fissure eruption follows seismic swarm and deformation

Eruptive activity. (Romolo Romano) "Strombolian activity started from the Southeast Crater on 19 December. The activity occurred at irregular intervals, becoming increasingly intense and continuous in successive days. Since the end of the 12 March-13 July 1985 eruption, more or less intense strombolian activity had been observed from several explosive vents (variable in number and position) on the floor of Bocca Nuova at variable depths (from 100 to 300 m or more from the rim of the vent).

"On 25 December at 0340 an eruptive fissure opened on the W side of the Valle del Bove (on Etna's SE flank), beginning at 2,750 m above sea level. The opening of this E-W-oriented fissure was preceded by a seismic crisis (see below). Strombolian activity soon started along this fissure from at least three explosive vents, while a lava flow began from the lower end of the fissure, covering, in a period of 18 hours, a distance of 1.5 km. The lava flow stopped at a point NE of Monte Centenari, at about 1,700 m elevation, within the Valle del Bove. Eruptive activity from the fissure stopped early the next morning. Activity resumed from the same place early 28 December. This second eruptive phase was characterized by weak strombolian activity from the three explosive vents, and created small spatter cones. The effusive activity decreased; a very viscous lava flow moved ~300 m from the origin, branching at ~2,600 m elevation. The eruptive phase ceased during the early morning of 31 December. A violent expulsion of ash and lapilli from the summit craters (E and W vents of the central crater, Southeast Crater, and Northeast Crater) during the first hours of the eruption was succeeded by more or less continuous and consistent emission of reddish ash.

"The Etna Guides (S. Carbonaro, O. Consoli, A. Mazzaglia, A. Nicotizza, and volunteers of the Alpine Rescue Team of the Italian Alpine Club (A. Cristaudo) have collaborated in collecting information about the eruptive activity.

Seismic activity. (M. Cosentino, M. DiFrancesco, and E. Lombardo) "A seismic crisis began during the early morning of 25 December with shocks located mainly between Piano Provenzana (NE flank) and the Valle del Bove. The shocks were very shallow (2 km or less). At the same time, the amplitude of harmonic tremor increased sharply. The shock that destroyed the hotel Le Betulle at Piano Provenzana, killing one person and injuring seven others, occurred on 25 December at 0338 and had a magnitude of 3.5. During the following 48 hours, about 200 more tremors with magnitudes of 1-4 were recorded. The strongest, M 4, occurred on 26 December at 0334, with its epicenter at Piano Provenzana. Focal depths were 2-3 km. The area of the epicenters remained between Piano Provenzana and Valle del Bove. Beginning 27 December, seismicity decreased in frequency, energy, and number of events, and stabilized to values of ~5-6 shocks/day. Their location was mainly in the eruptive area and on the E and W flanks (especially in early January). Similar activity was continuing on 10 January."

Newspapers reported that continuing seismicity included an event on 12 January at 0037, centered in the Zafferana Etnea area (11 km SE of the summit), that reached MM 6 and damaged some buildings. At least 3-4 minor shocks (one of MM 3) were felt the previous day.

Ground deformation. (G. Nunnari and R. Velardita) "During the second half of December, the tilt stations (Pizzi Deneri, NE flank, elevation 2,850 m; and Serra Pizzuta Calvarina, S flank, elevation 1,650 m) recorded a progressive inflation of the upper E flank. At the Pizzi Deneri station the variation was 13 µrad radially and 22 µrad tangentially between 20 December at 0900 and 23 December at 0900. The same stations recorded a variation of 45 µrad radially and 42 µrad tangentially between 24 December at 0900 and 25 December at 0900. The deformation produced during the first hours of 26 December reached a level that remained substantially unchanged as of 10 January."

Information Contacts: R. Romano, G. Nunnari, and R. Velardita, IIV; M. Cosentino, M. DiFrancesco, and G. Lombardo, Ist. di Scienze della Terra, Catania; La Stampa, Torino.

January 1986 (SEAN 11:01) Cite this Report

Strong flank seismicity

Seismicity has continued since Etna's SE-flank fissure eruption in late December. The following is from R. Romano. "Beginning 1 February, a series of shocks occurred on all ... flanks (table 2). The most energetic events occurred 1 and 2 February ~ 15 km SE of the summit (in the Dagala zone, in the area of Santa Venerina and Linera), with magnitudes between 3.0 and 3.6 and depths within 1 km. During the week, 50 shocks were also recorded by instruments, mainly on the E flank."

Table 2. Largest of a series of earthquakes on Etna's flanks, February 1986.

Date	Location	Distance from summit	Magnitude	Depth
3 Feb 1986	E of S. Pizzuta	--	3.0	1 km
4 Feb 1986	Between Linera and Guardia Mangano	16 km SE	2.5	1 km
5 Feb 1986	E of Mt. Pomiciaro	15 km NE	3.2	16 km
6 Feb 1986	N flank, E of Malvagna	--	3.1	4 km
7 Feb 1986	Between Mt. Pomiciaro and Linguaglossa	15 km NE	3.0	16 km

Information Contacts: R. Romano, IIV.

February 1986 (SEAN 11:02) Cite this Report

Ash and bombs from Northeast Crater

While spending the night of 5 March at the foot of Northeast Crater, geologists observed ash emission every 5-15 minutes with ejection of glowing red bombs 6-7 times/hour. Bombs reached the base of the crater. Significant degassing occurred from both of the central craters (The Chasm and Bocca Nuova). However, there were no explosions, nor was glow visible at night.

Information Contacts: F. LeGuern, CNRS; Compagnie Republicaine de Securité de Briancan.

May 1986 (SEAN 11:05) Cite this Report

Strombolian activity and gas emission

Explosive activity has continued from both central crater vents since the end of the SE flank fissure eruption. Strombolian activity could be seen from within ~ 100 m of the W vent (Bocca Nuova) rim, but ejected lava fragments rarely rose above the crater rim. Active vents within Bocca Nuova varied in position and number. Since the end of April, a vent on Southeast Crater has emitted hot pressurized gas. Northeast Crater has been partially obstructed by internal landslides; weak fumarolic activity occurred along the crater walls.

Information Contacts: R. Romano, IIV.

September 1986 (SEAN 11:09) Cite this Report

Strombolian activity and lava flow, then strong explosion

Strombolian activity and lava production, late July-23 September. Strombolian activity began from Northeast Crater at the end of July and continued with periods of greater (19 August) and lesser intensity. In early September, 20-30 explosions occurred/minute, with ejection of bombs and scoria to 100-250 m above the vent. A scoria cone ~ 40 m high formed inside the crater. Strombolian activity increased in the late afternoon of 13 September, and lava overflowed Northeast Crater's W rim early the next morning, feeding a modest-sized lava flow that moved NW. By 16 September, the flow had descended to 2,920 m altitude (~ 1.5 km from the main effusive vent at 3,190 m altitude) after crossing a trail (maintained by the Società Turistica Star). During the following days, small lava flows advanced a few hundred meters NW, NNW, WNW, and W, beside or on top of the first flow. This slow and discontinuous activity built a small lava field, with a volume that was estimated at a maximum of 0.25 x 10⁶ m³. On 22 September, the temperature of the flowing lava near the vent was 1,094°C at 40 cm below its surface. During the effusive phase, Strombolian activity varied in strength but generally remained at rather low levels. While sampling high-temperature gases and measuring oxygen fugacity on 22 September, Patrick Allard and others noted that the floor of the crater oscillated, rising by as much as 1 m with every explosion. During a summit-area leveling traverse the next day, a very strong tremor made automatic level readings difficult. Strombolian activity increased considerably, with bombs rising to 200 m above the vent and falling 300 m away. Strombolian activity also occurred at the bottom of the E and W vents (The Chasm and Bocca Nuova) of the central crater. This activity was of variable intensity, with changing numbers and locations of vents. Only rarely were lava fragments ejected above the vent rims.

Cessation of activity, early 24 September. During the early morning of 24 September, the scoria cone and a portion of the wall inside Northeast Crater collapsed into the vent area, leaving a fuming pit ~50 m deep. Effusive and explosive activity ended almost immediately, between 0600 and 0700. That morning, activity was limited to expulsions of reddish ash and white vapor. Steaming fissures and a small graben (~ 1 m wide and 1 m deep in places, wider nearest the crater) opened to the SW and NE (figure 23), with fissures reaching the Valle del Leone (1.5 km ENE of Northeast Crater) and the Piano delle Concazze, 2 km to the ENE. Activity from Bocca Nuova had also ceased. A leveling team in the summit region and N of Northeast Crater detected some intermittent tremor and measured substantial deflation that had occurred since the previous day.

Figure 23. (left) Sketch map of Etna's summit area, showing the new fissures and graben of 24 September and the area of 24 September bomb fall. Numbers along the route taken by observers show positions of (1) Allard, Benhamou, and Pennisi; (2) Bond, Décobecq, Kilburn, Murray, and Obreski; and (3) Sagot. (center) Provisional sketch map showing depth and percentage of ejecta cover after the 24 September explosion. (right) Maximum particle size with distance from Northeast Crater. Courtesy of J. Murray, C. Kilburn, D. Décobecq, and A. Bond.

Because of the abrupt cessation of summit activity and the possibility of violent vent-clearing explosions, the summit area was closed to tourists.

Resumption of explosive activity, afternoon of 24 September. A prolonged period of ash ejection accompanied by thunder and lightning started at about 1215, causing a light ashfall on the upper SE flank (figure 23). At 1312, large dark ejecta were seen rising to ~ 40-50 m above the vent, with stronger expulsion of small brown ash clouds, but no discrete explosions were heard. Episodic eruptions continued for the next 3.5 hours. Periods dominated by quiet emission of pink-brown ash alternated with periods characterized by ejection of black cypressoid and columnar ash jets, and expulsion of large tephra to ~200-350 m above the vent (figure 24). Electric discharges were common. Thick white convecting vapor clouds emerged separately from the S part of the vent area, at increasing rates. Continuous tremor and occasional stronger shocks were felt after 1515 by a gas sampling team working ~ 200 m S of Northeast Crater. There was no apparent time relation between the seismicity and eruptive activity.

Figure 24. Evolution of activity from Etna's Northeast Crater on 24 September. Courtesy of J. Murray, C. Kilburn, D. Décobecq, and A. Bond.

The following preliminary observations have been extensively updated by J.B. Murray.

Ash emission began to increase gradually at about 1645, changing to violent phreatomagmatic explosions. Black clouds, again cypressoid and columnar, initially rose to 400 m above the vent, merging by 1743 to produce a convective cloud that reached a relatively consistent height of ~ 1,000 m. Stronger falls of ash and small lapilli occurred SE of the summit, and bombs reached heights of 600-700 m. No [sounds] were heard, [apart from frequent dry cracks of] electrical discharges in the cloud [and the rushing of air in the rising column]. Incandescent ejecta were first seen at about 1800, and within 40 minutes lava fountains had developed at the center of a much wider column of dark ash. Heat from the fountains could be felt from a distance of ~ 800 m. ... Between 1815 and 1843, bombs fell progressively farther SW from the vent, with maximum ejection distance increasing from ~300 to 700 m, and maximum heights building from ~600 to 1,500 m.

Paroxysmal explosion, evening of 24 September. The paroxysmal phase began about 1845 with continuous louder rumbling and the sudden rise of a vertical lava fountain, ~ 300 m across, to 800-1,000 m. A dense black cloud surged down the E flank of Northeast Crater into the Valle del Bove. [Dense bombs up to 50 cm in diameter fell as far as 2,700 m to the SW, suggesting to Murray that they reached 2-3 km height]. ... The eruption cloud moved SSE, and ... the tephra fallout [rapidly] advanced ~2 km, showering observers [fleeing in vehicles] on the S flank (near the Torre del Filosofo; figure 23) with a dense blanket of ... scoria and ash [with occasional heavy bombs falling from 2-3 km height]. In a short time, the entire SE flank of the volcano was covered by pyroclastic material of sizes that varied with distance from the vent (figure 23). [Differential winds at higher altitude carried some scoria SW as far as Biancavilla (~ 15 km SW), where fragments measuring a few cm fell]. Tephra fall continued for almost 20 minutes.

[Subsequent topographic mapping] showed that pyroclastic material (scoria, lava fragments, and lithic blocks) [reached 4 m thick near the edge of Northeast Crater, and 5 cm thick] at a distance of 2 km (Torre del Filosofo). Scoria and lithic blocks up to a meter in diameter could be found within a radius of 0.5 km; at 2 km, scoria a few tens of centimeters across were observed. Hot scoria 11 cm in diameter melted roof tar 4 km S of the crater (at Piccolo Rifugio); hot lapilli to [7.5] cm across [scratched car windshields at] the tourist complex around Rifugio Sapienza and the base station of the cable car system 6 km from the vent; some scoriae as large as 15 cm were found 7 km from Northeast Crater at 1,700 m altitude (Serra La Nave); and 1.9-[cm] lapilli fell at Nicolosi (17 km to the SSE). Lapilli [0.5 cm in size reached Catania, 27 km away, where light ashfalls also occurred]. Catania airport (35 km from the summit) was closed from that evening until late the next morning.

[Bond, Décobecq, Kilburn, Murray, and Obreski] estimate that the tephra column reached 10-13 km altitude during the paroxysmal phase, in agreement with an independent estimate by Mueller [from Nicolosi. However, photos by J.P. Delouche, approaching the volcano from Siracusa, show maximum column height to be 6-7 km above the summit (9-10 km altitude)]. The press reported that the tephra column was visible from the Aeolian Islands (95 km N), and Agrigento (100 km WSW). At [1900] on 24 September, the explosive activity ceased completely. During the following days, Northeast Crater slowly emitted gas, vapor, and (rarely) reddish ash.

[Nearly 200 depths measured by Murray, Décobecq, and Bond yield a tephra deposit volume of 2.6 x 10⁶ m³, mostly of pumice density, or 0.4 x 10⁶ m³ dense rock equivalent (DRE)]. The volume of material emitted was estimated by IIV geologists at around a few million cubic meters ... . If most of the tephra were assumed to have been erupted during the final phase, the mean paroxysmal eruption rate was [~500] m³ DRE/s (2.7 x 10⁶ kg/s). Kilburn notes that the independently determined values for eruption rate and column height are consistent with the column height model of Wilson et al., 1978. Total energy release was [~9 x 10²¹] ergs. Vigorous explosive eruptions are relatively uncommon at Etna; [this century only four comparable events have occurred, in 1917, 1940, 1947,and 1960].

Minor activity, late September-early October. Strombolian activity from the two central crater vents, which ended 24 September with the collapse in Northeast Crater, resumed on the morning of 29 September. Gas, at times under pressure, was also emitted from Southeast Crater and a nearby gas vent before, during, and after the paroxysmal explosion. Emission of gas with fragments of old lava and/or incandescent lapilli was observed at times. The frequency of these ejections was very irregular, varying from a few minutes to several hours. As of 9 October, no significant changes in the activity of the summit craters have been noted.

Seismicity. Beginning 13 September, the seismic activity consisted only of explosion earthquakes probably related to the onset of the increased Northeast Crater activity. During the night of 22 September, three isolated seismic shocks with a maximum magnitude of 2.9 were recorded on the NW flank. Minor shocks were recorded until the night of 2 October, when a swarm of 30 events (maximum magnitude 3.3) occurred on the lower NW flank (between Maletto and Randazzo) at variable depths of ~ 20 km. A second swarm started during the morning of 5 October, again on the W flank, at the same depth. The strongest shock (M 3.8) occurred at 1228, and was felt at numerous locations on the volcano. The swarm ended that night, after ~ 40 weak shallow events were recorded on the W flank (Monte Minardo area). Another swarm of ~ 10 shocks occurred the morning of 7 October, also on the W flank, with a maximum magnitude of 3.3.

Harmonic tremor increased during the first phase of Northeast Crater eruptive activity (13 September). Similar tremor energy values were observed until ~ 5 hours before the 24 September eruptive event, when tremor energy began a gradual increase of about an order of magnitude. Energy values returned to normal around 2000 and no significant variations occurred in the following days.

Reference. Wilson, L., Sparks, R.S.J., Huang, T.C., and Watkins, N.D., 1987, The Control of volcanic column heights by eruption energetics and dynamics: JGR, v. 83 p. 1829-1836.

Further References. Amore, C., Giuffrida, E., Scribano, V., Lowenstern, J., and Müller, W., 1987, Emplacement and textural analysis of some present-day pyroclastic deposits of Mt. Etna (Sicily): Boll. Soc. Geol. It., v. 106, p. 785-791.

Murray, J., Décobecq, D., and Bond, A., 1989-90, L'Eruption paroxysmale du cratère Nordest de l'Etna du 24 Septembre 1986: LAVE Bulletin, no. 22, p. 11-23; no. 23, p. 5-18; and no. 24, p. 11-21.

Information Contacts: R. Romano, G. Budetta, T. Caltabiano, D. Condarelli, O. Consoli, and E. Lo Giudice, IIV; G. Luongo, IIV and OV; G. Ricciardi and G. Forgione, OV; S. Gresta, Univ di Catania; R. Clocchiatti, P. Gillot, G. Kieffer, J. Murray, and J. Tanguy, PIRPSEV; P. Allard, G. Benhamou, and M. Pennisi, Centre de Faibles Radioactivites; A. Bond, Univ of Lancaster; D. Décobecq, Univ Paris-Sud; C. Kilburn, Univ di Napoli.

October 1986 (SEAN 11:10) Cite this Report

Lava flows and Strombolian activity from SE fissures and crater

A new system of eruptive fissures opened at the base of the central crater on 30 October. The new eruption was marked by vigorous Strombolian activity and intense seismicity. Several new lava flows emerged from the fissures.

The seismic activity observed during the first several days of October continued during the following days. Both shallow and deep earthquakes occurred, mainly on the W flank of the volcano. The deepest earthquakes were at 20 km and maximum magnitude was 3.0.

An intense but brief seismic swarm that included > 40 shocks in one hour began at 2345 on 29 October. The strongest event (M 3.7), centered on the NE flank (at Piano Provenzana), occurred ~1/2 hour later at 0018. Only a few events were recorded during the following days.

Harmonic tremor remained at late September-early October levels until 30 October, when the seismic swarm was joined by a brief, ten-fold rise in tremor amplitudes, between 0000 and 0400, that accompanied the opening of a system of eruptive fissures. The 2-km-long fissure system, oriented ENE, stretched from the base of the central crater to the Valle del Leone (from 2,900 to 2,500 m above sea level (asl), on the W flank of the Valle del Bove). Several explosive vents that formed along the upper part of the fissure system were the source of gas and vapor emission, strong ash expulsions, and occasional phreatic explosions. Weak Strombolian activity occurred from the lower part of the fissure system (~ 2,500 m altitude) and several lobes of lava flowed away from the fissures. Eight hours after the start of the eruption, two main flows were moving SE. The southern flow had advanced ~ 2.5 km and reached the Valle del Bove at 1,750 m altitude.

During the early afternoon the fissure system continued to propagate downslope, creating a new eruptive fissure NW of Mt. Simone, around 2,300-2,200 m altitude, just behind and to the side of the N "wall" of the Valle del Bove. Violent explosive Strombolian activity started immediately, as four eruptive vents formed. Lava flows from the two lower vents coalesced into a single lobe that moved SE. In the late evening, strong lava fountaining began along a few hundred meters of the central part of the fissure system (around 2,600-2,500 m altitude). The ash and lapilli from this activity were transported by the wind 30 km to the SW.

Similar explosive activity was continuing the next morning. Lava formed three main flows (around 2,700 m altitude), that moved SE and ESE. Tremor amplitude decreased significantly, but increases were later recorded during various periods of increased eruptive vigor. Strong Strombolian activity from Southeast Crater began in the early afternoon. Isolated but violent explosions continued until the next day (1 November) when lava overflowed from Southeast Crater and moved SE for a few hundred meters. Southeast Crater lava effusion ended during the morning of 2 November and ash expulsions, sometimes violent, began.

During the first few days of November, violent explosions audible on the entire SE flank marked periods of intense ash expulsion from the new eruptive vents (particularly those around 2,300-2,200 m altitude). The numerous lava flows remained above 1,500 m altitude, forming a large lava field.

Strombolian activity from the bottom of the 2 central crater vents had continued through October. From the beginning of the 30 October eruption, vapor emission of fluctuating intensity alternated with expulsions of significant amounts of dark ash from these vents. Fumarolic activity occurred along the edges of Northeast Crater.

On 3 November a M 3.5 earthquake, the strongest since 30 October, occurred at 0833 in the lower part of the Valle del Bove. As of the morning of 10 November, weak Strombolian activity was occurring from six explosive vents, two around 2,500 m altitude, and four around 2,300-2,200 m. Lava from the two eruptive systems merged and formed a single flow. It advanced 200 m past Rocca Musarra (on the N side) and penetrated farther inside the Valle del Bove than any other flow, to 1,450 m. At least two large scoria cones were forming over the vents.

Information Contacts: R. Romano, G. Budetta, T. Caltabiano, D. Condarelli, and O. Consoli, IIV; G. Luongo, IIV and OV; S. Gresta, Univ di Catania.

November 1986 (SEAN 11:11) Cite this Report

Fissure eruption continues

"The eruption ... was continuing in early December. As of 9 December, two eruptive vents were still active, as was a pit crater at ~ 2,850 m altitude (figure 25) that generally showed strong gas emission but at times (15 November) violent expulsions of ash and/or sporadic ejection of incandescent material. A substantial spatter cone has formed at the eruptive vent at 2,600 m altitude, from which strong gas emissions have occurred since mid-November. The main lava channel originated at the base of the cone, and since the end of November has been an essentially continuous lava tube (with at least seven skylights in its roof) down to 1,900-2,000 m altitude, where a few ephemeral effusive vents have formed. Several lava flows fanned out from these vents, rarely going below 1,500 m and remaining within the Valle del Bove. The more active lava flows have generally moved E. On 19 November one of these reached 1,325 m altitude, ~ 5 km from the vent.

Figure 25. Sketch map of Etna's summit area and E flank showing new fissures, lava flows, and spatter cones.

"A large spatter cone (called Monte Rittmann in memory of our beloved teacher) formed around 2,300-2,350 m, and reached a height of ~ 100 m. From its base, a lava overflow started at the beginning of December and fed a flow that advanced ~700 m before stopping behind Monte Simone. Monte Rittmann has shown almost continuous Strombolian activity, more or less violent and often accompanied by strong explosions. Expulsions of ash have also been observed. The eruptive vents at lower elevation have not been active since 25 November. These vents, one exclusively explosive (at ~ 2,250 m altitude) and two primarily effusive (2,200 and 2,190 m altitude) were very active during the first weeks of the eruption, helping to form a large lava field. The flow fronts were generally wide (at times > 100 m) and high (at times > 10 m). An initial estimate, still to be confirmed, suggests that the volume of lava is around 25 x10⁶ m³. It is difficult at this time to evaluate the surface covered by the lava, but it should be > 4 km².

"From the E vent of the central crater (the Chasm) more or less violent emissions of reddish ash have continued without interruption. Only emissions of gas and vapor were recorded from the other summit-area vents.

"Only a few weak earthquakes were recorded during November and the first few days of December. Volcanic tremor remained at high levels (5-10x normal), with variations related to changes in the eruptive activity."

Information Contacts: R. Romano, T. Caltabiano, D. Condarelli, and O. Consoli, IIV; S. Gresta, Univ di Catania.

December 1986 (SEAN 11:12) Cite this Report

Lava flows; Strombolian activity; ash emission

"The eruption was continuing in early January. Strong gas emissions continued from the eruptive vent at ~ 2,600 m altitude. Lava continued to flow into a tube that extended from the base of the vent to ~ 1,800 m altitude, where there were ephemeral effusive vents that varied in number and position. The lava flows that originated from these ephemeral vents did not advance below 1,500 m altitude, and remained in the center of the Valle del Bove.

"The Strombolian activity at Conetto Rittmann (2,350-2,300 m altitude), at times from as many as three explosive vents, included periods of greater or lesser activity, but diminished gradually. From the beginning of January, the Strombolian activity was almost totally replaced by more or less violent explosions of gray ash. Lava flows originating at the base of Conetto Rittmann (recently more than two lobes have been noted) usually reached 1450 m altitude, passing N of Rocca Musarra, where they stagnated. The rate of lava production varied considerably with time. At the pit crater at ~ 2,850 m altitude, only gas emissions were observed. More or less violent explosions of reddish ash continued from the E vent of the central crater (La Voragine) alternating with periods (more rare) of vapor emission. Gas emissions from the other summit vents (Bocca Nuova, and Southeast and Northeast craters) were continuous but of varying strength.

"During this period, no seismic shocks were recorded. Volcanic tremor remained at rather high levels, with sporadic variations associated with the trend of the eruptive activity."

Further Reference. Kieffer, G., and Tanguy, J.C., 1987, L'activité de l'Etna en 1986: Bull. Sect. Volcanol. Soc. Géol. Fr., no. 3 (January 1987), p. 3-6.

Information Contacts: R. Romano, T. Caltabiano, and D. Condarelli, IIV; S. Gresta, Univ di Catania.

January 1987 (SEAN 12:01) Cite this Report

Lava flows in tubes; Strombolian activity and seismicity decline

"The eruption ... continues. Gas emission and rarely (12, 13, and 18 January) strong expulsions of ash occurred from the pit crater at ~ 2,850 m altitude. Only gas emission was observed from the spatter cone at ~ 2,600 m altitude, and it appears that lava effusion from its base ceased at the end of January.

"The Strombolian activity from Conetto Rittmann (2,350-2,300 m altitude) has decreased gradually, almost completely replaced since mid-January by more or less violent expulsions of gray ash, and irregular intervals in which only gas emission was observed.

"The effusive activity that originates from the base of Conetto Rittmann continued with alternating phases of greater or lesser intensity. Between 9 and 23 January several lava flows (four at times) were noted. These were fed at a moderate rate and descended to 1,500 m altitude, after passing Rocca Musarra to the N and S. As of mid-February, a lava tube extended from the base of Conetto Rittmann down to 2,000 m altitude. From there, small lava flows originated from many ephemeral vents, variable in location and duration. These flows moved mainly SE and E, covering lava from previous days, but remained inside the Valle del Bove, and never descended below 1,700 m altitude.

"Expulsions of reddish ash were observed at irregular intervals from both vents of the central crater (mainly from the E vent), while from Southeast Crater only gas emission of variable intensity was recorded. Weak fumarolic activity occurred from Northeast Crater.

"During the first two weeks of January no earthquakes were recorded. Tremor remained at high levels until the morning of 16 January, when tremor energy was reduced to 1/4 that of the preceding days. Seismicity resumed 27 January and continued for 5 days with weak, sporadic shocks on the N flank, at ~ 10 km depth. At the same time, tremor energy descended to levels typical of quiet periods at the volcano.

"Two strong earthquakes (M 4.2, depth 20 km) were recorded on 2 February at 1648 and 1659. Epicenters were ~ 40 km NW of the volcano and the events were felt in much of eastern Sicily. No additional significant earthquakes had occurred as of mid-February, and tremor remained at low levels."

Information Contacts: R. Romano, T. Caltabiano, and D. Condarelli, IIV; S. Gresta and C. Sturiale, Univ di Catania.

February 1987 (SEAN 12:02) Cite this Report

120-day eruption ends

"The eruption that began 30 October 1986 ceased at the end of February, probably on the 27th, after 120 days. The effusive activity that had originated from Conetto Rittmann diminished gradually. Only two lava flows, poorly fed, were noted around 20 February. These were moving across the lava field that had formed in previous months within the Valle del Bove, and did not advance below 1,800 m altitude. At the end of February, only gas emission, very vigorous at times, was noted at Conetto Rittmann. More or less impressive gas emission, mixed at times with a little ash, occurred from the two central crater vents. Consistent ash expulsion was rare. Gas emission continued from Southeast Crater. During the eruption, Northeast Crater had shown weak fumarolic activity, but emission of gas that sometimes contained a little ash was noted in early March.

"After the two earthquakes of 2 February, no significant shocks had occurred in the area as of 6 March. Throughout February, tremor energy remained at the low levels reached at the end of January. The presumed date of the end of all eruptive activity (27 February) is in accord with a decline in tremor energy, when values reached those typical of quiescence at the volcano."

Further References. Caltabiano, T., Calvari, S., and Romano, R., 1987, Rapporto sull'attività eruttiva dell'Etna nel periodo Gennaio 1986-Febbraio 1987: Bolletino del Gruppo Nazionale per la Vulcanologia, p. 215-231.

Carveni, P., Rasa, R., Scribano, V., and Sturiale, C., 1987, L'Eruzione Etnea del 1986-1987: Aspetti Fenomenologici e Dati Petrologici: Boll. Accad. Gioenia Sci. Nat. Catania, v. 20, p. 197-217.

Information Contacts: R. Romano, T. Caltabiano, and D. Condarelli, IIV; S. Gresta and C. Sturiale, Univ di Catania.

April 1987 (SEAN 12:04) Cite this Report

Phreatic explosions from Southeast Crater kills two, injures seven

An explosion from Southeast Crater on 17 April ejected tephra that killed two people and injured seven others.

During the first half of March, Northeast Crater occasionally emitted gas and vapor, sometimes with ash. During the second half of the month only weak fumarolic activity occurred from Northeast Crater, but more or less intense gas emission episodes that occasionally ejected ash occurred from the central crater's Bocca Nuova. Low-level volcanic tremor occurred during the same period but no earthquakes were recorded. Ten microshocks (M 1.0) occurred 23-25 March.

Sudden increases in sporadic tremor, lasting ~ 10-15 minutes, began 1 April. Geologists attributed the tremor to deep phreatomagmatic explosions. Activity increased during the first few days of April, reaching a maximum of 10 episodes of sporadic tremor on the 6th. The episodes lasted 30-40 minutes each and occurred at ~ 2-hour intervals. On 8 April > 50 microearthquakes were recorded. Only weak gas emission occurred from the central crater's E vent through early April. However, on 8 April at 0835 a violent phreatic explosion from that vent fed a 1-km-high eruption column. Abundant tephra was strewn to 300 m from the crater rim, with maximum dispersion to the NE. Geologists believed that similar explosions had probably occurred during the second half of March. The 8 April explosion was followed by a long period of relative seismic quiescence when only weak sporadic tremor was recorded. Beginning 12 April, 4-5 episodes of sporadic tremor were recorded daily.

Following several days of forceful gas emissions from Southeast Crater, tremor duration increased to a maximum of 30 minutes on the morning of 17 April. At 1335 a moderate-intensity phreatic explosion launched tephra SSE, killing two and injuring seven of the ~ 30 tourists who, the press reported, were standing ~500 m from the crater. A similar explosion on 12 September 1979 had killed 9 tourists and injured 23 others near the central crater's Bocca Nuova (04:09). The 17 April ejecta appeared to be older volcanic material. Tephra fragments 150 m from the crater rim reached diameters of 15 cm and at 250 m were a maximum of 5 cm. IIV geologists suggested that conditions for the 8 and [17] April explosions resulted from the collapse of the internal vent walls and subsequent gas accumulation.

Immediately after the [17] April explosion an increase in tremor was noted. The next day, three episodes of periodic tremor were recorded, each lasting ~ 90-120 minutes. Levels of tremor 2-3x normal continued through the end of the month. Only small quantities of gas were emitted from the central crater during the days following the fatal explosion. Weak Strombolian activity [from Southeast Crater] was observed during the night of 25 April and the morning of 26 April [and 10-16 May]. Vapor emission resumed after the end of the Strombolian activity.

Information Contacts: R. Romano, T. Caltabiano, D. Condarelli, O. Consoli, and G. Frazzetta, IIV; S. Gresta and C. Sturiale, Univ di Catania; La Republica, Rome; AP.

March 1988 (SEAN 13:03) Cite this Report

Inflation and seismicity

The following is from a joint French (CNRS/PIRPSEV)-Italian (CNR) monitoring program.

Ground deformation and microseismicity data are transmitted by an ARGOS satellite station, 1 km SSE of the central craters at 2,920 m asl (near the Torre del Filosofo). Two tiltmeters and a vertical geophone are installed inside a 50-m-long lava tube.

From November 1987 through January 1988, no ground deformation was detected and microseismicity was at a low level (100 events/day). In February, ~ 3 µrads/day of nearly continuous inflation was measured by the N-S component of the tilt instrumentation, but E-W tilt remained essentially flat (figure 26). Microseismicity remained at a low level until 25 February, when both the number of events and noise amplitude began to increase (figure 27). A sharp (30 µrad) N-S deflation occurred 29 February-1 March, with a further increase in the number of events (to 700-950/day) and noise amplitude.

Figure 26. Summit tilt measured 1 November 1987-10 April 1988 by the N-S (top), and E-W (bottom) components at site TDF, 1 km SSE of the central craters at 2920 m asl (near the Torre del Filosofo). Courtesy of the joint French-Italian Etna survey program.

Figure 27. Number of seismic events/day with amplitudes >4 Nm (top), and daily mean value of noise energy (bottom), measured at site TDF, 1 November 1987-12 April 1988. Courtesy of the joint French-Italian Etna survey program.

Seismicity continued to build 1-5 March, to 1,100 earthquakes/day. An additional 15 µrad of N-S deflation 5 March was accompanied by the onset of 20 µrad of rapid uplift to the E. From 5 March through early April, NNE-trending inflation has continued at ~ 4 µrad/day, and microseismicity has remained strong, reaching a maximum of 2,700 shocks/day on 8 April. Since the end of February, the 10-station ARGOS seismic network has located many shallow earthquakes in the NE quadrant of the volcano. Local and regional networks have recorded many earthquakes on Sicily's E coast, especially near Etna. Some reached M3 with hypocenters deeper that 10 km. One was felt during the night of 1-2 April by residents of Santa Venerina (15 km SSE of the summit) and Guardia-Mangano (18 km SSE). The ground deformation and microseismicity data suggested to the French/Italian team that significant stress modifications had been located beneath the central craters, and these have since moved to the E flank. No magma had reached the surface as of early April and degassing activity from Bocca Nuova and Southeast Crater remained normal.

Information Contacts: C. Archambault, Centre National d'Etudes des Telécommunications; F. Barberi, Univ di Pisa; R. Basile, Osservatorio Sismologico, Acireale; P. Briole and C. Pambrun, IPGP; J. Glot, IRIGM; J. Liparski, ICSC World Laboratory; O. Nicoloso, Nicolosi.

January 1989 (SEAN 14:01) Cite this Report

Strombolian activity from summit craters: inflation

After the October 1986-February 1987 eruption, activity has been confined to the summit craters. In the following report, frequent observations by IIV personnel with help from Italian Alpine Club guides are supplemented by data from geologists who reoccupied ground deformation networks 20 May-24 June and 16 September-7 October.

Bocca Nuova. Since the end of April 1988, Strombolian activity and/or degassing has continued at varying intensity. Explosive vents were active at different points on the crater floor, 150-250 m below the rim. Lava fragments only rarely reached the crater rim. Ash and lapilli ejections were occasionally observed, especially during periods of stronger and more continuous activity. In May and June, small explosions or gas bursts could be heard deep within the crater at a rate of 30-50/minute, with larger explosions about every 5 minutes. Loudness of the explosions varied considerably; they usually were not audible 400 m from the crater, but on 23 June, 4 were heard from Rifugio Sapienza, 5.5 km S, between 1214 and 1226. In September and October, the explosion rate was 30-40/minute. Strombolian explosions from three active vents on the crater floor, roughly 150 m below the rim, were observed about once every 5 minutes. Louder series of explosions were heard up to 3 km away on 23 and 28 September and 1 October. During the night of 1-2 October, a few fresh bombs landed just outside the crater rim and the next day bombs were rising to ~ 10 m below the rim. Violent activity that included lava fountaining was observed from a distance on 31 January 1989 from 1930 to 2100. Bocca Nuova was relatively quiet in early February.

La Voragine. The vent was partially obstructed until July, with activity limited to weak gas emission. Strombolian activity of variable intensity then started at the bottom of the crater, at more than 250 m depth. Ejecta only rarely reached the rim. On 23 August between 1610 and 1650, a series of pyroclastic explosions ejected juvenile material (lava fragments, scoria, lapilli, and ash) to a few hundred meters height. The tephra fell mainly on the E flank, to 400 m from the rim. Explosive activity ceased completely from the end of August until the beginning of September. During visits on 28 September and 6 October, Strombolian explosions were occurring from vents that appeared to be higher in the crater than those at Bocca Nuova. About 30 explosions/minute were counted on the 28th, with ~1/minute strong enough to eject bombs visible to the geologists, who could see 50-80 m into the crater. At night on 2 October, no noises could be heard from the rim, although faint glow was visible. In early February 1989, little activity was occurring from the crater.

Southeast Crater. Gas emission, sometimes under pressure, continued from a vent near the center of this complex of cones and depressions. By 4 October the gas emission had strengthened, ejecting blocks, apparently from the wallrock, and sublimates. Weak and irregular Strombolian activity began in early October. A small new vent opened between 24 and 25 November E of the previous vent, ejecting ash and other tephra. Some of the explosions were fairly vigorous, as on 27 November. The activity changed gradually from ash ejection to a nearly continuous explosive Strombolian activity, with periods of greater and lesser intensity. At times, lava fragments reached 250 m height, falling within a few hundred meters of the crater. Similar Strombolian activity was continuing in early February 1989.

Northeast Crater. Only fumarolic activity was observed until the end of July, varying in intensity with weather conditions. A small vent opened inside this crater on 24 July and grew with time. Very hot pressurized gases emerged, particularly soon after the vent opened. The vent was glowing at night in September. Smoke rings were occasionally emitted in September and October, similar to those observed from Bocca Nuova early in its development.

The following deformation and seismic data are from J.B. Murray.

Despite the increased seismicity and deformation recorded February-April 1988 (13:03), the June levelling traverse showed an unusually small amount of movement since September 1987. Subsidence of recent lava around Northeast Crater was <2 cm, an order of magnitude less than usual and the smallest recorded since the line was installed in 1975. Inflation of 1.6 cm measured 3.5 km NE of the summit was also unusual. Recently active areas generally showed subsidence, with downward movement of slightly > 1 cm at the 1983, 1985, and September 1986 dikes, and isolated larger movements of -6.6 cm at the 1986-87 fissure and -19 cm at the edge of Southeast Crater. The very large amounts of subsidence measured in recent years in the Valle del Leone have diminished considerably.

A very different pattern was measured during the September traverse, with broad inflation centered just SW of Bocca Nuova. Inflation extended over the entire traverse, reaching +5.3 cm at the center when compared to the southern reference station 2.5 km away, or +8.5 cm compared to stations at the N end of the traverse, 5 km away. This inflation was the largest recorded at Etna when no eruption had occurred between measurements. Most dry-tilt stations showed typical small, more or less random, tilts of apparently local origin. However, 4 stations 4-9 km to the SW showed westerly tilts of 20-30 µrad, suggesting that inflation may extend farther in that direction. Murray noted that summit inflation preceding summit eruptions was measured in May 1976, June and September 1977, September 1978, July 1980, October 1983, September 1984, and June 1986. Inflation episodes centered just SW of the summit have tended to precede Southeast Crater activity.

Small local shocks that were apparently related to summit activity were detected optically during measurements of the levelling line and dry tilt stations. Using the automatic level, relative amplitudes were obtained by noting the amount of crosshair movement against the levelling rod and correcting for distance. In June, seismicity was very quiet, with only four events noted in a week of levelling, all within 450 m of Bocca Nuova. The largest had an amplitude of ~ 60 µrad.

In September and October, seismicity had increased dramatically. On 23 September, 73 shocks were noted in 1 hour while levelling W of Bocca Nuova at a mean distance of 330 m from the rim. The shocks were much stronger than in June, with largest amplitudes reaching 250 µrad. Seismic events were detected as much as 4.6 km from the summit. W of Piccolo Rifugio, ~ 3 km from the summit, three shocks were detected in 1 hour, the largest of 35 µrad.

Information Contacts: R. Romano, T. Caltabiano, and O. Consoli, IIV; J. Murray and D. Norman, Dept of Photogrammetry and Surveying, Univ College London; D. Décobecq, Paris; J. Miller, T. Elliott, and B. Van Wyk de Vries, Open Univ; B. Bone, Lancaster.

May 1989 (SEAN 14:05) Cite this Report

Explosions from summit craters; small lava flow; high SO₂

The following, from IIV, describes activity March-April 1989.

Summit activity. (S. Calvari, M. Coltelli, and M. Pompilio.) Vigorous Strombolian activity at the two central craters (Bocca Nuova and La Voragine), persisted through March and April. At Southeast Crater, Strombolian ejections became strong and continuous during the last 10 days of March, similar to those of 24 December-24 January and 29 January-22 February. Strong explosions continued through April. A small lava flow emerged from the base of Southeast Crater's cinder cone on 15 April at 2300 and flowed over the crater's S rim. Lava effusion stopped early the next morning. Degassing continued at Northeast Crater.

Seismicity. (E. Longo, A. Montaldo, M. Patanè, E. Privitera, and S. Spampinato.) A total of 71 tectonic earthquakes (M >1.0 and S-P <5 seconds) were recorded on the Serra Pizzuta Calvarina seismic station (~ 13 km S of the summit craters) in March, compared to 194 events during all of 1988. The highest seismic energy release and the largest number of events (9, with two of M 2.7) occurred on 17 March. Tectonic events were fewer and smaller (M<=2.7) in April than in the first three months of 1989. Most of the largest events (M>=2) were located on the W flank at depths of ~ 15-25 km. High-energy volcanic tremor episodes were recorded 9-16 April and represent the only seismic evidence of the Southeast Crater eruptive episode on 15 April. After the effusive episode, the spectral amplitude of tremor greatly decreased, but remained higher than in March.

SO₂ emissions. (T. Caltabiano and R. Romano.) During the first half of March, SO₂ emissions from the summit craters were similar to relatively high February values at ~ 6,000 t/d. During the last half of March, SO₂ emissions increased to ~ 8,000 t/d, then decreased to ~2,000 t/d. After the lava effusion of 15-16 April, SO₂ emission rates rose to ~12,000 t/d, but decreased to ~3,000 t/d during the remainder of the month.

Ground deformation. (O. Campisi, G. Falzone, B. Puglisi, G. Puglisi, and R. Velardita.) Ground deformation at the Serra Pizzuta Calvarina borehole tilt station showed no significant variations during March and April.

Information Contacts: R. Santacroce, IIV.

June 1989 (SEAN 14:06) Cite this Report

Summit explosive activity

The following, from IIV, describes activity May-June 1989.

Summit activity. (S. Calvari, M. Coltelli, and M. Pompilio.) Vigorous activity at the two central crater vents (Bocca Nuova and La Voragine) continued in May. On the 4th, La Voragine ejected bombs and lapilli that fell as far as the rim of Cratere del Piano (roughly 300 m away), choking the crater bottom with tephra. In late May, explosive activity diminished and continued at a normal level throughout June. Discontinuous effusive activity was observed in May within Bocca Nuova, and bombs accumulated in the crater to ~ 100 m from the rim. From late May through most of June, many bombs, some of considerable size, fell outside the crater. This activity suddenly stopped in late June, when the small cone inside the crater collapsed, and was succeeded by sporadic scoria ejection from two vents. Mild Strombolian activity at Southeast Crater in May slightly eroded the scoria cone that had formed in April (14:05). Strombolian activity continued at a medium-low level in June, with occasional pulses ejecting small numbers of bombs over wide areas. The vent on Northeast Crater's floor continued to degas through May and June.

Seismicity. (V. Longo, A. Montaldo, M. Patané, E. Privitera, and S. Spampinato.) The frequency of tectonic seismicity in May and June was generally similar to that of the past year, with occasional seismic swarms. During the last two days in May, low-energy events were detected ~ 10 km below the volcano's central area. A seismic swarm, recorded 19-24 June on the W flank, was 13-15 km deep and included the largest events (M 3.1-3.2) of the month. One of the earthquakes (on the 24th at 0230) was felt by area residents. On 28 June, a small mainshock-aftershock sequence (11 events) was recorded, with the largest earthquake located near the S portion of the Valle del Bove at <5 km depth. From late June to 1 July, events with M 2.5-3.0 occurred 10-15 km beneath the summit. No significant variations in the volcanic tremor pattern were observed during May or June.

Ground deformation. (O. Campisi, G. Falzone, B. Puglisi, G. Puglisi, and R. Velardita.) Ground deformation measured at the Serra Pizzuta Calvarina borehole tilt station showed no significant variation in May or June. Measurements in May using the S trilateration network showed little deformation since l June 1988.

SO₂ emissions. (T. Caltabiano and R. Romano.) The average value of SO₂ flux in May 1989 was the lowest of the past year, but moderately high values returned in June. SO₂ flux was measured 3, ll, 17, and 24 May and 1, 7, 15, 22, and 29 June. Emissions fluctuated in May, with high values on the 3rd and 17th and low values on the 11th and 24th, reaching only 2,500 t/d on the latter date.

Tephra composition. (S. Calvari, M. Coltelli, and M. Pompilio.) January 1989 activity produced hawaiite tephra, with petrography and chemical composition similar to tephra from the previous year. Tephra emitted from Southeast Crater during 1988 had relatively more evolved compositions, but early 1989 tephra was less differentiated than material emitted by the other summit craters.

Information Contacts: R. Santacroce, IIV.

July 1989 (SEAN 14:07) Cite this Report

Summit Strombolian activity; little deformation in past year

Geologists observed Strombolian activity at three summit area craters (Bocca Nuova, La Voragine, and Southeast Crater; figure 28) and an incandescent gas vent in Northeast Crater during field work 26 May-1 July. Fresh-looking tephra was abundant W and SW of the summit craters, to 800 m from Bocca Nuova.

Figure 28. Sketch map of Etna's summit region, showing features active during field work 26 May-1 July 1989. Courtesy of C. Oppenheimer and J. Murray.

Bocca Nuova. Vigorous Strombolian activity from two vents on the crater floor, both building cones, was observed 29-30 May, 5, 18, 19, and 30 June, and 1 July. Small explosions and gas bursts averaged ~70/minute. Larger explosions ejected incandescent cowdung bombs, some of which fell 100 m beyond the crater rim. Crater depth was estimated at > 120 m. On 5 June, another glowing vent was visible on or near the flank of the largest active cone. Toward the S end of the crater floor, there was an irregularly shaped area of glowing lava, possibly a ponded flow or passive lava lake. Lava in one of the intracrater vents had a maximum brightness temperature of 1,019°C when measured with a 0.8-1.1 mm infrared thermometer. On 30 June, heat from one of Bocca Nuova's active vents was felt from the observation point on the NW rim.

La Voragine. Strombolian activity occurred from crater floor vents. Loud detonations were heard from the crater rim on 29 May; 17 were counted in 2 minutes. Ejecta were heard falling on the crater floor. During observations the evening of 5 June, four vents were visible, two of which were active. The largest of the 72 explosions counted in a 2-minute period sent bombs to 30 m above the rim. On 1 July, juvenile bombs were ejected by a glowing hornito or small cone on an apparent solidified lava lake. The 0.8-1.1 mm thermometer recorded a peak temperature of 821°C.

Southeast Crater. Strombolian eruptions continued from Southeast Crater's new cone 29 May-30 June, frequently ejecting incandescent tephra above the crater rim. On 4 June, bombs rose to 100 m above the cone. During a 10-minute period around noon, geologists counted 28 eruptions that projected bombs higher than the rim.

Northeast Crater. On 8 June, a vent 2-3 m in diameter was degassing near the middle of the crater floor. A peak brightness temperature of 462°C was recorded by an 8-14 mm infrared thermometer pointed at the vent's inner wall from ~ 50 m distance. Geologists noted that this instrument probably significantly underestimated the gas temperature (see 1 July data). There was no sign of fresh tephra. On 12 June at about 0850, four white "smoke rings" rose slowly from Northeast Crater. On 1 July, glow from the vent was visible during observations in low light shortly after 0600. A 0.8-1.1 mm infrared thermometer yielded a maximum temperature of 644°C, compared to 491° with the 8-14 mm instrument. Eight gas puffs and two more vigorous exhalations were counted in 1 minute.

Geodetic measurements. Very little vertical deformation has occurred since September 1988 (14:01). Slight subsidence was measured E of the summit, with a maximum displacement of 3 cm near the 1987 fissure (relative to a reference station 2.5 km SSW of the summit). A 3.5-cm swelling was measured on the Northeast Rift. A trilateration network on the upper E flank was reoccupied for the first time since June 1988, revealing movements of as much as 4 cm to the NE at stations in the Valle del Leone. The station on Monte Simone (4 km E of the summit) showed an anomalous displacement of 2 cm to the S since September 1987. Stations at Punta Lucia (1.5 km NNW of the summit) and Belvedere (2 km SSE of the summit) were assumed to be stable. Etna's summit elevation was determined at 3,318.4 m, using the base station near Piccolo Rifugio (2,516 m altitude) as a datum. Seismicity was detected optically through the levelling instrument, as in 1988 (14:01). During the early June levelling traverse, 36 shocks were observed, all within 2.2 km of the summit. The largest amplitudes noted were 70 µrad (1.5 km NE of the summit), 111 µrad (near Southeast Crater), and 123 µrad (400 m from Bocca Nuova).

Information Contacts: J. Murray and C. Oppenheimer, Open Univ; A. Jones, Univ of Lancaster; P. Cruddace, Univ of Newcastle; P. Aragno and S. Haefeli, SVG.

August 1989 (SEAN 14:08) Cite this Report

Explosions and lava flows; tephra reaches the coast

The following preliminary data is from R. Romano.

Strong Strombolian activity from La Voragine and Southeast Crater was followed by an explosive eruption from La Voragine during the late morning of 10 September. Tephra rose 600-700 m, and the resulting plume, carried E by the wind, deposited ash and lapilli along a narrow, well-defined, path that extended to the coast. After strong explosive activity and lava fountaining, lava spilled over the rim of Southeast Crater early the next morning, forming fluid, fast-moving flows that reached the Piano del Lago (on the upper S flank). During the nights of 11, 12, and 13 September, four more episodes of strong activity occurred, feeding lava flows that advanced SE, S, and SW; these were also very fluid and descended ~ 2 km to 2,640 m elevation. During this period, with brief exceptions, a small lava lake remained visible within Southeast Crater, and was the location of lava fountains that reached average heights of a few hundred meters.

A violent explosive episode that began at about 0900 on 13 September ejected incandescent pyroclastic material to more than 1 km height. Winds again carried the plume toward the E, leaving a narrow band of scoria, lapilli and ash that reached the coast. Press reports said that tephra fall lasted for ~ 15 minutes and some of the lapilli reached walnut size. No injuries were reported, but numerous cars were damaged, and traffic was slowed by nearly 4 cm of ash on the lower flanks. During the explosive activity, felt seismicity on the upper flanks increased substantially but subsided after a few hours.

The plume from the explosion at 0900 was not evident on weather satellite images, but data returned 4 hours earlier, at 0500, showed a plume 15-20 km wide extending ~ 100 km E from Etna. The plume had dissipated by about 0800. During the day on 14 September, no eruptive episodes occurred, and the magma column remained low.

Preliminary estimates suggest that an area of ~0.5 km² was covered by ~ 5x10⁵ m³ of lava. No estimates of the volume of pyroclastic material were available at press time. Similar activity occurred at the NE crater in 1977-78.

Information Contacts: R. Romano, IIV; A. Brown, NOAA/NESDIS; UPI.

September 1989 (SEAN 14:09) Cite this Report

Strong tephra emission; lava fountains >1 km; lava flows

The following supplements the preliminary report in 14:08.

Through 26 September, the eruption was dominated by vigorous Southeast Crater activity that fed upper-flank lava flows and ejected tephra that reached the coast. Fissures opened on the upper E flank 27 September, producing lava flows that advanced ~ 6 km before activity stopped on 9 October.

[Fourteen] strong eruptive episodes that occurred 11-26 September included vigorous explosive activity from Southeast Crater with lava fountains that rose > 1 km. Violent Strombolian activity alternated with periods limited to ash ejection, particularly during the first days of the eruption. Winds initially carried eruptive clouds E and S, then E and NE, with ashfalls reaching Catania (roughly 30 km SSE of the summit). Very fluid lava flows moved S and SSE (Piano del Lago), SE and E (Valle del Bove), and NE (Valle del Leone). The lava flows reached 2,600 m elevation (~ 2 km from the crater) in the Piano del Lago, and the base of the Valle del Bove's W wall at ~2,000 m (3-4 km from the crater).

A team from the Open Univ (P. Francis, C. Oppenheimer, and D. Rothery), the Jet Propulsion Laboratory (L. Glaze and D. Pieri), and IIV (T. Caltabiano) carried out field work 22-29 September. Lava fountaining and Strombolian activity occurred about every 10-12 hours from Southeast Crater. The activity fed many aa flows ~ 100 m long in addition to the more fluid flows that advanced farther downslope. Their detailed chronology of a 24 September Southeast Crater eruptive episode, apparently typical of 23-28 September activity, is shown in table 3.

Table 3. Description of the 24 September 1989 eruptive episode at Etna's Southeast Crater, observed by L. Glaze, C. Oppenheimer, and D. Rothery from 900 m away at the Torre del Filosofo. Temperatures were measured with a Cyclops 33 infrared thermometer (8-14 mm bandpass), but were lower than true values because the 1° field of view always included some air or cold ash.

Time	Description of activity
0940-0955	Gray ash clouds rose 50-100 m above the rim every few minutes. The Central Crater was fuming strongly, but produced no ash.
0955-1035	Sustained gray ash eruption to 100 m above the rim.
1038	Ash column production ceased, but explosions were audible. Peak column base temperature, 288°C.
1040	Bombs began to rise above the rim.
1050	Semi-continuous Strombolian ejection with some red incandescence. No distinct tephra column.
1103	50-m lava fountain; maximum temperature of 443°C at its visible base.
1105	Onset of fine ashfall at the Torre del Filosofo (TDF).
1108	Continuous noise; fountain to about 80 m above the rim.
1115-1117	Temperature at the fountain's visible base, 280-882°C. Brown smoke rose E of the crater, probably from lava advancing toward the Valle del Bove.
1120	Lava fountained to 160 m above the rim, surmounted by a convectively rising ash/scoria column.
1124	Maximum temperature of the visible column base 693°C with the Cyclops 33, but 983 with a Cyclops 52 (0.3 field of view, 0.1-1.1 micron bandpass).
1126	Centimeter-size scoria fall began at the TDF.
1129	Incandescent material rose above the rim from a second western source within the crater. The two sources soon joined to feed a single lava fountain with a sustained height of 250 m above the rim.
1136	A clast-fed lava flow began on the crater's SW flank. 2-cm tephra fell at the TDF a minute later.
1145	Brick-size bombs fell 100 m E of the TDF, where 4-cm tephra was falling 2 minutes later.
1200	Lava fountained to more than 300 m above the rim with jet engine roaring. A convective ash/scoria column rose to considerable (but undetermined) altitude.
1205	A fissure developed on the crater's SE flank, and lava fountaining from the fissure fed a flow. The fountain's infrared temperature was 614°C at 1211. By 1224, the fissure had become the source of the main column, with incandescent material rising 200-300 m.
1233	Roaring noise stopped for about 3 seconds, then activity declined and had virtually ceased by 1238.

Geologists from the Ruhr Univ visited Etna 22-30 September. Eruptive episodes that included lava fountains up to 500 m high, ash emission, and lava flows from Southeast Crater and associated fissures, occurred once or twice daily during their first five days. They provided the following chronology of activity observed from Nicolosi, 15 km to the S.

22 September, 2100-2330: Lava fountains to 500 m height, lava flows mainly directed toward the Valle del Bove.

23 September, 2000-2015: Vigorous lava fountains (probably higher than the previous night) and lava flows to the Valle del Bove.

24 September, 0930-1200: Initial small ash puffs from Southeast Crater were followed by high lava fountains. New fissures opened at the base of Southeast Crater, and lava flows moved S, cutting off the road to the Torre del Filosofo (900 m from Southeast Crater).

25 September, 0530-0900: Lava fountains rose 300 m, a 4-km vapor plume was ejected, and lava flowed into the Valle del Bove. Loud rumblings were heard from Nicolosi near the end of the activity. Strong ash emission from Southeast Crater and Bocca Nuova lasted from 0700 to 0900. 1900-2000: Lava fountained to 300 m height from at least four vents in Southeast Crater and a lava flow advanced toward the Valle del Bove.

26 September, 0600-0710: Lava fountains reached 400 m height and powerful ash ejection fed a column that rose 5-6 km above the summit within 30 minutes. Lava flowed into the Valle del Bove. At 0645, a brown, cauliflower-shaped ash cloud rose from the Valle del Bove, suggesting a possible flank outbreak. However, ash emission from that site ceased after a few minutes and no flank eruption was confirmed by other observers. 1210-1215: A series of ash puffs rose from Southeast Crater, but no additional eruption followed. 2000-?: High lava fountains were ejected, lava flowed to the Valle del Bove, and a new vent formed near Southeast Crater.

27 September, about 1200: Ash emission resumed from Southeast Crater. Dark gray ash clouds rose continuously to ~ 100 m above the vent before being carried E by strong winds. Ash emission continued through the evening. After nightfall, a bright glow was visible above the Valle del Bove and small fountains emerged from Southeast Crater once or twice/minute.

R. Romano reports that in the late evening of 27 September (around 2230) two new sub-parallel eruptive fissures opened on the upper E flank at 2,600 and 2,575 m altitude (between Valle del Leone and Valle del Bove, SE of Pizzi Deneri), preceded by a brief seismic crisis. Strombolian activity, violent at times, was initially continuous along the fissures, forming hornitos and scoria ramparts. Lava flows from the upper fissure did not extend beyond (but generally entered) the main lava channel formed by the primary effusive vent at the base of the lower fissure (2575 m altitude). The lava flows, moving generally SE, passed S of Monte Simone, widening at ~ 1,750 m altitude.

During the morning of 28 September an extensive field of NNW-trending non-eruptive fractures formed in the Piano del Lago, propagating in succeeding days to the W and S wall of the Valle del Bove. The fractures also extended downslope, past the edge of Serra del Solfizio, on a NW trend. By the morning of 2 October new fractures had opened to the Zafferana-Rifugio Sapienza road (route 92) ending around 1,500 m elevation, below the effusive vents of 1792. Total length of the fractures was ~6 km.

Ruhr Univ geologists climbed Etna on 28 September. Ash emission from Southeast Crater remained continuous. Around noon, brown ash plumes rose from the vent in pulses every 3-5 seconds, accompanied by block and bomb ejection. No glow was seen. Dense weather clouds obscured visibility during the afternoon, but a distinct increase in noise suggested the onset of Strombolian explosions. As night fell around 1800, weather clouds dissipated and Strombolian bursts were visible every 5-10 seconds, ejecting bombs and spatter to 300 m height. The lava flow in the Valle del Bove apparently emerged from a fissure in its NW part. The non-eruptive fractures that had opened parallel to and ~ 50 m W of the rim of the Valle del Bove during the morning, had vertical displacements that sometimes exceeded 1 m; some were 1.5 m wide and several meters deep. The next day, ash and bomb ejection from Southeast Crater increased considerably at about 0730, with dark gray columns rising 150-200 m despite a very strong W wind. Large bombs often rose higher, falling on the flanks of the cone that was rapidly growing around the vent. Expulsion of ash and blocks occurred every 5-10 seconds, accompanied by hissing and rumbling sounds. No glow was visible. Numerous impact craters as much as 1 m wide and 0.5 m deep, probably produced by the strong 13 September activity (14:08), were found at the site of the 1971 Observatory cone, 500 m SW of the active crater. At 1900, lava fountains were again visible in Southeast Crater, with bombs and spatter sometimes rising 350 m. Lava continued to flow into the Valle del Bove. Similar activity was continuing late 30 September.

R. Romano reports that during the following days a wide lava channel formed, extending E after passing Rocca Musarra to the S. Lava flows branched from this channel, passing a line connecting Monte Calonna and Monte Fontana on 6 October, and reached ~ 1,100 m elevation (~ 6 km from the fissure vents). The lava flows stopped ~ 3 km from the nearest town (Milo). Lava production from the vigorous effusive vent at 2,575 m altitude was very strong during the first days of its activity (30-40 m³/sec), started to diminish beginning 3 October, and stopped completely on 9 October.

Preliminary estimates indicate that a [3] km² area was covered by lava, and lava volume was [~24] x10⁶ m³ (within the Valle del Bove). No estimates are available for volumes of pyroclastic material and lava ejected by the Southeast Crater. Information remains preliminary and incomplete, and will be revised in coming months with more detailed reports, geophysical and geochemical data, and maps of the lava flows and fractures.

Information Contacts: R. Romano, IIV; B. Behncke, Ruhr Univ; D. Rothery, Open Univ.

October 1989 (SEAN 14:10) Cite this Report

Details of September-October eruption

The following report (quoted sections technically edited by F. Barberi, A. Bertagnini, P. Landi, and R. Rapuzzi) summarizes studies of Etna's recent activity.

Eruption chronology. "The vigorous Strombolian activity at three summit area craters (Bocca Nuova, La Voragine, and Southeast Crater) observed during May, June, and July (14:07) declined during the first 20 days of August, then progressively resumed in the last 10 days of the month. On 29 and 31 August, after some days of Strombolian activity, La Voragine emitted a 700-m-high tephra column with fallout of lapilli and ash that affected the SE flank to the coast, 19 km from the crater.

"In the first days of September, Strombolian activity also increased at Bocca Nuova and in the morning of 10 September an explosive eruption, identical to those of 29 and 31 August, occurred again at La Voragine. Beginning in the early hours of 11 September, Strombolian activity also resumed at Southeast Crater, then progressively evolved into lava fountaining. Lava spilled over the rim of Southeast Crater, forming two fluid, fast-moving flows that traveled ~2 km SE. Explosive activity and lava spillover then suddenly ceased, indicating lowering of the magma column in the conduit. On the evening of the same day, and 12 more times until 27 September (figure 29), new episodes of vigorous Strombolian activity, evolving into lava fountaining with effusion, were observed at Southeast Crater, each suddenly ceasing and giving rise to slow degassing followed by the resumption of less vigorous Strombolian activity. Lava flows emitted during these 14 effusive episodes were confined to the upper S and SE flank area (Torre del Filosofo-Cisternazza) and descended 2.5-3 km S and SE (figure 30)."

Figure 29. Schematic chronology of Etna's September-October 1989 eruption. Periods of eruptive activity on the NE and SE fractures are indicated by x's.

Figure 30. Topographic sketch map of Etna's summit and upper flanks, showing timing of fracture propagation 25 September-3 October (dashed lines). Thin arrows show paths traveled by 11-27 September lava flows from Southeast Crater and from vents at 2,900 and 2,850 m elevations on the SE and NE fractures respectively. Thick arrows show advance of the lava flows down the Valle del Bove (stippled) through 6 October. Contour interval, 200 m.

During fieldwork on the 23rd, geologists observed that the area between Southeast Crater and the TDF was covered by fresh aa, in a flow field that had advanced around the TDF and continued southward. The most distal lobes stopped moving on 22 September.

"Near the end of the lava fountaining phase, in at least six cases (13, 19, 22, 23, 25, and 26 September) a sustained tephra column was formed, with consequent lapilli and ash fallout over the E and SE flank to the coast. On [24] September, two fracture systems, trending [N40°E] and N140°E, opened on the flanks of the newly formed Southeast Crater cone, down to elevations of 2,800 and 2,900 m respectively. An appreciable quantity of lava spilled either over the Southeast Crater rim or from the two newly formed fractures on 25 September and in the following two days. In the morning of 25 September a lava flow from the NE fracture descended 3 km in the Valle del Bove, to 1,900 m (M. Simone area, figure 30). The last episode of lava fountaining and effusion at Southeast Crater occurred the morning of 27 September. Since that afternoon the crater has been characterized by Strombolian activity and ash emission."

On the evening of 27 September, the focus of activity shifted to the NE fracture system. "At about 2200 a small fast-moving flow was emitted from the terminus of the NE fracture, and descended 2 km in the Valle del Bove. The Strombolian activity of Southeast Crater then [temporarily] ceased, and between 2300 and 2330 a series of eruptive vents opened at 2,550 m elevation in the Valle del Leone (upper part of the Valle del Bove), preceded and accompanied by a vigorous seismic swarm. These vents were aligned along a N50°E fracture, on the extension of the fracture cutting the NE flank of the SE cone (figure 30). Lava poured from 3-4 vents, where degassing was minor with ejection of lava fragments to only a few meters height. The various lava tongues converged a short distance from the fracture into a main channel, 10 m wide, where lava advanced rapidly. At dawn on 28 September the flow had descended 5 km in the Valle del Bove, reaching Rocca Musarra at ~ 1,650 m elevation.

"That morning, the SSE fracture (extending N140°E from Southeast Crater) was also seen to have progressed downslope. This newly formed part of the fracture system affected a 100-m-wide sector, extending down 2.5 km (to Cisternazza) and to the upper (W) part of the Valle del Bove. Fracture propagation continued on 29 and 30 September, when the S scarp of the Valle del Bove was affected. On 1 October the fracture, accompanied by marked collapses along the fissure system, crossed the Valle del Bove scarp and propagated farther downslope, following the feeding fissure of the 1792 flank eruption. At 1200 on 2 October the fracture cut route SP92 connecting Zafferana to Rifugio Sapienza. The seismic activity that accompanied the entire fracturing process peaked at that time, with ~40 shocks/hour (figure 31). In the following hours, seismic activity rapidly declined and fracture propagation stopped at ~ 1,500 m elevation, 8 km from Southeast Crater. In the following three days only widening of single fissures was observed, with development of consistent compressive structures (uplift folding, reverse faulting) on both sides of the main extensional (open) fissure."

Figure 31. Daily number of seismic events recorded by station ESP, 1 January-5 October, 1989.

During fieldwork the night of 1 October (by C. Oppenheimer, M. Pompilio, M. Coltelli, and V. Scribano) the flow near the NE fracture's main vent was ~ 8 m wide, and its center was moving at faster than a walking pace. Blocks of lava tossed onto the flow welded instantly but did not sink. A maximum lava surface brightness temperature of 1,039°C was measured by a 0.8-1.1 mm bandpass infrared thermometer (recording for 10 minutes, 3 m from the flow top).

Guy Kieffer notes that the axes of the two fracture systems that opened during the eruption had both been frequently active during the eruptive cycle that began in 1971: the NE axis in 1971, 1978, 1979, and 1986-87; and the SSE axis in 1971, 1978, 1979, 1983, and 1985 (along a southward extension). The NE axis had also been active during the 1811, 1865, and 1928 eruptions, and the SSE axis in 1792, 1908, and 1910. As in the present eruption, fissures had opened from the SSE base of the central cone in 1874, 1911, and 1923 without producing any lava, while lava was emitted from N flank fissures. The 1989 eruption's SSE fracture had opened ~ 45 cm and had a right-lateral displacement of ~ 15 cm (on 7 October) where it crossed route SP92. Kieffer suggested that the SSE fracture was the result of an offset caused by intrusion below Southeast Crater, added to several years of accrued stresses as part of the E flank is forced eastward.

"Lava outpouring from the Valle del Leone fissure continued until 2 October without significant variation in the effusion rate. From 3 October, oscillations, but with a slow progressive decrease, were observed in the rate of lava effusion. During temporary phases of effusion rate increase, eruptive vents were reactivated at higher elevation on the NE effusive fracture. New hornitos were formed, 50 m above those at the 1,550-m vents, accompanied by a series of lava overflows. The effusion rate decreased further on 6 October and lava emission stopped during the night of 8-9 October.

"During the same period, explosive activity continued at Southeast Crater. After the late morning of 28 September ash-laden clouds were emitted from the crater, which also showed Strombolian activity of variable intensity." When observed by C. Oppenheimer on 29 September, discrete eruptions of ash and blocks about every 30 seconds were superimposed on continuous ash emission. Ballistic trajectories of incandescent bombs that rose >400 m above the crater were visible at night.

"Tephra were dispersed eastward by the wind, causing ash showers on Catania and eastern villages, especially on 3 and 4 October. Limited episodes of lava fountaining last occurred during the night of 3-4 October. Strombolian activity stopped during the night of 6 October, whereas discontinuous weak ash emission continued until 9 October. Southeast Crater appeared almost totally obstructed on 11 October. Ash emission and vigorous degassing continued, since 9 October, only at Bocca Nuova.

Lava flows. "Etna's 27 September-9 October flank eruption produced an aa flow field in the Valle del Leone-Valle del Bove ~ 6.5 km long and 5-10 m thick, with a volume of 10-20 x 10⁶ m³. The flows descended from ~2,550 to 1,100 m elevation. The average effusion rate is estimated at 10-20 m³/second, with peak daily average values during the first 4 days of eruption (until 2 October) of between 15 and 25 m³/second. Combinations of the overall emplacement characteristics (e.g. length-average effusion rate, length-volume, width/length-duration) of the flow fields lie within ranges typical for Etna's historic lavas. Velocity and dimension measurements of active overflows at the feeding vent (Valle del Leone, ~ 2,550 m asl) on 2 and 4 October suggest apparent viscosities for the initial lava of the order of 10,000 Pas, for bulk shear rates between 0.01 and 0.1/s. Thermocouple data yielded a surface temperature of 800°C on the overflow (after it had advanced ~ 50-75 m) on 2 October. Preliminary analysis of infrared data obtained on the ground on 5 October suggests a similar temperature for incandescent cracks in an active flow front ~ 6 km from the vent.

Petrology. "The lavas are porphyritic (P.I. = 30-40) alkali basalts with phenocrysts of plagioclase, clinopyroxene, and olivine, and microphenocrysts of Ti-magnetite. There are only minor differences, in size and relative abundance of phenocrysts, between the Southeast Crater flows and the Valle del Leone lavas. Two representative chemical analyses are shown in table 4. The 1989 lavas are slightly more mafic and magnesian than those of either the last Etna eruptions (1986-87 average) or Southeast Crater in 1988.

Table 4. Chemistry of 1989 lavas from Etna's Southeast Crater (11 September) and the Valle del Leone 93 October). Analyses by X-ray Flourescence at the Dipt. di Scienze della Terra, Univ. di Pisa, except Na₂O and MgO (Atomic Absorption Spectrophotometer) and FeO (titration) at IIV.

Oxide	Southeast Crater	Valle del Leone
SiO₂	47.46	46.70
TiO₂	1.78	1.78
Al₂O₃	18.11	17.36
Fe₂O₃	2.83	4.30
FeO	7.32	7.41
MnO	0.19	0.20
MgO	5.57	5.84
CaO	10.39	10.25
Na₂O	3.45	3.51
K₂O	1.99	1.81
P₂O₅	0.44	0.41
LOI	0.48	0.44

Civil Protection aspects. "The lava flow emitted from the SE fractures in the Valle del Leone did not present any serious civil protection problem. Flow fronts advanced very slowly at elevations lower than 1,200 m. The flow was confined within the totally uninhabited Valle del Bove and never threatened villages or lifelines. However, the propagation of the SE fracture system from Southeast Crater downslope caused serious concern. Because of strong seismic activity and marked uplift on that sector of the volcano, route SP92 was closed to traffic 24 hours before it was cut by the fracture. The terminus of the fracture was located in a zone that had been affected by flank eruptions in the past (e.g. in 1792). It was at low elevation (~ 1,500 m) and only 5-6 km from villages (Malpasso, Fleri), a distance that could be traveled by a fluid lava flow in a dangerously short time, considering that magma was at the surface in Southeast Crater vent (3,000 m elevation) and hence there was a very high potential load (1,500 m of lava column) on the fracture apex.

"The more probable paths of lava flow in case of effusion from a vent at 1,500 m elevation were estimated on a morphological basis. People living on the potential lava trajectories were alerted to the potential risk and a plan was established for their prompt evacuation.

"Scientific monitoring at the fracture terminus was expanded and reinforced with a mobile seismic network, precision levelling, microgravimetry, geodimeter lines, and soil gas geochemistry. I gas;sampling Visual observation points (24 hours/day) were established near the fracture apex and along the expected flow path, radio linked with the army units responsible for the emergency plans.

"The alert system was maintained until 16 October. Then, with six days having passed since the end of eruptive activity and without any sign of potential volcanic activation of the SE fracture, the eruption was considered concluded.

Seismicity. "Seismic activity has been monitored since early summer 1989, using both the IIV's permanent array (8 stations) and a temporary array operated by the OV (up to 11 three-component telemetered digital stations). The daily frequency histogram is shown in figure 31.

Pre-eruptive period."Five major seismic sequences were recorded from late July to late August; none of the events exceeded M 3.3. Focal depths, calculated with respect to the highest stations (at 2,900 m asl) ranged from ~ 15 km (3 August, 45 events) to

Eruptive period. "On 23-24 September, a swarm of 84 events (M >3.2) was located at ~20 km depth. Three days later, during a period of large fluctuations in tremor amplitude, intense microseismic activity preceded and accompanied the opening of the eruptive fissures on the E flank. Because of its weakness (only 19 events of M>2), this activity was clearly observed only at the nearest station (PDN, ~ 1 km from the new vents).

"More than 1,000 shallow events (depth

Volcanic tremor. "Volcanic tremor was monitored at stations PDN (hourly analysis) and SLN (real-time analysis). A rapid increase in tremor energy was recorded during the morning of 10 September. The level of tremor remained high for four days, with an estimated daily energy release of 1017 ergs (1010 J), then dropped by about an order of magnitude (figure 32). Between 18 September and 6 October, near-periodic (daily/half-daily) oscillations could be distinguished in the tremor amplitude (minor peaks in energy release on 19, 22, 25, and 27 September, and 4 October). With the end of the eruption on 9 October, tremor amplitude dropped to the pre-crisis level. Energy spectra analysis of 5-minute samples from station SLN shows steady peaks in the 1.4-1.9 Hz band, independent of energy level, while spectral displacements to higher frequencies were occasionally observed at station PDN.

Figure 32. Daily release of tremor energy recorded by SLN (Serra la Nave) station, 9 September-18 October, 1989.

Ground deformation - tilt. "Tilt data have been collected at an IIV borehole biaxial tilt station (SPC), located along the SE flank at ~ 1,600 m elevation. Continuously monitored tilt signals indicated a positive variation of the radial component (crater up), clearly exceeding the signal confidence limit, since the beginning of June 1989. The tangential component of the tilt remained practically flat until the beginning of the fracturing phase affecting the SE flank by 2 October. Both radial and tangential tilt underwent a sharp variation by the afternoon of 1 October, suggesting a rapid inflation of the Valle del Bove's S outer flank, where the fracture later propagated. The almost constant ratio between the two tilt components throughout this phase of the deformation process depicts a resultant tilt vector trending approximately N25°E (up) and totaling 14 µrad by the end of the deformation phase.

"Additional tilt data were obtained by two stations (sensor made of a pair of horizontal pendulums) installed by IIV and IPGP. The two automated stations (GIA and TRE) recorded an uplift of the summit area since the first 10 days of June (radial component, figure 33). Marked variations were recorded during the SE fracture propagation, particularly at TRE station, only 200 m from the fracture.

Figure 33. Radial (top) and tangential (bottom) data from the GIA horizontal pendulum tilt station, 21 May-13 October, 1989.

Ground deformation - geodimeter. "A trilateration network on the SE flank area had been previously surveyed in 1987, 1988, and May 1989. Daily EDM measurements were made on some of the network benchmarks since 30 September, before the fracture propagated downslope. Horizontal strain solutions for the main deformation phase that occurred on 2 October indicated an overall areal contraction (~152 ppm) with a minimum extension axis of about -206 ± 80 ppm striking N30°E; maximum shear was 260 ppm. Distance measurements across the main fracture system, at ~ 1,700 m elevation, indicated a local extension of up to ~ 1 m between May 1987 and October 1989.

Ground deformation - levelling. "Precise levelling surveys around the circumference of the volcano and across the new fracture system where it cuts route SP92 were carried out 2-16 October. With respect to September 1988, the N part of the volcano had remained stable, while relative sinking had occurred at the station closest to the central crater (20 mm) and across the fault at Piano Pernicana (25 mm; figure 34). Along route SP92, repeated surveys 6-16 October indicated a relative sinking near the new fracture system of ~ 14 mm.

Figure 34. Top: elevation changes between reoccupations of the level line in September 1988 and on 2-16 October 1989, at about 1,500-2,000 m elevation and 4-10 km from the central crater. Directions from the central crater are shown at top. Bottom: elevation changes between reoccupations of the segment of the level line crossing the SE fracture along route SP92 (figure 30), 6 and 16 October, 1989.

Microgravimetry. "On 3 October the pre-existing microgravimetric network (OV, IIV) was expanded near the fracture cutting route SP92. A new 2-km-long E-W line was established, with eight stations symmetrically arranged across the fracture, each coinciding with a precision levelling benchmark. Gravity measurements were carried out on 3, 4, 6, and 11 October. Differences from 3 to 4 October (figure 35) show a positive variation of the gravity field with a maximum (18 ± 7 microgal) corresponding to the fracture. Subsequent gravity variations remained mostly within the error range. Correction for levelling data does not appreciably modify these results.

Figure 35. Gravity changes across the SE fracture (indicated by arrows) along route SP92, 3-4 October, 1989.

Geochemistry - COSPEC data. "A slow increase in SO₂ output from the summit craters was observed in August 1989, with a transition from very low values (1,000 t/d) to medium-high values (~ 7,000 t/d). In the first half of September, SO₂ flux remained around medium values. Since 14 September, coinciding with the Valle del Leone effusive phase, SO₂ emission increased markedly with oscillation around 15,000 t/d, three times the average Etna values. [Measured rates of SO₂ emission exceeded 25,000 t/d on one day around 18 September and reached ~ 23,000 t/d on another day near 1 October].

Geochemistry - soil gases. "From 3 to 14 October, CO₂ was measured in the soil close to the terminus of the SE fracture. CO₂ concentrations were determined at a soil depth of 50 cm by an IR spectrophotometer, and varied from 0 to 1,500 ppmv, with a clear anomalous degassing at the fracture which showed a progressive decrease with time (figure 36). In addition, CO₂ concentration in the soil was measured continuously at one of the points. Two sharp peaks were recorded on 3 and 8 October, while later CO₂ concentrations remained quite constant (figure 37).

Figure 36. CO₂ concentration in soil across the SE fracture, at 1,600 m elevation (route SP92) 6-10 October, 1989. Dynamic gas samples are taken after pumping; static samples without pumping.

Figure 37. Data from continuous CO₂ monitoring of soil near the SE fracture, 3-15 October 1989.

"From 9 to 13 October another soil-gas survey was carried out across the fracture. Data from 140-cm soil depths did not show any anomalous H₂ and CO degassing but the data from 60-cm depths were significantly higher than atmospheric: they ranged from 3 to 12 ppmv for H₂ and 0.3-58.8 ppmv for CO. The meaning of this difference of gas concentration between 140- and 60-cm-deep holes must be further investigated."

Further References. Barberi, F., Bertagnini, F., and Landi, P., eds., 1990, Mt. Etna: the 1989 eruption: CNR–Gruppo Nazionale per la Vulcanologia; Giardini, Pisa, 75 pp. (11 papers).

Briole, P., Nunnari, G., Puglisi, G., and Murray, J., L'Eruption de Septembre-Octoberobre 1989 à l'Etna (Italie): quelques informations quantitatives fournies par la géodesie et l'inclinométrie: Comptes Rendus de l'Académie des Sciences, v. 310, série II, no. 13, p. 1747-1754.

Information Contacts: Many scientists and technicians were involved in the September-October Etna eruption, coordinated by the National Volcanic Group.
Scientific coordination and Civil Protection problems:F. Barberi, Univ di Pisa; G. Frazzetta and R. Santacroce, IIV; F. Innocenti, Univ di Pisa; G. Luongo, OV; R. Mazzuoli, Univ di Cosenza; L. Villari, Univ di Messina.
Volcanological Observations:R. Azzaro, S. Calvari, M. Coltelli, G. Frazzetta, G. Lanzafame, M. Pompilio, and R. Romano, IIV; V. Scribano, Univ di Catania; F. Barberi, A. Bertagnini, F. Innocenti, and P. Landi, Univ di Pisa; C. Kilburn, OV; L. Glaze, JPL.
Petrology:P. Armienti and F. Innocenti, Univ di Pisa; S. Calvari, M. Carà, M. Coltelli, and M. Pompilio, IIV.
Seismicity (24-hour monitoring):E. Privitera, R. Allotta, C. Cardaci, O. Cocina, D. Condarelli, V. Longo, A. Montalto, D. Patanè, A. Pellegrino, S. Rapisarda, S. Spampinato, and O. Torrisi, IIV.
Seismicity (OV mobile network and tremor):F. Ferrucci, G.P. Ricciardi, M. Calì, M. Capello, M. Castellano, U. Coppa, R. D'Alessandro, J. Dorel, D. Ereditato, V. D'Errico, G. Gaudiosi, C. Godano, and G. Milano, OV.
Seismicity – Univ di Catania:S. Gresta, G. Lombardo, and G. Patanè, Univ di Catania.
Ground deformation (IIV tiltmetry and geodimetry):L. Villari, Univ di Messina; A. Bonaccorso, O. Campisi, O. Consoli, B. Puglisi, G. Puglisi, and R. Velardita, IIV.
IIV-IPGP tiltmetry:P. Briole, G. Nunnari, G. Puglisi.
OV levelling:F. Obrizzo, H.A. Ali Naghi, C. Del Gaudio, C. Ricco, V. Sepe, OV.
Microgravimetry:G. Budetta, IIV; M. Grimaldi, OV.
Geochemistry (COSPEC):T. Caltabiano and R. Romano, IIV.
CO₂:M. Valenza, G. Capasso, M. Carapezza, W. D'Alessandro, S. Giammanco, S. Gurrieri, J. Hauser, and F. Parello, IGF, Palermo.
H₂ and CO:R. Cioni, G. Chiodini, A. Pescia, B. Raco, and G. Taddeucci, IGGI, Pisa, and Univ di Perugia.
Others:G. Kieffer, Univ Blaise-Pascal; C. Oppenheimer and D. Rothery, Open Univ.

November 1989 (SEAN 14:11) Cite this Report

Summit tephra emission; strong, fluctuating SO₂ emission

The following, from IIV, summarizes the much milder activity in November.

Summit activity. (S. Calvari, M. Coltelli, and M. Pompilio.) November summit activity was limited to discontinuous tephra emission from Bocca Nuova. Tephra emission episodes were frequent during the first two weeks of the month, often associated with deep explosive activity. Tephra emission became sporadic in the second half of November, although continuous activity was observed on the 19th. No juvenile material was ejected. La Voragine and Southeast Crater remained closed, with only weak fumarolic activity on their floors. Degassing from the vent at the bottom of Northeast Crater continued from previous months.

Seismicity. (E. Privitera, C. Cardaci, O. Cocina, V. Longo, A. Montalto, D. Patané, A. Pellegrino, S. Rapisarda, S. Spampinato, and O. Torrisi.) Seismic activity was very low in November. The three most energetic events following the eruption seismicity occurred 31 Oct at 0752 (M 3.0, 9 km depth, in the S. Alfio area, ~ 13 km E of the summit), 10 November at 0319 (M 3.6, 14 km depth, S of the seismic network near Pantano di Lentini, roughly 50 km S of Etna), and 20 November at 0754 (M 2.4, 15 km depth, in the Sciara del Follone area on the N flank). Recorded tremor remained similar to the pattern observed by the end of the eruption.

Ground deformation. (A. Bonaccorso, O. Campisi, G. Falzone, B. and G. Puglisi, and R. Velardita.) No significant variation has been observed in data from a borehole tilt station (SPC) on the SE flank at ~1,600 m elevation.

SO₂ flux. (T. Caltabiano and R. Romano.) SO₂ flux stabilized at intermediate values (~ 5,000 t/d) at the end of October, but increased in November, reaching 12,000 t/d on the 17th. Rates then declined, to 2,000 t/d on 28 November. A similar fluctuating pattern was observed during the three months (June-August) preceding the recent eruption, and during the same period in 1988 (not followed by an eruption).

Information Contacts: R. Santacroce, IIV.

December 1989 (SEAN 14:12) Cite this Report

Southeast Crater explosive activity drops tephra on nearby towns

Summit activity. (S. Calvari, M. Coltelli, O. Consoli, M. Pompilio, V. Scribano.) After only fumarolic emissions from Southeast Crater in November (14:11), renewed activity began on 16 December with continuous ejection of reddish cinders. The activity continued for the following two days, becoming weaker on the 18th. A new vent on the crater bottom, observed 21 December from the rim, exhibited strong explosive activity, but without visible tephra ejection. The activity became somewhat more intense during the following days. Only very small cinders (probably juvenile) reached the crater rim. Strong, deep, explosive activity was noted at Bocca Nuova, but there was no evidence of new tephra on the crater rim. La Voragine was obstructed and characterized by weak fumarolic emissions from the crater bottom. Gas emission from a vent on the floor of Northeast crater continued as before, but reddish cinders and gas were emitted on the 16th.

Seismic activity. (S. Privitera, C. Cardaci, O. Cocina, V. Longo, A. Montalto, D. Patane, A. Pellegrino, S. Spampinato.) Seismic activity in December returned to levels similar to those preceding the July-October seismic and eruptive activity (14:7-11). Five events with M>2 were recorded at 5-10 km depths on the Valle del Bove and the volcano's W sector. The most energetic event (M 2.8) occurred 9 December on the E part of the Valle del Bove at 9 km depth. The number and energy of low-frequency events increased, with maximum activity recorded on 16 December. Tremor amplitude also increased and was characterized by energy fluctuations, especially on the 18th and 19th.

Ground deformation. (A. Bonaccorso, O. Campisi, B. and G. Puglisi, R. Velardita.) Preliminary interpretation of the signal at the SPC borehole tilt station on the S flank showed no significant variation during December. Deformation measured on the NE trilateration network was characterized by shear, with almost equal moduli of the main strain axes. Distance measurements across the fracture on the volcano's S side indicate general stability relative to 7 October and 11 November surveys.

Summit crater SO₂ flux. (T. Caltabiano, R. Romano.) Samples collected 7, 20, and 29 December revealed that SO₂ flux had stabilized below the mean value of 4,000 t/d. A relatively low value (2,000 t/d) was recorded in late November. December 1989 SO₂ flux was slightly higher than the December 1988 trend, probably related to a longer-period flux component.

Early January activity. A seismic phase characterized by fluctuations in the mean amplitude of volcanic tremor began on 4 January at 1950 and was recorded at the ESP station of the permanent Mt. Etna seismic network. Iseismicity;amplitude By 5 January at 0120, the amplitude had stabilized at medium-high values. The most energetic phase was recorded between 0730 and 0922 on several seismic stations. During the following hours, tremor amplitude decreased, but sporadic 1-minute fluctuations brought the tremor amplitude to normal levels. The seismic phase was probably accompanied by lava fountaining at Southeast Crater, but bad weather prevented direct observation. The activity deposited lapilli and small scoria (up to 4 cm) on the NW side of the volcano in the Bronte-Randazzo area, with a dispersion axis oriented toward the town of Maletto (15 km NW of the summit crater). Scoria 13 km from the summit crater was 2-3 cm in diameter. Fieldwork in the following days revealed that a small amount of lava had poured over Southeast Crater's rim, probably due to lava fountaining. The 300-m lava flow, ~ 50 m wide and 1-2 m thick, reached the lowermost 1971 crater. As of 10 January, Southeast Crater showed no explosive activity.

Information Contacts: R. Santacroce, IIV.

January 1990 (BGVN 15:01) Cite this Report

Renewed Southeast Crater Strombolian activity; flank tephra fall and small lava flows; increased seismicity and SO₂

Summit activity. (S. Calvari, M. Coltelli, O. Consoli, M. Pompilio and V. Scribano.) Eruptive activity that resumed in December at Southeast Crater continued in January, with explosive episodes of Strombolian activity and lava fountaining 4-5, 12, and 14-15 January. The first episode of Strombolian activity deposited 1 to a few cm of ash on the NW flank. Lava poured from the S crater rim, reaching the 1971 eruptive craters (at least 200 m from the vent). A smaller amount of tephra ejected by similar activity on 12 January was carried a few hundred meters WNW by the wind. Lava spilled over the N crater rim, producing a flow 1.5 km long and 20-30 m wide that traveled NE along the September-October fracture system to ~ 2,700 m altitude. When activity ceased, Southeast Crater was completely obstructed by a solidified crust of lava.

The next day, Strombolian activity gradually increased, reaching maximum intensity on the morning of the 15th. Observations from a helicopter on 16 January revealed a new lava flow 50-100 m wide (apparently erupted 15 January) that had flowed over the E crater rim and traveled about 2.5 km SE down the Valle del Bove, stopping at ~2,000 m altitude (S of Sierra Gianicola Piccola).

Sporadic Strombolian explosions with variable intensities resumed 19 January and continued throughout the month. Bad weather prevented field surveys at the other active summit craters, but observations by helicopter showed degassing at the two central vents (Bocca Nuova and La Voragine) and Northeast Crater.

Seismic activity. (E. Privitera, C. Cardaci, O. Cocina, V. Longo, A. Montalto, D. Patane, A. Pellegrino, and S. Spampinato.) January seismicity increased from previous months. Tremor amplitude fluctuated, with increases on 5, 11-12 and 14-15 January, associated with strong explosive activity and lava emission at Southeast Crater. The number of low-frequency events of M<=1 increased from the single shock recorded in December, often becoming more numerous before and after variations in tremor amplitude. A large increase in the number of low-frequency shocks was recorded 19-20 January, but was not accompanied by variation in the tremor amplitude or an increase in energy release. A sequence of 18 events on the NNW side of the volcano at 10-15 km depth had a large energy release. At least nine events reached or exceeded M 2, with 2 main shocks (at 1200 and 1336 on the 28th) reaching M 2.7.

Ground deformation. (A. Bonaccorso, O. Campisi, G. Falzone, B. Puglisi, and R. Velardita.) January tilt recorded at the SPC and CDV borehole tilt stations on the volcano's S flank showed no significant variation from the previous month. EDM surveys across the fracture on the S side (along SP92) and on the N part of the Etna Sud trilateration network showed variations within instrumental error limits.

Summit crater SO₂ flux. (T. Caltabiano and R. Romano.) Samples collected from the summit craters on 8, 12, 16-18, 24, and 31 January showed increased SO₂ emission preceding eruptive activity. Emissions rose from ~4,000 t/d on 29 December to ~ 26,000 t/d measured 16 January following Southeast Crater explosive and effusive activity on the 14-15th. Emissions returned to moderate values on 17 January (~5,000 t/d) and remained near that level during measurments on 18, 24, and 31 January.

Information Contacts: R. Santacroce, IIV.

March 1990 (BGVN 15:03) Cite this Report

Lava fountains and flow then strong block ejection from Southeast Crater

Summit activity. (S. Calvari, M. Coltelli, O. Consoli, M. Pompilio, and V. Scribano.) February activity was characterized by a single strong eruptive episode at Southeast Crater. Summit-area craters generally remained quiet through the rest of February and March. The 1-2 February eruptive episode was similar to several in January. A gradual increase in Strombolian explosions was followed by lava fountaining, and lava flowed over the crater's E rim for 5 hours beginning at 2200 on 1 February. The flow turned toward the Valle del Bove, advancing to ~ 2,000 m altitude, near the terminus of the mid-January flow. During the morning of 2 February, discontinuous Strombolian activity was followed by ejection of scoria that seldom reached a few tens of meters from the rim. Activity changed at about 1330 to energetic, discontinuous explosions that generated rumbling heard at a considerable distance. Blocks more than a meter across fell within a few hundred meters of the crater; much of the slightly vesicular ash was non-juvenile. Similar activity continued until about midnight. After the eruptive episode, the crater was completely obstructed, without any gas emission, until 27 February, when sporadic ejection of dark tephra began from two vents on the crater floor. February activity at other summit-area craters was limited to vapor emission from floors and walls. Emissions were particularly strong from Northeast Crater, where the active vent's walls were strongly incandescent.

Degassing was continuous at the summit craters in March but was not accompanied by Strombolian activity. Degassing occurred from an elliptical vent on the W floor of La Voragine accompanied by sporadic rumbling. Gas was also emitted from two sites on the SE and NW floor of Bocca Nuova. Weak fumarolic activity, from collapse steps that have formed along concentric fractures in Southeast Crater, was strongest from the center of the crater. Degassing also continued in Northeast Crater. On 29 and 30 March, sporadic tephra ejection and incandescence were observed, apparently from a sudden rise in the magma column.

Seismic activity. (E. Privitera, C. Cardaci, O. Cocina, V. Longo, A. Montaldo, M. Patanè, A. Pellegrino, and S. Spampinato.) Volcanic tremor amplitude began a progressive increase on 1 February at 1239, probably associated with increased Strombolian activity at Southeast Crater. Amplitudes peaked at 1940 that day, and at 0048 the next morning as activity was changing from Strombolian to lava fountaining. Other substantial increases in tremor amplitude occurred at 0600-1100, 1855, and 1935. The first of two sequences of discrete earthquakes on 2 February began at 0352. Eight of the events, centered at ~15 km depth on the volcano's N sector, were larger than M 1, the strongest at M 2.6 between 0424 and 0619. The second series of shocks started at 1321, with the two largest events (M 2.8) at 1322 and 1337. Hypocenters were on the Valle del Bove at <1 km depth. From 3 February until the end of the month, seismic activity was at very low levels, with little variation in tremor amplitude or the number of low-frequency shocks. Nine fracturing events exceeded M 1, with a maximum magnitude of 2.5.

Seismic activity in March was characterized by a significant increase in the number of fracturing events. Swarms on 16 and 18 March totaled 124 shocks (M>=1) and brought the month's recorded earthquakes to 153, ~ 3 times as many as in January and February. The 16 March swarm began at 0530 and continued until 0050 the next day. Of the 107 shocks stronger than M 1, 28 were of M>=2 and three of M>=3. The bulk of the most energetic events originated from the central to W part of the edifice at 10-20 km depth, although one (at 1052) was located just NNW of the central crater at ~5 km depth. The strongest shock of the 18 March sequence, which included 17 events, occurred on the SW flank (a few kilometers S of Monte Nero) at ~10-15 km depth. An M 3.3 earthquake on 22 March at 1159 was ~15 km deep, roughly 6 km SSW of the summit (just S of Monte Vetore). The March seismicity was not accompanied by changes in volcanic tremor amplitude, which remained low throughout the month. The number and amplitude of low-frequency events showed little change after 3 February. A new seismic station (PZF) was installed on the lower NW flank (near Maletto), replacing station RCC, stolen in August 1989. With the new site, IIV's Etna network numbers 8 stations.

Ground deformation. (A. Bonaccorso, O. Campisi, G. Falzone, B. Puglisi, and R. Velardita.) Two tilt stations (SPC and CDV) operated during February, both on the S side of the volcano. Data from station SPC generally remained within resolution limits through February and March. A weak anomaly was recorded on the tangential component 18-20 February, then tangential data returned to the normal range. Radial values from recently installed station CDV remained within resolution limits through February, while tangential data began a (negative) excursion on 18 February that totalled 5 µrad by the end of the month. All instruments from this station were stolen on 1 March. Reoccupation of sites that form a triangle along the fracture zone between 1,800 and 1,500 m altitude on the S-SE flank (between benchmarks Bocche 1792, Serra Pizzuta Calvarina, and Mt. Stempato) did not show significant deformation since the previous measurements on 19 January.

Summit SO₂ flux. (T. Caltabiano and R. Romano.) Rates of SO₂ emission during Southeast Crater's eruptive episode on 2 February were three times mean values. Measurements 7, 14, and 21 February showed considerable variation. The five March measurements yielded SO₂ flux of 2,500-14,000 t/d, increasing at the end of the month.

Information Contacts: R. Santacroce, IIV.

October 1990 (BGVN 15:10) Cite this Report

Strombolian activity and lava fountaining from central craters; earthquakes and tremor; deformation

The following, from IIV, covers April-September 1990.

Summit crater activity. Eruptive activity was at Bocca Nuova and La Voragine, while only degassing was observed at the SE and NE subterminal craters. At the beginning of July, the mild degassing that had characterized the central vents during previous months evolved to Strombolian activity, sporadically ejecting juvenile products that reached the rim of Bocca Nuova. An intense eruptive episode began at Bocca Nuova on 7 August at about 1130, lasting for ~ 40 minutes. Strong Strombolian activity alternated with lava fountaining, producing a thick deposit (~10 cm maximum) of vesiculated scoria and Pele's Hair that accumulated on the N and NW sides of the crater rim. Wind carried lighter tephra 10 km NE, where it reached the villages of Vena and Presa (figure 38). Weak Strombolian activity followed, stopping early the next day. During the same period, La Voragine was limited to moderate Strombolian activity that stopped on 8 August. Increased tremor amplitude was recorded during the night of 7-8 August (see below), then tremor declined to low levels.

Figure 38. Sketch map of Etna, showing tephra dispersal during the 7 August Strombolian activity and lava fountaining.

Collapse of part of the wall between Bocca Nuova and La Voragine 9-10 August produced a landslide deposit that covered pre-existing vents on Bocca Nuova's floor. This deposit was soon penetrated by explosive activity, which formed two new vents characterized by weak Strombolian activity.

Throughout this period, activity at the SE subterminal crater remained limited to degassing. However, a considerable enlargement of the vent was observed in June, accompanied by strong incandescence of the inner walls. The temperature of the fumarolic gas, measured 8 August, reached 615°C. By the end of August, a larger degassing vent (~ 10 m across) had formed on the crater floor where fumarolic activity had previously been most intense. This vent produced only strong gas emission, without explosive episodes. Activity at the summit craters was limited to degassing of variable intensity in September.

Fault seismicity. Seismicity alternated between phases of relative quiet (April-June, September) and moderate to intense activity (July-August).

Moderate activity April-June was broken by four seismic sequences that occurred 25 April, 17-18 May, and 1-2 and 30 June (figure 39b). Seismic energy release (figure 39a) was also moderate (maximum M 3.0 on 17 May) and a total of 101 shocks of M >= 1 were recorded. The April-May seismicity mainly affected the W sector of the volcano, with seismic activity moving to the E (Valle del Bove) and NE flanks in June (figure 40). Average focal depths were ~15 km, except for the 1 June sequence, which had a focal zone at a depth of <=10 km (figure 41).

Figure 39. Top a): cumulative seismic energy release at Etna's S flank ESP station (figure 38) in the square-root of ergs (solid line) and radial component of ground tilt at nearby borehole station SPC (dashed line with squares). Bottom b): number of earthquakes (M³1) recorded at ESP station; April-September 1990.

Figure 40. Epicenters of earthquakes (M >= 2.5) at Etna, April-September 1990.

Figure 41. Foci of earthquakes shown in figure 40, projected onto a N-S cross-section passing through Etna's summit.

During the next two months, the most significant seismic episodes took place on 3 and 8 July, and 27 August. These sequences plus a general increase in background activity caused a significant change in the slope of the cumulative strain release curve. Energy associated with single events remained moderate, never exceeding M 3.1. The total of 148 events recorded in July decreased to 97 in August. The upper NE flank (10-25 km depth) and the Valle del Bove (6-12 km depth) were the areas most affected.

Another seismic sequence (78 events of M >= 1) occurred on the NW flank on 3 September; the average calculated focal depth was about 24 ± 4 km. Seismic activity then returned to moderate levels for the rest of the month.

Volcanic tremor. During April, May, and the first part of June, volcanic tremor amplitude recorded at a reference station (ESP) on the S flank fluctuated from low to moderate values (7-20 mV/_Hz). Beginning in the second half of June, an amplitude increase was observed (20-30 mV/_Hz) that lasted until 7 August. During the night of 7-8 August, a sudden further increase in tremor amplitude coincided with the violent Strombolian activity from Bocca Nuova (see above). After this episode, tremor amplitude returned to low levels (5-8 mV/_Hz), remaining at similar values until the end of September.

Ground deformation. EDM measurements were performed on two geodimeter networks, on the S and SW flanks. The southern network was measured in June, about a year after the last measurement in May 1989. The area covered by the network includes part of the main fracture system that affected the SE flank during the September-October 1989 eruption (14:8-10). Comparisons between May 1989 and June 1990 data showed significant distance variations, mostly for lines in the higher altitude sector of the network. The resulting deformation pattern was characterized by a significant areal contraction. The deformation ellipse was strongly polarized with the minimum extension axis (contraction) trending approximately N29°E. The southwestern EDM network was reoccupied in July, showing only minor slope distance variations from the previous measurements in June 1989. A weak areal contraction was observed. The calculated deformation ellipse had a minimum extension axis (contraction) striking approximately N7°E.

Tilt data were collected at a biaxial borehole station (SPC) on the S flank, close to the ESP seismic station. Recording was interrupted early April-early June by vandalism. The radial component indicated continuous inflation of the volcanic edifice from the beginning of July until early September, closely paralleling the seismic strain release (figure 39a). During the same period, the tangential component remained nearly flat, showing fluctuations within the confidence limit of about ± 2 µrads.

Information Contacts: IIV.

March 1991 (BGVN 16:03) Cite this Report

Periodic summit explosions; brief earthquake swarms; deformation

The following, from IIV, describes activity October 1990-March 1991. Explosive and/or Strombolian activity with strong degassing characterized Bocca Nuova, while the other summit craters generally showed almost continuous mild degassing.

Bocca Nuova. Intense Strombolian activity occurred from 4 or 5 vents that formed on the crater floor between 10 and 15 November. Ejecta only sporadically reached or went beyond the crater rim; most of the pyroclasts were ejected to moderate height, falling within the crater, where they accumulated with minor intracrater lava flows. The activity stopped abruptly on 24 December (associated with a deformation change; see below), and was succeeded that afternoon by strong continuous ash emission that lasted until the beginning of January. Weak Strombolian activity resumed for a few days in early January, ending by the 12th.

Southeast Crater. Typically mild, sometimes pulsating, gas emission was accompanied in December by weak ash ejection during times of the most intense similar activity at Bocca Nuova. A short period of mild Strombolian activity 4-7 January was the first significant eruptive event since the opening of a vent on the crater floor in April 1990.

La Voragine. Only discontinuous Strombolian activity 4-12 January was reported.

Northeast Crater. Frequent explosions occurred, but did not eject any juvenile tephra. Gas emission became intense in October and November, producing continuous incandescence of the degassing vent's inner walls that persisted through the report period.

Only sporadic summit observations were possible during February. These were limited to Southeast Crater, which was characterized by vapor emission. No information about March summit activity is available.

Seismic activity. Seismicity was moderate during October and November. On 7 December, a sequence of 26 events was recorded in a few hours. All were centered on the N flank at 7-24 km depth. Energy release was low, with no shocks exceeding M 2.2. Seven events on 9 January, at ~9 km depth on the SSW flank, were followed by a second swarm (42 events) on 26 January, which was deeper (14-20 km) and distributed over a wider area on the same part of the volcano. A deformation episode was recorded the same day by a nearby tiltmeter (see below). Another, shallower sequence occurred on the SSW flank on 2 February, in the same area as a sharp deformation episode on 24 December. Instrument problems prevented accurate location of a swarm on 8-9 February. A series of moderate earthquakes, on the N flank at ~ 21 km depth, was recorded 19-20 February. Seismicity declined in March.

Tremor amplitude was low in October, but increased 5-6 November, followed by a period of frequent amplitude fluctuations. On 27 November, tremor was strong enough to be detected for a few hours at seismic stations far from the summit craters. It then declined but remained at slightly elevated amplitude. No change in eruptive activity was reported on 27 November. Tremor continued to fluctuate into early December, then remained at low amplitude through March.

Ground deformation. Tilt data were collected at three borehole biaxial stations (SPC, CDV, and MDZ) on the S and SSW flanks. Summit inflation continued from previous months (at SPC), but slowed in November, and had nearly stopped by December. At nearby CDV, no significant radial tilt was detected, but the tangential component showed inflation toward the SW in October that reversed in November and continued on that trend until 24 December. A sharp deformation event was recorded that day on all three tilt stations, and a sudden change from Strombolian activity to continuous ash emission occurred at Bocca Nuova (see above). The pre-24 December trend then resumed at CDV, continuing through January, while similar behavior was shown by the tangential component at SPC.

Another sharp deformation event was recorded 26 January at station MDZ during a seismic swarm centered nearby (see above); a less intense deformation signal was detected at CDV.

Information Contacts: R. Velardita, IIV.

May 1991 (BGVN 16:05) Cite this Report

Strong degassing

Nearly continuous degassing was observed ... on 24 May. Northeast Crater's active vent was slightly incandescent and weakly emitting gas. Normal degassing, with sporadic rumbling, occurred at La Voragine, whose elliptical vent E of the central crater floor had reopened. The floors of Bocca Nuova and Southeast Crater were not visible due to their strong degassing.

Information Contacts: H. Gaudru, EVS, Switzerland; Franco Emmi, Etna guide.

July 1991 (BGVN 16:07) Cite this Report

Strombolian activity and continued strong degassing

Strong degassing continued .. during fieldwork in June and July. Strombolian activity was reported at a vent in the NE part of Southeast Crater. Small explosions occurred almost continuously, with more powerful blasts ejecting material to the level of the crater rim occurring every 10-15 minutes (in July). Meanwhile, a vent in the center of the crater gently degassed. In June, occasional emissions of small (<20 cm) sublimate-covered lithic blocks and scoria occurred from a 20 x 10 m pit in Northeast Crater. Lava was visible within the vent, which continued to glow through July. The vent widened internally, giving the appearance of a large chamber inclined in the direction of La Voragine. The elliptical vent at La Voragine crater (reopened prior to a 24 May visit; 16:05) showed incandescence in July, but not in June. Degassing continued from numerous fumaroles within the crater. The floor of Bocca Nuova crater was hidden by large quantities of gas in June, but in July two scoria cones were seen gently emitting vapor. At night, a strongly degassing vent on the SE side of the crater emitted tongues of incandescent gas at 15-minute intervals. A fumarole (56°C) was observed on the October 1989 fracture where it crossed the Canalone Della Montagnola at an altitude of ~ 2,200 m.

The following is from Steve Saunders. "A resurvey, in July, of an EDM network (67 lines) on the upper S flank showed a shortening of the majority of the lines (56), suggesting that minor deflation had occurred since the previous survey in July 1990. At that time, length increases along most lines were interpreted as resulting from minor inflation of the upper flanks since November 1989."

Information Contacts: H. Gaudru, EVS, Switzerland; T. De St. Cyr, Fontaines St. Martin, France; S. Saunders, West London Institute of Higher Education; W. McGuire, Cheltenham and Glouster College of Higher Education.

September 1991 (BGVN 16:09) Cite this Report

Summit-area Strombolian activity apparently ends; continued degassing

Strombolian activity in Northeast Crater had decreased by mid-July, and was no longer apparent on 23 August. Strombolian activity was observed in Southeast Crater in mid-July. All four summit craters were in a state of almost continuous mild degassing through August.

The following is from a report on activity 10-14 July, by J.P. Kloster in LAVE Bulletin no. 33, p. 4.

A network of curvilinear fissures, up to 2 m wide, covered the N, E, and SE parts of Southeast Crater. In the NW part of the crater, a vent 15 m in diameter emitted puffs of gas roughly every 3 seconds. Every half hour, a more violent explosion ejected lava fragments to 200 m above the vent, covering the walls of the crater and occasionally sending projectiles outside of the crater. The largest projectiles were estimated at around 5 kg, and were fluid enough to deform on impact. Two vents emitted slightly incandescent plumes at night. Each explosion was preceded by ~12 seconds of increased incandescence at the non-exploding vent, and corresponding intensification of glow at the exploding vent. On one occasion, a roughly 100-kg block of lava was ejected to 50 m height.

In the S part of Northeast Crater, a long-persistent vent, 5 m in diameter, emitted puffs of gas. At night, the emission was incandescent to 30 m height, with small lava fragments ejected during the most violent explosions. No projectiles fell beyond the crater rim.

About 70 m below Bocca Nuova crater's S rim, gas was strongly emitted from an E-W fissure, several meters wide and 12 m long, that probably formed in October 1989 (14:10). Explosions were heard emanating from the fissure area, roughly every 4-5 minutes. Night glow was visible at the fissure and at the vents of two coalesced scoria cones in the S part of the crater floor.

Very little activity occurred in La Voragine crater. One 20-m-diameter vent, on a small cinder cone, degassed quietly to several meters, and had night glow. Snow on the cone was largely covered by scoriae, suggesting recent activity.

No Strombolian activity or lava emission were observed during a 23 August visit to the summit by J. Dehn and B. Behncke. The vent in Northeast Crater had strong gas emission, accompanied by loud roaring noises, but no solid material was ejected. A dense continuous gas column was rising from Southeast Crater.

Information Contacts: J. Kloster, LAVE; J. Dehn and B. Behncke, GEOMAR, Kiel.

October 1991 (BGVN 16:10) Cite this Report

Minor Strombolian activity from several summit-area vents; little deformation

An 8-19 October resurvey of a 46-line EDM network on the upper S flank showed little movement since July, with maximum line-length changes of ~0.0015%. Activity at the summit craters was more energetic than in July but had the same general characteristics. Continued Strombolian activity in the NE sector of Southeast Crater periodically increased in strength, with large incandescent blebs of lava rising tens of meters above the crater rim. The open vent in Northeast Crater was degassing strongly and incandescent at night, while the two vents on the floor of Bocca Nuova had mild to strong Strombolian activity. E of Bocca Nuova, a single vent on the floor of La Voragine displayed weak Strombolian activity and daylight incandescence.

Further Reference. McGuire, W., Murray, J., Pullen, A., and Saunders, S., 1991, Ground deformation monitoring at Mt. Etna: evidence for dyke emplacement and slope instability: Journal of the Geological Society, London, v. 148, p. 577-583.

Information Contacts: S. Saunders, West London Institute; W. McGuire, Cheltenham and Gloucester College of Higher Education.

November 1991 (BGVN 16:11) Cite this Report

Brief SE-flank fissure eruption

Lava emerged from a fissure at 3,000 m altitude, apparently on the SE flank, for about an hour on 14 December. Light ashfalls occurred on small villages below the fissure. The eruption was preceded by hundreds of small earthquakes.

Information Contacts: AP.

December 1991 (BGVN 16:12) Cite this Report

Lava from SE-flank fissures covers about 5 km²; barrier constructed

The following, from R. Romano with additional information from J.C. Tanguy, supersedes the preliminary press report in 16:11. Information from Tanguy about the beginning of the eruption was collected thanks to G. Patanè, S. Imposa, R. Cristofolini, A. & O. Nicoloso, and G. Scarpinati.

A SE-flank fissure eruption began near the base of Southeast Crater early 14 December. Activity ended that day from the initial vents, but fissures propagated downslope where more vigorous lava production began the next morning. The eruption produced a substantial lava field and was continuing in mid-January.

After intense Strombolian activity at ... Bocca Nuova and Southeast Crater, eruptive fissures opened during the early morning of 14 December. These extended ~ 1 km SSE from the base of Southeast Crater (figure 42). Strong harmonic tremor was recorded between 0220 and 0420 by Univ di Catania seismometers. Ejection of lava fragments built modest cones and scoria ramparts along the fracture system, while small lava flows were extruded from some vents. More consistent lava production at the end of the fracture system fed a flow that advanced down the W wall of the Valle del Bove, branching into two lobes. These moved E, but did not exceed 1 km in length, reaching ~2,400 m altitude. When chief guide A. Nicoloso reached the area at about 0800, lava production had nearly stopped, although strong gas emission continued at Bocca Nuova and Southeast Crater. Activity from the fissures ceased completely during the morning. Another modest-sized eruptive fissure, oriented NE-SW, opened at the NE base of Southeast Crater, ejecting hot pyroclastic material.

Figure 42. Topographic map showing the 1989 and 1990 flows, and preliminary locations of the 1991-92 lava, eruptive fissures, and the barrier constructed in Val Calanna. The Piano del Trifoglietto is the broad plain covered by 1991-92 lava in the area of the "1991-92" label. Courtesy of R. Romano, T. Caltabiano, P. Carveni, and M.F. Grasso.

During the night, the NNW-SSE fissures that had been active the previous morning continued to propagate downslope. A second seismic crisis heralded the opening, at about 0245, of two sub-parallel eruptive fissures. These developed along a non-eruptive segment of the 1989 eruption's SE fracture, on the W wall of the Valle del Bove between roughly 2,400 and 2,200 m altitude, a total length of ~ 400 m. Strombolian activity began immediately along the new fissures and lava flowed E from the fissures' ends, extending ~ 1.5 km along the floor of the Valle del Bove by 0900 (observation by G. Scarpinati). The flows reached the base of the Valle del Bove during the afternoon, and advanced on the Piano del Trifoglietto, a plain at ~ 1,500 m altitude. That evening, at 2103, a strong shock was felt near Etna and to ~ 75 km SE (in the Siracusa area). Other isolated shocks and swarms of events with M <4 were recorded, particularly during the first few days of the eruption.

In the days that followed, Strombolian activity, sometimes intense, occurred from several points along the fissures, building small cones and scoria ramparts. Impressive phreatomagmatic explosions, accompanied by loud detonations, were clearly felt in towns at the foot of the volcano, especially during the eruption's first few days. The effusive activity created a system of lava flows, some with fronts hundreds of meters wide, which generally moved east, in the Piano del Trifoglietto.

By 20 December, lava had reached ~ 1,500 m altitude and superposition of lava flows began to be observed. During the evening of 23 December, a very wide lava front reached the Salto della Giumenta (at the head of the Val Calanna, ~ 4.5 km from the vent) and a few flows descended into it the next morning. Lava flows almost completely covered Val Calanna during the succeeding days, destroying orchards and drinking water facilities. On 2 January, a very wide flow front, ~ 10 m thick, had reached 950 m altitude (~ 5.5 km from the vent) and was advancing slowly. Construction began that day on a containment barrier along the E side of Val Calanna.

An extensive lava field had formed in the Piano del Trifoglietto, with individual lobes frequently superposing and combining. Overflows began from the N part of the lava field about 2 January, forming a separate flow around the N side of Monte Calanna on 5 January and rejoining the stagnant lava front in Val Calanna on the 7th. Flow fronts in Val Calanna had stopped by the morning of 9 January, while active superposed lobes were noted on the lava that had flowed N of Monte Calanna. The most advanced front was at ~ 1,100 m altitude and was tending to move E. The extensive (1-km-wide) main lava field fed numerous breakouts or ephemeral vents, from which modest flows advanced over earlier lava. The main lava channel, originating around 2,200 m altitude, was being vigorously fed and at times was tubed over.

By 14 January, Strombolian activity from the fissure vents had declined notably and explosions were no longer audible. Effusive activity was concentrated at a single vent, feeding a lava channel that subdivided into several flows at ~ 2,000 m altitude (at the base of the Valle del Bove's W wall). These moved onto the lava field formed earlier in the eruption but did not extend beyond 1,550 m altitude. The area covered by new lava had not grown since 9 January, but numerous ephemeral flows appeared on its surface. The containment barrier at the end of Val Calanna had not been tested as of 14 January, since the nearest flow had stopped ~150 m away (~6 km from the vent). As of 21 January the eruption was continuing, although apparently at a reduced rate.

Degassing from the summit craters has continued since the beginning of the eruption. Activity was sometimes intense, but ash was rarely mixed with the gas. Strombolian activity that was vigorous at times continued from various vents at the bottom of Bocca Nuova.

Romano noted that the activity has the characteristics of a classic "slow eruption" (Romano and Sturiale, 1982) and is very similar to the 1819 eruption that occurred in the same area of the Valle del Bove.

Preliminary estimates indicated that ~40 x 10⁶ m³ of lava had been ejected as of 9 January, with an effusion rate of around 15-18 m³/s. Measurements of the effusion rate on 11 January yielded a value of around 9 m³/s from the lava channel at 2,000 m altitude.

Reference. Romano, R., and Sturiale, C., 1982, The historic eruptions of Mt. Etna (volcanological data): Memoirs of the Geological Society of Italy, v. 23, p. 75-97.

Information Contacts: R. Romano and T. Caltabiano, IIV; P. Carveni and M. Grasso, Univ di Catania; J. Tanguy, Univ de Paris.

January 1992 (BGVN 17:01) Cite this Report

Lava production continues from SE-flank fissure but explosive activity declines

The following is from R. Romano. The SE-flank fissure eruption that began on 14 December was continuing as of early February. No notable decrease in the rate of lava effusion has been observed. Explosive activity along the eruptive fissure, which has been highly variable in intensity and duration, has mainly declined to sporadic ejections of lava fragments, limited expulsion of dark ash, and rare phreatomagmatic explosions. Strong gas emission was generally evident. Seismic activity has declined to isolated weak events.

The lava field in the SE flank's Valle del Bove has grown considerably, reaching a maximum width of 1.5 km in a few places, as flows from the N (dominantly) and S merged. Most of the lava was carried through a complex system of tubes originating at the main effusive vent, and emerged onto the lava field surface through numerous ephemeral secondary vents. These varied daily in number and position, and were concentrated in the middle of the lava field (around 1,550 m asl), but some have recently appeared at ~ 1,450 m altitude (at the base of Monte Zoccolaro, just before the break in slope at the Salto della Giumenta). Lava flows from the secondary vents generally advanced along the Salto della Giumenta, and were sometimes relatively continuous. In early February one of these reached, but did not surpass, the front of the eruption's longest flow, at 1,000 m elevation (in Val Calanna, ~6 km from the active fissure). Preliminary estimates indicate that > 6 km² has been covered by ~55-60 x 10⁶ m³ of new lava, an average volume for Etna's "slow eruption" type (Romano and Sturiale, 1982).

The summit craters remained open, emitting gases from small vents. High-temperature gas release was sometimes observed (as at the central crater's E vent, La Voragine, on 11 February). A little dark ash was recently emitted from the central crater's W vent (Bocca Nuova).

Information Contacts: R. Romano and T. Caltabiano, IIV; P. Carveni and M. Grasso, Univ di Catania.

February 1992 (BGVN 17:02) Cite this Report

Continued flank lava production

The following is from a report by the Gruppo Nazionale per la Vulcanologia (GNV) summarizing Etna's 1991-92 eruption.

1. Introduction and Civil Protection problems. After 23 months of quiet, and heralded by ground deformation and a short seismic swarm, effusive activity resumed at Etna early 14 December. The eruptive vent opened at 2,200 m elevation on the W wall of the Valle del Bove, along a SE-flank fracture that formed during the 1989 eruption.

Since the eruption's onset, the GNV, in cooperation with Civil Protection authorities, has reinforced the scientific monitoring of Etna. Attention was focused on both the advance of the lava flow and on the possibility of downslope migration of the eruptive vent along the 1989 fracture system. The progress of the lava flow has been carefully followed by daily field inspections and helicopter overflights.

Because of its slow rate of advance, the lava did not threaten lives, but had the potential for severe property destruction. The water supply system for Zafferana (in Val Calanna; figure 43) was destroyed in the first two weeks of the eruption ($2.5 million damage). On 1 January, when the lava front was only 2 km from Zafferana, the Minister for Civil Protection, at the suggestion of the volcanologists, ordered the building of an earthen barrier to protect the village. The barrier was erected at the E end of Val Calanna, where the valley narrows into a deeply eroded canyon. The barrier was conceived to prevent or delay the flow's advance, not to divert it, by creating a morphological obstacle that would favor flow overlapping and lateral expansion of the lava in the large Val Calanna basin.

Figure 43. Topographic sketch map showing Etna's 1989 and 1990 lava flows, with preliminary locations of the 1991-92 lava, eruptive fissures, and the barrier constructed in Val Calanna. The area covered by lava since 14 January is shown in a separate pattern. The GNV report, received near press time, included a map that differed somewhat in detail from this map, which was prepared by R. Romano, T. Caltabiano, P. Carveni, M.F. Grasso, and C. Monaco. See pg.4 of Barberi et al., 1990 for a map of the 1989 lava flows, fissures, and monitoring network.

The barrier, erected by specialized Army and Fire Brigade personnel in 10 days of non-stop work, is ~ 250 m long and ~ 20 m higher than the adjacent Val Calanna floor. It was built by diking the valley bottom in front of the advancing lava and accumulating loose material (earth, scoria, and lava fragments) on a small natural scarp. On 7 January, the lava front approached to a few tens of meters from the barrier, then stopped because of a sudden drop in feeding caused by a huge lava overflow from the main channel several kilometers upslope.

A decrease in the effusion rate has been observed since mid-January. There is therefore little chance of further advance of the front, as the flow seems to have reached its natural maximum length. The eruptive fracture is being carefully monitored (seismicity, ground deformation, geoelectrics, gravimetry, and gas geochemistry) to detect early symptoms of a possible dangerous downslope migration of the vent along the 1989 fracture, which continues along the present fracture's SE trend. Preparedness plans were implemented in case of lava emission from the fracture's lower end.

Many scientists and technicians, the majority of whom are from IIV and the Istituto per la Geochimica dei Fluidi, Palermo (IGF) and are coordinated by GNV, are collecting information on the geological, petrological, geochemical, and geophysical aspects of the eruption.

2. Eruption chronology. On 14 December at about 0200, a seismic swarm (see Seismicity section below) indicated the opening of two radial fractures trending NE and SSE from Southeast Crater. Very soon, ash and bombs formed small scoria ramparts along the NE fracture, where brief activity was confined to the base of Southeast Crater. Meanwhile, a SSE-trending fracture extended ~ 1.3 km from the base of the crater (at ~3,000 m asl) to 2,700 m altitude.

Lava fountaining up to 300 m high from the uppermost section of the SSE fracture continued until about 0600, producing scoria ramparts 10 m high. Two thin (~ 1 m thick) lava flows from the fracture moved E. The N flow, from the highest part of the fracture, stopped at 2,750 m altitude, while the other, starting at 2,850 m elevation, reached the rim of the Valle del Bove (in the Belvedere area), pouring downvalley to ~ 2,500 m asl. At noon, the lava flows stopped, while the W vent of the central crater (Bocca Nuova) was the source of intense Strombolian activity.

The SSE fracture system continued to propagate downslope, crossing the rim of the Valle del Bove in the late evening. During the night of 14-15 December, lava emerged from the lowest segment of the fracture cutting the W flank of the Valle del Bove, reaching 2,400 m altitude (E of Cisternazza). Degassing and Strombolian activity built small scoria cones. Two lava flows advanced downslope from the base of the lower scoria cone at an estimated initial velocity of 15 m/s, which dramatically decreased when they reached the floor of the Valle del Bove.

The SSE fractures formed a system 3 km long and 350-500 m wide that has not propagated since 15 December. Between Southeast Crater and Cisternazza, the fracture field includes the 1989 fractures, which were reactivated with 30-50-cm offsets. The most evident offsets were down to the E, with right-lateral extensional movements. Numerous pit craters, <1 m in diameter, formed along the fractures.

Lava flows have been spreading down the Valle del Bove into the Piano del Trifoglietto, advancing a few hundred meters/day since 15 December. The high initial outflow rates peaked during the last week of 1991 and the first few days of 1992, and decreased after the second week in January. Strombolian activity at the vent in the upper part of the fracture has gradually diminished.

Lava flows were confined to the Valle del Bove until 24 December, when the most advanced front extended beyond the steep slope of the Salto della Giumenta (1,300-1,400 m altitude), accumulating on the floor of Val Calanna. Since then, many ephemeral vents and lava tubes have formed in the area N of Monte Zoccolaro, probably because of variations in the eruption rate. These widened the lava field in the area, and decreased feeding for flows moving into Val Calanna. However, by the end of December, lava flows expanded further in Val Calanna, moving E and threatening the village of Zafferana Etnea, ~2 km E of the most advanced flow front. This front stopped on 3 January, on the same day that a flow from the Valle del Bove moved N of Monte Calanna, later turning back southward and rejoining lava that had already stopped in Val Calanna. Since 9 January, lava flows in Val Calanna have not extended farther downslope, but have piled up a thick sequence of lobes.

Lava outflow from the vent continued at a more or less constant rate, producing a lava field in the Valle del Bove that consisted of a complex network of tubes and braiding, superposing flows, with a continuously changing system of overflows and ephemeral vents.

3. Lava flow measurements. An estimate of lava channel dimensions, flow velocity, and related rheological parameters was carried out where the flow enters the Valle del Bove. Flow velocities ranging from 0.4-1 m/s were observed 3-7 January in a single flow channel (10 m wide, ~ 2.5 m deep) at 1,800 m altitude, ~ 600 m from the vent. From these values, a flow rate of 8-25 m³/s and viscosities ranging from 70-180 Pas were calculated. Direct temperature measurements at several points on the flow surface with an Al/Ni thermocouple and a 2-color pyrometer (HOTSHOT) yielded values of 850-1,080°C.

4. Petrography and chemistry. Systematic lava sampling was carried out at the flow fronts and near the vents. All of the samples were porphyritic (P.I.»25-35%) and of hawaiitic composition, differing from the 1989 lavas, which fall within the alkali basalt field. Paragenesis is typical of Etna's lavas, with phenocrysts (maximum dimension, 3 mm) of plagioclase, clinopyroxene, and olivine, with Ti-magnitite microphenocrysts. The interstitial to hyalopitic groundmass showed microlites of the same minerals.

5. Seismicity. On 14 December at 0245, a seismic swarm occurred in the summit area (figure 44), related to the opening of upper SE-flank eruptive fractures. About 270 earthquakes were recorded, with a maximum local magnitude of 3. A drastic reduction in the seismic rate was observed from 0046 on 15 December, with only four events recorded until the main shock (Md 3.6) of a new sequence occurred at 2100. The seismic rate remained quite high until 0029 on 17 December, declining gradually thereafter.

Figure 44. Daily number of recorded earthquakes and cumulative strain release (top), with amplitude (middle) and dominant frequency peaks of volcanic tremor (bottom) at Etna, 1 December 1991-mid-January 1992. Arrows mark the eruption's onset. Courtesy of the Gruppo Nazionale per la Vulcanologia.

At least three different focal zones were recognized. On 14 December, one was located NE of the summit and a second in the Valle del Bove. The third, SW of the summit, was active on 15 December. All three focal zones were confined to <3 km depth. Three waveform types were recognized, ranging from low-to-high frequency.

As the seismic swarm began on 14 December, volcanic tremor amplitude increased sharply. Maximum amplitude was reached on 21 December, followed by a gradually decreasing trend. As the tremor amplitude increased, the frequency pattern of its dominant spectral peaks changed, increasing within a less-consistent frequency trend. Seismicity rapidly declined and remained at low levels despite the ongoing eruption.

6. Ground deformation. EDM measurements and continuously recording shallow-borehole tiltmeters have been used for several years to monitor ground deformation at Etna. The tilt network has recently grown to 9 flank stations. A new tilt station (CDV) established on the NE side of the fracture in early 1990 showed a steady radial-component increase in early March 1991 after a sharp deformation event at the end of 1990 (figure 45), suggesting that pressure was building into the main central conduit. Maximum inflation was reached by October 1991, followed by a partial decrease in radial tilt, tentatively related to magma intrusion into the already opened S branch of the 1989 fracture system, perhaps releasing pressure in the central conduit.

Figure 45. Radial and tangential components measured by the CDV borehole tilt station on the NE side of Etna's 1989 fracture, 1 July—mid-January 1992. The signal has been filtered for daily and seasonal thermoelastic noise. Arrows mark the eruption's onset. Courtesy of the Gruppo Nazionale per la Vulcanologia.

The eruption's onset was clearly detected by all flank tilt stations, despite their distance from the eruption site. The signals clearly record deformation events closely associated in time with seismic swarms on the W flank (before the eruption began) and on the summit and SW sector (after eruption onset). The second swarm heralded the opening of the most active vent on the W wall of the Valle del Bove.

S-flank EDM measurements detected only minor deformation, in the zone affected by the 1989 fracture. Lines crossing the fracture trend showed brief extensions in January 1992.

The levelling route established in 1989 across the SE fracture was reoccupied 18-19 December 1991. A minor general decline had occurred since the previous survey (October 1990), with a maximum (-10 mm) at a benchmark near the fracture.

7. Gravity changes. Microgravity measurements have been carried out on Etna since 1986, using a network covering a wide area between 1,000 and 1,900 m asl. A reference station is located ~ 20 km NE of the central crater. Five new surveys were made across the 1989 fissure zone during the eruption (15 & 18 December 1991, and 9, 13, and 18 January 1992). Between 21 November and 15 December, the minimum value of gravity variations was about -20 mGal, E of the fracture zone. On 9 January, the gravity variations inverted to a maximum of about +15 mGal. Amplitude increased and anomaly extension was reduced on 13 January, and on 18 January gravity variations were similar to those 9 days earlier. Assuming that height changes were negligible, a change in mass of ~2 x 10⁶ tons (~2 x 10⁷ m³ volume), for a density contrast of 0.1 g/cm³ was postulated. However, if gravity changes were attributed to magma movement, a density contrast of 0.6 g/cm³ between magma and country rock could be assumed and magma displacement would be ~ 3 x 10⁶ m³.

8. Magnetic observations. A 447-point magnetic surveillance array was spaced at 5-m intervals near the fracture that cut route SP92 in 1989. Measurements of total magnetic field intensity (B) have been carried out at least every 3 months since October 1989. Significant long-term magnetic variations were not observed between February 1991 and January 1992, although the amplitude of variations seems to have increased since the beginning of the eruption.

9. Self-potential. A program of self-potential measurements along an 1.32-km E-W profile crossing the SE fracture system (along route SP92 at ~ 1,600 m altitude) began on 25 October 1989. Two large positive anomalies were consistently present during measurements on 5 and 17 January, and 9, 18, and 19 February 1992. The strongest was centered above the fracture system, the second was displaced to the W. Only the 5 January profile hints at the presence of a third positive anomaly, on its extreme E end. The persistent post-1989 SP anomalies could be related to a magmatic intrusion, causing electrical charge polarizations inside the overlying water-saturated rocks. A recent additional intrusion was very likely to have caused the large increase in amplitude and width of the SP anomaly centered above the fracture system, detected on the E side of the profile on 5 January 1992.

10. COSPEC measurements of SO₂ flux. The SO₂ flux from Etna during the eruption has been characterized by fairly high values, averaging ~ 10,000 t/d, ~ 3 times the mean pre-eruptive rate. Individual measurements varied between ~6,000 and 15,000 t/d.

11. Soil gases. Lines perpendicular to the 1989 fracture, at ~ 1,600 m altitude, have been monitored for CO₂ flux. A sharp increase in CO₂ output was recorded in September 1991, about 3 months before the eruption began (figure 46). Measurements have been more frequent since 17 December, but no significant variation in CO₂ emission has been observed. Samples of soil gases collected at 50 cm depth showed a general decrease in He and CO₂ contents since the beginning of January. Soil degassing at two anomalous exhalation areas, on the lower SW and E flanks at ~ 600 m altitude, dropped just before (SW flank—Paternò) and immediately after (E flank—Zafferana) the beginning of the eruption, and remained at low levels. A significant radon anomaly was recorded 26-28 January along the 1989 fracture, but CO₂ and radon monitoring have been hampered by snow.

Figure 46. CO₂ concentrations measured along Etna's 1989 fracture, late 1990-early 1992, showing a strong increase about 3 months before the December 1991 eruption. Courtesy of the Gruppo Nazionale per la Vulcanologia.

The following, from R. Romano, describes activity in February and early March.

The SE-flank fissure eruption was continuing in early March, but was less vigorous than in previous months. An area of ~ 7 km² has been covered by around 60 x 10⁶ m³ of lava, with an average effusion rate of 8 m³/s. The size of the lava field (figure 43) has not increased since it reached a maximum width of 1.7 km in mid-February.

Lava from fissure vents at ~ 2,100 m asl flowed in an open channel to 1,850 m altitude, then advanced through tubes. Flowing lava was visible in the upper few kilometers of the tubes through numerous skylights. Lava emerged from the tube system through as many as seven ephemeral vents on the edge of the Salto della Giumenta (at the head of the Val Calanna, ~ 4.5 km from the eruptive fissure). These fed a complex network of flows in the Salto della Giumenta that were generally short and not very vigorous. None extended beyond the eruption's longest flow, which had reached 6.5 km from the eruptive fissure (1,000 m asl) before stopping in early January. Ephemeral vent activity upslope (within the Valle del Bove) ceased by the end of February. Lava production from fissure vents at 2,150 m altitude has gradually declined and explosive activity has stopped. Degassing along the section of the fissure between 2,300 and 2,200 m altitude was also gradually decreasing.

Small vents were active at the bottom of both central craters. Activity at the west crater (Bocca Nuova) was generally limited to gas emission, but significant ash expulsions were observed during the first few days in March. High-temperature gases emerged from the E crater (La Voragine). Collapse within Northeast Crater, probably between 26 and 27 February, was associated with coarse ashfalls on the upper NE flank (at Piano Provenzana and Piano Pernicana). After the collapse, a new pit crater ~ 50 m in diameter occupied the site of Northeast Crater's former vent. Activity from Southeast Crater was limited to gas emission from a modest-sized vent.

Seismic activity was characterized by low-intensity swarms. A few shocks were felt in mid-February ~ 12 km SE of the summit (in the Zafferana area).

Reference. Barberi, F., Bertagnini, F., and Landi, P., eds., 1990, Mt. Etna: the 1989 eruption: CNR-Gruppo Nazionale per la Vulcanologia: Giardini, Pisa, 75 p. (11 papers).

Information Contacts: GNV report:F. Barberi, Univ di Pisa; L. Villari, IIV. February-early March activity:R. Romano and T. Caltabiano, IIV; P. Carveni, M. Grasso, and C. Monaco, Univ di Catania.
The following people provided information for the GNV report. Institutional affiliations (abbreviated, in parentheses) and their report sections [numbered, in brackets] follow names.
F. Barberi (UPI) [1, 2], A. Armantia (IIV) [2], P. Armienti (UPI) [2, 4], R. Azzaro (IIV) [2], B. Badalamenti (IGF) [11], S. Bonaccorso (IIV) [6], N. Bruno (IIV) [10], G. Budetta (IIV) [7, 8], A. Buemi (IIV) [4], T. Caltabiano (IIV) [8, 10], S. Calvari (IIV) [2, 3], O. Campisi (IIV) [6], M. Carà (IIV) [10], M. Carapezza (IGF, UPA) [11], C. Cardaci (IIV) [5], O. Cocina (UGG) [5], D. Condarelli (IIV) [5], O. Consoli (IIV) [6], W. D'Alessandro (IGF) [11], M. D'Orazio (UPI) [2, 4], C. Del Negro (IIV) [7, 8], F. DiGangi (IGF) [11], I. Diliberto (IGF) [11], R. Di Maio (DGV) [9], S. DiPrima (IIV) [5], S. Falsaperla (IIV) [5], G. Falzone (IIV) [6], A. Ferro (IIV) [5], F. Ferruci (GNV) [5], G. Frazzetta (UPI) [2], H. Gaonac'h (UMO) [2, 3], S. Giammanco (IGF) [11], M. Grasso (IIV) [10], M. Grimaldi (DGV) [7], S. Gurrieri (IGF) [11], F. Innocenti (UPI) [4], G. Lanzafame (IIV) [2], G. Laudani (IIV) [6], G. Luongo (OV) [6], A. Montalto (IIV, UPI) [5], M. Neri (IIV) [2], P. Nuccio (IGF, UPA) [11], F. Obrizzo (OV) [6], F. Parello (IGF, UPA) [11], D. Patanè (IIV) [5], D. Patella (DGV) [9], A. Pellegrino (IIV) [5], M. Pompilio (IIV) [2, 3, 4], M. Porto (IIV) [10], E. Privitera (IIV) [5], G. Puglisi (IIV) [2, 6], R. Romano (IIV) [10], A. Rosselli (GNV) [5], V. Scribano (UCT) [2], S. Spampinato (IIV) [5], C. Tranne (IIV) [2], A. Tremacere (DGV) [9], M. Valenza (IGF, UPA) [11], R. Velardita (IIV) [6], L. Villari (IIV) [1, 2, 6].
Institutions: DGV: Dipto di Geofisica e Vulcanologia, Univ di Napoli; GNV: Gruppo Nazionale per la Vulcanologia, CNR, Roma; IGF: Istituto per la Geochimica dei Fluidi, CNR, Palermo; IIV: Istituto Internazionale di Vulcanologia, CNR, Catania; OV: Osservatorio Vesuviano, Napoli; UCT: Istituto di Scienze della Terra, Univ di Catania; UGG: Istituto di Geologia e Geofisica, Univ di Catania; UMO: Dept de Géologie, Univ de Montréal; UPA: Istituto di Mineralogia, Petrologia, e Geochimica, Univ di Palermo; UPI: Dipto di Scienze della Terra, Univ di Pisa.

March 1992 (BGVN 17:03) Cite this Report

Lava production continues from SE-flank vent; town threatened by lava flow

Most of the following is from R. Romano.

The fissure eruption ... was continuing in mid-April. Lava production from the main vent at 2,100 m altitude (in the W wall of the Valle del Bove) has remained almost constant, accompanied by degassing of varying intensity. By mid-April, 85 x 10⁶ m³ of lava that had emerged at an average rate of 8 m³/s was estimated to cover an area of >7 km².

From March through mid-April, lava from the main vent immediately entered a complex tube system, reappearing through ephemeral vents ~ 5 km downslope, below the Valle del Bove. The vents formed on the edge of the Salto della Giumenta, at the head of the Val Calanna a few kilometers from Zafferana Etnea, population ~ 7,000 (see figure 43). No ephemeral vents or lava overflows have been observed since the end of February in the wide lava field that had developed in the S part of the Valle del Bove.

On 14 March, lava reached the base of the barrier constructed in early January at the bottom of the Val Calanna. During the second half of March and the first few days of April, lava from the ephemeral vents gradually filled the area from the base of the Salto della Giumenta to the barrier. On 3 April, vents began to form within the Salto della Giumenta, feeding flows inside the Val Calanna. By the morning of 7 April, lava was only a few meters from the top of the barrier, with an active front along the barrier's entire length. That afternoon, lava flowed around the S side of the barrier and began to advance along the access road in the Val Calanna. The next afternoon, lava spilled over the central part of the barrier, and began to move down the gorge of the neighboring Portella Calanna valley. Lava advanced rapidly, aided by the steep slope, covering 1 km in 5 days. At least six earth barriers were built to contain the lava, but none were successful. By 14 April, lava was overflowing the last barrier, at ~ 780 m elevation, 1.5 km from the inhabited center of Zafferana Etnea and 7.5 km from the main vent.

Efforts were also made to slow or halt the advancing lava by disrupting the feeder tube system. Experiments with directed explosives, designed to blast holes in the lava field and encourage lava breakouts, began on 13 April in the upper Valle del Bove and Val Calanna. Lava destroyed two isolated houses above Zafferana on 14 April and covered nearby orchards, but the lobe threatening the town had virtually stopped by the next day and evacuation plans were postponed. New lava approached Zafferana over earlier flows in the succeeding days, and was again within a kilometer of the town by 20 April.

Degassing from the summit craters has gradually decreased following the collapse episode in Northeast Crater at the end of February (17:02). Additional Northeast Crater collapses 21-29 March triggered ash ejections accompanied by distinctive seismicity. Moderate gas emission from the summit vents observed by B. Behncke on 21 March was punctuated around 0900 by several low-energy ash emissions from Northeast Crater. At 1230 on 24 March, a dark-gray, convoluted ash plume rose to ~ 1 km above the summit within ~ 5 minutes, and also appeared to spread laterally at its base. The plume gradually dissipated during the following 30 minutes, depositing tephra to the E.

Information Contacts: R. Romano, T. Caltabiano, and M. Porto, IIV; P. Carveni and M. Grasso, Univ di Catania; B. Behncke, GEOMAR, Kiel; Il Mattino, Napoli; AP; UPI; Reuters.

April 1992 (BGVN 17:04) Cite this Report

SE-flank fissure eruption continues; lava diversion attempted

Lava has emerged from a SE-flank fissure in the W wall of the Valle del Bove since 15 December, covering an estimated 7.3 km² with ~ 100 x 10⁶ m³ of lava. A well-developed tube system carried lava downslope, threatening the town of Zafferana Etnea and prompting attempts at lava diversion (figure 47). The lava production rate, as observed through numerous skylights along the main lava tube, has remained relatively constant, but distal flow fronts advanced at varying rates. The apparent intensity of gas emission from the eruptive fissure changed with weather conditions. During the last 10 days of April, fumarolic activity was observed in the W wall of the Valle del Bove, extending upslope from the eruptive fissure along its NNW trend. This zone was active on 14 December during the initial phase of the eruption.

Figure 47. Topographic sketch map showing Etna's 1989-92 lava flows, with preliminary locations of the 1991-92 eruptive fissures, and the barrier constructed in January in Val Calanna. Areas covered by lava since 14 January and 10 March are shown in separate patterns. Asterisks mark sites of lava diversion experiments in April and May. Courtesy of R. Romano, T. Caltabiano, P. Carveni, and M.F. Grasso.

Lava overwhelmed a series of barriers in early April, and advanced 1 km down a gorge (within the Valle di Portella Calanna) toward Zafferana during the second week in April. This flow stopped on 15 April at 750 m elevation, roughly 1.5 km from the inhabited center of Zafferana. Numerous ephemeral vents began to form below 1,000 m elevation on 19 April (on the E edge of Val Calanna, in which a barrier had been built in early January). Flows from these vents covered lava from previous days along the gorge below Portella Calanna. The longest stopped during the evening of 25 April at 755 m altitude, ~ 7.5 km from the eruptive fissure and 1.5 km from the center of Zafferana. Lava flows originated from a large ephemeral vent at the head of Val Calanna in the beginning of May, passing Portella Calanna atop previous flows on 6 May and reaching 850 m asl that evening.

Ephemeral vents also developed upslope, within the wide lava field that had formed in the S part of the Valle del Bove during previous months. The first formed around 1,900 m altitude (at Monte del Rifugio Menza) on 22 April, and a second occurred near the center of the lava field, at around 1,550 m elevation (near Poggio Canfareddi) on 25 April. Flows from these vents were not very substantial and were no longer active a few days later. On 5 May, only a modest active vent at the N edge of the lava field (around 1,600 m elevation) was observed.

Experiments with the use of explosives, cement blocks, and, more recently, lava blocks continued at skylights in the main lava tube (in the upper Valle del Bove, at around 2,100 m altitude, on 17, 21, and 29 April, and 4 May) and at ephemeral vents (near Portella Calanna on 15 April and in Val Calanna on 6 May). These were designed to cause lava overflows and thus reduce the amount of lava carried in tubes toward inhabited areas. As of early May, it was difficult to evaluate whether these experiments had favorably affected the course of the eruption. On 4 May an overflow began from a skylight in the main lava tube at around 2,100 m altitude, where blocks of cement had been dropped and explosives detonated on previous days. The modest overflow moved over the lava field that had formed in the preceding months. However, during this time, numerous ephemeral vents, varying daily in number and location, remained active above Zafferana at the head of Val Calanna (in the Salto della Giumenta).

Slow, weak degassing continued through early May from the summit craters. Weak ash ejections, caused by internal collapse, were observed only from Northeast Crater, on 22 April. Early April-early May seismic activity was much reduced from previous months.

Information Contacts: R. Romano and T. Caltabiano, IIV; P. Carveni and M. Grasso, Univ di Catania.

May 1992 (BGVN 17:05) Cite this Report

Fissure eruption continues; lava diverted; lava field described

The following is from R. Romano. Lava production from the fissure ... was continuing without noticeable variation in mid-June. Gas emission, from four explosion vents between 2,335 and 2,215 m elevation, has diminished along the upper part of the fissure. The main lava channel has roofed over, but lava was visible through a skylight beginning at 2,205 m elevation, where the effusion rate was estimated at 6-8 m³/s and the flow velocity at ~ 1 m/s on 7 and 13 June. Three more skylights were open along the main channel to 2,020 m asl. An overflow occurred on 12 June from one of the skylights, at 2,075 m altitude, but lava advanced only a few meters before returning to the main channel. This overflow was still active the next day. Ephemeral vents from the main tube remained active through the end of May: in the Valle del Bove; below the Valle del Bove in Val Calanna; and near the distal end of the flow field, along a deep gully under Portella Calanna (figure 48). Lava flows emerged more or less continuously from the latter vents, but did not descend below 800 m altitude. The total volume of lava produced by the eruption is estimated at 150 x 10⁶ m³.

Figure 48. Status of activity within Etna's flow field on 18 May 1992, after 153 days of activity. Modified by Hughes and Bulmer from map by Romano in 17:4. Contour interval, 100 m.

Lava diversion. An earthen barrier built in a valley above the town of Zafferana Etnea in early January was breached by lava on 7 April. Lava overran a series of additional barriers the following week but stopped before reaching the town. Subsequent hazards efforts focused on reducing the lava supply to the end of the flow, by obstructing the main lava tube near the vent and disrupting lava production at ephemeral vents (17:3-4).

F. Barberi and L. Villari report successful lava diversion from the main tube, at a site 500 m downslope from the primary eruptive vent. In this area, at ~ 2,000 m elevation on the W wall of the Valle del Bove, lava was carried through a single tube locally broken by skylights. On 27 May, about 2/3 of the tube's lava was diverted into an artificially excavated channel by blasting through the 2-3-m-thick wall of the right levee. Two days later, bulldozers obstructed the natural channel by pushing large blocks of lava into it. By 1815 that day, all of the lava output (~30 m³/s) was flowing into the artificial channel. In effect, the diversion returned the active flow front to its position a few days after the onset of the eruption. Lava was moving downslope along the same path as the earlier main flow, but was > 6 km upslope from its previously most advanced front.

Flows generated by lava diversion efforts. R. Romano reports that as of 13 June, a vent remained active at the site of the first lava diversion. Although the vent has been shrinking, it continued to feed a flow that has advanced over lava from previous months, forming tubes and various ephemeral vents, many of which were near the S wall of the Valle del Bove. The ephemeral vents produced two lava flows, one near the S wall of the Valle del Bove at around 1,700 m elevation, the other in a more central position, at ~ 1,800 m asl on the main lava field. The lava flows that formed after the first diversion advanced more than a kilometer over the center of the lava field. Flows that followed the second diversion remained predominantly near the S wall of the Valle del Bove, passing and encircling a site at 1,575 m asl (Poggio Canfareddi), 2 km from their point of origin, on 3 June. This lava front stopped advancing on 5 June and several superposing lobes began to develop.

Seismicity and summit activity. Weak seismic activity began on 29 May, followed by an increase in volcanic tremor on 31 May that continued until the next day. Ash emissions, sometimes voluminous, occurred from the central craters at irregular intervals on 31 May and 1 June, first from the W vent (Bocca Nuova) then from the E vent (La Voragine). Only weak degassing preceded the ash ejection, but gas emission became more consistent beginning 2 June. COSPEC measurements yielded SO₂ flux values of ~ 10,000 t/d. Flashes from the summit craters were observed during the evening of 7 June from the W flank. Fieldwork on 12 June revealed that Northeast Crater was obstructed, with only fumarolic activity along the walls.

EDM data. S. Saunders reports that four lines of an EDM network on the upper S flank were remeasured on 7 May, showing a 138-ppm contraction that was interpreted as deflation during the eruption. Between July and October 1991, total extensional strain along these lines was 88 ppm, indicating pre-eruption inflation. Strain along these lines has returned to near pre-eruption levels.

Landsat Thematic Mapper data. The following is from D. Rothery. "The 1991-92 sustained lava eruption of Etna provides an opportunity to study lava flow development by remote sensing. The first cloud-free Landsat Thematic Mapper (TM) image of the eruption was recorded on 2 January at approximately 1000 (figure 49). Landsat repeats its coverage on a 16-day cycle; the next cloud-free acquisition was on 22 March and we are still awaiting receipt of those data. By manipulating radiance measurements in two wavebands, we hope to be able to constrain the surface temperature distribution of this flow along its length. The most noteworthy aspects of the 2 January data are: 1) There is a narrow 700-m length near the source that is radiant in TM band 4 (0.76-0.90 mm wavelength). As far as we know, this is the first time that thermal radiance in TM band 4 has been reported over a volcano. Field observations (A. Borgia) on 2 and 3 January show that this feature corresponds to a 10-15-m-wide open channel at the source of the flow. 2) The entire 6.5-km-long active flow is radiant in TM band 7 (2.08-2.35 mm wavelength). At least some of the areas that are also radiant in band 5 (1.55-1.75 mm) occur when the flow spills down a steep slope, breaking apart the raft of blocks and crust that otherwise blanket the underlying lava at near-magmatic temperatures."

Figure 49. Extracts of Landsat TMr images of Etna, 2 January 1992, in band 4 (0.76-0.90 mm wavelength, left) and band 7 (2.08-2.35 mm wavelength, right) at pixel sizes of 30 x 30 m. In band 4, much of Etna is snow-covered (white), while the active lava flow is the darkest land feature because of its very low reflectance in this part of the spectrum (very-near infrared). Thermal radiance is confined to a narrow channel near the source and is not evident at this scale. In band 7, the active flow is radiant through most of its length. Bright lines are caused by sensor overload. Courtesy of D. Rothery.

Lava field characteristics. The following is an excerpt from a preliminary report by Wyn Hughes and Mark Bulmer, describing the eruption as of 18 May.

Lava leaving the eruptive vent advanced through a tube system that extended downslope to the foot of the western backwall of the Valle del Bove at 1,850 m asl. Several skylights were spaced at intervals along it. At the break in slope, numerous active ephemeral vents issued new lava-flow units onto the surface of the flow field (figure 48). These did not travel far from their source. Surface activity was otherwise absent within the Valle del Bove; lava was being efficiently transported through tubes toward the flow front. One tube system (with skylights and fume) could be traced through the center of the flow field in the Valle del Bove, toward Val Calanna. At the distal end of the Valle del Bove, several pressure ridges were visible, oriented perpendicular to the underlying ground slope.

Most of the surface activity was occurring in Val Calanna, where intense ephemeral vent activity was issuing new lava-flow units onto the flow-field surface. Lava was being supplied to this area through a series of tubes that descended from the Valle del Bove. Most of the activity in Val Calanna appeared to be supplied by a major tube system that could be traced (by skylights and fume) descending the backwall along its S margin (Salto della Giumenta). A smaller tube system probably supplied some ephemeral vents on the N margin of Val Calanna (S foot of Mte. Calanna).

In Val Calanna, effusive activity was mainly concentrated along the S margin of the flow field, where lava had ponded along the S wall of Val Calanna, and behind the man-made earthen barrier. From there, ephemeral vents in the crust fed numerous new lava-flow units, supplying three regions. Where lava moved directly NE, these were progressively widening the flow field at 1,050 m altitude. Flows that initially moved NE, but then changed to a more easterly direction, were supplying units that flowed around the N margin of the buried man-made barrier. Near the barrier, although active aa-textured flow fronts and channel-fed flow units could be traced on the surface of the flow field, most of the activity that contributed to its widening was supplied from tubes in the previous days' flow units. Ephemeral vents at 1,000 m elevation on the N margin of the buried man-made barrier supplied new flow units that were widening the field to the NE. However, these flow units were abutting the distal levee of the 1852-53 flow field, which was largely hindering the widening. On 18 May, some of these slow-moving tube-fed lavas managed to flow out of Val Calanna, and began the steep descent towards Zafferana. This activity was occurring on the NE side of the flow field. Three ephemeral vents had opened just below the S margin of the man-made barrier. A short distance downslope, flows from these vents combined to feed a front that advanced quite rapidly down the SW side of the flow field on the night of 17 May. By the next morning, and after destroying an abandoned dwelling during the night, the rate of advance had decreased, with the front at ~ 870 m asl. All of these active regions were being channel/tube-fed by lava from along the S wall of Val Calanna, which in turn was being supplied by tubes that descended from the Valle del Bove.

Flow-field morphology. Although the flow field was widening somewhat towards the NE end of Val Calanna, the activity was dominated by ephemeral vents extruding new flow units onto the surface of the original field. This was mainly occurring at ~ 1,800 and 1,050 m altitude, where the backwalls of the Valle del Bove and Val Calanna give way to their respective floors (figures 48 and 50). The surface activity was rapidly burying aa channel-fed flow units from early in the eruption. They could only be seen among the flows that had gone around the N margin of Mte. Calanna, and as isolated inliers on the floor of Val Calanna.

Figure 50. Profile of the pre-eruption terrain in the 1991-92 lava field at Etna. Sites of ephemeral vent activity and zones of lava tubes and channel-fed units are shown diagrammatically. Courtesy of J.W. Hughes and M. Bulmer.

New flow units from ephemeral vents generally emerged with pahoehoe surface textures, in contrast to the early activity whose products had entirely aa textures. The flow-field surface on the floor of Val Calanna, as already occurred in the Valle del Bove, was slowly becoming dominated by pahoehoe textures. Small-scale pahoehoe textures, similar to those described by Pinkerton and Sparks (1978) for the sub-terminal 1975 flow field, prevailed around the ephemeral vents in Val Calanna. However, among the more active vents, pahoehoe slab textures that characterized the near-vent surfaces of new channel-fed flow units progressively changed to aa with increasing distance from the vent area.

Comparison with historical flow fields on Etna. The current ephemeral vent activity within the 1991-92 flow field is consistent with the pattern of historical eruptions that lasted > 100 days (Hughes, 1992). By then, the early channel-fed aa activity that characterized the lengthening and widening phases in the flow field's growth had given way to a tumulus-building phase at the vent area — for example, 1865 (Fouque, 1865); or at a break in slope below the vent area — for example, 1950-51 (Cumin 1954) and 1983 (Frazzetta and Romano, 1984). Important in the emplacement of the 1983 flow field was the evolution of the main supply channel near the vent into a lava tube. By the eruption's 60th day, the tube formed a continuous link between the vent and the lava mound that had accumulated around the break in slope at 2,000 m altitude. The hydrostatic pressures generated within the lava tube were then sufficient to lift and fracture the roof of the lava mound, allowing the escape of lava through ephemeral vent activity. This sequence of events signified the early stages of tumulus development. The present activity occurring at 1,800 m altitude within the Valle del Bove is similar.

The second area of ephemeral vent activity away from the vent area and initial break in slope appears, however, to be unique to the 1991-92 flow field; a similar phenomenon has not been documented for Etna flow fields of the last 250 years. For most, the concave profile of the volcano's flanks (figure 51) meant that once the lava had descended from the steep upper slopes it only encountered progressively gentler gradients. However, the terrain over which the 1991-92 lavas have flowed is much more irregular, with a terraced appearance. The steep terrain around the vent in the upper Valle del Bove is duplicated downslope in the upper reaches of Val Calanna. The morphologic positions of the ephemeral vent activity within the Valle del Bove and Val Calanna are similar (figure 50); both occur at the foot of a steep slope down which lava is transported through tubes. It must be concluded that conditions favoring tumulus construction have also been duplicated within Val Calanna.

Figure 51. Profiles of the N, S, E, and W flanks of Etna. Courtesy of J. W. Hughes and M. Bulmer.

References. Cumin, G., 1954, L'eruzione laterale del Novembre 1950-Dicembre 1951: BV, v. 15, p. 3-70.

Fouque, F., 1865, Sur l'eruption de l'Etna du 1st Fevrier 1865: C. Rend. Acad. Sci. Paris; v. 60, p. 1331-1334; and v. 61, p. 210-212.

Frazzetta, G., and Romano, R., 1984, The 1983 Etna eruption: event chronology and morphological evolution of the flows: BV, v. 47, p. 1079-1096.

Hughes, J.W., 1992, The Influence of volcanic systems on the morphological evolution of lava flow fields: Ph.D. dissertation, University of London, 255 p.

Pinkerton, H., and Sparks, R.S.J., 1976, The subterminal lavas, Mount Etna: a case history of the formation of a compound lava flow field: JVGR, v. 1, p. 167-182.

Information Contacts: F. Barberi, Univ di Pisa; L. Villari, IIV; R. Romano and T. Caltabiano, IIV; P. Carveni, M. Grasso, and C. Monaco, Univ di Catania; W. McGuire and A. Morrell, Cheltenham and Gloucester College of Higher Education; S. Saunders, West London Institute; D. Rothery, A. Borgia, R. Carlton, and C. Oppenheimer, Open Univ; J. Wyn Hughes and M. Bulmer, Univ College London.

June 1992 (BGVN 17:06) Cite this Report

Continued flank lava production

Lava production continued from the fissure that opened in the W wall of the Valle del Bove on 15 December. Gas emission from 4 vents in the upper part of the fissure (2,215-2,235 m altitude; figure 52) fluctuated daily, probably with changes in weather conditions. However, gas emission has diminished since the eruption's initial months.

Figure 52. Sketch map of the fissure system and the upper part of the lava field at Etna, June 1992. Contour interval, 50 m. Courtesy of Romolo Romano.

No variation was evident in the movement of lava visible through a skylight high in the main channel, at 2,205 m altitude. Lava was also seen flowing through a skylight in lava tubes that formed in June along the channel into which lava was artificially diverted on 27 May (~ 1,980 m elevation) (17:05). From there, lava advanced through a complex series of tubes past the field that had formed in recent months. Lava again reached the surface around 1,800 m altitude from a changing number (generally 3-4) of ephemeral vents at varying locations representing tube bases. Lava flows extruded from these vents have generally been modest, have remained in the center of the lava field, and have not advanced beyond 1,600 m asl. As of the morning of 9 July, only one flow was active within the Valle del Bove, near the center at around 1,670 m altitude, with a fairly well-fed front. The volume of lava produced during ~7 months of eruption is estimated to be around 165 x 10⁶ m³.

Seismic activity during the period was characterized by low energy release. Significant increases were observed 8-9 July, when events of 2-4 Hz were recorded. The most significant perturbations were detected on 8 July at 1554, for 180 seconds, and at 1601 for 130 seconds. Tremor was almost nonexistent, obscured by seismic noise that characterizes periods of low activity at the volcano.

More or less voluminous gas emissions occurred from two vents at the bottom (~100 m from the rim) of the two central craters (Bocca Nuova and La Voragine). Incandescence caused by superheated gases (>1,000°C) from the vent in La Voragine was sometimes visible. Gas also emerged from a vent that has opened in Southeast Crater. Northeast Crater appeared to have been completely obstructed by internal collapse. COSPEC measurements of SO₂ flux from the summit crater showed relatively high values of ~ 8,000 t/d.

Information Contacts: R. Romano and T. Caltabiano, IIV; P. Carveni, M. Grasso, and C. Monaco, Univ di Catania; G. Luongo, OV.

July 1992 (BGVN 17:07) Cite this Report

Continued lava production from SE-flank fissure; lava diversion summarized

The following, from R. Romano, describes activity from early July through early August.

Early July-early August activity. The eruption ... was continuing after ~ 8 months. Gas emission from the upper part of the fissure has greatly diminished lately, although abundant white vapor was often observed, probably because of weather conditions. Fieldwork on 5 August revealed no notable changes in effusive activity from previous months. The lava flow was visible through a skylight at the beginning of the main lava channel (at 2,205 m asl) and through two smaller skylights at 2,100 m altitude. From there to ~ 1,800 m, lava flowed through a complex system of tubes, resurfacing from numerous ephemeral vents that varied in number (generally about 10) and location (mainly in the center of the lava field). From these ephemeral vents (all between 1,800 and 1,700 m elevation) very modest lava flows emerged. These advanced a few hundred meters at most, never moved past 1,600 m altitude, and remained within the pre-existing lava field. The total volume of lava produced by 234 days of activity was estimated at 170 x 10⁶ m³.

No significant changes were observed at the central craters, where gas emission continued. The more active vent in early August was at the W crater (Bocca Nuova). Northeast Crater has remained obstructed for a few months, with only weak fumarolic activity on the inner walls. Internal collapses continued to occur. Gas emission from Southeast Crater was unchanged.

Seismic activity was low, with only 22 recorded events from early July through early August. The majority of the seismicity was characterized by swarm sequences in the summit area. The most significant, on 11 August, consisted of four shocks with a maximum magnitude of 2.5. Harmonic tremor was of very low energy and showed no variation over time.

The following is from a report by L. Villari.

Civil Protection problems and lava diversion. An earthen barrier was erected at the E end of Val Calanna by the beginning of January 1992, to prevent or delay the advance of lava into a narrow valley leading directly to the nearby (~ 2 km downslope) village of Zafferana Etnea (17:02). Lava expanded into the large Val Calanna basin in February and March, and began to accumulate against the inner wall of the barrier on 14 March. By the end of the month, lava almost completely filled the Val Calanna basin and rose slowly up the barrier's inner wall. Several lobes successively reached the barrier, and the lava field progressively grew and thickened, reaching the barrier rim by 7 April. Lava first overflowed the barrier, along its N sector, during the evening of 8 April, quickly followed by other lobes along the S and central part of the barrier's rim. Lava covered ~ 1 km during the first few hours, merging downslope into a single stream that advanced quickly toward the village. The flow's confinement in a narrow valley favored more rapid progress downslope. Three minor earthen barriers were rapidly constructed along the valley (10-11 April, 830 m asl, 110 m long, 12 m high; 11-12 April, 810 m asl, 90 m long, 6 m high; 13-14 April, 770 m asl, 160 m long, 12 m high) to slow the advancing flow. The barriers were built, like the major one at the E end of Val Calanna, by digging the valley bottom in front of the advancing flow and accumulating the loose material on a small natural scarp. Because the valley is narrow, the confined basins were only able to contain small volumes of lava, and the flow's advance was only briefly delayed (for hours to a day). The front reached <1 km from Zafferana (at Piano dell'Acqua) on 16 April, ~1.5 km from the major barrier and 8 km from the eruptive fissure (figure 53).

Figure 53. Sketch map of the 1991-92 lava field at Etna. 1. 1991-92 eruptive fissure; 2. 1989 fracture system; 3. 1991-92 lava flows; 4. lava flows downslope from the barrier at the E end of Val Calanna; 5. lava flows fed by the diversion. Dots mark individual houses in the Zafferana and Milo areas. Courtesy of L. Villari.

At that time, morphologic conditions prevented any other local intervention to slow the lava advance. The creation of any possible artificial obstacle to the advancing front would divert the flow toward inhabited areas not necessarily threatened by the natural flow path. Diversion efforts were therefore concentrated far upslope, near the eruptive vent.

Attention was primarily on a skylight in the main lava tube at ~ 2,000 m altitude on the W wall of the Valle del Bove, a few hundred meters from the active vent. The diversion's early focus was blockage of the main tube carrying lava to the active front, by sliding solid rocks and concrete blocks into the flowing lava. Access problems required transport of solid materials to the site by helicopter, to be directly unloaded into the lava stream, or accumulated around the skylight's rim for later use. Lava tube blockage was also assisted by blasting large volumes of solid lava and welded scoriae forming the flow levees. This was partially successful and contributed to slowing the advance of the active front by several days.

Despite these efforts, on 5 May, a major new flow emerged from Val Calanna atop the 10 April flow, reaching Piano dell'Acqua on 11 May, 120 m beyond the 16 April flow and ~ 500 m from the outskirts of Zafferana. On 22 May, a further attempt to divert lava from the main natural tube to an artificially excavated channel high in the Valle del Bove produced a vigorous lobe that traveled 1 km in a few hours. Only 1/3 of the lava was spilled into the artificial channel, and the new flow roofed over within two days, with a significant loss of supply from the main natural flow.

A four-phase intervention plan was then defined (figure 54): a) digging an artificial channel to drain the main natural tube; b) cutting the lateral tube wall to a minimum thickness (2-3 m) that could be blasted through with a single charge; c) blasting the lateral wall; d) blocking the natural tube to divert all of the lava into the artificial channel.

Figure 54. Sketch of the lava diversion carried out at Etna, 27 May 1992. Courtesy of L. Villari.

Phases a and b were accomplished in about a week. A 7-ton charge, set off in a single explosion on 27 May at 1636, opened a large breach in the natural tube and caused spillage of ~ 80% of the flowing lava. The natural tube was progressively blocked by sliding solid materials into it during the next two days, and the flow was totally diverted into the artificial channel by 29 May. The artificially channeled flow went down the W slope of the Valle del Bove and remained confined inside the valley. The diversion effort stopped the most advanced front that had been moving toward Zafferana, by removing its source of supply.

The artificially channeled lava flow had extended to 1,550 m asl in the S part of the Valle del Bove (at Piano del Trifoglietto) by 30 May. Lava output from the ephemeral vents in Val Calanna quickly decreased, and molten lava was not evident within a few days.

The effusion rate from the eruptive fissure decreased sharply 31 May-1 June, causing the active flow front to be confined within the Valle del Bove, as activity resumed in the central craters. Several hours of continuous ash emission occurred from the W crater (Bocca Nuova) on 31 May, and an incandescent blowhole formed in the E crater (La Voragine) following gas blasts on 1 June. Noisy gas emission continued from La Voragine in succeeding days.

During June, lava flowing in the artificial channel expanded within the Valle del Bove to ~ 1,650 m elevation, overlapping the lava field that had formed since January. The effusion rate was reduced ~ 50% by the end of June, and the upper part of the artificial channel became a tube. The longest flow did not extend more than 1.5 km from the diversion point at 2,000 m altitude. At the end of June, the newly generated lava field, overlapping the old one, covered ~ 0.8 km².

Northeast Crater. Repeated inner-wall collapses have been observed in Northeast Crater since February. They became quasi-continuous from 26 February through mid-March, associated with explosive activity that ejected blocks and caused a little fine reddish ashfall. From the end of March until 23 May, the collapses were limited to episodes lasting only several hours each, associated with only minor fine ashfall. The crater bottom dropped ~70 m, leaving a pit ~100 m across in place of the previous funnel-shaped depression.

Lava flow measurements. Lava-channel dimensions, flow velocity, and related rheological parameters were observed at a skylight along the lava tube at 2,000 m altitude, and at ephemeral vents in the Val Calanna area, 7 km downstream at 1,000 m elevation. Flow velocities at the exit of the lava tube (~ 4-5 m wide and 5 m deep) in May and the beginning of June were 0.5-1 m/s; flow rates and viscosities were 15-25 m³/s and 100-300 Pas. At the ephemeral vents and the single-channeled flows (1-4 m wide and 1-2.5 m deep), March-May flow velocities were 0.1-0.3 m/s. The calculated flow rate ranged from 0.1 to 4 m³/s, with a corresponding viscosity of 150-1,300 Pas. (See the report by Murray, below, for velocities and flow rates from late June through mid-July).

Direct measurements in June along the main channel (10-40 cm below the lava surface) at 2,000 m altitude, using an immersion thermocouple (Pt-PtRh) yielded temperatures of 1,053-1,068°C. Values were similar (1,030-1,068°C) at several ephemeral vents (10-60 cm inside the lava flow) in the Val Calanna area from March until the end of May.

Petrography and chemistry. Analysis of lava sampled near the vent and at the flow fronts showed no significant variations in chemical or petrologic composition (17:02). All are porphyritic hawaiites (Mg## 52-54), with phenocrysts of plagioclase (15-25 volume %), clinopyroxene (7-10%), olivine (2-3%) and minor (~ 1%) Ti-magnetite.

Seismicity. Low-level seismic activity characterized February-June, despite the continuing eruption. The daily rate was quite low, with only 24 fault-derived earthquakes of M >1 recorded during the period, a rather low value for Etna. No variations were evident in the daily rate or the cumulative strain release (figure 55). Most of the recorded shocks were centered on the SE flank. Maximum local magnitude was 2.8. There were no significant changes in the pattern of volcanic tremor amplitude. Two short episodes of increasing amplitude, on 31 May and 1 June, had maximum overall amplitudes slightly lower than during the December 1991 eruptive phase.

Figure 55. Daily number of seismic events (M >1) and cumulative seismic strain release recorded at Etna, December 1991-June 1992. Courtesy of L. Villari.

From 26 February until May, seismic stations on the upper flanks recorded many shocks characterized by an emergent onset and low frequency content. At least three waveform types were recognized. All of the shocks were located near the summit craters at <1 km depth. At the same time, morphologic changes were noted within Northeast Crater, associated with the emission of non-juvenile tephra. Most of these shocks were believed to be linked to rockfalls within Northeast Crater. Some explosion shocks were recorded during the same period. These phenomena were most common in February and March, then gradually decreased, disappearing entirely by 23 May.

Ground deformation. Continuous monitoring of ground tilt in a shallow borehole network showed only minor variations since the eruption began in December 1991. No sign of the expected deflation of the volcano was noted, despite the large volume of magma that has been erupted.

EDM networks on the S, SW, and NE flanks, previously surveyed in 1991, several months before the eruption began, were re-measured in late spring and early summer. Contraction was observed, mostly on the SW and NE flanks, while the S flank did not show any appreciable change in line length. The overall deformation pattern of the volcano appears consistent with shallow magma injection into the eruptive fissure, trending roughly NNW-SSE (figure 56). GPS surveys in April-May 1992 detected significant contraction of lines, mostly on the W flank, compared to previous surveys in June-July 1991 (figure 57).

Figure 56. Cumulative areal dilation measured at 3 EDM networks on the flanks of Etna, 1981-92. Courtesy of L. Villari.

Figure 57. Variations in slope distance between GPS measurements at Etna in 1991 and 1992. Heavy lines show contraction, dashed lines show extension. Courtesy of L. Villari.

The following, from J.B. Murray, describes eruptive activity and the results of deformation studies, 9 June-14 July.

Lava flows. The rate of lava production from the vent in the W wall of the Valle del Bove was much lower than in April. Active flows were visited on 28 June, and 7, 10, 12, and 13 July. Central flow speeds of 2-10 m/minute (depending on slope), widths of 1.5-6 m, and a rate estimated at around 0.3-0.4 m³/s were noted at a single flow on 28 June. A flow about twice as big was seen to the E, suggesting a total discharge of the order of 1 m³/s. Flow fronts were only advancing to ~ 1.2 km from the vent on 28 June, but discharge seemed slightly increased during July visits to the fronts, which were about 2.2 km from the vent on 7 July, and 2.6 km by 13 July.

Summit activity. Continued collapse was occurring around the edge of Northeast Crater, with rockfalls every few minutes or so. Particularly big collapses were seen on 8 July between 1556 and 1610. Southeast Crater had strong high-temperature fumaroles, but no Strombolian activity.

The floors of the two central craters both had single vents that continuously discharged hot gas without any explosions. The vent in La Voragine was ~3 x 10 m, glowed bright red in daylight, and beginning 10 June emitted gas in voluminous puffs from which radiant heat could be felt. There were no signs of fresh bombs or scoriae around the vent. The depth of Bocca Nuova was estimated at ~160 ± 20 m.

Vertical movement. A 25-km levelling traverse, and heights derived from trigonometric levelling during trilateration, yielded details of vertical displacement of 241 stations across the summit and upper flanks since September 1991. Subsidence occurred along a narrow strip extending SSE from the summit, with maximum movements reaching just over 1 m (at two stations between Cisternazza and Belvedere). This central strip is flanked by a swelling to the W of 3-7 cm, and a much larger swelling to the E that reaches 37 cm (at Serra Giannicola Piccola). Southeast Crater has dropped 87 cm and Northeast Crater 48 cm, and the NE rift has risen another 3.4 cm (near Monte Pizzillo). These movements are similar to displacements seen over eruptive dikes in 1989, 1986, 1985, and 1983, but the swelling to the E is higher and broader than any previously recorded.

Horizontal movement. The summit trilateration network shows E-W extensions of 1-1.5 m since September 1991 across the graben and fissures leading S to the eruption site. It is clear that the main feeder dike passes between the Torre del Filosofo and Belvedere, and probably crosses into the Valle del Bove just E of Cisternazza (figure 53). Movements of this magnitude are not unusual during Etna's flank eruptions, and are similar to those recorded during the four eruptions mentioned above.

After network adjustment, some individual station vectors showed unexpected movements. Many of the stations E of the summit also show large eastward displacements, with two (near the Serra Giannicola Piccola) showing 1.3 m of eastward movement, and much of the Valle del Leone having moved 0.5 m ENE. The region at the top of the valley's E wall is cut by new N-S fissures, and SE of Southeast Crater is a region of complex fissuring N of a new cinder cone.

Dry-tilt data. Results from the 30 dry-tilt stations confirm that this eruption is a major one among recent eruptions. In addition to the expected large tilts near the eruptive fissures (192 µrad near Cisternazza), unusually large post-September 1991 tilts of 115 and 92 µrad occurred ~ 4 and 5 km SW of the summit (at Monte Palestra and Monte Vituddi). Unexpectedly large tilts were also recorded ~ 7 km NW and 4.5 km WNW of the summit (at Monte Maletto and Monte Nunziata), and both the Punta Lucia and Pizzi Deneri stations have abruptly increased their tilt to the E, as after the 1981 eruption.

The observed dry tilts are exceptional and suggest that something fairly fundamental has occurred. Only the 1981 eruption had tilts of this size at distant stations. That eruption marked a major turning point in Etna's deformation. After 1981, five stations that had previously been stable, even during flank eruptions, tilted during the next few years by amounts that eventually totalled as much as 1,000 µrad.

Information Contacts: L. Villari, R. Romano, and T. Caltabiano, IIV; P. Carveni, M. Grasso, and C. Monaco, Univ di Catania; G. Luongo, OV; J. Murray, Open Univ.

August 1992 (BGVN 17:08) Cite this Report

Increased lava emission from break in main tube

The eruption ... appears to have become more vigorous in early September. Until 2 September, activity was similar to previous months, with lava flowing through a complex system of tubes and resurfacing from ephemeral vents of varying number (recently about 4) and location. Lava flows from the ephemeral vents were generally of modest size, advancing only a few hundred meters and remaining within the pre-existing 1991-92 lava field. Gas emission from the upper part of the fissure has remained similar to past months, with modest variations linked to weather conditions.

The roof of the main lava tube broke open late in the evening of 2 September, near a former skylight at ~2,150 m altitude and above the site of artificial lava diversion in May (at ~2,000 m elevation; 17:07). The flow from the broken tube first moved ENE above the lava field, then along its S side over terrain not previously covered by lava from this eruption. Lava advanced ~ 1 km to 1,700 m altitude by the next morning, then slowed to a stop during the succeeding days, reaching ~1,650 m elevation. The main lava tube, with two fuming skylights, remained active on 4 September below 2,000 m altitude. The only large ephemeral vent was at around 1,700 m asl, in the central part of the lava field. Another overflow occurred during the morning of 9 September at around 1,980 m altitude, below the lava diversion area. The flow advanced across the central part of the lava field, quickly reaching 1,650 m elevation. The total volume of lava produced by 272 days of activity was estimated at 190 x 10⁶ m³.

Activity from the central crater's two vents remained similar to previous months, with continuing gas emission, strongest from the W vent (Bocca Nuova). Gas, sometimes voluminous, also continued to emerge from two small vents in Southeast Crater. Northeast Crater remained obstructed by debris. Landsliding persisted from the walls, particularly in the N and S parts of the crater. Very weak fumarolic activity occurred from Northeast Crater's inner walls. SO₂ flux from the summit craters, measured by COSPEC, remained at relatively low levels (~ 2,000 t/d) during August, but measurements in early September yielded higher values, ~ 5,000 t/d.

From 15 August through 11 September, 176 seismic events were recorded, characterized by low energy release. The most significant activity was a sequence of 43 summit-area events 6-7 September, with a maximum magnitude of 3.2. Harmonic tremor has been nearly absent.

Information Contacts: R. Romano and T. Caltabiano, IIV; P. Carveni, M. Grasso, and C. Monaco, Univ di Catania; G. Luongo, OV.

September 1992 (BGVN 17:09) Cite this Report

Lava flows from tube system remain within 1991-92 lava field

The SE-flank fissure eruption ... continued relatively unchanged in September and early October 1992. Gas emission from the upper part of the fissure was similar to previous months, varying with weather conditions. Lava continued to flow through a complex tube system, emerging from ephemeral vents at frequently changing locations. The resulting lava flows were generally modest-sized, advancing only a few hundred meters over the pre-existing lava field. This pattern of activity changed only when a substantial increase in the amount of lava moving through the main tube caused an overflow through a skylight. On 3 October at about 1830, lava began to emerge from a skylight at 2,150 m altitude, preceded by vigorous emission of white vapor. The overflow remained active on 8 October, and lava had advanced about 1 km. A similar episode occurred from the same location in early September. During 8 October fieldwork, numerous ephemeral vents were also active. Three were in the area of May's artificial lava diversion around 2,000 m altitude, three at ~ 1,800 m elevation (around Serra Pirciata), and 3-4 others near 1,700 m asl. Flows from the ephemeral vents remained modest in size, did not advance beyond 1,650 m altitude, and stayed within the Valle del Bove. Total lava volume from 300 days of activity was estimated at around 210 x 10⁶ m³.

Gas continued to emerge from two small vents on the floor of the central craters, at ~ 100 m depth. Gas emission generally occurred under pressure from the W crater (Bocca Nuova). A small vent on the S edge of Southeast Crater continued to emit gas. Northeast Crater remained obstructed by debris, with landslides still occurring in its N and S parts.

SO₂ emission, measured by COSPEC, continued to increase. During the first 10 days of October, values exceeded 10,000 t/d, twice Etna's average SO₂ flux.

Seismicity remained at low energy between 11 September and 13 October. About 230 microearthquakes were recorded, centered mainly in the summit area. The largest (M 3.0) occurred on 16 September at 0650 and was felt in nearby towns. On 27 September, a brief sequence of 7 events occurred on the W flank. The strongest shock (M 3.7), at 1255, was felt to ~ 70 km away (in the Siracusa area). Tremor has been nearly absent.

Information Contacts: R. Romano and T. Caltabiano, IIV; P. Carveni, M. Grasso, and C. Monaco, Univ di Catania; G. Luongo, OV.

October 1992 (BGVN 17:10) Cite this Report

More vigorous lava production and gas emission

The eruption ... appears to have become slightly stronger in recent weeks. A small increase in the effusion rate was apparent during the report period (13 October-12 November) at the main vent (2,210 m asl) after lava production had remained relatively constant for the previous several months. Lava initially moved through a single tube, with a surface trace marked by four skylights from 2,210 to 2,150 m altitude. The lava resurfaced (beginning at ~1,780 m elevation) within the lava field formed in past months. Three large ephemeral vents fed wide, thick flows, some of which advanced more than a kilometer within the lava field. On 11 November, the front of one flow was at 1,600 m altitude, in the center of the lava field. Small flows also emerged from tens of minor ephemeral vents, with locations that changed daily. Characteristic cumulo-domes formed in areas with high concentrations of ephemeral vents. The total volume of lava produced by 334 days of eruption was estimated at ~ 240x10⁶ m³.

Gas emission from the upper part of the eruptive fissure was also a little stronger than in previous months. Fluctuations in the apparent gas emission rate remained linked to weather conditions. Vigorous degassing continued from Southeast Crater and from the central crater's two vents. Rare, modest ash ejections occurred from the W vent of the central crater (Bocca Nuova). Weak fumarolic activity continued from the walls of Northeast Crater, still obstructed by debris. SO₂ flux, measured by COSPEC, remained high, ranging from 5,000 to 10,000 t/d, typically around 8,000 t/d.

Seismicity remained at low levels 13 October-12 November. About 100 events were recorded, mainly in the summit area, with magnitudes of 1.1-3.4. A large proportion of these occurred during the first week in November. The 34 events detected 3-4 November included a swarm of 15 summit-area shocks between 0500 and 0537 on the 3rd; the strongest, at 0500, had M 3.0. Of the four summit earthquakes recorded between 1220 and 1249 on 9 November, three had magnitudes exceeding 2.5, including the strongest of the report period, M 3.4, at 1249. Harmonic tremor has been nearly absent.

Information Contacts: R. Romano and T. Caltabiano, IIV; P. Carveni, M. Grasso, and C. Monaco, Univ di Catania; G. Luongo, OV.

November 1992 (BGVN 17:11) Cite this Report

Lava emerges from tubes onto 1991-92 lava field; small summit ash ejections

Lava production became more vigorous during the first half of November, but seemed to be decreasing in early December, a year after the SE-flank eruption began. After emerging from the vent, lava initially flows through a single tube, with a surface trace (from ~2,210 to 1,980 m altitude) marked by at least five skylights. Lava then continues into a complex of tubes, emerging from numerous ephemeral vents (which varied daily in number and location) onto the extensive lava field that has developed in past months. On 9 December, the ephemeral vents formed a linear zone between 1,700 and 1,600 m altitude, feeding small flows that did not advance below 1,580 m. The larger flows advanced NNE on the N side of the lava field, while other flows moved mainly toward the E. After 361 days of activity, the eruption's total lava output was estimated at 255 x 10⁶ m³.

Gas emission from the upper part of the eruptive fissure was less vigorous than in early November, with fluctuations linked to weather conditions. Small ash ejections from the central crater's W vent were observed, particularly during the first few days of December. Degassing from the summit craters was otherwise unchanged, and Northeast Crater remained obstructed. SO₂ flux, measured by COSPEC, remained at high levels, ranging from 6,000 to 10,000 t/d and averaging ~8,000 t/d.

Between 13 November and 8 December, 140 microshocks were recorded at Etna, mainly in the summit area. Energy levels remained low and magnitudes did not exceed 2.9. Several small seismic swarms occurred. The most vigorous, on 28 November between 0624 and 0858, included 10 events of M 1.7-2.9 centered in the summit area. The number of shocks increased briefly 28-30 November, when 62 were recorded. No harmonic tremor was detected.

Information Contacts: R. Romano and T. Caltabiano, IIV; P. Carveni, M. Grasso, and M. Porto, Univ di Catania; G. Luongo, OV.

December 1992 (BGVN 17:12) Cite this Report

Continued lava production; summit degassing

The eruption ... continued without major changes through early January 1993. Lava frequently flowed NE and NNE, and by early January there had been a notable expansion of the upper part of the lava field toward the NE. A new lava overflow was observed at the end of 1992 and the beginning of 1993 along the main lava tube above 2,000 m elevation. The overflow fed three distinct lobes that advanced a few hundred meters, to ~ 1,900 m asl. Lava continued to flow through the main tube, and was visible in early January through three skylights between 2,210 and ~ 1,900 m elevation. From there, the main tube divided into a complex tube system, from which lava emerged onto the surface at ~1,700 m altitude through small ephemeral vents. On 8 January, about six ephemeral vents were visible, feeding small flows that advanced NNE and E over the lava field formed in previous months. The NNE flow reached 1,650 m elevation, the E flow 1,600 m. The volume of lava produced by 394 days of activity was estimated at ~ 270 x 10⁶ m³.

Gas emission from the upper part of the eruptive fissure was not very intense. Apparent fluctuations were linked to weather conditions. Summit-crater degassing was similar to the previous month. Northeast Crater remained obstructed, with only weak fumarolic activity on the inner walls. SO₂ flux, measured by COSPEC, was still relatively high at ~ 7,000 t/d.

Of the 83 seismic events recorded 9 December-11 January, 51 occurred in four swarms, all located in the summit-crater area, with magnitudes of 1.5-3.3. The most significant swarm, on 2 January, had 17 events, with the strongest (M 3.3) at 1342. This swarm was accompanied by a slight increase in the amplitude of tremor, otherwise nearly absent during the period.

Information Contacts: R. Romano and T. Caltabiano, IIV; P. Carveni, M. Grasso, and M. Porto, Univ di Catania; G. Luongo, OV.

January 1993 (BGVN 18:01) Cite this Report

Continued lava production extends lava field; summit degassing; low seismicity

The eruption ... is now Etna's longest flank eruption of the 20th century, surpassing the 372 days of E-flank activity in 1950-51. However, dominantly effusive eruptions from the summit area's Northeast Crater have persisted for many years (May 1957-February 1964; January 1966-April 1971; and September 1975-January 1977) and intermittent explosive activity from the central crater has continued since 1979.

The most active flows advanced NE and NNE, extending the upper part of the 1991-93 lava field toward the NE. On the morning of 4 February, lava flowing in the main tube was visible through two skylights, and emerged from small ephemeral vents on the N and S sides of the lava field. The approximately five northern ephemeral vents, between ~1,900 and 1,600 m elevation, were the most impressive, and fed the strongest flows, to the NNE. The small S vents, two of which were very close to the S wall of the Valle del Bove at 1,550 m asl, were the sources of very modest flows that moved E. Flows from both sets of vents advanced over the pre-existing lava field, and did not extend beyond elevations of 1,600 m (N vents) and 1,550 m (S vents). The volume of lava produced by 429 days of activity was estimated at 280 x 10⁶ m³.

Gas emission from the upper part of the eruptive fissure has declined notably, and as of mid-February only the former explosive vent at the fissure's lower end (2,215 m elevation) remained active. Degassing from the summit craters was similar to previous months. Modest ash emissions, caused by internal rockfalls, occurred rarely from the central crater's W vent. During the early morning of 3 February, phreatic explosions from Northeast Crater ejected old lava fragments to tens of meters W of the rim. A modest ashfall occurred on the E side of the crater, and ash was still visible on the snow during the following days. Northeast Crater was obstructed again after this activity, and the next day only vigorous fumarolic activity was noted on the crater floor. SO₂ flux, measured by COSPEC, declined from ~ 7,000 t/d in December to 5,000-6,000 t/d in January, about average at Etna.

Seismicity remained at low energy levels during the report period (12 January-15 February). All of the 125 seismic events (M 0.7-3.4) recorded during the period were centered in the summit-crater area. The seismicity included only one swarm (23 events, maximum M 3.4) on 3 February between 0527 and 0623. All were low-frequency events (1-5 Hz) and occurred as wave-trains that resembled spasmodic tremor. With that exception, volcanic tremor was absent.

Information Contacts: R. Romano and T. Caltabiano, IIV; P. Carveni, M. Grasso, and C. Monaco, Univ di Catania; G. Luongo, OV.

February 1993 (BGVN 18:02) Cite this Report

Lava flows continue; volume estimates reported

The following information, based on the report of the IIV, covers the period December 1992 through February 1993.

The eruption ... continued as lava gently flowed from the vent on the W wall of Valle del Bove, significantly expanding the flow field formed after the flow diversion of May 1992 (17:05). Lava moved to Piano del Trifoglietto through a forked lava tube, emptying through several ephemeral vents located mainly on the N and S sides of the flow field (figure 58). In the first half of December, lava escaped mainly through the S vents. Many small flows gradually covered Poggio Canfareddi Hill, previously isolated by flows moving E toward Mt. Zoccolaro. In the second half of December, activity shifted to the N vents, expanding the flow field over a flat area that had not been covered by lava from the current eruption. Using data from a GPS survey done in January, the total volume of lava erupted through 1992 was estimated to be 198 ± 40 x 10⁶ m³. The lava covers an estimated 6.7 x 10⁶ m² and the mean rate of lava production is 6m³/s.

Figure 58. Topographic sketch map of the active portion of the 1991-93 lava flow field; 1. Flow field formed from 27 May 1992 through February 1993; 2. Flow field before 27 May 1992; 3. Limit of active lava flows by November 1991; 4. Directions of the main active flows December 1992-February 1993; 5. Lava tubes. Courtesy of IIV.

By January 1993, lava flows from the S vents advanced to the Poggio Canfareddi area and a complex network of minor flows reached the foot of Mt. Zoccolaro at 1,530-m elevation. Lava continued to flow from the N vents, expanding the field 400 m to the N. On 27-29 January, a fast-moving lobe of lava flowed to the NE, reaching 1,500 m elevation, 4 km distant from the eruptive fissure.

Effusive activity declined in February, ceased at the S vents by 8 February. Flow from the N vents was less than in previous months and shifted to vents on the northern-most side of the flow field. The new flows did not expand the flow field.

The seismic network recorded five swarms of long-period events. Fourteen events with M >1 occurred on 1 December, 14 events on 23 December, five events on 25 December, 51 events on 30 December-2 January, and 26 events on 3 February. No event exceeded M 3. The swarms were located in a small focal volume between the summit craters and Pizzi Deneri (~2 km NE) at depths asl. Volcano-tectonic seismicity during the period remained low (only three events) comparable to that observed throughout 1992.

The 9-station bore-hole tiltmeter network recorded no significant deformation except for a sharp event 18-19 December. Steady degassing from the Etna summit craters was observed and a weak ash emission occurred on the morning of 3 December from the Bocca Nuovo vent. Minor landslides repeatedly affected the E inner wall of the NE crater until January. The crater floor had sunk by early morning on 3 February.

The following report from geologists at the IIV and the Univ di Catania with seismic information from G. Luongo, updates and complements the official IIV report above.

A lava flow, at least a few hundred meters wide, has formed on the NE side of the lava field that has been building since 27 May 1992 (figure 58). The flow, in the vicinity of Monti Centenari (2 km NE of the active fissure), is completely independent from the old field and is moving E in the middle of Valle del Bove. The lava of this flow is visible from between 2,205 and 1,700 m through a series of skylights on the main tube. Lava is surfacing through 4-5 ephemeral vents at ~1,500 m elevation; the vents active in the past on the N, S, and central parts of the old lava field have closed. On the morning of 12 March, the most advanced flows had reached 1,425 m elevation and were moving over lava of previous eruptions. By 1300 on 14 March, the lava front was at 1,400 m elevation, ~ 5 m wide, 1 m high, and moving at an estimated 1 m/h.

The estimated volume of lava produced after 458 days of activity is 295 x 10⁶ m³. This estimate was calculated using the same method as previous estimates reported in the Bulletin, but is ~ 50% higher than the GPS value reported above. No significant changes in degassing of the summit craters were noticed. Northeast crater is still obstructed, with very active fumaroles along the inside walls. COSPEC measurements of SO₂ flux remained normal (5-6 x 10³ t/d), except in early March when measured values were 12.5 x 10³ t/d.

Between 12 February and 15 March, 169 events of M 1.2-2.9 were recorded, mainly in the summit crater area. The majority of events appeared to be related to active degassing at the surface, with characteristic frequencies of 1-6 Hz. Volcanic tremor was completely absent.

Information Contacts: IIV. The last three paragraphs are fromR. Romano, T. Caltabiano, M. Grasso, and M. Porto, IIV; P. Carveni and C. Monaco, Univ di Catania; G. Luongo, OV.

March 1993 (BGVN 18:03) Cite this Report

1991-93 eruption ends

The following, based on the report of the IIV, describes activity in March.

The 1991-93 eruption ended on March 30 after 473 days of continuous lava flows. Lava stopped flowing to the S side of the flow field in mid-February, but continued to flow from several vents at 1,700-1,650 m elevation on the N side of the field, covering previous flows from the current eruption. Shortly after 8 March, an overflight revealed a thin flow that had traveled 0.5 km from an ephemeral vent at 2,020 m elevation. On 11 March a large lava flow moved toward the Valle del Bove over an area not yet covered during this eruption. Flowing 1.5 km from a large ephemeral vent at the end of a tube at 1,550 m elevation, lava spread down some gullies, stopping after 3 days at 1,390 m elevation, 5 km from the eruptive fissure (figure 59).

Figure 59. Topographic sketch map of the active portion of the 1991-93 lava flow field; 1. Flow field formed after 27 May 1992 through March 1993; 2. Flow field before 27 May 1992; 3. Limit of active flows through February 1993 ; 4. Directions of the main active lava flows in March 1993; 5. Lava tube. Courtesy of IIV.

Lava flows declined in the second half of March. On 21 March a vigorous flow emerged from a vent at 1,850 m elevation and traveled several hundred meters NE in a few hours before slowing and finally stopping within two days. The remaining ephemeral vents gradually disappeared and the last small lava flow was observed on the morning of 30 March. In the following days, fieldwork at the eruptive fissure and along the upper lava tube revealed that no molten lava remained in the tube and that the delivery system was cooling.

Steady degassing continued through March at the summit craters. The floor of Northeast crater dropped another several meters. Seismicity remained low, especially from 1-10 March. For the month, 65 long-period events and 8 volcano-tectonic events (maximum M 2.4) were recorded. The only notable swarm occurred on 28 March when 10 events were recorded in two minutes. There were no significant variations in the volcanic tremor amplitude. Four of the 9 bore-hole tiltmeters recorded a sharp deformation event of moderate amplitude at the beginning of March.

The 1991-93 eruption began on 15 December 1991 and lasted 473 days. It was probably the largest eruption at Etna in the last 300 years, covering ~ 7 km² with >250 million m³ of lava.

The following information compiled by volcanologists at the IIV, Univ di Catania, and OV complements the official IIV report above.

The lava flow that had reached 1,400 m elevation on 14 March (18:02) stopped on 17 March. At about 1700 on 21 March a modest lava flow escaped through a skylight on the main lava tube just below 2,000 m elevation. It was accompanied by intense degassing from the upper part of the eruptive fissure. Through 25 March lava was observed flowing inside the main vent at 2,205 m and small, short-lived flows issued from ephemeral vents in the N part of the lava field at ~ 1,900 m elevation. Poor weather prevented detailed observation of the last days of the eruption.

Degassing (vapor and gas) from the upper part of the eruptive fissure declined. By 20 March it was difficult to observe from a distance. Degassing increased at the summit craters (especially from the central crater) during the final phase of the eruption. Through 9 April, the NE crater, where recent rockfalls had occurred, continued to be obstructed and weak fumarolic activity was present along the walls. COSPEC measurements of SO₂ flux revealed a sharp increase during the last half of March (>16 x 10³ t/d on 23 March). Measurements in April indicated the flux was returning to a normal level of 6-8 x 10³ t/d.

From 16 March to 19 April, 337 seismic events were recorded. They ranged from M 1.0-3.0 and showed characteristic frequencies of 1-6 Hz. All were located in the summit crater region except a M 2.7 at 0649 on 14 April that was located low on the E flank. Volcanic tremor was totally absent.

During the 1991-93 eruption an estimated 300 x 10⁶ m³ of lava flowed from the fissure on the W wall of Valle del Bove at an average rate of 7.3 m³/s.

Information Contacts: The first section is from the official report of theIIV. The second section is fromR. Romano, T. Caltabiano, M. Grasso, and M. Porto, IIV; P. Carveni and C. Monaco, Univ di Catania; G. Luongo, OV.

April 1993 (BGVN 18:04) Cite this Report

Steady degassing; seismicity low

Steady degassing from the summit craters followed the end of the 1991-93 eruption on 30 March (18:03). Increased gas emissions were noted at the central (Voragine) and SE craters (see figure 59) in April, but no morphological changes were detected. The floor of Northeast Crater sank a few meters in early April and remained obstructed by fallen material.

Seismic activity was low with only two volcano-tectonic events recorded. The highest magnitude event (M 2.7) occurred 14 April on the SE flank of the volcano at ~ 10 km depth. Long-period events were similar to those recorded in March, but fewer in number. There was also a decreasing trend in volcanic tremor spectral amplitude. No major changes were recorded by shallow bore-hole tilt stations on the slopes of the volcano.

Information Contacts: IIV.

May 1993 (BGVN 18:05) Cite this Report

Steady degassing continues; seismic swarm

Following the recent eruption's end in March, steady degassing was observed in May from all of the summit craters except Northeast Crater, which remained obstructed by debris in the bottom. Seismicity increased from two volcano-tectonic events in April (18:04) to 23 in May (M 1-3.2). Most of the events occurred between 1206 and 2039 on 24 May. At the same time, an earthquake swarm with 21 discrete events occurred below the NNW flank of the volcano at 13-26 km depth. The number of long-period events also increased compared to the last two months, but tremor amplitude and frequency were unchanged. Inflation was detected at one shallow bore-hole tilt station, but no other tilt variations were recorded.

Information Contacts: IIV.

March 1994 (BGVN 19:03) Cite this Report

Summary of activity since the end of the 1991-1993 eruption

Only steady degassing has been observed at Bocca Nuova, Voragine, and Southeast summit craters following the December 1991-30 March 1993 eruption. Northeast Crater, obstructed by debris that fell from the inner wall, has not shown appreciable degassing.

On 3 August 1993 the Bocca Nuova bottom sank ~30 m during one hour of strong degassing and ash emission that produced an ash column hundreds of meters high; small blocks and a few fresh bombs fell close to the vent. Unusually strong noise was heard and ground vibration was felt at the summit area during this explosive activity. These phenomena also enlarged the unstable crater rim, causing rockfalls for several weeks. Activity did not change significantly through the end of 1993; continuous degassing activity was observed at all craters except Northeast Crater, where reddish ash emissions in early October were probably related to release of overpressurized gas.

A slight renewal of seismicity was observed after the end of the eruption. Fracturing was the probable cause of 83 events (M >1); 14 of them were M 2.5. The cumulative strain-release trend was almost flat throughout the entire period, the only significant episode was a seismic swarm on 24 May 1993 (twenty-one M 1 shocks; Mmax = 3.2). The seismic activity was mainly located on the N and SE sides of the volcano; the N events had hypocentral depths of 12-26 km, whereas the SE events were <10 km. Volcanic tremor amplitude remained low during 1993; a moderate increase was recorded in July. Also, 27 long-period earthquake swarms were recorded in 1993. The best constrained hypocentral locations revealed a source volume below the summit area at a depth of <=3 km.

Tilt recorded at most of Etna's bore-hole stations showed a continuous small deflation of the radial component that started during the 1991-93 eruption. This tilt was confirmed by general contraction measured by the three EDM networks.

The following report is from S. Saunders and W.l McGuire. An EDM network high on the S and E flanks has been reoccupied 13 times between 1981 and 1993. Measurements have revealed >5 m of lateral displacement associated with four rifting events. The network was at least partly re-occupied in April, July, and November 1993. All three surveys came after the cessation of effusive activity in March 1993 (18:03). Compared to the immediately preceding measurements, 1993 data showed that N-S trending lines, broadly parallel to the eruptive fracture and the W rim of the Valle del Bove, lengthened by small amounts (30-60 ppm). Lines trending E-W, perpendicular to the fracture zone, showed no significant length changes between November 1992 and November 1993. These data confirm that the rifting process is contemporaneous with the initial propagation of the feeder dike for the 1991-93 eruption, with little additional dilation-related lateral displacement during the later stages of activity or following the end of lava effusion.

Information Contacts: IIV; S. Saunders, West London Institute; W. McGuire, Cheltenham & Gloucester College of Higher Education.

July 1994 (BGVN 19:07) Cite this Report

Explosive degassing from La Voragine; fumarole temperatures reported

The following describes [fieldwork] on 1-27 June and 10-18 July 1994.

"As during visits in June-July and September-October 1993, Northeast Crater was blocked and inactive, but collapse was continuing around the edge with minor rockfalls every few minutes or so. Southeast Crater was also little changed from 1993, with a quietly degassing vent under the SE rim, but no indication of gas coming out under pressure. There was strong high-temperature fumarolic activity around the crater rim, temperatures being generally highest in the cracks.

"The Chasm (La Voragine) had a single vent in its floor measuring ~ 8 x 10 m, discharging gas continuously under pressure in rhythmic puffs at a rate of ~ 30 puffs/min. On 17 June and 12 July only, distinct explosions could be heard at the rate of 1-8/min. These were the first signs of explosive activity since the end of the 1991-93 eruption, and an indication that the Strombolian degassing that has characterized the summit over the past few hundred years is resuming.

"Bocca Nuova vent was degassing almost totally silently from two vents, one to the SE and one to the W; however, on 27 June when the weather was calm, 13 very faint gas puffs/min could be heard. The SE vent seemed similar to last year, measuring ~ 10 m in diameter, but the W vent had collapsed and enlarged considerably, now measuring perhaps as much as 50 m in diameter. On the early morning of 16 June a reddish tinge to the plume above Bocca Nuova was first noticed. Upon closer inspection on 17 June, the SE vent was seen to be pouring out thick clouds of red dust, apparently a result of internal collapse within the vent, while the W vent continued to emit white fume only. Dust emission intensified in the following days, causing the downwind side (S through W) of the summit to become a striking red color. The activity was continuing in mid-July.

"The levelling traverse showed comparatively small vertical movements since September 1993. The area near Belvedere, and other areas over the dyke intruded during the 1991-93 eruption, had subsided by up to 2 cm, as had the NE rift zone near Monte Pizzillo. During the same period, a small area ~1 km SW of the summit inflated by just over 1 cm. Horizontal movements measured since October 1993 showed generally small or insignificant changes, with nearly all lines recording changes of >1 cm. Only two stations appear to have moved by more than this; a station on the E edge of Southeast Crater had shifted 3 cm E relative to nearby stations, and a station close to the NW edge of the Bocca Nuova had moved 2 cm W. These movements are consistent with expansion of the central magma column as it refills.

"Surface temperatures were measured between 1 and 27 June at four active fumarole areas with a Minolta/Land Cyclops Compac 3 hand-held radiometer (8-14 mm). Temperatures were not corrected for spectral emissivity, so all radiant temperatures are given here as brightness temperatures. On the NE rift zone, nine areas of fumaroles were observed near the N edge of the 1966-67 lavas (between 2,450 and 2,500 m altitude). Temperatures for fumaroles at the two lowest of these areas ranged between 33 and 50°C. Another area of fumaroles observed at the upper rim of the W wall of the Valle del Bove around Belvedere, above the 1991-93 dyke, had temperatures in the 57.5-84.7°C range. Temperatures measured at fumaroles and cracks in the still-cooling 1991-93 lava-flow field in the Valle del Bove were between 85 and 221°C. The locations and temperatures of fumarole areas measured in the vicinity of the summit craters are given in table 5. Temperatures of the vents within the central craters were also measured from the crater rim: 342°C for the Chasm vent, and 159 and 81.5°C, respectively, for the SE and W vents of Bocca Nuova. Active fumaroles were observed, but not measured, along the 1991-93 fissure zone and 14 December 1991 cones and flows between Southeast Crater and Belvedere, along the October 1986 fissure zone, and in the Valle del Bove below Monte Simone."

Table 5. Fumarole temperatures in the vicinity of Etna's summit craters, measured on 18 and 27 June, and 14 October 1994. Courtesy of Andrew Harris, Open University.

Date	Fumarole / Rift Locations	Temperature (°C)
27 Jun 1994	NE Crater - at N rim	50.4-65.0
27 Jun 1994	NE Crater - rifts at NW rim	56.0-141
27 Jun 1994	NE Crater - at dip in NW rim	45.5-97.4
27 Jun 1994	NE Crater - at E rim	51.4-85.6
18 Jun 1994	Bocca Nuova - on N slope	40.5-75.6
18, 27 Jun 1994	Bocca Nuova - inside N rim	42.2-54.3
27 Jun 1994	Bocca Nuova - rifts at N rim	52.0-74.4
18 Jun 1994	Bocca Nuova - at SW rim	52.0-65.7
18, 27 Jun 1994	Central Craters - at S rim	40.6-82.6
27 Jun 1994	Between central and SE Craters	59.1-81.3
18, 27 Jun 1994	SE Crater - rifts and fumarole at N rim	51.2-312
27 Jun 1994	SE Crater - rifts and fumarole at W rim	60.0-208
14 Oct 1994	NE Crater - fumarole at N rim	39.2-77.4
14 Oct 1994	NE Crater - rifts at NW rim	153-246
14 Oct 1994	NE Crater - fumarole at W flank	50.4-74.2
14 Oct 1994	NE Crater - fumarole at W rim	41.0-210
14 Oct 1994	NE Crater - fumarole at S rim	50.5-221
14 Oct 1994	Bocca Nuova - fumarole at N flank	50.1-75.5
14 Oct 1994	Bocca Nuova - rifts and fumarole at N rim	47.3-74.5
14 Oct 1994	Bocca Nuova - fumarole at SW rim	50.0-72.4
14 Oct 1994	Central Craters - fumarole at S rim	49.2-82.4
14 Oct 1994	Fumarole between central and SE craters	50.2-82.8
14 Oct 1994	SE Crater - rifts and fumarole at N rim	57.5-482
14 Oct 1994	SE Crater - rifts and fumarole at NW rim	56.4-218
14 Oct 1994	SE Crater - rifts and fumarole at W rim	46.8-99.5
14 Oct 1994	SE Crater - rifts and fumarole at S rim	49.9-88.0
14 Oct 1994	SE Crater - rifts and fumarole at E rim	68.5-180
14 Oct 1994	SE Crater - rifts and fumarole at NE rim	52.2-121

Information Contacts: J. Murray and A. Harris, Open Univ; L. Platt, Sheffield Univ; D. Renouf, UK.

October 1994 (BGVN 19:10) Cite this Report

Minor explosive degassing and higher fumarole temperatures

The following describes [fieldwork] between 23 September and 14 October 1994.

"There are continuing signs that activity is increasing. At the Chasm (La Voragine), 1-4 very low rumbles/min were heard, but on 14 October six explosions much louder than those heard in June/July (19:07) were heard in 10 minutes. The Bocca Nuova was also producing around one distinct long explosive blast per minute, as opposed to the faint gas puffs heard in the summer. However, no audible explosions were heard when the Chasm was active on 14 October. Northeast and Southeast craters were quiet as in June/July, but temperatures more than 100°C higher were measured at the fumaroles on their outer slopes. Another sign of increasing activity was that during the five days of levelling (25-30 September), 22 earth tremors were detected by the shaking of the instrument. This is > 10 times higher than 1993, and the largest total of tremors noted in this way since September 1991, before the 1991-93 eruption.

"The levelling traverse showed a slight subsidence of the summit since June 1994, the maximum value being just under 3 cm compared to the Piano Provenzana, 6.5 km NNE of the summit. The subsidence is more or less concentric around the summit, with the exception of some stations on the upper E flank and over the 1991-93 dyke, which have subsided nearly a centimetre more than those nearby.

"On 14 October the areas of active fumaroles measured during June were visited. These were measured again using a Minolta/Land 330 hand-held radiometer (8.5-14.5 mm). Temperatures were not corrected for spectral emissivity, so all radiant temperatures are given as brightness temperatures (table 5). At the N, W, and S rim of Northeast Crater, maximum fumarole and rift temperatures were 105-135°C higher than those measured in June. H₂S was also smelled in the vicinity of these high-temperature fumaroles. Higher maximum temperatures were also measured from rifts at the N rim of Southeast Crater, these being up to 170°C higher than those measured in June. It is stressed that these rises in temperature may be the result of different fumaroles being measured on the two dates, though in view of the thorough coverage in June this seems unlikely. Elsewhere, fumarole temperatures were similar to those measured in June. Fumarolic activity only was observed on the floor of Northeast Crater, which was measured from the rim at 40.1°C. The bocca on the floor of the Chasm was measured from the crater rim at 339°C. At the Bocca Nuova, a temperature of 173°C was measured for the SE bocca and of 40.7°C for the NW floor; these were measured from the crater rim. At Southeast Crater, fumaroles decreased in temperature and number around the W and E rims, such that fumaroles were few and cool on the S rim."

Information Contacts: J. Murray and A. Harris, Open Univ.

June 1995 (BGVN 20:06) Cite this Report

Small explosions in May followed by larger ash plumes in June

The following report from the Istituto Internacionale di Vulcanogia (IIV) describes activity from December 1994 to June 1995. Additional information came from Open University geologists, from Henry Gaudru (SVE), and fromaviation notices. Fumarole temperatures measured by Open University geologists in the vicinity of the summit craters increased at Northeast Crater (NEC) between June and October 1994 (table 6). Temperature increases were greatest at the fumarole field on the S rim of the crater, and decreased towards the N rim.

Table 6. Changes in maximum fumarole temperatures measured at Etna's summit craters between June and October 1994. Courtesy of Open University.

Crater Area	Location	June 1994 Maximum Temp (°C)	October 1994 Maximum Temp (°C)	Temperature increase (°C)
NE Crater	Fumaroles at N rim	65	77	12
NE Crater	Rifts at NW rim	141	246	105
NE Crater	Fumaroles at W rim	97	210	113
NE Crater	Fumaroles at S rim	86	221	135
Bocca Nuova	Fumaroles on N flank	76	76	0
Bocca Nuova	Fumaroles and rifts (N rim)	74	74	0
Bocca Nuova	Fumaroles at SW rim	66	72	6
Central Craters	Fumaroles at S rim	83	82	-1
Central Craters	Between S rim and SE crater	81	83	2
SE Crater	Fumaroles and rifts-N rim	312	482	170
SE Crater	Fumaroles and rifts-W rim	208	218	10

After several months of steady degassing from the summit craters, Bocca Nuova produced a short sequence of mild explosive events on 10-12 December 1994, characterized by brownish columns of non-juvenile ash rising

In January 1995 several ash puffs from NEC were observed. They were more frequent between 31 January and 3 February, but continued all month, forming a thin ash layer around the crater rim. The most significant activity from NEC in the following two months was strong steam degassing, sometimes with ash.

An intense episode of ash emission from NEC occurred at 1000 on 9 May. Red-brown ash and accretionary lapilli fell on Milo, a village on the middle slope of the volcano. No block fallout was observed near the crater rim, and steam emission continued unchanged.

On 23 May at 1605 a new NEC explosion ejected lithic blocks; most of them were affected by fumarolic alteration that changed hard lavas and scoriae into very brittle materials with vivid white, yellow, purple, and reddish colors that were very easy to recognize on the discontinuous snow mantle. The area of fallout was ~0.2 km² and the maximum block volume reached 0.2 m³, however, most of the blocks were only a few centimeters in size. No juvenile material was found among the fall products and the event resembled to a pure phreatic explosion that ejected very altered material picked up from the walls of the December 1994 degassing vent and the NEC crater bottom. On the morning of 26 May an explosion visible (by SVE members) from the N flank at 1,800 m elevation generated a gray ash-and-vapor plume above NEC. When the SVE group reached the summit area, small blocks were visible around NEC and near the lower slope of Bocca Nuova.

On 30 May a weak, ash-bearing plume was observed from an airplane by J.B. Murray. Stronger activity from the vicinity of Bronte was noted on 8 June, when thick ash clouds up to 70 m high were reported late in the morning. On a 12 June summit visit, scattered wall rock (lying

The IIV reported gas explosions and inner-crater wall collapses from Bocca Nuova in June. Gas emission came from two vents on the crater bottom, the northernmost of which produced some small phreatic explosions that threw several centimeter-size lithic-lava blocks up to 50 m NE beyond the crater rim. Some ash emission from NEC was observed during June. Murray reported that as of mid-June guides had stopped taking tourists to the crater edge because of the danger from explosions. The situation reminded Murray of the activity following the 1983 eruption (SEAN 08:04), when a series of sudden, large non-magmatic explosions occurred from the NE crater.

Aviation notices (SIGMETs) were issued for Etna on 21 June when an ash cloud reportedly rose 4,200 m. Another notice on 25 June described an ash cloud ~18 km E from the central crater at an altitude of 2,100-4,200 m. IIV video surveillance showed no eruptive columns during 21-25 June 1995, although on 21 June the camera was out of order and on the afternoon of 23 June foggy conditions obscured the upper slopes. On 22 June light ash from NEC fell on the IIV high-mountain observatory at Pizzi Deneri (2,850 m elevation), NE of the summit craters.

Information Contacts: Mauro Coltelli, CNR Istituto Internazionale di Vulcanologia, Piazza Roma 2, 95123 Catania, Italy; John B. Murray and Andy Harris, Department of Earth Sciences, The Open University, Milton Keynes MK7 6AA, United Kingdom; Nicki F. Stevens, Department of Geography, University of Reading, Whiteknights, P.O. Box 217, Reading RG6 2AH, United Kingdom; Henry Gaudru, Societe Volcanologique Europeenne (SVE), C.P. 1 - 1211 Geneva 17, Switzerland.

July 1995 (BGVN 20:07) Cite this Report

Gas-and-ash explosions followed by sustained Strombolian activity in late July

Eruptive activity from Etna's summit craters continued in July. Sustained Strombolian activity resumed in Bocca Nuova vent on 29 July. Details will be provided next month.

At Bocca Nuova crater, a degassing vent in the N part of the crater floor produced very frequent gas explosions followed by collapses inside the vent, and then by red ash emissions. Ash emissions started on the morning of 25 July, and ash formed a thick carpet inside the crater. Ash plumes rose ~100 m above the crater rim and caused ashfall on the W flank. A small percentage of juvenile material was identified in the ash. Another vent at the SE margin of the crater floor produced only gas explosions with no ash. The interior of Bocca Nuova had vertical walls and a nearly flat zone in the SE part of the floor, ~100 m below the crater rim, that gently sloped NW. The flat zone occupied 40% of the crater floor, the remaining part being covered by collapse debris. The inner part of the collapsed zone had sub-vertical walls and a floor sloping NE.

In the SW corner of the Northeast Crater floor a vent produced strong gas emissions with occasional inner collapses and red ash expulsions. Samples of ash showed an increase in juvenile component compared to May. Northeast Crater was pit-shaped, with sub-vertical inner walls covered by red ash. The floor was ~150 m deep and had a step oriented NE-SW, which separated the flat zone of the NW sector, gently sloping SE, from the SE portion sloping SW. Activity at the funnel-shaped Voragine (Chasm) consisted of continuous, weak gas emission from the central vent with neither explosions nor ash emissions. Southeast Crater produced only a weak degassing activity.

Information Contacts: Sonia Calvari, Istituto Internazionale di Vulcanologia, Piazza Roma 2, I-95123 Catania.

August 1995 (BGVN 20:08) Cite this Report

Magmatic activity resumes in Bocca Nuova and Northeast craters

Strombolian activity resumed at Bocca Nuova vent on 30 July and in Northeast Crater on 2 August. Etna's last magmatic activity within its summit craters stopped 3 years and 7 months earlier, two days after the beginning of the 1991-93 flank lava flow eruption (BGVN 16:12). During that 15-month-long eruption and the following 28 months, the four summit craters exhibited continuous steam emission with frequent non-juvenile ash puffs, several collapses, and some strong phreatic explosions from Northeast Crater and Bocca Nuova. No morphological changes were observed in August at either Voragine or Southeast craters, where gas and steam emissions continued as in previous months.

On 30 July the first red spatters were observed inside Bocca Nuova, but bad weather prevented an evaluation of the intensity of this new magmatic activity. Observations the next day revealed that the vent was located in a new pit crater (20-30 m wide and ~50 m deep) on the N part of the crater floor. That part of the crater floor collapsed in June 1994, and probably dropped again in June 1995 when some phreatic explosions occurred (BGVN 20:06). The vent was a few meters across, and magma was sometimes visible during pulsed degassing episodes frequently interrupted by mild Strombolian explosions. The most energetic events were lava jets lasting 15-20 seconds that threw large spatters 120-130 m above the vent to the crater rim. The activity climaxed on 2 and 3 August when lava jets frequently rose up to a few tens of meters above the crater rim. Strombolian activity stopped abruptly on the night of 4 August, leaving a thick tongue of lava on the pit floor. During the Strombolian phase no spatter fell beyond the crater rim; most fell close to the vent inside the inner pit. In the days following 4 August, several ash emissions were observed at Bocca Nuova, which gradually resumed its quiet degassing. No further activity at Bocca Nuova was observed through the end of August.

Until 2 August, no lava emissions had been observed from Northeast Crater since September 1986 (SEAN 11:09); only scoria was ejected on 13 May 1991 (BGVN 16:07). Strombolian explosions during 2-3 August issued from a small vent in the lowest part of the crater, ~150 m below the crater rim. Almost continuous spatter ejections never reached the crater rim. During 3 August the activity gradually changed to puffs of black ash that continued in the following days. After ash emissions decreased, three incandescent degassing points on the crater floor were seen for several days. On 18 August, Strombolian activity resumed and during the night some incandescent bombs rose above the crater rim. Ash emission the following days prevented observations inside the crater, but no blasts were heard. On 29 August, another 1-day phase of Strombolian activity was followed the next day by ash emissions that marked the end of this eruptive episode.

Information Contacts: Mauro Coltelli, CNR Istituto Internazionale di Vulcanologia, Piazza Roma 2, 95123 Catania, Italy.

September 1995 (BGVN 20:09) Cite this Report

Ash emissions and another episode of Strombolian activity from the summit craters

A strong episode of black ash emission from Northeast Crater (figure 60) during the late morning of 13 September lasted only a few minutes, sending an ash plume 100 m above the crater rim. Red ash emissions from Bocca Nuova and Northeast Crater continued until about 20 September, but explosions of variable frequency and intensity were heard from both throughout the month. Voragine (Chasm) and Southeast Crater exhibited only weak degassing in September. Poor weather prevented internal crater observations.

Figure 60. Topographic sketch map of Etna's summit craters (stippled), September 1995. Shaded areas within the craters indicate collapsed, degassing pits, and solid points are active boccas producing Strombolian activity. Within Bocca Nuova, the hatched area indicates the deepest part of the crater floor. Courtesy of the Istituto Internazionale di Vulcanologia.

On the evening of 2 October explosive Strombolian activity resumed at Northeast Crater from two small vents, aligned NNE-SSW in the lowest portion of the crater floor, ~150 m below the crater rim (figure 60). During observations the next morning, loud vigorous explosions were almost continuous, throwing scoria above the crater rim. A slight decrease in the frequency and energy of the explosions occurred that afternoon, although some incandescent bombs fell on the outer crater slope. Activity continued to decline during the night, and on the morning of 4 October Strombolian explosions were restricted to a single vent ejecting bombs up to a few tens of meters above the crater floor. By the evening of 5 October only incandescent degassing vents were present. During the same period, Bocca Nuova exhibited frequent red-brown ash emissions alternating with normal degassing. Ash emission was occasionally accompanied by incandescent bomb ejection. The ash puffs, more copious on the morning of 3 October, were produced by the same partially collapsed vent that was the site of Strombolian activity in August (BGVN 20:08).

Bombs collected on the crater rim (the first accessible material since the end of the 1991-93 eruption) were geochemically comparable with the 1991-93 lavas. The bombs were porphyritic hawaiite with phenocrysts of plagioclase (~16 volume %), clinopyroxene (~4%), olivine (~1%) and Ti-magnetite microphenocrysts in an intersertal groundmass.

Information Contacts: Sonia Calvari and Massimo Pompilio, CNR Istituto Internazionale di Vulcanologia, Piazza Roma 2, 95123 Catania, Italy.

October 1995 (BGVN 20:10) Cite this Report

Frequent Strombolian explosions and ash emissions from Northeast Crater and Bocca Nuova

The Istituto Internazionale di Vulcanologia (IIV) report below provides an overview of activity during October. IIV reports generally summarize the temporal evolution of volcanic phenomena during the whole month, skipping some trivial details, and frame the ongoing activity in the context of phenomena over a period of years.

Reports detailing activity during short visits made by visiting volcanologists provide a different perspective on the volcanism. One such report for some days in October was provided by a team led by Open University (OU) volcanologists conducting routine deformation measurements during 9 September-14 October. Short visits to the summit craters on 7, 12, and 14 October were also made by Boris Behncke, with additional observations from Carmelo Monaco and Marcello Bianca (University of Catania), Maria Felicia Monaco (Bari University), and others.

Review of July-September 1995 activity. Strombolian activity resumed at Bocca Nuova on 30 July and in Northeast Crater on 2 August (BGVN 20:08). On 30 July spatter was observed inside Bocca Nuova from a new pit crater on the N part of the crater floor. The activity climaxed on 2 and 3 August, when lava jets rose above the crater rim, then stopped on the night of 4 August. Strombolian explosions during 2-3 August issued from a small vent in the lowest part of the crater. Two more Strombolian episodes occurred on 18 and 29 August. A strong explosion from Northeast Crater on 13 September sent an ash plume 100 m above the rim. Ash emissions from Bocca Nuova and Northeast Crater continued until about 20 September, but explosions were heard throughout the month (BGVN 20:09). The OU team noted light ashfall 2-3 km away in the third week of September, and heavier ashfall 50 m from the Bocca Nuova rim on 27 September.

Overview of October 1995 activity from IIV. After a short period of Strombolian activity at Bocca Nuova and Northeast Crater at the beginning of October, alternating mild Strombolian activity and ash emission characterized their activity for the rest of the month. On 8 October almost continuous rumbling noises (like roaring jets) were heard from both craters. On the morning of 12 October intense ash emissions took place from both craters. Bocca Nuova displayed small short-lived ash puffs (5-7/hour), while from the Northeast Crater a dense ash column rising as high as 900 m developed repeatedly (2/hour). IIV field parties working in the summit area reported that the ash emission were accompanied by falling rock noises. However, successive surveys observed neither juvenile nor lithic blocks on the crater rims.

After 12 October Strombolian activity progressively resumed at Northeast Crater and continued with variable intensity until the end of the month. On 19 October Strombolian activity was relatively vigorous and the scoria ejections, up to few tens of meters from the crater rim, were almost continuous. A survey on 25 October revealed an appreciable decrease of the explosion frequency. Bocca Nuova exhibited intermittent ash emissions after 12 October. As during previous activity, they originated in a depressed area of the NW crater floor. Explosions observed on 19 October were accompanied by ejection of a black (lithic?) block to a few tens of meters above the crater floor, but neither glowing at the vent or ejection of incandescent bombs were observed. After 19 October intermittent ash emission progressively decreased, and in the last week of the month weak Strombolian activity resumed at Bocca Nuova. Significant eruptions on 9 and 14 November will be reported in the next Bulletin.

Deformation measurements. Preliminary results from the OU team indicate little ground deformation since October 1994 over most of the network. Summit levelling showed insignificant movement (-5 mm near the summit, +7 mm on the N flank) apart from the area above the 1991-93 dike, which between the W side of Cisternazza and Belvedere showed a fairly consistent subsidence of 17-24 mm. Preliminary GPS computations suggested a radial expansion about the summit of ~15 mm. Dry-tilt stations showed no large tilts.

Details of 1-7 October activity. Observations from the Northeast Crater rim on the afternoon of 1 October by the OU team revealed two faintly glowing vents, ~3-5 m across, on the crater floor. The following night, bright summit glow was seen from Nicolosi (15 km S), and on the morning of 3 October loud explosions from Northeast Crater were heard from the trail 800 m W, which had been covered with a thin layer of red ash overnight. Explosions were again heard late in the afternoon from ~7 km away, and light ash fell near Monte Corbara (5 km NW). While approaching the crater at 1815 on 3 October, two guides and an Italian TV camera crew returning from the rim warned of bombs falling outside the crater. As the OU team moved towards the high ground behind the crater, a large explosion sent brightly-glowing juvenile bombs just over the rim, rolling toward them. A few seconds later a single bomb ~20 cm across landed 10 m away, 100-200 m from the rim. Similar bomb ejections to smaller distances occurred about every 2 minutes until the team descended at 1845. On 7 October, Behncke noted a dense steam-and-gas plume from Northeast Crater. Most of the plume and occasionally some ash rose from the SSE part of the crater floor; falling stones were frequently heard.

Detonations from within Bocca Nuova heard by the OU team on 1 October were only audible from the rim. One vent on 4 October was explosively exhaling gas, and the other was collapsing, producing brownish ash clouds. Behncke observed small Strombolian explosions from Bocca Nuova on 6 October, but only ash emissions the next day. On the 7 October visit, Behncke observed frequent ash plumes from Bocca Nuova accompanied by rumbling noises and the sound of falling stones; Strombolian explosions were frequent.

The Chasm (La Voragine) quietly emitted fumes on 1 October. On 4 October the OU team climbed into Southeast Crater to the edge of the vents, which emitted gas quietly and not under pressure, apart from one area just below the S rim. On 7 October, Behncke heard small explosions, but no ejections or incandescence were seen after sunset.

Details of 12-14 October activity. Between 0800 and 0900 on 12 October a series of collapses within Northeast Crater generated a thick ash cloud. Pulses of rapidly rising ash plumes resulted in a vertical column 800-1,000 m above the summit. After 0900, a dilute gas plume rose from Northeast Crater while Bocca Nuova sent frequent ash emissions 200-300 m above the summit. When Behncke reached the crater rim shortly after 1230, there were vigorous steam emission and explosions from Northeast Crater.

Behncke saw incandescent spots in the central Northeast Crater floor that gradually increased in number and intensity. Pyroclastic ejections became more frequent and vigorous, and soon the incandescent areas were hidden by gas and dilute ash plumes. The ash plumes first rose slowly to ~100 m above the crater floor, but gradually rose higher and became more heavily ash-laden. About 5 minutes after the onset of ash venting, dense convoluting ash clouds began to rise above the rim. Bomb and ash emission steadily increased. The high-pressure gas emission noise at the beginning of this activity changed to a dull rumbling connected with the ash emission. Short pulses of bomb emissions every 5-10 seconds were followed by a dark ash puff. After ~10 minutes, the ash puffs merged into a continuous column that rose hundreds of meters above the rim. Around 1345 vigorous emissions ejected black ash plumes ~1 km above the summit. Periodic ash emissions from Northeast Crater gradually became less vigorous before ceasing that evening.

On 12 October (0800-0900), the OU team heard detonations from Bocca Nuova, mainly from a vent on the E side of the floor, but the larger vent on the NW side occasionally threw 20-cm-diameter lithic blocks 30-50 m high. Ash emissions seen by Behncke after 1230 occurred every 2-5 minutes from the pit on the NW crater floor. Each emission began with block and/or bomb ejections followed by a dense ash plume. The bombs and blocks rose out of the ~50-m-deep pit but remained ~100 m below the rim, whereas the ash plumes rose 100-500 m above the summit. An open vent in the SE crater floor displayed continuous gas emission with occasional explosions that ejected dense gas clouds.

Shortly after 1700 on 14 October Behncke saw a central glowing vent in Northeast Crater. Vigorous high-pressure gas emission produced a roaring noise, and the plume was almost vapor-free. During the first 30 minutes of the visit, glowing spatter was occasionally ejected from the vent. As degassing increased, numerous incandescent spots became visible, aligned more or less concentrically around the vent. After the first half hour, Strombolian bursts became more vigorous, ejecting bombs ~50 m above the pit. About 10 minutes later, the explosions again intensified, and the crater floor around the vent, which appeared more funnel-shaped, was covered with incandescent bombs. Ejections rose ~100 m above the vent but remained far below the crater rim.

Information Contacts: Massimo Pompilio, CNR Istituto Internazionale di Vulcanologia, Piazza Roma 2, 95123 Catania, Italy; John B. Murray and Fiona McGibbon, Dept. of Earth Sciences, The Open University, Milton Keynes MK7 6AA, United Kingdom; Nicki Stevens, NUTIS, Reading University, Whiteknights, P.O. Box 227, Reading RG6 2AB, United Kingdom; Phil. Sargent, Sue Elwell, and Sarah Cooper, Civil Engineering Dept., Nottingham Trent University, Burton Street, Nottingham NG1 4BU, United Kingdom; Boris Behncke, Dept. of Volcanology and Petrology, GEOMAR, Wischhofstr. 1-3, 24148 Kiel, Germany.

December 1995 (BGVN 20:11) Cite this Report

Six lava fountaining episodes from Northeast Crater

On 2 August 1995 explosive activity resumed at Northeast Crater (NEC) (BGVN 20:08). In August and September the activity was sporadic and low in intensity (BGVN 20:09), but after 2 October a vigorous Strombolian phase was observed (BGVN 20:10). Explosive activity occurred again during 19-22 October.

On 1 November there was vigorous spattering and bubbling of magma in a 15-m-wide pit on the NEC floor. Magma degassing formed large bubbles that burst, throwing spatter to the crater rim. In the following days the activity was discontinuous and less intense.

Lava fountaining episodes, 9-14 November. At 0014 on 9 November there was a sudden increase in volcanic tremor, but bad weather prevented summit observations. Between 0105 (at Trecastagni) and 0110 (at Catania, 30 km SSE) ash and lapilli fallout covered the SE flank (figure 61), eventually reaching as far as Siracusa, 75 km from the vent. The episode lasted only a few minutes and the material on the lower slope amounted to a few tens of grams per square meter, although rare dense lapilli broke some skylights and car windows. Fieldwork the next morning revealed that the NEC eruption produced a lava fountain followed by a strong phreatomagmatic blast. Part of the S rim collapsed inside the NEC and was later ejected. A welded spatter deposit several meters thick mantled the upper slope of the NEC cone and was overlain by a few centimeters of ash and lapilli. The bombs varied from 2-3 m close to the vent, to 25 cm at 2.5 km downwind. Several large accidental lithics (up to 1 m) occurred in the very proximal deposit. A large amount of spatter fell into the crater, raising its floor by several tens of meters. The crater appeared completely sealed, with wide red cracks on the crust of the spatter pile. The total volume of tephra from the 9 November eruption was ~1.5 x 10⁶ m³.

Figure 61. Map of the Etna area showing areas affected by ashfall on 9, 14, and 27 November, and 23 December 1995. Courtesy of IIV.

On 10 November a new lava fountain episode at NEC was observed from Catania around 0400-0530. Pulsating magma jets climbed up to 300 m above the crater rim; some were expelled up to 500 m. An ash-and-lapilli column ascended ~5,000 m and was blown SE. The spatter deposit was limited to the upper part of the volcano and in a narrow strip extending ~3 km SE; little ash fell on the middle slopes. The estimated volume of the pyroclastics was a few tens of thousands of cubic meters.

A third episode took place around 0600 on 14 November, and lasted ~3 hours. Between 0800 and 0900 the paroxysmal phase sent dense black ash columns through a white cloud covering the summit until they reached 5,000 m altitude. During the entire episode a non-continuous sustained eruptive column was observed and each ash puff contributed to a plume bent downwind that reached its buoyancy level at 6-7 km altitude. Ash and lapilli rained on the NE flank down to the coast (figure 61), leaving only a few grams of material per square meter on the middle and lower slopes. The proximal spatter deposits, mapped two days later, partially covered the previous ones on the cone and extended ~2 km NE in a band a few hundred meters wide. Lithic blocks and ash were less abundant than in deposits from the 9 November episode. The crater bottom was sealed by back-fallen welded spatter and was ~50 m below the crater rim, 100 m higher than before 9 November. The total volume of tephra from the 14 November eruptions was ~350,000 m³.

The volcano remained quiet after the 3rd episode. Within NEC, only a few large cracks on the welded spatter crust emitted fumes. Bocca Nuova crater showed a normal continuous degassing; Southeast and Voragine craters continued their steam emission.

Lava fountaining episodes, 22-27 November. Late on 22 November continuous glows were observed at NEC and some bangs were heard on the lower slopes. Beginning around midnight, two hours of fire fountaining and intense red glow was visible from Catania. The lava jets remained fairly low (~100 m above the crater rim) so the proximal spatter deposit mantled only the upper part of the cone, whereas the fine material fell on the SE flank as far as the coast. However, the total volume of the erupted material was limited to a few tens of thousand cubic meters, close to that of the second episode.

After the 22 November episode the vent was closed again by material that fell back into the crater. Three days later some bangs were heard at NEC and glow was observed during the night of 26-27 November. That morning seismic tremor rose suddenly and at 0715 an ash-and-lapilli column rose from the volcano. Cloud cover prevented direct observations. Ash and lapilli were carried by strong winds and fell on a narrow band of the N flank down to its foot (figure 61). Lapilli fallout ended around 1000, but the explosive activity continued for several hours. The thickness of the scoria-fall deposit varied from decimeters close to the vent to ~1 mm at 12 km away. The total tephra volume from this 5th eruptive episode was estimated at 0.4-0.5 x 10⁶ m³.

Fieldwork two days later revealed that the proximal spatter deposits of the 22 and 26 November episodes were thinner than earlier ones. Lithic blocks were less abundant than in the 9 November deposits, but large ballistic scoriaceous bombs were found up to 500 m from the vent. The crater floor was completely sealed by fall-back spatter, but every 40-60 minutes a gas pocket broke the solid crust and a single lava bubble burst. These phenomena were observed for a few more days.

Activity during December. In the first half of December the summit craters were quiet, with continuous steam emissions, except for NEC, which had no open vent. A short explosive phase was reported on the night of 6 December. Poor weather conditions prevented observations until 16 December, when continuous Strombolian activity was seen at a small vent on the crater floor; a cone grew within a few days. The activity was characterized by the bursting of single magma bubbles alternating with degassing jets and spatter lasting from tens of seconds to a few minutes. This intense Strombolian activity continued for several days.

Around 1100 on 23 December strong bangs were heard from skiers on the upper slope. Very soon the bangs became frequent and black ash puffs were observed from NEC. Between 1215 and 1220 the first jet of magma rose above the crater rim, followed shortly by several pulses of magma jets and a large eruptive column. Between 1235 and 1305 the paroxysmal phase occurred, with jets of magma that rose 500-600 m (measured on the video record of the surveillance camera at La Montagnola, 2,700 m elevation on the S flank). Fragments from the top of the jets fed an eruptive column that reached 9.5 km altitude (6.2 km above the summit). Clear weather allowed observation of the column from many places on Sicily, as far as the city of Palermo 190 km away. Abundant ash and lapilli fell on a wide band of the NE flank down to the coast (figure 61). A brownish ash plume was emitted by Voragine during the entire paroxysmal phase of the eruption. Around 1330 the eruption quickly declined, but isolated explosions occurred until the evening. This episode was the most energetic among the six at NEC during November and December 1995.

The proximal deposit mantled the NEC cone with meters of welded spatter. In the W and E saddles between NEC and the Central Cone, spatter formed two thick lava flows a few hundred meters long. The E flow was still active during the night of 23-24 December; downslope movement of fluid material in the core produced continuous collapses of large incandescent blocks at the flow front. Crater modifications included the thick new scoria bank and widening and lowering of the S crater rim. Ballistic clasts had been thrown up to 600 m from the vent and landed as cow-pie bombs up to 2 m in diameter. The distal deposit from the eruptive column was made of scoriaceous bombs and lapilli up to 10-15 km from the vent, and from lapilli and a minor ash up to the shoreline, 22 km away. The bombs were very brittle, flat, and up to 30 cm in diameter at 6 km from the vent (observed while still in the air). The scoria-fall deposit formed a continuous band from the vent to the coast, damaging fruit plantations, vehicles, and buildings. The Messina-Catania freeway had to be cleared of a scoria deposit along a 4-km-long stretch. The deposit thickness along the dispersal axis was 6-7 cm at 6 km, 3-4 cm at 13 km, 3 cm at 16 km along the freeway, and 1-2 cm at 20 km near the coast. The estimated total volume of pyroclastics erupted on 23 December was ~3 x 10⁶ m³.

On the days after 23 December eruption only a few blasts were heard from NEC, but on the nights of 27 and 28 December discontinuous glow was again seen, sometimes similar to those produced by mild Strombolian explosions. No further activity was reported at NEC or the other craters through the end of the year.

Tephra characteristics. Bombs and lapilli erupted during the November-December 1995 episodes are highly vesiculated and show glassy and smooth surfaces. Only in the volcanics erupted on 9 November are both vesicles and surfaces filled by reddish, fine-grained non-juvenile material. Juvenile ash consists of: 1) poorly vesiculated tachylitic (glassy) grains; 2) highly vesiculated clasts with glassy, smooth surfaces, and many Pele's hair and shards in the finer fraction; and 3) loose crystals covered in some cases by a thin film of glass.

Generally rounded grains with variable alteration form the non-juvenile fraction. In the ash fraction of all deposits, juvenile material is always the most abundant (60-100%), and preliminary investigation indicates that it increased with time. The juvenile fraction is ~60% of the 9 November ash, ~80% of the 14 November ash, and ~100% of the ash erupted during the following episodes (23 and 27 November, 23 December). The proportions of different juvenile components also changed during the eruptive sequence.

Scoria erupted during the November-December explosive episodes are, like most of Etna's historical volcanics, porphyritic hawaiites with phenocrysts of plagioclase, clinopyroxene, and olivine, and microphenocrysts of Ti-magnetite in a hyalopilitic groundmass. The scoria are more vesiculated and slightly less porphyritic than those erupted in October 1995. The chemical composition of November-December scoria is rather homogeneous even if the 9 and 14 November material is slightly more differentiated than those erupted after 23 November. Overall, the composition of the November-December volcanics is comparable to those of the Strombolian activity at NEC during the first half of October, and to the products erupted in the first days of the 1991-93 eruption.

Seismicity. Seismicity recorded by the permanent seismic network (12 stations; figure 62), during November-December 1995 was characterized by remarkable phases of increased volcanic tremor amplitude. Earthquake activity stayed at very low levels. A few tens of shocks took place and the only significant episode occurred on 24 December when a minor swarm (6 events; Mmax=3.2) was located near Mt. Maletto (NW slope of the volcano) at a depth of ~15 km.

Figure 62. Map of Etna showing locations of seismic stations, tilt stations, and EDM networks maintained by the Istituto Internazionale di Vulcanologia as of December 1995. Courtesy of IIV.

Since the end of August 1995 volcanic tremor recorded at Pizzi Deneri (PDN: ~2 km from NEC, 2,820 m elevation) and Serra Pizzuta Calvarina (ESP: ~7 km from NEC, 1,590 m elevation) stations has shown an increasing trend. This pattern became more evident in late September, when some increases in tremor amplitude were recorded for durations ranging from tens of minutes to a few hours. The most relevant increases in tremor amplitude occurred on 22-23 September, 2, 3 and 21 October, 9, 10, 14, 22-23, and 27 November, and 23 December. This tremor amplitude pattern correlated with visually observed NEC eruptive activity.

The volcanic tremor spectral amplitude temporal pattern at PDN and ESP stations showed a clear amplitude increase. Spectral amplitude peaks were superimposed on the increased trend and corresponded to the episodes listed above. Dominant peaks in tremor spectra recorded at PDN and ESP stations showed a high-frequency (~3.5 Hz) trend coincident with the high tremor amplitude. Each amplitude increase showed similar characteristics.

Ground deformation. After the end of the 1991-93 eruption deformation was dominated by steady inflation, mostly affecting the W and NE slopes. Positive trends of areal dilatation, cumulating at ~14 ppm, were clearly apparent on the SW and NE flank EDM networks (figure 62) following the 1991-93 eruption, while the S network was characterized by a flat trend of areal dilatation for several years. Both the SW and NE networks followed comparable trends, only differing in the recent sharp positive gradient variation (10 ppm) shown by the latter between August and October.

The shallow bore-hole permanent tilt network (figure 62) indicated a progressive increase (starting by the second half of 1993) in the radial tilt component recorded at the stations on the W flank (MSC: 50 µrad) and on the N flank (MNR: 10 µrad), while the S slope showed no appreciable positive variation until July 1995. The eruptive activity resumed at the summit craters by late July-early August, and the renewed ejection of magma appeared to be strictly related in time to the positive variation of the radial tilt at SPC (~15 µrad) and the sharp increase of areal dilatation in the NE sector. Radial tilt at PDN was affected by a sharp negative variation (35 µrad) at almost the same time.

September EDM survey on the S flank. J. Moss noted that reoccupation of a different S-flank EDM network in September 1995 showed only minor line extension since eruptive activity resumed in August. Significant extensions of lines perpendicular to the Valle del Bove accompanied dike emplacement prior to the 1991-93 eruption. However, the July 1995 survey showed only minor changes since July 1994. Over 80% of the lines measured between those two surveys showed extension, suggesting a pattern of broad edifice inflation. The small strain rates suggest that no magma was intruded into this part of the S rift zone prior to September 1995.

Information Contacts: M. Coltelli, M. Pompilio, E. Privitera, S. Spampinato, and S. Bonaccorso, CNR Istituto Internazionale di Vulcanologia (IIV), Piazza Roma 2, 95123 Catania, Italy (URL: http://www.ingv.it/en/); Jane L. Moss, Cheltenham and Gloucester College of Higher Education, Francis Close Hall, Swindon Road, Cheltenham GL50 4AZ, United Kingdom.

February 1996 (BGVN 21:02) Cite this Report

Two additional significant eruptive episodes during January-February

After the sixth eruptive episode at Northeast Crater (NEC) on 23 December 1995 (BGVN 20:11/12), continuous steam emission was observed at the other summit craters in early January. After sunrise on 4 January, ash puffs were observed at Bocca Nuova crater (BN). The abundant black ash emissions were apparently not linked to explosive activity; the frequency of ash puffs ranged between 2 and 5/minute and slowly declined during the afternoon. The next day only a white plume was present. A few small ash puffs observed on 5 and 9 January came from BN and NEC.

In the early morning of 17 January, a strong explosion from NEC ejected lithic material. Intermittent blasts (up to 15 minutes apart) were heard during the day, but no ejections were observed. Fieldwork two days later revealed that Strombolian explosions with ash puffs had occurred from two vents in the NW part of the Bocca Nuova crater floor, in the same place where activity resumed at the end of July 1995 (BGVN 20:08). The Voragine crater produced unusually strong gas blasts, but no sign of eruptive activity was observed. NEC produced a strong explosion at 1010, but then remained quiet without any gas emission. A 20 January explosion at NEC had similar characteristics. Explosive activity on 21 January was more intense and caused ash emission mainly from BN, but some strong blasts also came from NEC during the day.

Seventh eruptive episode. During the night of 24 January, red glows were intermittently observed at NEC, and after 0600 on 25 January lava jets inside a dense ash cloud were observed by the surveillance video camera at La Montagnola (3.5 km from the summit). This seventh eruptive episode, 33 days after the start of the previous one, probably began around 0130 when a strong increase in tremor amplitude was recorded by the summit stations of the IIV seismic network. A pulsating ash column developed around 0430 and was flattened down to the ground by strong winds. The lava jets were fairly low (~100 m above the crater rim) so the spatter deposit mantled only the upper part of the NEC cone, whereas fine material was blown onto the NE flank. Lapilli fallout ended around 1045, but the explosive activity continued for several hours. The lapilli-fall deposit covered a sector of the volcano >20 km long and 3.5 km wide at 12 km from the vent, where the thickness of the deposit was 1-2 mm. The volume of the pyroclastic material erupted during this episode was estimated at ~500,000 m³.

During the night of 26-27 January several strong blasts from the summit were heard in the nearest villages and strong red glows were sometimes observed at the summit. This activity was marked by short periods of high tremor amplitude. At sunrise two intense ash emissions from NEC were observed by the video surveillance system. Aerial observations revealed that one or more short lava-fountaining episodes occurred at NEC during the night. A hot spatter deposit covered a wide band on the upper SE flank down to 2,500 m elevation; no fine distal deposit was observed. Ash puffs and blasts were observed and heard from BN and NEC in the following days (in particular on the morning of 28 January) up to around 1000 on 30 January when tremor amplitude increased and ashfall was reported by skiers on the S flank. However, these phenomena vanished in the afternoon.

The summit craters remained quiet in early February, showing continuous steam emission sporadically darkened by minor ash. However, tremor amplitude fluctuated above background levels. On 8 February copious ash emitted by BN thinly covered the snow on the S flank.

Eigth eruptive episode. Another fire fountaining episode at NEC began at 2335 on 9 February and ended around 0115 the next day. Pulsating lava jets reached 200 m above the crater rim. Lapilli fallout covered a narrow band (1-3 km wide) from the vent to the shoreline (25 km away) on the SE flank (figure 63). A light ash fallout reached the town of Catania. However, the estimated volume of eruptive products was the estimated volume of eruptive products was < 300,000 m³.

Figure 63. Map of the Etna area showing zones affected by ashfall in November-December 1995, 21 January 1996, and 9 February 1996. Coordinates are UTM. Courtesy of IIV.

Minor eruptive activity continued until 0145-0200 on 10 February. A strong explosion at 1022 ejected a large amount of material from NEC. Several ash puffs occurred during the day at NEC and BN craters. In the late evening the ash emission at BN increased and Strombolian activity resumed at NEC, marked by increased tremor amplitude that decreased again during the night. At dawn on 11 February several ash puffs were observed at BN; this activity decreased during the day but around 1700 the tremor amplitude increased again and strong Strombolian activity resumed at NEC. Eruptive activity continued through 2130 and then dropped.

On 12 February numerous ash puffs were observed at both BN and NEC. At 0030 the following day strong Strombolian activity was observed at NEC by the surveillance camera. The intensity of explosions grew up to 0130 when another sharp tremor amplitude increase was recorded. Strombolian explosions often threw incandescent bombs up to 200 m above the crater at a rate of ~5/minute until 0200. Strombolian activity gradually decreased and after 0300 was seldom observed. At sunrise several black ash puffs were observed at both BN and NEC craters and ash emissions became less frequent at 1100.

Ash puffs were next observed on 14 February, becoming more frequent on 17-18 February and during the morning of 19 February when BN produced almost continuous ash emissions for periods of up to tens of minutes. At sunrise on 21 February the snow was covered by a thin ash layer. At 1757 pulsating red glows were visible above NEC; at 1830 the glow became continuous until sunrise the next day (22 February). Higher intensity glow occurred for up to a few tens of minutes when bomb ejections were recognized.

During 22 February activity was apparently low, with only a few ash puffs from NEC. At 0240 on 23 February red glows resumed at NEC and continued through sunrise. Red glow resumed at 1820, alternating between a few tens of minutes of strong activity and longer periods of reduced activity. The same phenomena occurred the following night but poor visibility prevented good observations.

Good visibility on the night of 24-25 February permitted detailed observations of the Strombolian activity at NEC. It was continuous all night and produced by two vents; the rate of explosions ranged between 1 and 5/minute, and ejecta rose to a maximum of 150 m above the crater. During daytime no evidence of this activity was recognizable from the surveillance camera, but the next night (25-26 February) the two vents were often active simultaneously and their frequency of explosions exceeded 5/minute; moreover, the strong explosions at the start of each higher intensity phase threw bombs up to 300 m above the crater.

Poor weather conditions after the morning of 26 February prevented regular observations. Decreasing tremor amplitude in late February suggested that the period of quasi-continuous Strombolian activity at NEC ended during daylight on 27 February.

Information Contacts: Mauro Coltelli, CNR Istituto Internazionale di Vulcanologia (IIV), Piazza Roma 2, Catania, Italy (URL: http://www.ingv.it/en/).

March 1996 (BGVN 21:03) Cite this Report

Intermittent ash emissions and Strombolian activity from two summit craters

Adverse weather conditions that prevented observation of the summit in late February (BGVN 21:02) continued throughout March. Ash puffs from Bocca Nuova crater (BN) were seen during some clear periods on 1 and 5 March, and on the morning of 6 March several black ash emissions were observed. Between 1200 and 1300 a sequence of ash puffs was produced from Northeast Crater (NEC). At 1530, another dense black ash puff was emitted from BN. At sunset the snow mantle was discontinuously covered by a thin ash layer. Ash emissions were again observed during some clearings on 7 March.

On 11 March around 2300 a one-hour long increase in tremor amplitude was recorded at the summit stations. During the afternoon of 12 March the weather improved and after sunset pulsating red glows were observed above NEC by the surveillance camera. Glow produced by the Strombolian activity after 1730 was almost continuous until changing to pulses at 1840 and disappearing at 2100. At the climax, red tracks of volcanic bombs were recognizable up to 150 m above the crater rim. The eruptive episode was marked by increased seismic tremor amplitude similar to that of the previous night.

On the morning of 14 March weather conditions became worse and the video link was interrupted. The video link was restored on 21 March and some minor ash emissions were observed. The observations by the video camera remained intermittent due to the poor weather. Around 2000 on 30 March a remarkable increase in low-frequency events and explosion earthquakes was recorded at all stations of the seismic network; poor weather prevented visual confirmation. The phenomena continued until 2100 on 31 March and during the daytime strong pulsing steam emissions, sometimes with ash, were observed at NEC and BN.

Strombolian activity that began the day after the eighth fire fountaining episode (9-10 February) continued in April, building several nested spatter and scoria cones on the NEC floor; these rose as high as the crater rim.

Information Contacts: Mauro Coltelli, CNR Istituto Internazionale di Vulcanologia (IIV), Piazza Roma 2, Catania, Italy (URL: http://www.ingv.it/en/).

June 1996 (BGVN 21:06) Cite this Report

Crater glow, gas emissions, and mild Strombolian eruptions

Visiting scientists made observations of eruptive activity during late May and June. The observations revealed continued activity similar to that previously described for this eruptive phase (BGVN 20:06-20:11/12 and 21:02-20:03).

Observations during 26 May-3 June. Activity at the summit craters was described by Marco Fulle following visits on 26 and 30-31 May and on 1 and 3 June.

Bocca Nuova was filled by thick steam on the afternoon of 26 May, but there were many strong explosions. A vent on the SE side of the crater was emitting steam jets. A vent with a lava pond on the crater floor was ejecting meter-sized lava clots 20 m high. When the pond level was close to the bottom, Strombolian explosions rose 50 m. Northeast Crater (NEC) erupted thin ash and black bombs, but later produced Strombolian explosions every 10-50 seconds that sent a few bombs 50 m above the rim directed towards the E. No bombs fell outside the crater.

Observations of NEC beginning in the late afternoon of 30 May were made for 18 hours from Pizzi Deneri and the W rim of NEC. Strombolian explosions ejected black bombs 100-200 m above the rim at 1-40 second intervals. On the morning of 31 May many meter-sized incandescent bombs were ejected well beyond the SW crater rim due to a strong wind. After 30 minutes, this activity changed to predominantly ash eruptions. Eruption intensity soon increased again, ejecting lava clots and dark bombs well above the rim.

For two hours on the evening o f 1 June observers watched from the W rim of Bocca Nuova and Voragine. Bocca Nuova contained two vents with active lava ponds aligned N-S. The N vent produced Strombolian explosions 50 m high every 10-30 minutes. The S vent produced Strombolian explosions 10-30 m high every 5-20 seconds. A third vent in the SE side of the crater produced steam eruptions every 2-10 minutes with red glow during the steam ejections. Voragine produced steam jets when NEC was inactive. During five hours of observations at NEC from the W rim on 3 June, Strombolian explosions every 2-50 seconds rose 100-200 m.

Observations during 1-20 June. While making GPS measurement of a deformation network on the volcano's upper S flanks on 1-20 June, J.L. Moss and co-workers observed summit activity.

During 1-5 June, no explosions or ash clouds were observed, but the summit vents were vigorously steaming. On 6 June, local guides reported explosive activity at NEC. On 9 June steam degassed strongly from the summit craters, and yellowish fumes escaped from Southeast Crater.

On the night of 10 June Bocca Nuova exhibited two strongly glowing vents on the crater floor, each producing mild Strombolian explosions every 5-10 seconds and ejecting material to heights of a few meters. Larger explosions took place about every minute, but no material was ejected above the crater rim. At La Voragine crater (the Chasm), a single glowing vent on the crater floor produced mild, audible, Strombolian explosions every 5-30 seconds that ejected material a few meters high.

At NEC Moss's group felt radiant heat and saw intense heat shimmering above radial fractures around the crater rim. Very strong gas emissions prompted them to wear gas masks. The crater was filled with dark (non-glowing) solidified lava; it formed a fractured dome from which a dense gas/water mixture escaped. No Strombolian activity was observed.

During 13-17 June, loud explosions were heard in the Valle del Bove, up to 3 km from the summit. Black ash clouds periodically rose 100 m above NEC.

Information Contacts: Marco Fulle, Osservatorio Astronomico, Via Tiepolo 11, I-34131 Trieste, Italy; J.L. Moss, Centre for Volcanic Research, Cheltenham & Gloucester College, Francis Close Hall, Swindon Road, Cheltenham GL50 4AZ, United Kingdom; S.J. Saunders and V.A. Buck, Brunel University, Department of Geography & Earth Science, Borough Road, Isleworth, Middlesex TW7 5DU, United Kingdom.

July 1996 (BGVN 21:07) Cite this Report

Crater glows, Strombolian eruptions, and two fire fountaining episodes

During June eruptive activity was very strong. Two episodes of fire fountaining occurred at Northeast Crater (NEC), the first on 6 June and the second on 25 June.

On 2-3 June there were many Strombolian explosions at NEC. After two days of quiescence, the 9th episode of fire fountaining since November 1995 was recorded at 2015-2110 on 6 June by the seismic network and surveillance video camera. Poor weather conditions prohibited clear observations. Volcanic tremors increased after 0550 on 6 June, with tremor amplitude reaching a maximum at 1944 and returning to normal around 2300. Lapilli and ash dispersed NW up to a few kilometers from the vent (figure 64).

Figure 64. Areas covered by lapilli and ashfall deposits formed by the 9th (6 June) and 10th (25 June) lava fountaining episodes. Coordinates are UTM. Courtesy of IIV.

Red glow appeared above NEC around midnight on 7 June. From 0200 to 0400 on 8 June, there were almost continuous strong Strombolian eruptions. Between 2240 on 8 June and 0355 on 9 June, and on the evening of 9 June (2020-2200), the "La Montagnola" surveillance video camera recorded red glow above NEC and weak Strombolian activity inside the crater. On the nights of 10 and 11 June, red glows lasted a few minutes. During 0400-1200 on 12 June, ash explosions took place at NEC at intervals of 10-20 minutes. On the early morning of 13 June Strombolian activity at NEC resumed for ~20 minutes, and during 1755-1900 on 13 June there was almost continuous ash emission. The video camera system was not operational during 14-17 June. Explosions took place at NEC during 2317-2350 on 17 June, and during 0004-0300 on 18 June strong and continuous Strombolian activity was recorded. From 18 to 24 June Strombolian activity was low and sporadic.

At 2347 on 25 June, the 10th episode of fire fountaining began. The paroxysmal phase lasted for 35 minutes (0015 to 0050), and at 0055 on 26 June the episode ended. The fire fountains rose ~300 m, and a column of lapilli and ash reached several kilometers above the summit. The lapilli fell on the NE flank of the volcano (figure 64) and extended as far as Taormina, 28 km from the vent. Ashfall was also observed in Messina, 70 km away. An increase of volcanic tremors with oscillation of amplitude was recorded after 2200 on 24 June. The maximum amplitude of volcanic tremors was reached at 2230 on 25 June and lasted for more than one hour.

After the 10th eruptive episode, NEC remained quiescent until the morning of 28 June. At around 1700 that day, strong ash explosions opened a new vent on the W side of the crater floor that had been sealed by fire-fountain spatter. In the last week of June, Strombolian activity also resumed at Bocca Nuova crater (BN). Several red bombs were thrown up to the crater rim.

Beginning on 2 July, the surveillance camera recorded continuous red glow during all the nights in July, indicating persistent Strombolian activity inside NEC. During the first ten days of July, explosive activity at NEC was relatively low, then gradually increased and became vigorous on the early morning of the 14th. On 16 July Strombolian activity abruptly decreased. The next day several black ash puffs were observed, eruption intensity increased again, and a second vent inside the crater began to erupt. During 18-20 July, Strombolian activity was very strong and the magma level inside the vents was high. Jets of magma rising up to 200 m resulted in the fast growth of two cinder cones.

Two eruptive fissures formed on the W and S flanks of the cone at NEC on the morning of 21 July. The fissure on the W flank (N70°W, 40 m long, ~3,220 m elevation) issued a lava flow that was active until that afternoon and produced a small lava tongue, which was 100 m long, 10 m wide, and 2 m thick. The W lava flow continued until 22 July. A lava flow from the S fissure moved on the flank of NEC that borders the Voragine crater at ~3,230 m elevation.

On the morning of 23 July, lava spilled from an ephemeral vent on the lowest portion of the E rim at NEC (at an elevation of ~3,250 m). The vent drained a crusted lava flow field that had formed in the previous days and covered the E side of the crater floor. The lava overflow traveled E for more than 1 km inside the Valle del Bove, and its front reached an elevation of ~2,650 m, above the hornitos chain from the 1986 eruption. Close to the vent, the lava flow was ~2 m deep and ~1 m wide, but at a few tens of meters away from the vent, it was up to 10 m in width. On the morning of 25 July, a preliminary estimate of the lava output rate was 0.3 m³/s. Direct thermocouple measurements of the lava flow temperature gave a maximum value of 1,080°C. On 28 July the lava issuing from the E side of NEC crater rim stopped, resumed a few hours later, then stopped on the morning of 29 July.

The lava erupting inside the Voragine crater stopped on the morning of 30 July, and resumed a few hours later. On 31 July the lava flow and gas emission continued, and lava filled the degassing vent of the Voragine crater at a rate of ~0.5 m³/s.

On 1 August eruptive activity increased very quickly, and on the night of 3 August three lava flows poured from the NEC crater rim and moved down the E slope of the summit cone into the Valle del Bove. Explosive activity continued at NEC and threw large bombs up to 300 m above the crater rim.

Information Contacts: Mauro Coltelli and Paola Del Carlo, CNR Istituto Internazionale di Vulcanologia (IIV), Piazza Roma 2, Catania, Italy (URL: http://www.ingv.it/en/).

October 1996 (BGVN 21:10) Cite this Report

Southeast Crater resumes activity after five-years

The following summarizes the monthly reports of the Istituto Internazionale di Vulcanologia (IIV) for the period August-7 November 1996.

Activity during August. Strombolian activity continued from two vents in the cinder cone on the W border of the Northeast Crater (NEC) rim. There were almost continuous explosions; bombs and lapilli were thrown up to several tens of meters above the crater rim. Lava flowed from the NEC effusive vent on the S flank down into Voragine crater.

On 3 August an ash emission lasted three hours and three lava flows produced by ephemeral vents on the E rim of NEC moved toward the Valle del Bove. Activity increased on 4 August at 2045 and continued until the morning of 8 August without interruption. During these days explosions were heard in the villages Zafferana Etnea and Nicolosi (15 and 10 km from NEC, respectively). Three to four new vents emerged; they were aligned roughly N-S, produced Strombolian explosions, and modified the shape of the cinder cone from circular to elliptical.

Activity increased again on the morning of 14 August when several blasts from the middle flank of the volcano were heard. Two vents erupted together throwing lapilli and bombs up to 300 m above the NEC. An aa lava flow from the E slope of the cone moved into Valle del Bove, and sudden high lava jets were observed at the vent in front of the Voragine crater.

On 15 August some ash emissions occurred, and red glow was observed continuously during 15 and 16 August. During the night of 16-17 August the Strombolian activity suddenly decreased. On 17 August a few explosions ejected both incandescent and dark material. During the night of 17-18 August the lava flow in Valle del Bove stopped. On 19 August the lava flow in the Voragine also stopped and overall there was no eruptive activity. Poor weather conditions prevented clear observations.

On 21 August from 1040 to 1130 small Strombolian explosions occurred at NEC. On 28 August from 0700 to 1230 several ash explosions coincided with collapse of the cinder cone inside the NEC.

Activity at Bocca Nuova crater was characterized by mild and discontinuous Strombolian eruptions from vents in the N part of the crater floor. The other two summit craters, Southeast Crater and Voragine, produced only steam emissions. Although the degassing vent in the Voragine crater was filled almost continuously by lava from 21 July to 19 August, it remained open and degassing for the whole period.

Activity during September-October. Gas and steam were continuously emitted from the summit craters during September. On 17 September at 2100, weak Strombolian activity was observed at NEC for one hour.

On 1 October at 2100 Strombolian activity resumed at NEC with an explosive sequence. Initially the explosions occurred every 5 minutes; from 2230 the glow of the explosions became continuous and stronger, lasting all through the night. During the daylight of 2 October, puffs of black ash were observed until midday. Bad weather condition prevented observation for some days, and when the summit craters became visible they emitted only gas and steam.

Another short period of Strombolian activity occurred during 13-14 October, beginning around 1200 on 13 October with several small black ash puffs every 10-20 minutes. Weak red glows observed at night on NEC indicated low Strombolian activity. The following morning ash puffs were still emitted at NEC; eventually during the day the ash emissions became less frequent and then disappeared.

On 18 October a single ash explosion occurred and on 20 and 23 October several ash puffs were noted. These explosions opened a large pit crater on the E side of the intracrater cinder cone built during the strong eruptive activity of July and August.

On the N floor of Bocca Nuova (BN) during October, an incandescent hole produced sporadic weak Strombolian activity. The occurrence of ash in the plume after 24 October marked an increase in explosivity. Voragine had no eruptive activity in October; only quiet steam emission and some puffing were observed at the large hole on the lower part of the crater floor.

Activity during 1-7 November. On 2 November some intense red flashes were reported from BN and NEC at 0045; within the next 20 minutes larger explosions produced stronger glows at BN. Strombolian emissions at BN resumed during 0125-0130 and during 0205-0210, but ejecta reamined within the crater and minor emissions continued until 6 November when one ash puff reached 1 km above the summit. The emission came from an old degassing vent located on the inner wall, on the SE side of the crater. The associated explosion enlarged the vent and caused debris from the inner walls to cover a wide portion of the S crater bottom. A few small lava blocks fell on the S crater rim and a brown, totally non-juvenile ash deposit covered the E sector of the summit cone of the volcano down to a few km from the crater.

These events preceeded the resumption of activity at Southeast Crater (SEC), ending five years of complete inactivity (quiet since Autumn 1991, shortly before the beginning of 1991-93 eruption). On 6 November, after the large phreatic explosion at BN, very low Strombolian activity was reported from two vents on the floor of SEC. The close temporal occurrence of these phenomena and the alignment of the Strombolian vent of BN, the phreatic vent of BN, and the Strombolian vent of SEC, suggested that a very shallow magma intrusion moved from BN toward SEC and triggered its Strombolian activity. However, such interplay is normal among the Etna summit craters when the magma level reaches a very shallow depth. During the evening of 6 November some very low glows were observed above the SEC. In the following days SEC eruptive activity remained at very low levels of intensity.

Overflights of the summit craters on 5, 6, and 7 November confirmed that Strombolian activity occurred at BN almost continuously from one or more closely spaced vents on the top of the intracrater cone.

Information Contacts: Mauro Coltelli and Paola Del Carlo, CNR Istituto Internazionale di Vulcanologia, Piazza Roma 2 Catania Italy (URL: http://www.ingv.it/en/).

February 1997 (BGVN 22:02) Cite this Report

Summary of activity since November 1996

The following summarizes the activity observed at Etna from November 1996 through March 1997.

Activity during November 1996. On 2 November both Bocca Nuova (BN) and Northeast Crater (NEC) produced Strombolian activity lasting all night. On 6 November an old degassing vent on the inner wall on the SE side of the crater emitted one ash puff that reached 1 km in height. The associated explosion enlarged the vent and caused debris from the inner walls to cover a wide portion of the S crater bottom. A few small lava blocks fell on the S crater rim and a brown, totally non-juvenile ash deposit covered the E sector of Etna's summit a few kilometers down from the crater. The same day Southeast Crater (SEC), quiet since Autumn 1991, began very low Strombolian activity from two vents on its floor. During the evening of 6 November glow was seen above the SEC, but in the following days eruptive activity remained very low.

Overflights on 5-7 November confirmed that Strombolian activity occurred at BN almost continuously from one or more closely spaced vents on the intracrater cone. Besides almost continuous ash puffs produced on 10 and 11 November at BN, there were two large ash explosions on 16 and 18 November.

The surveillance video camera captured intervals of night glows over NEC (from 0110 to 0130 on 23 November; from 1812 to 2100 on 24 November; and for a half-hour during the night of 27-28 November). At SEC between 23 and 28 November weak Strombolian activity occurred sporadically. BN produced several discrete Strombolian explosions from 2005 to 2140 on 28 November.

Activity during December 1996. The summit craters erupted infrequently in the first half of December and more frequently in the second half. On 15 December Strombolian activity was reported at both craters during 2340-0200. At NEC episodes of Strombolian activity occurred on 17 December (1730-2140), 18 December (0150-0438, 1830-0045), 19 December (1740-1747, 2125-2215), and 21 December (0400-0540, 1730-1800).

During the morning of 16 December some ash explosions occurred at BN; in the morning of 19 December there was both an ash plume and ash puffs. A small wall collapsed on 21 December at BN's S vent adding particulate to the summit plume.

Between 22 and 24 December some short periods of Strombolian activity were recorded at both NEC and BN. At SEC during December there were no available video records; however, direct observations revealed only very weak and discontinuous activity.

Activity during January 1997. BN's Strombolian activity was reported at multiple times: 1800-2100 on 7 January; 2348-0102 beginning on 9 January; during several ~1-hour intervals, 11-13 January; and as weak, continuous activity, 14-24 January. More episodes occurred at 1940-2130 on 27 January; at 0800- 1400 on 29 January; at 0800-0900 on 30 January; and at 0400-0500 on 31 January.

NEC's Strombolian activity took place at these times: 2000-2100 on 7 January; several ~1-hour episodes between 11-13 January; and sporadic weak episodes, 20-22 January. Later, from 25 January until the end of the month, the eruptive vigor rose; ash emissions occurred during 0800-1400 on 29 January and eruptions could be watched from a distance from sunset until 2200 on 30 January.

On 25 January, at 1920 SEC began one hour of very weak Strombolian activity. The activity of SEC had formed a small cinder cone inside the crater and some short fan-shaped aa lava flows departing from the cone.

Activity during February-5 March 1997. The first half of February was characterized by the continuous emission of ash from BN; bomb and lapilli ejections inside the crater were reported on 11 February. There was strong degassing from NEC but weak emissions from Voragine Crater. Inside SEC the small cinder cone spattered continuously, though weakly. During the second half of February both BN and NEC plumes frequently contained ash.

A field survey on 5 March revealed that some cinder cones formed in BN. One of these cones threw bombs up to the crater rim and a vent in the SE part of the crater gave off strong emissions of gas and red ash. Fresh lava tongues were identified on 5 March at the W edge of the SEC cinder cone. A later image of SEC (11 March) is shown in figure 65. Voragine crater only degassed whereas NEC collapsed slightly as indicated by minor debris in the crater.

Figure 65. Aerial view of SEC on 11 March 1997 showing the intracrater cinder cone and the small lava flow first seen on 5 March. Photo by A. Amantia; provided courtesy of CNR-Istituto Internazionale di Vulcanologia.

Information Contacts: Mauro Coltelli and Paola Del Carlo, CNR Istituto Internazionale di Vulcanologia, Piazza Roma 2, Catania, Italy (URL: http://www.ingv.it/en/).

May 1997 (BGVN 22:05) Cite this Report

New map of the craters Voragine and Bocca Nuova

A map prepared from observations carried out on 11 April of Voragine and Bocca Nuova craters is presented in figure 66. The position and altitude of the points shown by stars were measured with ranging binoculars (model 1500 DAES; on loan courtesy Leica-France) from two observation points (circles) on the rim of the craters. Photos of the crater interior were also used to draw the map.

Figure 66. Map of the Etna craters prepared using LEICA binoculars. Courtesy of P. Briole, O. Consoli, C. Deplus, and J-L. Froger, IPGP.

Bocca Nuova crater measured ~170 m deep and had two active cones on the crater floor. The N cone, 25 m above the crater floor, was the most active. Its Strombolian activity threw ejecta close to Monumento, a spot on the crater's N rim. The S cone, 35-40 m above the crater floor, appeared composed of two coalescent cones, and was less active then the N one.

The depth of the Voragine crater measured ~150 m. Quiet steam emission was observed escaping from the large hole on the lower part of the crater floor.

Information Contacts: Pierre Briole, Orazio Consoli, Christine Deplus, and Jean-Luc Froger, Institut de Physique du Globe de Paris, Case 89, 4 place Jussieu, 75252 Paris Cedex 05, France.

June 1997 (BGVN 22:06) Cite this Report

Summary of April-June 1997 activity

During April the mild Strombolian activity of Southeast Crater (SEC) continued at the same level as in previous months (BGVN 22:02). Every night the surveillance video camera at "La Montagnola" recorded episodes of Strombolian activity that lasted from a few minutes to an hour, with some isolated explosions. Direct observations on 11 April revealed that the small SEC cinder cone had changed its shape and was still producing new lava flows from the breaks on its flanks. Strombolian activity occurred also at Bocca Nuova (BN) with spattering as high as the crater rim. On the N side of the crater floor a cone was spattering from one of its numerous vents. On the SE side a new vent opened near an older one; both were strongly degassing and mildly spattering. Strong degassing was observed both at Voragine and Northeast Crater (NEC). In addition, the collapse of NEC's floor was indicated by debris in the crater. Field surveys during the second half of April revealed no variations in the volcanic activity or in the craters' appearance.

During May, Strombolian activity at the N and S vents of BN varied daily in intensity from low-level degassing and minor eruptive activity to magma boiling on the crater floor and almost continuous Strombolian explosions. Volcanic bombs were thrown as high as the crater rim, but none fell out of the crater. SEC continued to produce minor, almost continuous gas explosions and some spattering from the dome-shaped cone. Lava emissions generally lasted for a few hours. This hornito-style activity was eventually interrupted by sudden vigorous explosions caused by temporary blockage of the conduit. Examination of bombs and lava blocks that had fallen beyond the SEC rim confirmed that the magma was more crystal-rich and viscous compared to the scoriaceous material erupted by BN. No explosive activity was reported at NEC except a few small brown ash emissions, probably caused by collapse of the degassing vent's walls. Enlargement of the pit-shaped vent was seen during a survey with a Civil Protection helicopter.

During June the explosive activity gradually increased at both BN and SEC. In particular SEC's hornito-style activity was frequently interrupted by intense explosions, but there was no appreciable variation in lava emission. BN activity remained within the crater boundaries with minor lava flows; eventually bombs thrown out of the crater fell on the cone's upper N slope.

Information Contacts: Mauro Coltelli and Paola Del Carlo, CNR Istituto Internazionale di Vulcanologia, Piazza Roma 2, Catania, Italy (URL: http://www.ingv.it/en/).

July 1997 (BGVN 22:07) Cite this Report

Continued activity from three craters through mid-July; crater descriptions

The following summarizes observations, organized by crater (figure 67), made by Boris Behncke of the activity and morphology of Etna's summit craters during visits on 14 June, 11 July, and 16 July 1997. Additional observations of activity through 18 July are reported.

Figure 67. Sketch map of Etna's summit craters as of July 1997. Locations of eruptive vents and recent lava flows are indicated. Courtesy of Boris Behncke.

Voragine. This crater was degassing from a central pit during visits in October 1995 and September 1996. Lava effusion from nearby Northeast Crater into Voragine in July-August 1996 did not fill the pit. However, during 14 June the pit was obstructed, with only wisps of steam escaping from its E rim. The 1996 lava flows from Northeast Crater had been almost completely removed by collapse. On 13 July the crater reopened. Mountain guides reported ejections of ash and possibly fresh scoria.

Northeast Crater. After the activity of late 1995 to late 1996, Northeast Crater became Etna's highest summit, surpassing the remains of a 1964 cone on the SE rim of Bocca Nuova. The 1995-96 activity and subsequent collapse completely altered the crater, which had a deep pit with vertical walls in early October 1995. The SW part of the crater contained a cluster of small cones and partially overlapping craters; none were active on 14 June. The N part of the crater was occupied by a lava platform which filled the crater in June-July 1996. The W edge of this platform was made of large tilted slabs. A lower platform covered by a lava flow from the cone cluster partially encircled a deep ~100-m-wide pit that was the site of Strombolian activity. Loud roaring from the pit on 14 June preceded emissions of dense yellowish ash-bearing gas plumes at intervals of 1-2 minutes. Activity on 11 July (when viewed from Bocca Nuova) appeared similar; there were no incandescent ejections after sunset.

Bocca Nuova. Since the resumption of magmatic activity in July 1995, two principal eruptive centers have been active in the ~150-m-deep pit: one vent at the base of the SE crater wall, and a group of vents in the NW sector of the crater. The former only emitted gas during the past two years; the latter exhibited periodic Strombolian activity and lava effusion. On 14 June the SE vent had Strombolian explosions every 10-15 minutes, with fragments rising 50-70 m; on 11 July explosions reached the crater rim (>100 m above the vent) and fresh bombs were found to the SE outside of the crater. The NW vent cluster consisted of three boccas aligned NW-SE on 14 June that generated nearly continuous small Strombolian bursts and lava emission from an area to their E. At times the northern vent filled with bubbling lava. On 11 July three vents were aligned E-W; lava effusion occurred from vents to their E or SE.

During a visit on 16 July, a large spatter cone with a crater 20-30 m wide had formed in the NW area of activity, where there had been three small vents only five days earlier. The crater of this new cone was filled with vigorously boiling and spattering lava. Explosions from the SE eruptive vent occurred about every 3-5 minutes, at times ejecting bombs high above the SE rim (~150 m above the vent). Similar activity continued through 18 July.

Southeast Crater (SEC). On 14 June noises characteristic of Strombolian activity were heard ~2 km S of the crater, but no ejections rose above the crater rim. Daily observations from Catania (~30 km S of the summit) began on 7 July, coinciding with a slight intensification of activity from SEC. At night, nearly continuous Strombolian bursts were visible. During the following evenings activity appeared more discontinuous, with periods of activity up to 20 minutes separated by up to several hours. A visit to the crater on the evening of 11 July found that a cinder cone in the N part of SEC had almost risen as high as the crater rim. Strombolian activity, in cycles lasting ~15-20 minutes separated by intervals up to 20 minutes, sent bursts as high as 150 m above the vent. An incandescent lava flow from a vent ~20 m below the cone's summit moved down the S flank of the cone, extending ~200 m to the S base of the inner wall of SEC. Slightly older flows around the active lobe still had incandescent spots. Despite the episodic explosive activity, effusive activity appeared reasonably constant. Night observations from Catania during the following days disclosed continuing explosive activity from SEC.

The floor of Southeast Crater, gradually being filled by a growing cone and lava flows, had risen to within <10 m of a low point on the SE crater rim by 16 July. As of 18 July the cone in SEC's N half was as high as the crater rim (~50-70 m above the lowest part of the crater floor). Lava flows issued more or less continuously from boccas on the upper S and SE flanks of the cone, forming a complex lava field to the S, SE, and E. At night, explosive activity from the cone's summit is visible from Catania.

Information Contacts: Boris Behncke, Istituto di Geologia e Geofisica, Palazzo delle Scienze, Corso Italia 55, 95129 Catania, Italy.

August 1997 (BGVN 22:08) Cite this Report

Strombolian activity and lava overflows; all four summit craters active

The following report, jointly submitted by scientists from the Università di Catania and the Istituto Internazionale di Vulcanologia, expands on information from the first half of July (BGVN 22:07) and adds observations of activity at each crater through the end of the month. A review of the eruption since July 1995 places the current activity into context. Between 19 and 31 July, moderate eruptive activity continued from the summit craters, including occasional small overflows from Southeast Crater (SEC). Magmatic activity began at the Voragine in mid-July, followed by continuous Strombolian activity from a central pit in Northeast Crater (NEC) at the end of July (after about eight months of relative quiet). A visit on 5 August revealed magmatic activity from all four summit craters (figure 68).

Figure 68. Sketch map of Etna's summit craters as of late July 1997, showing vents active in 1996-97. For Bocca Nuova, locations A and B indicate eruptive centers. Numbered features in Northeast Crater identify: 1) the cluster of cones and craters active in July-August 1996 (the two westernmost craterlets are collapse structures formed after that activity); 2) tilted slabs of lava and agglutinate; 3) the outer platform; 4) the inner platform covered by lava flows from the cones; and 5) a collapse pit over the central conduit. Courtesy of Boris Behncke and IIV.

Review of activity since July 1995. Magmatic activity resumed in Etna's summit craters in July 1995, more than two years after the end of the voluminous 1991-93 E-flank eruption in Valle del Bove. Initially this activity was limited to Bocca Nuova (BN), the westernmost of Etna's four summit craters, but it soon extended to nearby NEC. During November 1995-August 1996, NEC was the site of spectacular explosive and effusive activity, including ten episodes of high lava fountaining (BGVN 20:11/12, 21:02, 21:03, 21:06, 21:07, and 21:10), while BN continued to emit pyroclastics and small intracrateral lava flows on a moderate scale. In early November 1996, magmatic activity resumed at SEC, which had been inactive since late 1991 (BGVN 21:10). SEC activity was initially very mild, gradually building a small intracrateral cone. In late January 1997 it began to emit minor lava flows that were confined to the ~200-m-wide crater. Activity at SEC and BN continued through late June 1997 without major modifications. Etna's fourth summit crater, Voragine (also known as The Chasm), has been actively degassing from a pit on its floor without the emission of any juvenile material in past years.

Voragine. The central degassing pit was obstructed by talus on 14 June, with only minor wisps of steam escaping from the pit's rims. Apparently, a lava flow erupted into the Voragine from NEC in July- August 1996 had partially collapsed, covering the pit. On the evening of 13 July 1997 dense gas clouds possibly containing some ash were seen rising from the Voragine for about 15 minutes. On 18 July, the Voragine was found in a state similar to previous years, but the day after, fluid lava had risen to the lip of the central pit. A small cone (~5 m high) began to grow over the former pit on 24 July; this cone was the site of mild but continuous Strombolian activity, throwing incandescent bombs to several tens of meters above the vent. Similar activity continued through 28 July, but a visit to the crater on the following day revealed that eruptive activity had stopped and only weak steaming occurred from the new conelet.

Northeast Crater (NEC). The intense activity of 1995-96 and subsequent collapse completely altered the morphology of NEC, which was a single deep pit until early November 1995. The WSW part of the crater was occupied in July by a cluster of partially overlapping craters and small cones, some being minor collapse features (figure 68, number 1). The northern part of NEC contained an outer platform ~30-50 m wide (figure 68, number 3) of agglutinate that filled the crater in June-July 1996. The W edge of the platform was marked by large craggy slabs of lava (figure 68, number 2), which were tilted upwards as the lava fill subsided. A lower inner platform in the central northern part of NEC (figure 68, number 4) was covered by late lava flows erupted from the cone cluster. In the southern central part of the crater there was a collapse pit (figure 68, number 5) ~100 m across that showed vigorous degassing and possibly deep-seated Strombolian activity. During a 20-minute visit to NEC on 14 June loud roaring noises were followed by pit emissions of dense yellowish gas plumes containing some ash at intervals of 1-2 minutes. On 14 July ash emissions occurred from the crater, a day after similar emissions from the Voragine. During the last week of July, there was a gradual resumption of Strombolian activity, which had become continuous by the 31st. Most of this activity was confined to the pit, but occasional larger explosions ejected incandescent bombs high above the summit of NEC.

Bocca Nuova (BN). Since the resumption of magmatic activity in 1995, two principal eruptive centers have been active in this crater, one at the base of its vertical SE wall (figure 68, location A) and another in the NNW sector of BN (figure 68, location B). Throughout July, Center A consisted of two closely spaced vents that built a large half-cone against the crater wall, ~30 m above the crater floor. While one of the vents at times displayed quasi-continuous small Strombolian bursts, the other produced very violent explosions at intervals ranging from 30 seconds to 5 minutes, often ejecting bombs >150 m above the vent. These explosions were accompanied by detonations that could be heard several kilometers away. During some of the largest explosions bombs fell on the SE rim or outside BN to the S in the area of the former summit crater platform.

Center B had a highly variable number of explosive and effusive vents that formed a complex cone surrounded by a lava field covering almost the entire crater floor. Between early June and about 15 July, Strombolian activity occurred from several closely spaced vents with diameters not exceeding 10 m each while lava issued from vents at some distance from the explosive ones. By 16 July there was one large vent ~30 m across at the top of a broad cone. The vent was filled with vigorously boiling and fountaining lava, with some fountains ejecting spatter as high as the crater rim (~100 m above the vent). By late July, a second cone was growing on the E side of the first one; both exhibited lava splashing and fountaining while lava issued from vents at the base of the cones. The floor of BN underwent repeated and rapid resurfacing during this time and the maximum depth of the crater was 114 m (determined with laser rangefinder) at the end of July.

A 5 August visit revealed four erupting vents, two in the northern eruptive area and two on the half-cone growing in the SE corner of the crater. Bursts of bombs and spatter often rose significantly higher than the crater rim, reaching heights of up to 200 m above the SE vents. Large explosions from these vents at times ejected bombs onto the SE rim of BN and over the S flank of the central cone, making this area very dangerous.

Southeast Crater (SEC). This crater is gradually being filled by the growing intracrateral cone and lava flows, and lava has spilled onto its outer slopes. Explosive and effusive activity occurred at variable intensity from vents varying continuously in size, number, and location. The main focus of activity was at the summit of the cone (~20 m above its N base and ~40 m above its S base) in the central northern part of SEC (figure 69), but effusive activity often took place on the flanks of the cone, either from small hornito-shaped cones or from wedge-shaped purely effusive vents. More rarely, lava flows were directly emitted from the explosive summit vents.

Figure 69. Development of the intracrateral cone and lava flows at Southeast Crater of Etna during July 1997. Active flows are indicated as white areas; recent but inactive flows by a dark pattern. "Fortino" is a small stone shelter built on the highest point of the W crater rim. Courtesy of Boris Behncke and IIV.

Activity increased in early July, and explosions became visible from Catania (~30 km S) at night. During the following days Strombolian activity was discontinuous, occurring in cycles that lasted 10-15 minutes separated by quieter periods of similar duration. Visits to the crater once or twice per week, and helicopter overflights, documented shifts in eruptive vents and development of lava flows (figure 69). By 11 July the level of the intracrateral lava field had risen to within a few meters of the lowest part of the crater rim (on the SE side of SEC; figure 69a); late on 19 July a small lava tongue spilled over the SE crater rim, advancing ~30 m downslope before stopping. On that evening, the intracrateral cone had three explosive vents; the most vigorous one was the lowest and easternmost (figure 69b). Lava issued in surges from that vent, forming a high lava ridge with several steep-sided pinnacles on the SE flank of the cone. A second minor overflow onto the SE flank occurred on 22 July, forming a second lava lobe on top of the first one, but without reaching farther downslope. During the following days, Strombolian activity became continuous.

On 25 July the intracrateral cone had grown by ~10 m since 19 July, and two explosive vents on its summit ejected bombs ~100 m high. Lava effusion from a hollow-shaped vent fed a flow that advanced towards a low point on the NE crater rim (figure 69c). Effusive activity occurred in pulses coinciding with periods of increased explosive activity at the cone's summit. Larger volumes of lava began to spill onto the outer SE flank of SEC on 27 July, forming a black tongue ~150 m long and 50 m wide. On the 29th, lava effusion occurred both on the NE and SE sides of the cone (figure 69d), but the lava field showed little growth because the flows on the SE flank apparently overlapped rather than extended downslope. Continuous explosive activity from a single summit vent ejected bombs ~200 m above the vent, and pyroclastics fell onto the high W rim of SEC, in the area of a small stone shelter ("Fortino" in figure 69d). During the night of 31 July-1 August, another overflow formed a new lava lobe on the N side of the earlier flows, and advanced some 30 m farther downslope.

Activity at SEC on 5 August continued in the same manner as in previous weeks with vigorous explosions at an intracrater cone and lava effusion from its eastern flank. Several small overflows from the SE rim had spilled onto the cone's flank almost every day in early August, and a small overflow had occurred onto the NE flank.

Information Contacts: Boris Behncke, Istituto di Geologia e Geofisica, Palazzo delle Scienze, Università di Catania, Corso Italia 55, 95129 Catania; Mauro Coltelli and Paola del Carlo, Istituto Internazionale di Vulcanologia, Piazza Roma 2, 95123 Catania, Italy (URL: http://www.ingv.it/en/).

September 1998 (BGVN 23:09) Cite this Report

Summary of summit eruptive activity during August 1997-January 1998

The following report summarizes activity observed at each of the four summit craters of Etna from August 1997 through 15 January 1998. Events through 8 January 1998 at Bocca Nuova, Southeast Crater, Northeast Crater, and Voragine are described below separately. A seismic crisis during 9-12 January was followed by a brief decrease in activity at all of the craters. Significant eruptive episodes after mid-January 1998 will be described in future issues.

Information for this report was compiled by Boris Behncke at the University of Catania and published on his internet web site. The compilation was based on personal visits to the summit, telescopic observations from Catania, monitoring of images posted on the internet from the camera maintained by the Istituto Internazionale di Vulcanologia (IIV), and other sources.

Visits to the summit craters in late September and early October 1997 revealed continuing vigorous activity from Bocca Nuova and Southeast Crater while more sporadic activity was occurring at the Voragine and Northeast Crater. This pattern continued through November and December. The overall activity on 8 January 1998 at Bocca Nuova, Northeast Crater, and Voragine was notably diminished; it was the lowest observed in six months.

Activity at Bocca Nuova. During late August, lava ejections from Bocca Nuova (BN) became significantly more vigorous. Both eruptive centers in this crater often ejected lava bombs outside the crater, with many falling on its S rim. Occasional explosions ejected bombs on the lower S flank of the central cone. The number of active vents in Bocca Nuova increased to seven on 28 August, but was down to five just two days later. The bombardment and explosions led to collapse on the E side of Bocca Nuova, lowering the septum between BN and Voragine (informally named "diaframma" among local volcanologists), and eroding the remains of a 1964 cone.

Visits to the summit in late September and early October revealed continuing activity. As of 14 October, Bocca Nuova's activity was gradually increasing, and the crater was being filled in. The northern of its two eruptive centers had a broad cone with a crater 50-100 m wide, which at times was completely filled with fountaining lava. Fountains often sent spatter and bombs high above the rim, and large ejecta fell outside the crater up to 100 m away. Bombs as large as 40 cm in diameter fell onto the area where the best views of the erupting cone in BN are obtained. Explosions in the SE eruptive center at times sent pyroclastic material all over the S flank of Etna's summit cone.

On 6 November the northern eruptive center was vigorously active. The cone at that site had grown to ~50 m below the NW crater rim. The SE eruptive center was much less violent than in previous months; on the crater wall above it a large overhanging hollow had been carved out by explosions. On the evening of 6 November, Strombolian explosions occurred at intervals of 1-5 seconds, with some jets rising up to 200 m above the cone's summit. An episode of spectacular lava fountaining from BN occurred on 25 November when huge bursts of incandescent bombs developed into a continuous fountain from the SE eruptive center. On 28 November the clouds over the mountain cleared, permitting the view of a huge vapor column rising almost vertically to about 1,500 m above the summit. This unusually large plume was due to an approaching cold front that led to increased condensation.

Explosive activity and gas emissions within BN accompanied a lava flow from Southeast Crater during 9-11 December. Intermittent activity on 12 December, stronger than during the previous 17 days, ejected high bursts of incandescent bombs from BN's southeastern vents. Activity through 15 December was very vigorous, and eruptions continued through 21 December. Glow was visible above BN's two eruptive centers on 26 December and over the E part of the crater on 31 December.

On the evening of 7 January, several jets of incandescent bombs rose over the SE crater lip, and a few bombs fell onto the remains of the 1964 cone. As of 8 January the large cone in the N part of the crater floor had partially collapsed, creating a crater ~150 m in diameter. Frequent rockfalls occurred within this crater. Subsidence of the cone and the adjacent crater floor had created a set of circumferential fractures several meters wide. The most recent activity at this eruptive center appears to have been the extrusion of a lava flow that covered the E and SE sides of the BN floor. The vents at the SE eruptive center were the site of weak Strombolian explosions every 10-15 minutes. Most, if not all, activity occurred from the lowermost vent in the SW part of the eruptive center. A complex cone around these vents had grown notably since the visit on 6 November 1997, with the rim of the highest vent being at about the same elevation as the N rim of Bocca Nuova. Large parts of the crater wall above the SE eruptive center had collapsed, probably before the most recent cone growth (all collapse debris was buried).

Activity at Southeast Crater. Strombolian and effusive activity continued from Southeast Crater (SEC), whose intracrater cone could be seen on 1 September through a gap in the NE crater rim from coastal areas to the E. During a visit on 30 August, lava fountains rose up to 150 m above the cone, and three vents were active. There had been significant infilling of the deep southern part of SEC since effusive activity shifted to the cone's NW flank sometime before 11 August. Before then, lava had repeatedly spilled onto the SE flank of the cone.

Visits to the summit craters in late September and early October revealed continuing vigorous activity. While effusive vents were active on the W base of the cone from 10 August to mid-September, lava again issued from E-flank vents in late September, causing renewed overflows onto the outer SW flank of the cone. By mid-October the cone within SEC had grown to about the height of the highest point on the crater rim. Explosive activity was the same as during previous months, and lava effusion continued from the flanks of the cone.

At dusk on 2 November there were continuous Strombolian bursts from SEC. A visit on 6 November revealed very weak and erratic Strombolian activity. For the first time in many months there was no lava effusion at SEC, although guides at Torre del Filosofo reported that a small lava flow had spilled over the low SE rim of the crater three days earlier. After sunset on 6 November, Strombolian bursts from SEC could be seen from Catania (Palazzo delle Scienze).

Telescope observations from the roof of the Palazzo delle Scienze in Catania on 3-4 December revealed vigorous Strombolian activity at SEC and significant growth of its central conelet, which stood much higher than the surrounding crater rims. Activity on the evening of 5 December was documented with the IIV camera until bad weather hid the summit. At dusk, activity at SEC increased, and strong explosions heralded lava emission to the NE side of the intracrater cone. A more significant lava flow was erupted from SEC on the late afternoon of 9 December, accompanied by vigorous explosive activity at the intracrater cone and within Bocca Nuova. The SEC lava flow overrode previous flows on the SE flank of the cone.

The 9 December lava flow was visible on 11 December, contrasting against freshly fallen snow. Seen from Palazzo delle Scienze, this flow extended much farther downslope than previous flows on the SE flank of the cone, but its front was still several hundred meters from the steep W flank of Valle del Bove. The flow had apparently stopped (no steam was visible at the contact of the lava with the snow). Two smaller lava lobes were erupted onto the SE flank of SEC's cone, about two-thirds of the way down the cone's flank. The active central cone appeared to have lost some height during the strong explosions; Strombolian activity was still vigorous and at times accompanied by weak ash emissions. Vigorous activity at SEC, with some large explosions, continued during 12-15 December, with lava flows spilling over the SE rim and some SE-flank lava extending far beyond the base of the cone. The new flow passed only about 600 meters NE from the Torre del Filosofo mountain hut, ~1 km from SEC. As of 17 December the lava flows erupted from SEC during the previous few days were still confined to the SE flank of the cone. None of the new flows had extended as far as those on 9 and 12-13 December. Over 20-21 December, nearly continuous explosive activity at the SEC intracrater cone sent lava onto its SE and SSE flanks. The cone regained the height lost after 5 December. A 22 December afternoon episode of vigorous lava fountaining as high as 200 m from SEC lasted about 1 hour. A lava flow erupted onto the SE flank of SEC appeared to be no longer than ~200 m.

Activity at SEC in late December and early January was spectacular. On 25 December, continuous Strombolian activity occurred from the central conelet and lava flowed down the SE flank to its base, covering previous flows. Three active lava flows were visible on the SE flank on the 26th. Sometime between early 29 and early 30 December, more lava flows spilled down the S flank of SEC, and a peculiar flow moved down on the SW flank, bifurcating on the lower slope. On the evening of the 30th, active flows were visible on the S flank while the SW flow only showed incandescence in its upper part. On the evening of 31 December, incandescent lava was visible on the lip of SEC in many places while active flows were descending on the S flank. On 7 January the SW flow was incandescent along its full length, with the W lobe extending to the base of the SEC cone.

On 8 January Southeast Crater gave off continuous Strombolian explosions from two vents at the summit of the intracrater cone and lava emission from its SE base. The summit of the cone was distinctly (~5-7 m) higher than the highest point ("Fortino") on the NE rim of SEC. Lateral growth of the cone was most significant in the N and NE parts of SEC where all lava flows and effusive vents active between July and September 1997 had been buried. The lava field surrounding the central cone had risen significantly, causing overflows on the E, SE, S, and SW sides. Only a segment of the NE crater rim stood a few meters above the lava fill; the W and NW part of the rim stood 20 m above the lava field and the cone's base. Three craters were present on the central cone, two of which were erupting. Activity would occur from one vent at any given time while the other was silent. The N vent ejected bombs and scoriae onto the N and NW crater rim and beyond. The S vent produced loud bangs and showered the E and SE flanks of the cone with pyroclastics. The effusive vent on the SE side of the cone had crusted over, and lava issued only on the SW rim of SEC where it overflowed, forming a narrow (1.5 m) flow with distinct lateral levees extending to the base of the SEC cone. The flow bypassed a cone formed in 1971 on its E side; when reaching the almost horizontal plain below the steep SW flank of SEC, it broadened and thickened notably and advanced slowly in the direction of the 1971 "Observatory cone." Within 3.5 hours on 8 January, the flow front advanced ~15 m through thick snow, forming an offshoot on the W side of the ~20-m-wide lava front. None of the other flows on the S flank of SEC showed any signs of movement or incandescence. The distance from the Torre del Filosofo mountain hut to the nearest flow front was ~1 km; the active flow did not threaten this structure.

Activity at Northeast Crater. During the second half of July Northeast Crater (NEC) occasionally ejected incandescent bombs from a deep pit in the central part of the crater; fine ash fell outside the pit. Visits to the summit craters in late September and early October revealed sporadic activity. NEC frequently emitted ash plumes during the first week of October, and on the evening of 10 October, incandescent ejections rose as high as 50 m above the crater rim. Strong gas emission was occurring from NEC on 11 December. NEC was essentially quiet on 8 January, with only light steam emissions from its central pit and some of the June-August 1996 vents in the SW part of the crater. Steam emission was more abundant, and at times pulsating, from a collapse pit in the S part of the crater. This pit was also the site of frequent avalanching and rockfalls that generated plumes of brown ash. No fresh magmatic products were found in the vicinity of the central and southern pits.

Activity at Voragine. A small cone began to form on the floor of Voragine in late July, and Strombolian activity was observed on 5 August. On 30 August, the cone was mildly steaming, and the surrounding deposit of black scoriae was partly covered by blocks that had collapsed from the septum between Voragine and Bocca Nuova. The first effusive activity from the Voragine in many years occurred in late September, forming a small lava field on the crater floor. Strombolian activity was weak on 28 September but very vigorous on 9 October; one day later it was again weak. The Voragine was explosively active from the central conelet on 6 November, and another weakly explosive vent had formed at the SW base of the diaframma between the Voragine from Bocca Nuova.

The cone in the central part of the Voragine was quiet on 8 January, with only slight emission of bluish gas. Its horseshoe-shaped crater was open to the SE; a small lava flow had issued from the open side of the cone. The vent on the SW side of the crater floor, which was first observed on 6 November 1997, had enlarged and was surrounded by a low half-cone leaning against the base of the diaframma. This vent produced weak explosions that mainly expulsed hot gas and a few pyroclasts. When viewed from the E rim of the Voragine, the conduit of this vent was seen to be inclined SW, diving below the diaframma.

Seismic crisis of 9-12 January 1998. The most intense seismic crisis during the current eruptive cycle occurred during 9-12 January and caused widespread media attention. From the afternoon of 9 January through 11 January about 200 earthquakes occurred in an area on the W and SW flanks of the volcano. The strongest shock (M 3.7) damaged a church in Biancavilla. No other damage or injuries were reported. Most epicenters were between Monte Nunziata and Monte Palestra, two ancient cones on the W flank. Seismicity diminished late on 10 January.

Strong ash emissions from BN on the morning of 11 January indicated further collapse in that crater, caused by earlier subsidence of the magmatic column. It is assumed that the magma intruded into a new fracture within the W side of the volcanic edifice. On 12 January ash emission from BN was almost continuous, but strong ash emissions also occurred from NEC. Activity at SEC continued with Strombolian bursts and emission of lava flows onto the SW, S, and SE flanks of the cone. The peculiar SW flow seemed to be waning; during the previous few days it had formed several minor lobes adjacent to the main one; the flow front seemed to have reached the base of the 1971 "Observatory cone."

Another seismic swarm occurred below the W flank on the afternoon of 12 January, with twelve earthquakes in 20 minutes, the strongest being M 3.1. Epicenters were closer to the summit craters than those of the preceding swarm, clustering 2-3 km E of Monte Palestra. Focal depths were ~4 km below sea level; no damage was reported. No significant change was noted in the eruptive activity at Southeast Crater, which had three active flows moving down its SW, S, and SE flanks.

Summit activity during 13-15 January 1998. Strombolian activity on the evening of 13 January at the intracrater cone in SEC was vigorous, while active lava was only visible near the crater rim in three places. A very faint glow reappeared at the SE eruptive center in BN. Strong ash emissions occurred from BN throughout the day. Seismic and eruptive activity were low on 14 January. The only visibly active crater was SEC, which was vigorous on the 13th but showed a marked diminution of activity towards midnight. At nightfall on 14 January SEC had very few and weak explosions, and there was no active lava flow on its outer flanks. No glow was visible above BN. This was the lowest level of activity observed in about a year. Seismic activity resumed late on 14 January with a series of about ten weak earthquakes below the W flank (Monte Palestra area) and several shocks beneath the SW slope, some 5 km above Biancavilla. Hypocenters were ~6 km below the surface on the W flank but much shallower on the SW flank. Activity at SEC dropped to very low levels: very few and weak explosions from the intracrater cone were observed on 14 January and no active lava was visible on the outer flanks of the crater.

Information Contacts: Boris Behncke, Istituto di Geologia e Geofisico, Palazzo delle Scienze, Università di Catania, Corso Italia 55, 95129 Catania, Italy.

October 1998 (BGVN 23:10) Cite this Report

Summary of eruptive activity from summit craters during January-May 1998

The following report summarizes activity observed at each of the four summit craters of Etna from 15 January through May 1998. Southeast Crater was active throughout this period, with explosions and lava flows both within the crater and on the flanks of the cone. Activity at Bocca Nuova alternated between ash emissions from collapses and vigorous magmatic eruptions until early April. Voragine exhibited intermittent low-level activity. Northeast Crater had a lava fountaining episode in late March, its first significant activity since August 1996. Additional summit crater eruptive episodes after May 1998 will be described in future issues.

Seismicity on the W flank. Seismic activity resumed on 15 January with weak tremors ~6 km below the W flank (Monte Palestra area) and several shallow shocks on the SW slope. Seismicity was low but a tremor occurred on the W flank, and another directly below the summit craters, on 19 January. After about two weeks of relative seismic quiet, earthquakes occurred again below the W flank on 31 January and below the summit craters on 1 February. Mild seismic activity was occurring again on 9 February in the Monte Palestra area (W flank at around 2,000 m), in the same area that has been affected repeatedly by seismic activity since late December.

Activity at Southeast Crater. On 16 January, explosive and effusive activity resumed at Southeast Crater (SEC). On 18 January there were three active lava flows on the southern slopes of SEC. A lava flow which moved towards the W rim of Valle del Bove stopped shortly on 20 January. After two days of weak or absent eruptive activity, SEC resumed Strombolian activity on 22 January. On 28 January a lava tongue extended to the W rim of Valle del Bove; at dusk there was vigorous explosive activity and two small lava flows were visible. During the evening of 29 January, Strombolian activity occurred from the intracrater cone while a lava flow was overflowing down the SE flank.

Clear weather on 4 February revealed fresh lava flows on the S and ESE flanks of SEC. Explosive activity continued on 9 February while small lava flows moved down its SE flank. On 10 February, SEC was the site of continuous powerful Strombolian explosions that dropped bombs and scoriae beyond the crater rims. Activity alternated between two vents, only one erupting at any given time. The S vent produced fountains that showered the whole southern sector of SEC with bombs. The N vent sent vertical fountains of bombs up to 200 m high. Some bombs that fell on the W crater rim were up to 30 cm long. Smaller projectiles even fell at the lower slope of the main cone, 100 m from the erupting vent. Lava flowed from a vent on the SE side of the intracrater cone. A lava tongue spilled over the crater rim on its ENE side. Other recent lava tongues had extended just beyond the base of the cone; the longest flow to the ESE (produced in mid-December 1997) had advanced to within ~50 m of the W rim of Valle del Bove. The only significant remainder of SEC's former rim is on the W and NW side where it stands 15 m above the lava field surrounding the central cone. In all other areas the crater is filled and has overflowed in many places. The appearance of the crater's interior is that of a low lava shield topped by a cone that is 30-40 m high.

By 11 February, growth on the NW side of the intracrater cone had raised its summit by at least 1 m since the day before. Two vents were active in its summit crater, and for the first time these were seen to erupt simultaneously. The vigor of the activity increased notably after 1930, when jets of bombs frequently rose up to 250 m above the vent. Lava from the vent on the SE base of the intracrater cone rapidly covered the SE sector of the crater floor and began to spill down the upper outer flank of SEC. By 2000, it had extended some 50-100 m downslope. Activity continued at similar levels through 15 February.

Strombolian activity was intermittent on 17 February, and degassing alternated with bomb ejections while a lava flow slowly moved down the SSE flank of the SEC cone. New lava flows from the intracrater cone covered ~25% of the crater floor, and a new lava lobe began spilling down the outer flank of SEC adjacent to the still-active SSE flow. A lava flow on the SW flank of SEC during 20-25 February appeared to be flowing on the NW side of the January flow. Strombolian activity occurred on the night of 25 February, and a very minor lava lobe spilled over the SE crater rim.

The eruption continued on 5 March with lava effusion on the flanks of SEC. As of 11 March lava continued to spill down the SE flank of SEC. Around 16-19 March, SEC appeared to be the only center of eruptive activity with weak Strombolian activity accompanied by minor overflows of lava. Lava flows began moving down the SSW flank of SEC on 20 and 21 March, but explosive activity was weak. During the Northeast Crater episode of 27-28 March, SEC was intensely active, with vigorous and continuous Strombolian bursts, and a lava flow spilling down the SW flank of the SEC cone. Moderate Strombolian activity continued, but effusive activity on the SW flank ceased sometime during 29 March.

Significant morphologic changes were noted on 6 April that had occurred since the previous visit on 17 February. The summit of the intracrater conelet had collapsed or been destroyed in late March. A depression on the lower E flank of the conelet was the site of a new effusive vent. The effusive vent area that had been active for many months in the S and SE sectors of the conelet's flank was inactive. Lava had buried the old rim of SEC on all sides except the W and NW where the old rim stood a few meters above the lava field. Lava had overflowed onto the northern outer flank of SEC, forming a short lobe. On the SW flank of SEC a lava flow active from mid-February until early March had extended to near the base of the 1971 "Observatory Cone".

The new effusive vent on the eastern base of the conelet had apparently formed only shortly before the visit because the depression around it had not yet been filled. Extrusion at this site had been preceded by subsidence at the base of the conelet. Meter-sized slabs of older lava had been uplifted and tilted, and fresh lava was being squeezed through the cracks, accompanied by high-pressure gas venting. A more vigorous flow issued from a U-shaped vent, similar to ephemeral vents seen on other occasions. Yet another flow began to issue from below an upheaved slab of older lava with spectacular lava stalagtites on its bottom. These two flows spilled 150 m down the NE flank of SEC.

Explosive activity on 6 April occurred from two vents within the crater of the central conelet, but they never erupted simultaneously; one vent was very noisy while the other erupted silently. SEC continued to erupt on 27 April, with small Strombolian explosions and lava effusion. Scientists who visited the crater on 14 May reported that lava was overflowing onto the flanks, and Strombolian activity was occurring from the summit of the conelet.

Vigorous explosive and continuous effusive activity as well as morphological changes were observed at SEC during a visit on 21 May with students from North Dakota State University. The central conelet was observed at close range, and the main effusive vent could be approached amidst a rain of light scoriae. Strombolian activity occurred from a single vent in the NW summit area of the conelet. Explosions occurred incessantly, and many ejected bombs 200 m above the vent. As on many other occasions, a distinct periodicity could be noted in the activity, each cycle culminating in a series of powerful Strombolian blasts heavily charged with meter-sized bombs. Overlapping lobes on the E side of the conelet had built a low shield, and the depression which had formed at the E base of the conelet was completely filled.

Vigorous explosive activity occurred on 24 May from the central conelet of SEC, and two flows were descending the SE cone. Some explosions ejected incandescent bombs at least 200 m high. Giovanni Sturiale and Boris Behncke, both of Catania University, visited SEC on 28 May; the central conelet was somewhat higher in the vent area than on 20 May. The main vent at the E base of the conelet was issuing lava that spilled over the E rim of SEC (buried under at least 30 m of lava since July 1997). Most flows stop at the base of the cone and are followed by the formation of new flows. Vigorous explosive activity dropped bombs on the N side of the central conelet. The current activity is known as Etna's "persistent summit activity" which became famous from descriptions of Northeast Crater which in the 1950's to 1970's produced similar activity.

Activity at Bocca Nuova. Very dense gas emissions were occurring from Bocca Nuova (BN) on 19 January; some contained ash. Explosions from BN were audible 8 km from the summit on 20 January, but magmatic activity alternated with collapses, generating dense ash plumes. Bright glow was visible on 22 January. BN was emitting white steam with some dark ash plumes derived from crater wall collapse on 28 January. On 28-29 January periods of intense incandescence indicated vigorous but intermittent activity at both the SE and the N eruptive centers.

Intense glow was again visible at BN on 4 February, indicating vigorous intracrater activity. Activity on 8 February continued without significant changes; there were emissions of dark ash indicating collapse of the crater walls. Magma again withdrew from BN (as indicated by internal collapse) on 9 February. Later that day collapse in BN ended; at nightfall, bright incandescence was visible.

The overall appearance of BN on 10 February was similar to before the collapses that accompanied the seismic crises on the W flank. The collapse had affected only the summit areas of the two large cones, and the N cone had subsided several meters. Activity had resumed at both cones. Jets of bombs, at times mixed with ash, rose tens of meters above the vents, and occasional explosions ejected bombs. Eruptive activity from the northern cone had resumed at a new vent close to the center of BN. A vent in the deepest part of the ~150-m-wide crater of the cone was vigorously degassing. A third vent rarely produced spectacular ash emissions. The main eruptive vent (on the S rim of the cone) was in constant eruption, with powerful bomb ejections about every 2 seconds. Many ejections rose above the W rim of BN, which stands 70-80 m above the vent. Every 5-10 minutes, this vent would produce larger eruptions, ejecting continuous fountains mixed with ash.

Activity in BN increased notably when seen on 11 February. Activity was continuous at both cones. During the afternoon, periods of near-continuous ash emissions were accompanied by powerful explosions. At night, both eruptive areas produced intense continuous glow. Occasional larger explosions ejected bombs up to 150 m above the SE rim of Bocca Nuova. The eruption in BN continued on 15 February without significant modifications. There were vigorous bomb ejections, many of which dropped bombs on the outer slopes of the main summit cone.

During another visit on 17 February, both eruptive centers of BN were active. One vent, 30-35 m in diamater, was ejecting continuous lava fountains and occasional large jets to above the crater rim. The northern eruptive center was the site of continuous very narrow incandescent fountains, and a small lava flow. Occasional violent explosions occurred from the vent on the southern rim of the collapse structure which had been the most active vent in this area one week earlier. Activity in BN during 20-23 February was characterized by low-level bomb ejections with occasional larger jets of bombs. Virtually continuous ash emissions began at BN on the afternoon of 24 February. The ash emissions were followed that evening by vigorous magmatic activity, probably from the SE vents, that caused a bright fluctuating glow until daylight.

BN continued to erupt in early March, although the activity appeared to decrease. On 5 March there was weak activity at BN. As of 11 March sporadic night glow was visible at BN. This crater was completely inactive during a 6 April visit. Wholesale collapse had occurred at the N and SE eruptive areas. A vast collapse depression had formed at the former, leaving only the N part of the large cone that had grown there until the end of 1997. Explosion sounds heard on 27 April possibly came from BN. The local mountain guides reported on 21 May that there had been no recent activity at BN. Activity resumed from BN at the end of May after several months of little activity.

Activity at Voragine. Eruptive activity reportedly included the Voragine on 20 January, but it was inactive during a summit visit on 10 February. During a 6 April visit, the first to this crater since 10 February, a few minor morphologic changes were noted. The most significant was the formation of a new crater <10 m in diameter on the central conelet. Some growth had occurred, and the crater floor was covered with finer-grained tephra. The SW vent at the base of the septum between Voragine and BN had enlarged to ~40 m in diameter. This vent was the only site of eruptive activity within the crater during the visit. Large explosions every 3-5 minutes ejected bombs tens of meters high, some of which flew into BN. Scientists at the summit on 14 May reported vigorous activity from the vent in the SW part of the Voragine and numerous fresh bombs. Loud detonations on 24 May indicated explosive activity; some were accompanied by dense vapor and gas plumes.

Activity at Northeast Crater. In one of the most spectacular eruptive events of the past few years, Northeast Crater (NEC) produced a 2-hour episode of lava fountaining during the night of 27-28 March. The event marks a resumption of more vigorous activity at NEC, which has displayed only weak activity since August 1996.

Volcanic tremor was registered by seismic stations in the summit area early on 27 March. At about 1000, Northeast Crater began to emit ash plumes that continued until shortly after 1600. By nightfall, sporadic ejections of incandescent bombs sometimes rose several hundred meters above the crater. The Strombolian ejections gradually increased in intensity and became virtually continuous by 2200. Shortly before midnight, the ejections merged into a continuous pulsating fountain rising 300-350 m above the rim of the active vent within the collapse pit in the S-central part of the crater. Large bombs fell onto the lava platform and into the adjacent Voragine and BN craters, some fell 1 km S and SW of the vent. Loud detonations were heard on the E and SE flanks where hundreds of thousands of people watched the display at a safe distance. By about 0130, the activity began to decline and was virtually over after 0200. This eruption appears to be another episode of lava fountaining similar to those at the same crater between November 1995 and June 1996, and many times during the late 1970's and early 1980's. The next day, NEC emitted a few ash plumes several hundred meters above the summit, but there was no evidence of renewed Strombolian activity.

When the crater was visited on 6 April, centimeter-sized, highly inflated scoriae were abundant a few hundred meters S of the 1971 "Observatory Cone," and the deposit was nearly continuous on the W side of that cone, with maximum clast sizes exceeding 5 cm. Closer to SEC the deposit was no longer continuous, but clasts up to 10 cm long were found. Close to NEC, little fallout was found. A few impact craters were seen in the N part of the Voragine floor while on its N wall bombs had formed a nearly continuous cover. On the S and SE rim of NEC the deposit was at most a few meters thick. The inner terrace surrounding the central pit, previously 5-10 m below the outer terrace, had subsided at least 10 m, exposing huge caverns in the vertical scarp along which subsidence took place; these were formed during the summer of 1996 when the crater was filled with lava which crusted over and later drained. The dimensions of the central pit had changed little, but its floor had risen to within ~50-60 m of the lowest point on the rim. There was no evidence of fresh ejecta around these vents indicating that no significant eruptive activity had taken place there since the 27-28 March eruption.

Local mountain guides reported on 21 May that there had been no recent activity at NEC. However, on the morning of 1 June there was a series of ash emissions.

Information Contacts: Boris Behncke, Istituto di Geologia e Geofisica, Palazzo delle Scienze, Università di Catania, Corso Italia 55, 95129 Catania, Italy.

November 1998 (BGVN 23:11) Cite this Report

Summary of eruptive activity from summit craters during June-September 1998

The following report summarizes activity observed at each of the four summit craters of Etna (figure 70) from June through September 1998. In early June, Northeast Crater was quiet while Bocca Nuova, Southeast Crater and Voragine were displaying the highest level of activity seen in many months. Generally high levels of activity continued until a major explosive eruption from Voragine on 22 July. Strong Southeast Crater explosions on 15 September destroyed the intracrater cone, which was soon replaced.

Figure 70. Map of the summit craters of Mount Etna, 10 July 1998. Courtesy of J.C. Tanguy and G. Patanè.

During early July all four craters were erupting simultaneously, a fact never recorded since their birth; only the Central Voragine has degree of permanence; Northeast Crater (NEC) appeared in 1911, the Bocca Nuova (BN) in 1968 and the Southeast Crater (SEC) in 1971.

Most of the information for this report was compiled by Boris Behncke at the Istituto di Geologia e Geofisica, University of Catania (IGGUC), and published on his internet web site. The compilation was based on personal visits to the summit, telescopic observations from Catania, and other sources. Additional separate reports were provided by Tanguy and Patanè (10-14 July observations) and Murray, Stevens, and Craggs (15 September observations). Aviation notices were issued by the Toulouse (France) Volcanic Ash Advisory Center.

Activity at Southeast Crater (SEC). There were at least three explosive vents on the intracrater cone during 4-5 June. Activity usually alternated between the N and S vents. When both exploded simultaneously, a third NW vent produced weak incandescent projections. Vigorous growth around the vents elevated the summit to 20 m above the SEC rim. Lava flowed towards the NE flank where it spilled down to the base of the SEC cone. During a visit on 11 June, SEC had the usual two vents active, and fresh bombs scattered over the crater floor. Recent flows had built a high mound on the E side of the cone; an active flow issued from the vent area. By the morning of 15 June the lava flow at SEC had reached its southern base and was advancing slowly.

Explosive activity on 22 June occurred from three vents on the intracrater cone, and lava issued from a vent halfway up the S flank. Explosive Strombolian activity occurred in distinct cycles separated by quiet periods of up to one hour, although lava effusion persisted. The beginning of each cycle was marked by a flame of burning gas at the summit. More vigorous bursts would then follow at a larger vent. Explosions would become increasingly frequent and rise higher (up to 150 m above the vent), showering the southern part of SEC with bombs. Activity would then shift back to the SW vent where each Strombolian burst was accompanied by a gas flame. Intermittent explosive and effusive activity continued on 24 and 28 June.

During a summit visit by Behncke and members of L'Association Volcanologique Europeenne (LAVE) of Paris on 4 July, explosive activity at SEC was intense, with bombs falling outside the crater. Activity from the top of the intracrater cone sent jets of bombs and scoria up to 150 m. Lava issued from three vents, one feeding a flow over the SW crater rim. On the evening of 7 July LAVE members reported that the active lava flow on the SW flank of SEC was ~200 m long. The summit visit on 13 July was made by Giovanni Sturiale, Sandro Privitera, and Behncke (IGGUC), and Jürg Alean. At SEC, Strombolian activity was vigorous, bombs fell frequently outside the crater, and lava emission was continuing. Recent lava had filled the SW part of the crater to within 1-2 m of the rim. In all other areas the pre-1997 rim of SEC has been buried by overflowing lava. Jürg Alean visited on 14 July and reported that SEC continued to produce Strombolian activity. From the Torre del Filosofo hut a small lava flow could be seen descending the SE flank of SEC; incandescent blocks frequently detached from the flow front.

Vigorous activity occurred at SEC during the 22 July Voragine episode, and during the days after activity was limited to SEC where vigorous lava fountaining and effusion occurred. On 24 July, Sturiale and Privitera observed vigorous Strombolian activity, with many bombs falling outside the crater. However, SEC activity declined and virtually ceased by the end of July.

As of the night of 17-18 August, there had been no resumption of the SEC eruption. The crater was seen erupting later on 18 August by Privitera. When Monaco and Behncke visited on 20 August, virtually no activity was observed. As of 26 August SEC appeared quiet, although the activity in July had built the intracrater cone to 40-50 m higher than the crater rim. Bombs were scattered all over the crater area and beyond. Two post-22 July lava flows had spilled onto the S and NE flanks. No activity occurred during a visit by Behncke and Sturiale on 9 September.

Explosive activity from SEC was observed by scientists from Open University (Murray and Stevens) and the University of London (Craggs) on the morning of 15 September. Several ash clouds erupting from the summit between 0745 and 0800 were seen from 10 km S. At 0815 bomb-laden ash clouds were observed from near the Piccolo Rifugio (4.5 km S of the summit craters). At 0822 an exceptionally large explosion sent meter-sized bombs ~300-400 m above the crater rim. One more minor explosion was observed before the summit was obscured at 0826. Observation recommenced at the Pizzi Denieri volcano observatory. The summit was usually obscured by clouds, but five explosions during 0928-0936 were audible above gale-force winds and engine noise. Ash clouds were seen from Mt. Nero on the NE rift (6 km from the summit craters) at 1003, and at 1006 an explosion was heard.

Explosions continued all afternoon, causing ashfall in inhabited areas on the E flank. During the afternoon, while conducting fieldwork 50 km S of Etna, Behncke and Sturiale saw black ash fountains piercing weather clouds above the summit. These pyroclastic jets rose several hundred meters above the summit before drifting E. Observations by Behncke on 19 September revealed that the explosions ejected lithics and fresh bombs, which were abundant in the saddle between SEC and the main summit cone. Some of the bombs were up to 5 m across and had flattened upon impact. Bombs tens of centimeters in diameter formed a continuous deposit on the NW side of the crater. Most of the intracrater cone was destroyed, and a crater ~80 m across formed in its place (figure 71).

Figure 71. Sketch drawing showing Southeast Crater of Etna as seen from the NW on 19 September 1998. The former intracrater cone has been replaced by an explosion crater that contains a small new cone with two erupting vents, and a small non-eruptive vent that lies below the major breach in the crater wall in the left center. Lava that had overflowed the SW crater rim until July 1998 is shown in a dark pattern at right. Courtesy of Boris Behncke.

Vigorous activity on 17 and 18 September ejected bombs described as having been "several meters across" by a group of British geologists led by J.B. Murray working in the area. The beginning of a lava flow down the NE flank of SEC is not known, but it was reported by mountain guides to have been moving on 17-18 September. During a 19 September visit by Behncke, Strombolian bursts occurred from two vents in the explosion crater, around which a small cone had begun to grow. Lava emission from a vent high on the SEC cone was feeding a flow that advanced towards Valle del Leone.

Activity at SEC was continuing on 21 and 25 September with intense Strombolian activity; incandescent bombs jetted 150-200 m high. Continued vigorous activity during the last week of September caused rapid growth of the intracrater cone until ti was higher than ever before, having almost entirely covered the remains of its predecessor.

Activity at Bocca Nuova (BN). Eruptive activity during 4-5 June was occurring at both previously active areas. Night incandescence and bomb ejections were seen in a deep pit within the SE eruptive area. Noisy activity occurred at the NW eruptive area, at the bottom of the collapsed cone that had grown in 1997. At least five vents were producing explosions and lava fountains accompanied by bursts of burning gas. Several lava flows extended over the crater floor.

Observations were made for 30 minutes on 11 June from the crater rim. The SE vents had fountains of ash and bombs rising ~50 m. At the NW eruptive area, three vents were active, and the collapse pit was filled with pyroclastics and recent lava flows. Two large (30 and 50 m diameter) vents were in the central part of the filled pit while a smaller vent (~5 m in diameter) lay 50-70 m S; this latter one produced weak lava sputterings, building a low hornito. The two larger vents showed a repetitive eruptive behavior for the first 15 minutes of observation, then erupted simultaneously in a series of ash-free lava fountains. For about ten minutes there were bomb ejections from both major vents. Centimeter-sized scoria and Pele's hair were deposited all over the SE sector and on SEC.

Activity was less intense on 15 June; during a 1-hour stay in the summit area, strong explosions from the large cone ejected ash-rich jets of bombs up to 100 m above the crater rim. Visits to BN are dangerous due to frequent blasts of large quantities of meter-sized bombs. Most blasts observed on 22 June lasted up to 10 minutes. The source vent lay in the partially collapsed 1997 cone at the N eruptive area; it produced almost continuous minor explosions between the large detonations, ejecting large clots of fluid lava. A small vent to the south ejected minor sprays of meter-sized bombs. Continuous lava fountaining occurred from a SE vent. During the 22 June visit the central vent was the site of pulsating gas jets, and vigorous lava fountaining occurred at the larger SW vent. A large asymmetrical cone leaning against the thin wall between the Voragine and BN had grown around the vent. Vigorous activity was continuing on 24 and 28 June.

During a summit visit by Behncke and members of LAVE on 4 July, all four summit craters were active. The summit visit on 13 July by Sturiale, Privitera, Behncke, and Alean showed low levels of activity; a small cone had grown around the main vent. The N eruptive area was the site of Strombolian bursts every 5-10 minutes. A fairly large cone had grown at this vent, the first time that significant cone growth had occurred in BN since late 1997. Lava had covered the S crater floor.

A visit by J.C. Tanguy and G. Patanè during 10-14 July revealed that, with respect to the preceding year, the bottom of BN had raised considerably owing to the tephra deposition, so that the strongest explosions from the NW vent (figure 72) sometimes showered the external slope with bombs. By 12 July the explosions were reduced in strength and frequency. Jürg Alean visited on 14 July and reported that the N cone produced fountains heavily charged with bombs; many fell on the crater rims and in the Voragine.

Figure 72. Sketch of the Bocca Nuova and Voragine craters at Etna, 10 July 1998. Courtesy of J.C. Tanguy and G. Patanè.

Vigorous activity occurred at BN during the 22 July Voragine episode. On the afternoon of the 23rd, Carmelo Monaco (IGGUC) saw bright incandescence in BN even in bright daylight from an airplane approaching Catania. Activity was noted on 25 July and increased the following day according to Claude Grandpey (LAVE); activity at the NW area occurred from a small vent while the SE area had three vents emitting gas and bombs. In late July and early August, numerous vents erupted explosively at the NW area; subsidence of the central crater floor by a few meters occurred on 1 August. The SE vents displayed spectacular lava cascades from one vent into the other, the lower vent filling until an explosion cleared it. Kloster (LAVE) reported a lava lake in this area on 7 and 10 August, but during the following days there was only Strombolian activity.

On 20 August Monaco and Behncke observed moderate eruptions at the N vent area. Besides the summit vent, there were at least four smaller flank vents which had erupted recently. On 26 August frequent ash emissions were occurring. Growth of a small cone above the diaframma (septum between the craters) culminated in the fracturing of this cone and a cascade of lava into BN in late August.

A visit to the summit by Behncke and Sturiale on 9 September revealed that one vent at the summit of the NW cone was the site of Strombolian bursts alternating with bomb and ash emissions. Four smaller vents on the flanks on the cone were weakly degassing. Weak Strombolian activity occurred from two SE vents where a small cone was growing in a collapse depression. Behncke saw activity at similar levels on 19 September. As of 25 September there was low-level activity.

Activity at Voragine. On 3 June, near-continuous cannon-shot like detonations were heard kilometers away, and Marco Fulle (Osservatorio Astronomico, Trieste) observed magma bubbles within the vent burst at the onset of fire-fountaining episodes. When observed during 4-5 June, the vent in the SW crater floor had enlarged notably since 6 April and shifted away from the diaframma, and a low pyroclastic cone had grown around it. On the evening of 4 June, activity at the Voragine was observed for about 4 hours. A sustained fountain jetted from the vent, showering the SW part of the crater floor with bombs; many also fell into BN. This fountain lasted about 75 minutes, followed by pyroclastic material sliding from the inner walls of the vent into its throat. After a few minutes, a small vent opened below the inner SE rim of the vent and emitted jets of incandescent lava. Ejections soon resumed at the main vent, and a flame of burning gas persisted at the subsidiary vent accompanied by weak pyroclastic sprays. A new period of fountaining at the main vent resulted in the continuous fall of bombs into BN. The subsidiary vent was soon buried. At times, portions of the inner walls collapsed, causing ash-rich fountains.

The Voragine was not visited on 11 June, but very strong explosive activity was heard more than 10 km S, and high fountains contained meter-sized bombs. On 15 June the focus of activity had shifted to the central vent, previously active between July and December 1997. This vent ejected continuous lava fountains while a lava flow covered the E half of the crater floor. Fountains played up to 200 m above the vent, with all bombs falling back into the crater. At times, the magma level dropped, and the character of the activity changed to discrete explosions. The SW vent exhibited noisy gas emissions alternating with ash emission and lava fountaining. Vigorous activity was continuing on the evening of 24 June. During a summit visit on 28 June, Monaco observed fountaining from the central vent; the SW vent was less active and mostly ejected ash.

A scoria deposit extending SE, produced by a Voragine lava fountaining episode on 1 July, was examined by Behncke and members of LAVE on 4 July. Both vents in the Voragine were in vigorous, alternating activity. Eruptive cycles at the SW vent produced jets of fragmented pyroclastics. As activity waned at this vent, projections of large bombs would initiate at the central vent, increasing in frequency and height into a pulsating fountain at least 100 m above the crater floor.

Stefano Branca (IGGUC) reported that frequent explosions were audible throughout 6 July at Viagrande, a village at the SE flank of Etna; air concussions associated with the explosions shook windows and rattled doors. The explosions probably originated at the Voragine, the site of recent noisy activity. On 7 July explosions were still audible but less intense. Members of LAVE observed activity that evening from the SW vent that dropped bombs as far as the S rim of NEC.

A visit by J.C. Tanguy and G. Patanè during 10-14 July revealed activity at the large SW cone (figure 72) near the diaframma and from a central cone. By 12 July the two vents hurled large lava lumps and bombs in a fountain-like manner, some of which fell outside the crater. On 13 July this activity was stronger. That afternoon activity decreased, but two flows began from a fissure NE of the central cone. Lava rapidly invaded the northern, lowest part of the Voragine. During the peak effusive activity the two lava flows reached a speed estimated at 3-4 m/s. On the morning of 14 July, only the SW vent showed Strombolian explosions. Lava flows had entirely disappeared under a layer of tephra erupted during the night.

During a visit on 13 July by Sturiale, Privitera, Behncke, and Alean, the most vigorous activity occurred at the Voragine. On 12 July, lava fountains roared up to 200 m above the crater rim for three hours from the SW vent. Powerful jets of bombs mixed with ash were also ejected. The cone around the SW vent was higher in places than the diaframma; the vent was 30-50 m across. Activity varied from isolated powerful explosions to long-lasting lava fountains. At times dense ash plumes with large bombs rose from the vent. Explosions from the central cone blasted lava in all directions. Small lava fountains and ash emissions occurred from two fissures. On at least 20 occasions during 90 minutes of observation the magma surface in the vent domed up, forming a huge bubble that exploded. Explosions later ejected meter-sized bombs to 200 m or higher; many fell into BN, outside the Voragine, or on the E slope of the main summit cone not far from SEC. Jürg Alean visited on 14 July and reported that both vents showed intense activity. The SW vent was filled almost to the rim by lava which was fountaining vigorously. The central vent displayed a similar eruptive behavior as on the previous visit, but no lava bubbles were observed. On 20 July lava fountaining from the Voragine was common.

A major eruptive event began from the Voragine at about 1835 on 22 July. The following is based on preliminary information from scientists of the IGGUC (mainly Giovanni Sturiale and Sandro Privitera) and others who visited after the event as late as 20 August. According to eyewitnesses on the SW side of the main summit cone, huge lava fountains rose from the Voragine, and heavy tephra falls began in the summit area. A large mushroom-shaped tephra column rose up to 10 km above the summit. The plume was then driven S and SE, and widespread ashfalls occurred more than 30 km away. Sand-sized tephra fell in Catania, leaving a deposit about 1 mm thick. For the first time since 24 September 1986 (when NEC had a powerful explosive eruption) the Fontanarossa airport of Catania had to be closed (it was reopened after 15 hours). The Toulouse (France) Volcanic Ash Advisory Center issued 17 aviation notices warning pilots about the ash during 22-29 July. The tephra falls caused traffic problems on roads and highways. Close to the summit, a thick scoria deposit buried the dirt roads leading to the Rifugio Torre del Filosofo and around the western base of the main summit cone. Sturiale and Privitera reported that at Torre del Filosofo the thickness of the scoria deposit was about 50 cm.

It appears that both vent areas produced lava fountains and a tall tephra column. Rapid accumulation of ejecta in the saddle on the NW rim led to a lava flow between the NEC and the main summit cone (figure 73). The flow covered the road connecting the N and S flanks of Etna, and eroded a deep scar into the the S flank of the NEC cone. Continuing pyroclastic activity produced a thick scoria and bomb deposit, with bombs up to 5 m in length. A scoria fan extended 1-1.5 km NW. In the area of the diaframma a lava flow covered the crater floor to several meters depth. On the E flank of the main summit cone a thick pyroclastic deposit formed. In towns on the E and SE flank, the tephra deposit was a few millimeters to a few centimeters thick. Morphological changes within the Voragine consisted mainly of a large amount of filling of the crater followed by subsidence. Parts of the SW crater rim also collapsed.

Figure 73. Sketch map of Etna's summit craters showing features frequently mentioned in the updates, and approximate extent of recent lava flows as of 5 October 1998. Active vents are indicated as gray dots in the craters. Courtesy of Boris Behncke.

Vigorous activity occurred simultaneously at BN and SEC on 22 July Voragine event, indicating that the episode affected much of the central conduit system at some depth, possibly due to the rise of a batch of fresh gas-rich magma. Lava fountaining from the Voragine continued intensely through the night of 22-23 July.

According to Grandpey (LAVE), the Voragine appeared "full of materials" on 25 July with no trace of the former intracrater cones. No further activity occurred until 3 August when Kloster (LAVE) saw explosions ejecting bombs. Two days later, three vents erupted in the center of the Voragine. On 7 August small flows on the crater floor were followed by explosive activity. Powerful Strombolian activity with bomb ejections and ash emission caused light ashfall on the SE flank on 18 August, reaching the outskirts of Catania.

On 19 August explosive ash emissions sent small plumes up to several hundred meters above the summit. When Monaco and Behncke visited on 20 August, vigorous activity occurred from two vents. Very light ashfalls on 21 and 24 August reached Catania; ash emissions were also produced on 26 August. A number of reports indicated continued activity through the end of August.

On 6 September bombs fell on the outer W slope of the Voragine and on 7 September ash emission occurred throughout the day. A visit to the summit by Behncke and Sturiale on 9 September revealed continuous moderately strong Strombolian activity from a SW vent; sporadic explosive activity from the vent next to the diaframma sent bombs over the crater rim. At least three other vents were quietly degassing. Similar activity was continuing as of 19 September. On 30 September strong ash and gas emissions rose hundreds of meters.

Activity at Northeast Crater (NEC). Deep-seated Strombolian activity within the central pit resumed in mid-May according to Vittorio Scribano (Istituto di Scienze della Terra, Catania University). Night glow was observed on the evening of 22 June from 3 km NE. During a summit visit by Behncke and members of LAVE on 4 July, all four craters were active; for the first time since 28 March eruptive activity was observed directly at NEC. The eruption site was a 30-m-diameter vent in the NW part of the central pit while a SW vent (~15-20 m in diameter) emitted dense vapor plumes. Small Strombolian bursts from the larger vent occurred every 2-5 minutes, with most ejecta falling back into the pit.

A visit on 13 July by Sturiale, Privitera, Behncke, and Alean revealed mild Strombolian activity from the central pit that ejected bombs. When Monaco and Behncke visited on 20 August, NEC was degassing quietly. Strong fumarolic activity was occurring on 26 August and 9 September.

Information Contacts: Boris Behncke, Istituto di Geologia e Geofisica, Palazzo delle Scienze, Università di Catania, Corso Italia 55, 95129 Catania, Italy; J.C. Tanguy and G. Patanè, University of Catania, Istituto di Geologia e Geofisica, 55 Corso Italia, 95129 Catania, Italy; John Murray and Nicki Stevens, Department of Earth Sciences, Open University, Milton Keynes, United Kingdom; Emma Craggs, Geology Dept, Royal Holloway College, University of London, United Kingdom; Volcanic Ash Advisory Center (VAAC) Toulouse, Météo-France, 42 Avenue Gaspard Coriolis, F-31057 Toulouse cedex, France (URL: http://www.meteo.fr/vaac/)

December 1998 (BGVN 23:12) Cite this Report

Episodic eruptions from Southeast Crater during October-December

The following report summarizes activity observed at each of the four summit craters of Etna from October through December 1998. Bocca Nuova and Voragine exhibited some explosive activity during this period, but Northeast Crater was quiet. Southeast Crater had 15 distinct eruptive episodes. Most of the information for this report was compiled by Boris Behncke at the Istituto di Geologia e Geofisica, University of Catania (IGGUC), and posted on his internet website. The compilation was based on personal visits to the summit, telescopic observations from Catania, and other sources.

Activity at Southeast Crater (SEC). Poor visibility precluded observations after 30 September, when intense activity was rapidly building the intracrater cone and a new lava flow was spilling down the SW flank of the SEC cone (figure 74). On the evening of 1 October, no incandescence was visible at the crater, and brief glimpses of the summit during the following days revealed that no further growth of the intracrater cone had occurred. A group encamped ~800 m S of SEC reported that on 4 October there were no eruptions, but that activity renewed during the night.

Figure 74. Sketch map of Etna's summit craters showing recent eruption products as of 1 November 1998. The approximate extent of recent lava flows from Southeast Crater has been added. This map is not completely accurate regarding the distribution of the new flows, but locates some frequently mentioned features. Courtesy of Boris Behncke.

The summit was visited on 5 October by a group including Boris Behncke and Giovanni Sturiale (IGGUC), Marco Fulle (Trieste Astronomical Observatory), and Jürg Alean (Stromboli On-line). Strombolian bursts hurled incandescent bombs up to 200 m above the vent. A small conelet a few meters high that had grown around this vent was destroyed by explosions around 1300, and the active vent widened to 8-10 m diameter, with a low pyroclastic mound around it. Meter-sized lava blobs jetted continuously from the vent, and bombs showered SEC and its N flank. Many explosions were caused by the bursting of magma bubbles. Although the intracrater cone had grown significantly, it did not entirely fill the 15 September explosion crater. Alean stayed on the summit until the late evening of 5 October and returned the next afternoon. Strombolian activity culminated in a paroxysmal eruptive episode (the sixth since the crater resumed its activity on 15 September) on the evening of 5 October when fluid lava moved ~1 km down its E flank within a few hours. Strombolian activity at the intracrater cone was weaker, but increased slightly during the evening.

Vigorous eruptive activity resumed on the evening of 11 October at SEC, which had shown only low levels of activity during the preceding days. The renewed activity (the eighth eruptive episode) consisted of lava fountains and a lava flow that extended ~700 m downslope adjacent to the 5 October flow. Strombolian activity at the intracrater cone continued the next morning. Fulle reported "zero activity" at SEC on 13 October.

The episode of lava fountaining and lava emission during the night of 11-12 October was the seventh at SEC since the reawakening of the crater on 15 September. The activity had established a repetitive pattern of periods of relative calm or very low-level activity that lasted up to several days, followed by episodes of very intense Strombolian activity that culminated in lava fountains and short-lived, rapid effusion of lava flows for 1-2 days. The same crater displayed a series of episodes in September 1989 that marked the uprise of a voluminous batch of fresh, gas-rich magma, and culminated in a flank eruption in Valle del Leone. That eruption was accompanied by the formation of a non-eruptive fracture system down the SW flank to about 1,600 m elevation, close to one of the most densely populated areas on Etna. The new eruptive episodes at SEC, however, were of much smaller magnitude and occurred at greater intervals, and there was no geophysical evidence that magma was intruding at shallow levels into the fracture systems that radiate from the central conduit system.

Strombolian activity at SEC resumed on the evening of 16 October, after three days of no eruptive activity. According to Fulle, who witnessed the resumption of activity, there were first some high-pressure gas emissions during the late afternoon, without the ejection of pyroclastics. Strombolian activity had initiated sometime before 1900. Remote observation with binoculars from 5 km N of Catania by Sturiale during the night of 17-18 October revealed that the intracrater cone fractured on its southern side and issued lava. While Strombolian activity from the summit vent of the intracrater cone culminated in about nine hours of paroxysmal activity with lava fountains several hundred meters high, the new lava flow advanced in up to five lobes a few hundred meters downslope, slowing at the base of the SEC cone. Further flows spilled down the E and W sides of the cone. According to Sturiale, the most intense activity occurred around 0300; the episode ended at around 0630. The intracrater cone had merged with the N outer flank of the pre-1997 SEC cone; the summit of the cone was conservatively estimated to stand at 3,220 m, 30-40 m higher than the highest pre-1997 rim of SEC.

On 24 October SEC produced its ninth eruptive episode since 15 September. Activity began to intensify at around 1700 and was at its climax between 1900 and 2100 when Strombolian bursts jetted hundreds of meters above the cone. At times several vents appeared to be active. The main lava flow advanced to the base of the intracrater cone where it bifurcated into at least five lobes that spilled down the S flank. As of 2100, these active lobes had reached the base of the cone, and movement appeared to be slowing. Another lava flow spilled down the SW side of the SEC cone. Like the previous episode, the 24 October eruption was preceded by about 24 hours of weak Strombolian activity on the evening of 23 October. The paroxysmal event itself lasted only a few hours but was very intense, with about 2 hours of near-continuous lava fountaining. The lava flows on the S flank came close to the tourist lookout ~500 m N of the Torre del Filosofo hut, and then turned SE towards Valle del Bove, reaching ~1 km in maximum length. The SW lava flow did not extend beyond the base of the SEC cone. By 2300 all activity was over, but a brief revival of Strombolian activity occurred at around 0200 the next morning.

The tenth eruptive episode from SEC in seven weeks took place on the early morning of 1 November. In a characteristic pattern established during the recent episodes, the 1 November event was preceded on 31 October by the resumption of very mild Strombolian activity, and an increase in seismicity. While no effusive or explosive activity was evident until shortly after midnight (observation by Sturiale), lava began to spill down the S flank of the SEC cone before 0030. Low fountains began to play in the summit vent by 0130, and continued through at least 0430. The culminating phase began at around 0500 and lasted two or three hours; during this phase lava fountains continuously jetted hundreds of meters above the erupting vent, and numerous lava lobes spilled down the S flank of the SEC. Two lobes stopped about 100-150 m short of the tourist outlook, but other lobes turned SE at the base of the cone and reached ~600 m from the crater. Loud explosion noises were audible in towns on the lower flanks of Etna. It appears that initially the magma rose within the conduit and overflowed quietly without being accompanied by vigorous degassing, and this relatively quiet phase lasted a few hours. The 24 October episode was also reported to have initiated with the quiet overflow of lava prior to vigorous fountaining.

Behncke and Carmelo Monaco (IGGUC) visited the summit craters starting on 1300 on 1 November, roughly six hours after the end of that morning's eruptive episode and cessation of all lava outflow. Mild Strombolian activity continued through 1700, but there was no active or incandescent lava and Behncke was able to approach the spillover point on the S side of the intracrater cone, walking on still-hot but stagnant lava emplaced that morning. The spill-over area was a narrow channel, ~10 m deep, whose upper sides were plastered with large spatter; this channel extended to the base of the intracrater cone where it divided into two major channels that fed the lava flows on the outer S flank of the SEC cone. About 20-25 m farther W a similar spillover channel partly filled with 1 November ejecta was probably active during the 24 October episode.

The most striking effect of the five eruptive episodes since 5 October was the growth of the intracrater cone, which had become an imposing structure occupying almost all of the former SEC depression. A crater ~25-30 m wide occupied the summit of the intracrater cone.

Weak and infrequent Strombolian activity began again on the evening of 6 November; the next morning, SEC produced eruptive episode 11. Strombolian activity gradually increased through the night of 7 November and early morning, and the culminating phase of the episode began around 0830 on 8 November. By 1100, vigorous fountaining from the summit was accompanied by lava outflow onto the S flank. Shortly after 1330 the main phase of the episode was over, and no active lava was visible.

As of 16 November there had been no significant activity since 7 November, as revealed by seismic data (information from G. Patanè of the Osservatorio Sismologico di Acireale and IGGUC) and the lack of morphological changes to the summit cone. Sandro Privitera (IGGUC) reached the Torre del Filosofo hut on 15 November and witnessed a single ash emission from the cone before clouds hampered observations.

After 11 days of silence SEC produced its 12th eruptive episode in nine weeks on 18 November. After several days of weak seismicity, earthquakes began to increase in frequency during the late afternoon of 17 November (information from Patanè), and weak Strombolian activity began sometime around 2000 (information from J.C. Tanguy). This activity continued throughout the night, gradually increasing in vigor. The most intense activity occurred around 1030-1130 with high lava fountains, frequent ash emissions, and lava overflow onto the S flank. By 1230, most pyroclastic activity had ceased, and lava movement apparently stopped, although vigorous steaming from the new lava continued, and intense seismicity persisted for some time.

The 13th episode occurred on 29 November, again after a quiet interval of 11 days. Due to bad weather conditions, the activity could not be observed, but loud detonations were audible 25-30 km from the summit. The effects of this episode were studied during a visit on 3 December by Behncke. Lava had spilled through the breach in the S crater rim and reached the base of the cone. The summit of the newly formed cone at SEC was climbed to observe the vent that had produced all the recent activity; there was no eruptive activity, and only weak gas emissions occurred. The summit crater was ~50-80 m wide, its rim being highest on the SE side. The crater floor was relatively flat and had a central pit ~15 m wide in its center. From the crater rim it was possible to see that the summit of SEC was only about 20 m lower than the rim of the former summit crater (elevation 3,260 m), and thus SEC has grown at least 60-80 m since mid-1997.

It was SEC more than 14 days later that SEC began its fourteenth eruptive episode in three months, on 13-14 December. As usual, Strombolian activity began some 24 hours or so earlier. Carmelo Monaco (IGGCT) heard explosion sounds at Montagnola from the direction of SEC, but clouds prevented observations. However, at about 1930 the summit became visible from Catania, when Strombolian bursts occurred every few seconds. Between 2000 and 2030 a growing incandescent spot became visible below the fountain. During the next two hours, lava spilled down the S flank, and pyroclastic ejections became gradually stronger. The culminating phase began at about 0430, marked by strong seismic activity (information from Patanè). Tephra was carried S, leaving a dark streak on the snow. On 14 December, when viewed from Catania, the cone of SEC was covered with new pyroclastics and appeared to have grown; activity had returned to low levels.

The fifteenth eruptive episode from SEC occurred on 29 December, after the longest quiet interval between two episodes observed so far, and was essentially similar to the preceding episodes, with vigorous lava fountaining, tephra emission, and small lava flows.

Activity at Bocca Nuova (BN), Voragine, and Northeast Crater (NEC). The summit craters were visited on 5 October by Behncke, Sturiale, Fulle, and Alean. NEC was limited to forceful gas emission from a 30-m-wide vent on the floor of its about 80-m-deep central pit. Activity in the Voragine occurred in one vent in its SW part, which was ~100 m wide, tens of meters deep, and ejected bombs in near-continuous bursts; four other vents in the Voragine were degassing quietly. Within BN, both the NW and SE vent areas produced Strombolian activity. At the former, two vents in the W part of the cone were the sites of continuous minor bomb ejections culminating in fountains ~100 m high every 5-15 minutes. Only very few bombs fell outside the crater, but abundant fresh-looking bombs indicated that stronger activity had occurred within the preceding two days. Extensive fracturing of the lava flow that had entered the Bocca Nuova on 22 July indicated that minor subsidence had also affected a wider area. At the SE vents continuous Strombolian activity occurred from two vents in the collapse depression formed in early 1998.

Alean reported that activity in the Voragine and the SE vents in BN was stronger on 6 October. Fulle indicated that low-level activity persisted through 10 October and that during his observations on 12 and 13 October there was ongoing eruptive activity in BN and the Voragine. Eruptions from the SW vent in the Voragine ejected bombs into BN. An increase in the vigor of the ejections of the NW vent in BN was noted by Fulle on 15-16 October; explosions from that site ejected large (up to 1.5 m) black bombs onto the NW and N crater rims. On the morning of 25 October there was a dense gas plume issuing from BN.

Behncke and Monaco observed activity at BN and the Voragine on 1 November. In the former, the NW cone did not produce visible eruptions although explosion sounds could occasionally be heard. In the SE eruptive area three vents were the site of Strombolian activity. For the first time since the 22 July eruption it was possible to enter the Voragine, which was much shallower than before that event. Only the large SW vent was erupting, but that activity was very deep-seated, and only on one occasion did bombs rise above the lip of the vent. Very little degassing occurred from the large central vent, and the general impression was that the Voragine was quieter than at any time during the past six months. A weak gas plume was seen rising from the NEC central pit. There was continued weak activity in BN and Voragine through at least 10 November.

Information Contacts: Boris Behncke, Istituto di Geologia e Geofisica, Palazzo delle Scienze, Universitá di Catania, Corso Italia 55, 95129 Catania, Italy.

February 1999 (BGVN 24:02) Cite this Report

Extensive lava flows discharging from a 4 February fissure on the SE flank

The following report summarizes activity observed at Etna from January through February 1999. Bocca Nuova exhibited minor explosive activity through early February, but Northeast Crater and Voragine were quiet. Southeast Crater had seven distinct eruptive episodes between 5 January and 4 February; the latest was accompanied by the opening of a new eruptive fissure at its southeastern base. The information for this report was compiled by Boris Behncke at the Istituto di Geologia e Geofisica, University of Catania (IGGUC), and posted on his internet web site. The compilation was based on personal summit visits, observations from Catania, and other sources cited in the text.

Activity at Southeast Crater (SEC) until 23 January. After one week of relative quiet, the sixteenth eruptive episode of SEC since 15 September occurred shortly before noon on 5 January; this was preceded by weak Strombolian activity that started around midnight. The paroxysmal phase was characterized by vigorous fountaining, and lava flowed towards the northeast while tephra was driven southwest by the strong wind. Loud detonations were audible in towns on the flanks of Etna.

Episode 17, during the night of 9-10 January, was preceded by mild Strombolian activity; the paroxysmal phase occurred shortly after midnight. Lava presumably flowed NE again and tephra fell NE; Fiumefreddo, ~8 km SW of Taormina, received a light showering of ash. Loud detonations during the final phase were audible over a wide area, and clear weather conditions permitted many in the Catania area to watch the spectacular display.

After the shortest repose interval observed since early in the current eruptive sequence in September, episode 18 took place on the morning of 13 January, between about 0630 and 0930. Visibiliby was hampered by clouds, but loud detonations were audible in a wide area around the volcano. Ash fell as far as Giarre, ~15 km E.

The next eruptive episode occurred on 18 January, shortly after 0800, and lasted ~ 45 minutes. Minor Strombolian and effusive activity had occurred earlier during the night. As in preceding episodes, the culminating phase was characterized by initial strong lava fountaining which gradually became more ash-rich, generating a dense eruption column. Due to calm conditions, the column rose several kilometers above the summit (3 km as estimated from Catania) and attained a spectacular mushroom shape visible in the morning sky from all around the volcano. At the SEC cone itself, the heavy fallout and rapid accumulation of pyroclastics led to frequent avalanches, especially on the steep eastern side. After 0830, dull explosion sounds were audible to as far as Catania, accompanying the rhythmic uprush of dark ash. The activity declined rapidly at 0845, but ash emissions became again more forceful after 0900 and continued sporadically for several hours, accompanied by sliding of hot pyroclastics from the steep E side of the cone. No information was available about lava flows although it is likely that they occurred, possibly on the NE side of SEC.

SEC erupted again after only two days and four hours of inactivity, shortly after noon on 20 January. Increased gas emission began at ~ 1215, and by 1240 a lava fountain appeared at the vent of the SE Crater cone. This fountain rapidly rose to a height of several hundred meters, and the column which rose above it became more and more ash-rich. Less than 15 minutes after the onset of the eruption there occurred the first slides of hot pyroclastics from the upper part of the cone, and five minutes later the whole cone and part of Etna's main summit cone were veiled by a black curtain of falling bombs and scoriae. By 1300, the vertical eruption column had risen several kilometers above Etna's summit. Ten minutes later the activity began to decline rapidly, and by 1315 the eruptive episode was essentially over, with only a few ash puffs being emitted during the following 30 minutes.

During a summit visit by Boris Behncke and Giovanni Sturiale (IGGUC) on 21 January, the crater was completely quiet, and only a few weak fumaroles played on the SW and E crater rims. The cone at SEC had grown higher than 3,250 m, about as high as the rim of the former Central Crater (filled by lavas and pyroclastics in the 1950's and 60's). While its flanks were steep and regular on most sides, obliterating any trace of the pre-1998 crater rim, a deep V-shaped notch was present in the northern crater rim through which lava had spilled onto the cone's flanks during recent eruptive episodes. These lavas had formed a fan-shaped lava field on the northeastern base of the cone, extending to the rim of Valle del Bove.

Behncke and Sturiale also investigated the pyroclastic deposits of the recent eruptive episodes which extended in relatively narrow fans from SEC in various directions. During the 18 and 20 January epidsodes, most fallout had occurred in a radius of <1 km from the cone, mainly on the SE side of the former Central Crater where 0.5-1 m of pyroclastics had accumulated since late 1998. Meter-sized bombs had fallen up to 500 m from SEC, creating spectacular impact craters. Among the most peculiar features of the recent eruptive products was a small lahar on the southwestern side of SEC which extended ~300 m from the base of its cone; this was probably produced during the 5 January episode. Records of lahars are relatively rare in the recent history of Etna, the most notable occurring in 1755.

On the morning of 23 January, SEC was the site of yet another eruptive episode that began at about 0630 and probably lasted less than one hour. Due to the absence of wind, an eruption column rose several kilometers above the summit then drifted slowly SE. In Catania, the ashfall was not dense, but people in the streets felt particles entering in the eyes; these particles were less than 1 mm in diameter and left a thin, discontinuous film on the ground. More serious effects were caused by the fallout in the upper southern parts of the mountain where skiing was rendered impossible by scoria on the snow. The repose period between this and the previous eruptive episode was two days and 18 hours.

There appears to have been no significant seismic or eruptive activity between 23 January and 4 February; the few clear views during that period revealed no morphological changes.

The January eruptive episodes continued to build the SEC cone, which has changed beyond recognition from its mid-1998 appearance. The large crater formed in 1990 at the summit of the SEC cone was completely filled, and a new, tall summit grew over it, burying any trace of the 1990 crater and much of the lava flows erupted from mid-1997 to late July 1998. After the 23 January episode the cone's new summit was at ~ 3,270 m elevation, almost 90 m higher than the highest point of the 1990 crater rim in 1997.

New eruptive fissure opens on 4 February. A new eruptive episode from SEC began at 1600, producing a spectacular eruption column visible from Catania and all around the mountain. Like previous episodes, this event was characterized by vigorous fire-fountaining, tephra emission, and lava, and was preceded by a gradual increase in gas emissions and then mild Strombolian activity. The activity began to culminate at around 1600 when a tall fountain jetted from the summit crater of the cone, and lava spilled through the breach in the N crater rim.

Sometime around 1630, the SE side of the cone fractured, and a new vent opened about halfway down the cone's flank, producing a tall lava fountain 250-350 m high and feeding a dense, ash-laden eruption column. An eruption column rose ~ 2-3 km above the summit before being driven SE, dropping fine ash on the flanks. Lava soon began to flow SE from this vent (figure 75). At about 1640, a row of incandescent spots appeared below the newly formed vent, indicating that a fissure had begun to propagate downslope from the base of the SEC cone. Vigorous lava fountaining and tephra emission from the new vent on the SE flank of SEC diminished rapidly shortly after 1700, but activity continued at the smaller vents on the fissure below that vent, at ~ 2,950 m elevation, and lava advanced rapidly towards the rim of Valle del Bove. At nightfall, both this lava flow and the lava erupted at the beginning of the episode onto the northern side of SEC were brightly incandescent and well visible from towns on the eastern side of the volcano, causing rumors of the opening of fractures on both sides of the cone. However, the northern flow soon stagnated and cooled, and no further lava emission occurred on that side for the remainder of February.

Figure 75. Sketch map showing Etna's summit craters SEC, Voragine (V), and Bocca Nuova (BN). The approximate extent of lava flows emitted during the 4 February eruption are in medium gray and those following the 4 February eruption are in black. Flows erupted from 1971 to 1993 are shown in light gray. Courtesy of Boris Behncke.

On 5 February, lava had begun to spill into Valle del Bove, forming a cascade on its steep western wall. The flow advanced very slowly, and had not yet reached the valley floor (at ~2,000 m elevation) on the next day when the new eruptive fissure was visited by Behncke and Giuseppe Scarpinati (L'Association Volcanologique Européenne, LAVE). Mild explosive activity was building several hornitos in the upper part of the ~100-m-long, SE-trending fissure at the base of the SEC cone while lava was issuing from numerous vents along the whole length of the fissure, feeding several channellized flows and some minor a`a flows. The effusion rate was estimated at 5 m³/s or more, significantly higher than during previous mainly effusive eruptions near Etna's summit craters (mainly at NE Crater in the 1970's) and similar to the effusion rates of some of Etna's flank eruptions. Pahoehoe lava was abundant around the effusive vents. The cone of SEC was found to be fractured from its summit down to its base, but only the main 4 February vent appeared to have produced significant eruptive activity while only minor spatter and scoriae were found in the part of the fracture between that vent and the still-active fissure.

On 15 February, Behncke and Scarpinati again visited the eruptive fissure and observed its activity for about 4 hours. By that day the lava spilling into the Valle del Bove had reached ~ 2,000 m elevation. There was no sign that the activity was diminishing, and the effusion rate remained perhaps as high as 5 m³/s.

Lava continued to issue from a number of effusive vents on the active fissure, forming at least two main rivers and several smaller and short-lived flows. In the course of a few hours Behncke and Scarpinati saw some of the lesser flows cease and others reactivate, forming blocky a`a while the more vigorous and long-lived flows moved in well-defined channels and showed no significant flux variations. Numerous short lava tubes, well-developed flow channels, and secondary vents had formed. Most effusive activity occurred ~50-100 m downslope from the upper end of the fissure, but several vents were also higher upslope. In the uppermost part of the fissure, numerous hornitos had formed, most of them concentrated in three clusters, and this area had countless incandescent vents producing high-pressure gas emission accompanied by a persistent hissing noise. The largest hornitos formed thin, vertical spires up to 3 m high while others were small humps a few tens of centimeters high. There was little explosive activity; only one vent in the uppermost hornito cluster rarely ejected incandescent pyroclastics.

Similar activity continued through the end of February. Lava flowed into the Valle del Bove, forming numerous lobes that moved on top or adjacent to earlier flows, and the farthest flow fronts did not extend much beyond 2,000 m elevation, remaining above the Monti Centenari, a cluster of cones formed during the 1852-53 eruption on the floor of Valle del Bove. The flow field gradually widened to ~500 m on the rim, and flows were issuing from numerous ephemeral vents on the W slope of the Valle.

Activity at Bocca Nuova (BN), Voragine, and Northeast Crater (NEC). Little significant activity occurred at these craters during January-February 1999 except for a brief resurgence of activity at BN during the week preceding the 4 February SEC events. During the 21 January visit by Behncke and Sturiale, spattering and Strombolian activity occurred deep within the large crater in the southeastern part of BN, accompanied by dense gas emission.

The cone in the northwestern part of BN produced violent noisy explosions every few minutes which ejected fountains of bombs high above the crater rim; ejecta frequently fell outside the crater, mostly to the W but in a few cases also SW and S. Between the explosions, deep-seated minor activity occurred within the 50-80-m-wide crater of the cone. No effusive activity had taken place in BN since it was invaded by lava from Voragine on 22 July 1998.

Bright crater glow was visible above BN in the first nights of February, the first time in about five months. This glow persisted during the night of 3-4 February but was much weaker on the evening of 4 February, indicating a drop of the magma level, probably related to the opening of the eruptive fissure on the SE base of SEC earlier that day. During the following week, only infrequent weak glows were visible above BN and then vanished altogether.

Very little activity except profuse steaming was observed within the Voragine during the 21 January visit by Behncke and Sturiale, who were able to descend into this crater and arrived at the "diaframma," the septum that separates the Voragine from Bocca Nuova. The floor of the crater was very flat in its eastern part, while a cluster of four craters with low cones occupied its central-western portion. The central crater, ~50 m wide and 30 m deep, was completely quiet; on its W side a much shallower, ~20-m-wide crater contained a 2-m-wide degassing hole with overhanging walls on whose floor numerous incandescent spots could be seen. A small crater with a diameter of less than 20 m, and ~ 10 m deep, lay on the SE side of the central crater. The largest crater in the Voragine was in the SW part of the Voragine and was between 70 and 100 m wide and more than 50 m deep with very steep and unstable walls, so that its floor could not be seen. Eruptive activity occurred at depth; as could be judged from the noises this was similar to the activity observed in the southeastern BN vents on the same day. A fifth vent that was active in August and early September 1998 on the crest of the "diaframma" appeared to have collapsed into the large SW vent, and only a part of its cone remained standing.

Information Contacts: Boris Behncke, Istituto di Geologia e Geofisica (IGGUC), Palazzo delle Scienze, Università di Catania, Corso Italia 55, 95129 Catania, Italy.

March 1999 (BGVN 24:03) Cite this Report

Additional details of mid-October 1998 activity at Southeast Crater

This report provides additional details of activity during 10-15 October 1998, along with a map of the lava flows emplaced at that time. These events were the seventh episode in a cycle of activity beginning on 15 September 1998. The cycle was characterized by periods of low or no activity interrupted by intense Strombolian fountains and lava flows at Southeast Crater (SEC) (BGVN 23:12). Observations of SEC between 1900 and 1920 on 10 October revealed Strombolian explosions which sent ejecta ~100 m above the crater rim approximately twice every 10 minutes. By 1800 on the 11th, observations from Nicolosi, ~15 km from SEC, indicated that Strombolian activity was increasing, with 16-17 explosions/minute sending ejecta to heights of ~200 m. By nightfall on the 11th, glow from the lava flow extending E from SEC was observed. Upon arrival at Torre del Filosofo (~1 km S of the SEC) at 1930, the explosions had increased to roughly one every 3 seconds and channelized aa lava proceeded down the E flank of SEC. Ejecta reached 100-300 m, typically landing within 300 m of the rim. By midnight, Strombolian activity was near-continuous. The lava fountaining was not Hawaiian in style because discrete explosions could be discerned.

By the morning of 12 October activity had declined to 6-12 explosions/minute, and by the morning of 14 October no explosions were observed. On 14 October, Harris, Sherman, and Wright mapped the flow emplaced during the night of 11-12 October (figure 76). The flow was a single-unit, ~750 m-long aa flow with distinct channelized and leveed portions in the proximal and medial sections. The distal section extended ~100 m into the Valle del Bove. Flow thicknesses were typically ~2 m, but levees were up to ~5 m high. Temperatures measured in cracks varied from 70 to 457 °C. The flow followed the S margin of another recent flow. The latter flow was presumably emplaced during 5-6 October and the highest temperature obtained on it was 55°C (BGVN 23:12). Measurements taken at this time indicated a length of ~500 m for the 5-6 October flow (figure 76).

Figure 76. Sketch map of Etna showing E-directed aa flows from Southeast Crater (SEC), 14 October 1998. The North arrow points towards the right. The lavas were emitted during 5-6 and 10-11 October 1998. The map was created based on field measurements made by Andrew Harris, Sarah Sherman, and Robert Wright.

Information Contacts: Andrew Harris, HIGP/SOEST, University of Hawaii, 2525 Correa Road, Honolulu, HI 96822 USA; John Murray and Robert Wright, Department of Earth Sciences, The Open University, Milton Keynes, MK7 6AA, UK; Andrew George, Gwel an Bendra, Penhale Lane, St. Cleer, Liskeard, Cornwall, PL14 5EB, UK; Jon Hearn, 20 Ringwood Rd., Twerton, Bath BA2 3JJ, UK; Sarah Sherman, 3015A Alencastre Pl., Honolulu, HI 96816, USA.

May 1999 (BGVN 24:05) Cite this Report

Lava emission continues through May from Southeast Crater into the Valle del Bove

The following report summarizes activity observed at Etna from March through May 1999. The information for this report was compiled by Boris Behncke at the Dipartimento di Scienze Geologiche (formerly Istituto di Geologia e Geofisica), University of Catania (DSGUC), and posted on his internet web site. The compilation was based on personal visits to the summit, observations from Catania, and other sources cited in the text.

Almost all activity has been limited to the eruptive fissure that became active on 4 February at the southeastern base of Southeast Cone (SEC). During early March, lava continued to flow into the Valle del Bove, forming a lava field (figure 77) composed of numerous lobes. The activity was visible from Catania and other locations on 5 March, with the flow field incandescent over its length from the W rim of Valle del Bove down to ~2,000 m elevation.

Figure 77. Sketch map of Etna showing the Valle del Bove and the area of lava flow-field that has developed since 4 February 1999, as of 4 June 1999. The lavas erupted during 1989-93 are shown in various shades of gray, previous flows (since 1971) are shown in lighter shades. 1995 to early 1999 lavas are not shown. Key: NE=Northeast Crater; V=Voragine; BN=Bocca Nuova; SE=Southeast Cone; TDF=Torre del Filosofo; MO=Montagnola; RS=Rifugio Sapienza; MC=Monti Centenari. Courtesy of Boris Behncke.

Observations on 3 March. On 3 March, the area of activity was visited by Giovanni Sturiale and Boris Behncke (DSGUC), and Christophe Baudin, a visitor from Belgium. The most recent lava to flow through the notch in the N rim of SEC, on 4 February, was covered with a thin layer of reddish ash and showed no heat emission. The inclined floor of the notch was ~3-5 m wide and covered with rubble; the width at its rim was 15-20 m. Only a few glimpses were caught of the interior of the crater, but at several tens of meters depth there was an inner terrace surrounding a narrow central pit. The width of the crater at its rim was at most 50 m. Gas and vapor escaped from several fumarolic areas on the SW and E crater rims. On the SE side of the crater there was a fuming pit ~15-20 m wide. Below this pit, on the outer flank of the cone, a vigorously steaming fissure segment extended ~100 m downslope; below this was the oval-shaped main vent of the 4 February episode.

Eruptive activity from the 4 February fissure consisted of very weak, and intermittent, ejections of pyroclastics, and quiet outflow of degassed lava. A cluster of about 10 hornitos at the upper end of the fissure were covered with sulfur. Relatively regular observations during 27 February-3 March (information from Giuseppe Scarpinati, Carmelo Monaco, and Christophe Baudin) indicated irregular activity at the hornitos. There was vigorous spattering at one of the main hornitos on 27 February, a new hornito began to grow on 28 February about 70-80 m downslope from the main group, and on 2 March a short-lived lava extrusion occurred from the base of one of the uppermost hornitos. On these occasions the hornitos were the site of high-pressure gas emissions that produced loud hissing.

During the 3 March visit, all hornitos were unusually quiet. High-pressure gas emission occurred from a few locations 50-80 m downslope. No flowing lava was visible, but a row of skylights lay 100-150 m downslope from the hornitos. About 100 m farther downslope the lava appeared at the surface in a well-defined flow channel. Several other lava flows were slowly moving across the lava field. At the rim of the Valle del Bove one main flow spilled into this vast depression, forming a pronounced ridge where it disappeared in another lava tube. Lava resurfaced a few hundred meters further downslope through numerous ephemeral vents, forming narrow flows that extended to the floor of the Valle. The farthest active lava was at ~2,000 m elevation, above the Monti Centenari, a cluster of 1852-53 cinder cones of which only the summits now protrude (figure 77).

The mean output was several cubic meters per second; the volume of lava produced in one month of activity was between 5 and 10 x 10⁶ m³. Although this is a very rough estimate, with an error of ~50%, it indicates more production than other long-lived effusive eruptions in the summit area, which had effusion rates of < 1 m³/s.

Observations on 11 and 13 March. A group of DSGUC geologists (Behncke, Mariangela Porravecchio, Giuseppe Paradiso, and Antonella Lentini) visited the eruptive fissure at the base of the SEC on 11 March. Above the rim of Valle del Bove, all lava was flowing in tubes. There are apparently two main lava tubes ~30 m apart at the rim of Valle del Bove. The more southerly tube ended just above the crest of the Valle where the lava appeared at the surface, and two ephemeral vents emitted lava further downslope. The northerly lava tube extended much further into the Valle, and surface flows appeared halfway down its W slope, at ~2,500 m elevation. The active flow-fronts appeared to be somewhere above 2,000 m elevation. No activity had occurred at the hornitos in the uppermost part of the fissure, but degassing occurred from several incandescent fumaroles. Geologists from Palermo University measured temperatures of ~1,030°C in one of these fumaroles.

There appeared to be little activity elsewhere, although something that appeared to be a phreatic steam explosion came from Bocca Nuova's southeastern vent area. It formed a convoluted cloud but contained little or no ash, and it produced no sound.

On the late afternoon of 13 March the eruptive fissure was again visited by DSGUC geologists (Behncke, Monaco, Betty Giampiccolo, and Marcello Bianca). There were only minor changes compared to two days earlier. The southern lava flow sent numerous branches spilling over the rim of Valle del Bove. Little had changed at the northern lava flow. The output was still as high as 5 m³/s, and the effusive episode that began on 4 February was estimated to have produced >15 x 10⁶ m³ of lava, an amount typical of a "slow" flank eruption (Etnean flank eruptions are generally classified into those with relatively low effusion rates, such as the 1983 and 1991-93 eruptions, and high-effusion rate eruptions like those of 1981 or 1989).

During late March lava continued to flow into Valle del Bove. While a major flow issued from an ephemeral vent about halfway down the W slope of Valle del Bove, several smaller lobes were visible on the crest of the Valle on the evening of 24 March.

Observations on 7 April. Effusive activity continued in early April, though at a slightly diminishing rate. Lava flows continued to spill into the Valle del Bove, but their fronts stopped before reaching the base of the steep slope. A visit was made on 7 April by Behncke and geologists of Catania and Switzerland together with Marco Fulle (Trieste Astronomical Observatory) and Roberto Carniel (Stromboli On-line). Numerous small surface flows were active in two areas above the rim of Valle del Bove, one about halfway between the rim and the hornitos at the upper end of the 4 February fissure, and the other just above the rim. In the lower area, three or four small flows slowly advanced a short distance from their vents, which lay around spectacular tumulus, or pressure ridges, formed as magma pushed from below, raising blocks and slabs of older lava up to 5 m. The constant effusion since 4 February had formed an impressive, delta-like ridge on the Valle del Bove rim.

The upper area of activity, at ~2,850 m elevation, had five or six vents around a smaller tumulus. Two vents produced voluminous flows that descended tens of meters and had spectacular cascades. A small vent produced a flow that moved in a 20-cm-wide, S-shaped channel; this vent froze over in less than two hours, and a new ephemeral vent became active 20 m downslope. Strong gas emission occurred from two places in the upper part of the 4 February fissure. The cluster of hornitos at the end of the fissure was quiet while profuse steaming occurred from the upper part of the fracture that split the southeastern side of SEC on 4 February. On the W wall of the Valle del Bove, lava issued from a number of ephemeral vents about halfway down the slope, feeding flows that advanced a few hundred meters.

While lava effusion continued unabated, the rate of lava production appeared lower than during the first six weeks of the eruption, possibly in the range of 1-3 m³/s. The volume of lava produced thus far exceeded 20 x 10⁶ m³.

Observations on 14 April. Decreased lava effusion from the 4 February fissure was observed by Behncke and a German television team on 14 April. Near the W rim of Valle del Bove, lava came to the surface in a few places and produced very small flows. Halfway between the Valle del Bove rim and the hornitos, two main vents fed chanellized flows. Activity was more vigorous than the lower area, but had decreased markedly since one week before.

A notable feature is the formation of pressure ridges, tumuli, and small-volume extrusions from cracks in older lavas. Most of this was caused by very slow intrusion of lava from tubes towards the surface once the tube was blocked or slowed, forcing the lava upwards. Lava oozed through the cracks and formed new flows, but in many cases the lava formed bulbous protuberances which often resembled the lobes of pillow lavas forming underwater.

Observations on 30 April. Behncke and others descended into the Valle del Bove on 30 April. One main effusive vent, at ~2,700 m elevation (~100 m below the rim of Valle del Bove), was feeding several flows which in part disappeared into lava tubes and resurfaced tens of meters downslope. The mean effusion rate appeared to be around 1 m³/s or slightly less. The maximum flow length was ~300 m. The farthest flow fronts were stagnant above the floor of the Valle del Bove. There was no explosive activity around the effusive vents. Only one feeder tube appeared to be active, located in the central part of the field on the W slope of Valle del Bove.

Observations on 12 May. During early May, little significant change affected the activity. Lava flowing from the area of the 4 February fissure through a lava tube appeared at the surface at ~2,600 m elevation on the W wall of Valle del Bove. Active lava fronts did not extend below 2,000 m.

On 12 May, Behncke and Scarpinati visited the summit area, including Bocca Nuova and SEC, and entered the Valle del Bove. The summit craters were quiet, apart from near-continuous passive emissions of light brown ash from the NW vent of Bocca Nuova. This activity, which was most likely caused by internal collapse, was entirely noiseless and ash plumes barely rose above the crater rim. A deposit several centimeters thick covered the S, SE, and E sides of the main summit cone.

After descending from the main summit cone to the saddle which separates it from the SE Cone, Behncke climbed to the summit of the SEC. The crater was practically gas-free, so it could be seen that its floor had collapsed and the conduit was no longer open. There was, however, some gas and vapor emission from the upper part of the fracture which had split the SE flank of the cone on 4 February.

There was no visible activity anywhere above the Valle del Bove rim, the only surface flows appearing ~200-250 m below the original eruptive fissure, in Valle del Bove. Lava was issuing from two ephemeral vents on the N and E sides of a large tumulus. It was ~10-15 m across and consisted of uplifted, tilted, craggy blocks of older lava and minor volumes of more recent smooth-surfaced pahoehoe. The N vent fed a small well-channelized flow while from the vent on the E side of the tumulus lava was squeezed out like toothpaste.

Behncke and Scarpinati heard continuous cracking and knocking sounds from below, and small rockfalls from the sides of the tumulus were frequently observed; rocks at the surface of the tumulus were slowly fracturing. It was evident that magma was forcefully pushing from below, and lava was rising slowly within cracks between the blocks at the surface. After about 15 minutes of observation, Behncke and Scarpinati left the unstable tumulus area and continued their observation from 15 m upslope. For another 20-30 minutes, the tumulus gradually extended in all directions. Fracturing on the slope above the tumulus indicated a larger volume of magma arriving at the end of the feeder tube and nearing the surface.

After about 35-45 minutes of observation, the large blocks of older lava began to fall apart while ever larger rockfalls and collapses occurred on the flanks of the tumulus. After this, the entire tumulus area became highly mobile, and its E and SE sides, perched above the steep Valle del Bove slope, began to slide downhill, producing spectacular cascades of incandescent blocks and exposing the fluid, incandescent interior. The most dramatic phase, which lasted no longer than 5 minutes, saw the virtual unfolding of the whole structure as older blocks slipped into the Valle del Bove. Where the observers had walked only 30 minutes before, an incandescent chasm 15 m wide and 5-6 m deep opened, and lava slowly flowed from draining lava tubes. Fresh lava welled up at the W end of the collapse depression, rapidly filling it and spilling over its SE rim, causing further rockfalls. Some rocks at least 20 m³ in volume fell, with fresh incandescent lava attached to them. The overflowing lava appeared to be more voluminous than that which had previously issued from the two vents.

The previously active flows, cut off from their supply, soon stagnated, and small lava tubes with still-incandescent walls became visible. Fresh lava spilled down in a southeasterly direction, forming two branches which traveled 100-150 m in about 30 minutes.

Observations on 15-19 May. Surface activity resumed at the 4 February fissure on 15 May, after about a month of lava flowing through tubes to the Valle del Bove. A luminous spot in the hornito area was sighted through binoculars on the evening of 15 May by Giuseppe Scarpinati from his home in Acireale. Earlier that day Harry Pinkerton (Environmental Sciences Division, University of Lancaster) and others working in the area had noted no active lava. The next day (16 May), lava was slowly extruded from three small vents. The rate of emission increased during the following two days, and a larger vent fed sluggish flows that advanced across the N part of the flow-field.

On 19 May, Behncke, Antonella Lentini, Mariangela Porravecchio (DGSUC), Valentina Giambarresi (Catania University), and others visited Etna's summit area and the effusive vents. A part of this group climbed to the SEC summit. Since the previous visit by Behncke on 12 May, all emissions of vapor from the obstructed crater floor had ceased. The crater floor was ~70 m below the W rim, and the crater walls were vertical in most places. Fumarolic activity was occurring from numerous locations around the crater rim.

While the group stayed on the SEC summit, ash emissions from Bocca Nuova and Northeast Crater produced dilute plumes ~100-150 m above the respective crater rims. Rumbling sounds came from the direction of the Voragine or (less likely) Northeast Crater. No visible emissions were associated with the noise, and no more sounds were heard when everybody had returned to the hornito area.

The new vent 80-100 m below the hornitos lay in a drained channel ~3 m wide in its central portion. The shift of the currently active vent downslope was evident in the form of a ridge built by a series of crusted-over vents. The emission of lava was frequently accompanied by strong degassing, indicating that the lava here was more gas-rich than that issuing from the ephemeral vent on the Valle del Bove slope. Some 20 m downslope from this active vent, one of the initial three vents (of 16 May) was still extruding small amounts of bulbous lava, forming a tumulus.

The visit to the ephemeral vent on the Valle del Bove slope was highly instructive regarding the properties of effusive vents and lava channels. Lava was still flowing from two vents on the floor of the depression formed during the 12 May collapse of the large tumulus. Flow fronts did not extend to the Valle del Bove floor. Four or five well-channelized flows ~1 m wide were moving down the slope; towards their fronts two of these flows were seen to thicken and broaden to 2-3 m height and 5 m width.

The floor of the depression left after the tumulus collapse was partially covered with new lava, mostly aa with one small lobe of very smooth pahoehoe, and the main effusive vent had shifted ~2 m downslope. A second effusive vent 4-5 m downflow produced a small volume of lava.

Investigation of what remained of the collapsed tumulus revealed that the two effusive vents observed on 12 May had not been completely destroyed. Vent 1 lay on the N side of the tumulus, and while still active it had fed lava into a well-defined channel. Vent 2, on the E side of the tumulus, had squeezed out lava much like toothpaste, which had spilled down the steep E face of the tumulus. Both vents were cut off from lava supply as the tumulus collapsed, and when the area of vent 1 was observed shortly thereafter, lava was still draining from the flow channel. Observation on 19 May revealed that the channel had completely drained, its depth being ~1.5 m (compared to a width of 0.8-0.9 m). This is a much higher depth-width ratio than in most other lava channels on Etna and many other volcanoes, but normally lava channels are not drained as completely as in this case since the supply of lava decreases gradually, allowing some of the lava to remain and "freeze" on the channel floor.

Vent 2, one week after the cessation of its activity, was a roughly circular hole open towards the downslope side, and evolving into a thoroughly drained flow channel that had been hidden under the lava when observed before the tumulus collapse. Like at vent 1, this flow channel was deeper than wide. The vent 2 channel is on much steeper terrain, but this apparently had no effect on the depth and width of the flow channel. The vent itself, ~1.5 m wide at its rim, widened at depth to a subcircular cavity from whose floor some bulbous lava had oozed, probably, at some stage of the tumulus collapse. This indicates that there had been a lava pocket ~1 m below the vent. Vent 2 was surrounded by peculiar lava features. There was something like a "basal" lava type, of chocolate brown color, and with a very smooth ripply surface, onto which patches of black, scoriaceous lava were attached. Many of these features are almost certainly related to the frequent and rapid shifting of the locus of extrusion, and the shearing of actively extruding lava along solidified lava on the vent or flow channel walls.

Effusive activity from the 4 February fissure continued at a slowly decreasing rate through the end of May. This decrease was accompanied by an apparent increase of activity in the summit craters, possibly caused by the rise of the magma in the central conduit system below these craters, as less magma escaped through the 4 February fissure. A new surge of activity at this fissure occurred in mid-June; more detail will be provided in a future Bulletin.

Information Contacts: Boris Behncke, Dipartimento di Scienze Geologiche, Palazzo delle Scienze, Università di Catania, Corso Italia 55, 95129 Catania, Italy.

June 1999 (BGVN 24:06) Cite this Report

Lava-flow temperature measurements

During the winter of 1998-99, Southeast Crater underwent a series of short eruptions. On 4 February 1999 a similar outbreak led to fracturing of the SE cone with subsequent lava flows to the NNE and SSE (observation by Giuseppe Scarpinati). The SE flow developed a lava field between 2,900 and 2,800 m elevation on the rim of the Valle del Bove (BGVN 24:05), with numerous branches that nearly reached its bottom at about 2,000 m elevation. This mild effusive activity was characterized by very small and slow degassed lava flows coming from ephemeral vents through the superficially congealed crust of the field.

Temperature measurements were carried out on lavas from several of these effusive vents during the first days of April. Special thanks are due to Antonio and Orazio Nicoloso and the Etnean Guides for assistance in the field. Consumable "Temtip" Pt / Pt-10%Rh thermocouples were used following a procedure described in Archambault and Tanguy (1976). The maximum lava temperature recorded at depths of 40-60 cm within the fluid lava was 1,085 ± 5°C (figure 78), slightly higher than that measured during the last two major flank eruptions of 1983 and 1991-93 (1,070-1,080°C). As already shown in Archambault and Tanguy (1976), such small lava flows showed a strong thermal gradients, so that measurements made at 5-15 cm depth give results 10-15°C lower than the true internal temperature (figure 79). This means that devices reaching only the superficial parts of the flows are unsuitable for such temperature measurements.

Figure 78. Histogram showing the number of Etna lava measurements at each temperature; the 16 measurements were taken at depth on fluid lava.

Figure 79. Lava flow temperatures measured at Etna during early April plotted versus depth. Different symbols (circles, squares, and triangles) represent different sets of measurements.

Although relatively low for a trachybasalt (or basaltic hawaiite) lava, the temperature of 1,085°C is consistent with their high crystal content of ~40% phenocrysts. As usual in recent Etna lavas, these phenocrysts consist of plagioclase, clinopyroxene, olivine and titanomagnetite lying in a glassy alkaline groundmass.

Reference. Archambault, C., and Tanguy, J.C., 1976, Comparative temperature measurements on Mount Etna lavas: Journal of Volcanology and Geothermal Research, 1, 113-125.

Information Contacts: Roberto Clocchiatti, Lab. Pierre Sue, CEA Saclay, France; Charles Rivière, CGE, France; Santo La Delfa, Giuseppe Patanè, and Jean-Claude Tanguy, University of Catania, Italy.

September 1999 (BGVN 24:09) Cite this Report

Summary of June-September activity; powerful eruption from the Voragine on 4 September

The information for this report was compiled by Boris Behncke at the Dipartimento di Scienze Geologiche, University of Catania (DSGUC), and posted on his internet web site. The compilation was based on personal visits to the summit, observations from Catania, and other sources cited in the text. Additional information was provided by Jean-Claude Tanguy (DSGUC), mostly about the activity during September.

Mild eruptive activity resumed at Etna's summit craters (figure 80) in early June, and gradually increased through late August before culminating with a powerful eruptive episode from the Voragine on 4 September. During the same period, lava continued to flow from fissures at the base of Southeast Crater (SEC), and occasional phases of mild lava spattering built hornitos and spatter cones at the eruptive vents.

Figure 80. Sketch map of the summit craters of Etna, based on fieldwork between 7 September and 1 October 1999 by Behncke and others. Courtesy of Boris Behncke.

Activity during June 1999. During early June, lava emission from the 4 February fissure on the SE base of SEC continued at a low rate. Lava issued from ephemeral vents and flowed for a few hundred meters towards the W face of the Valle del Bove (VdB).

The following information regarding activity from 30 May to 2 June was provided by John Guest (University College London, UK) and Angus Duncan (University of Luton, UK). Several explosions were heard from the summit craters on 30 May. On 1 June a brief bright red glow was seen over Bocca Nuova (BN). The active lava pile in the vent area at the foot of SEC on 2 June had increased in thickness since 30 May. Fresh lava now partly buried the 'old' tumulus of altered lava blocks, but a new tumulus had formed a few meters downflow. On 3 June Sandro Privitera (IGGUC) observed three emissions of reddish gray ash to more than 500 m above the crater.

On 4 June the two main sites of activity were generally the same as on 19 May (BGVN 24:05): an effusive vent ~25 m below the hornitos at the upper end of the fissure that became active on 4 February, and a cluster of vents at about 2,600 m elevation on the W slope of the VdB. The upper site had shifted ~30-40 m upslope. During the 16 days between the two visits, the site of lava emission had shifted frequently, sending lava flows in various directions. By 4 June lava flows had covered most traces of the tumulus collapse depression formed on 12 May. It appeared that the effusion rate had remained nearly constant for about 2 months (at ~1 m³/s). About 25-30 x 10⁶ m³ of lava had accumulated since 4 February on the western VdB rim and the slope below.

A brief visit on 10 June by Behncke and Francesca Ghisetti (DSGUC) revealed that the output of lava from the 4 February fissure had increased. The active vents were ~10-20 m below the hornitos at the upper end of the fissure. One vigorous vent was on the fissure, but lava also issued from within and on the margins of recent flows on the SW side of the lava field. A flow down the N side of the lava field appeared to have spilled over the rim of VdB. One vent continued to emit lava on the western VdB slope.

Weak explosive activity at the 4 February fissure resumed in mid-June, accompanied by an increase in the lava output. According to Giuseppe Scarpinati (L'Association Européenne Volcanologique, LAVE), an intermittent glow in the eruption area was visible from Acireale (SE of Etna) on the evening of 16 June. This glow was also clearly visible from Catania on the following evenings, and lava was seen extending from the glow area.

By the afternoon of 19 June one large and several smaller hornitos had grown on a large lava shield, ~50-80 m below the cluster of hornitos built during February-March 1999. Two lava rivers extended a few hundred meters in the direction of the VdB. The effusion rate had increased to 2-3 m³/s (it had been less than or equal to 1 m³/s during the previous month), and the volume of lava emitted since 4 February exceeded 30 x 10⁶ m³.

Between 19 and 23 June there was a notable decrease in activity at the eruptive fissure. After a visit on 26-27 June, Scarpinati reported that variable emission of lava from the 4 February fissure continued. Scarpinati also noted that the Voragine produced explosions, but made no direct observations.

On the evening of 29 June Behncke noted that the 4 February fissure had one eruptive site that produced mild lava spattering and two lava flows. Spattering from three closely spaced vents threw blobs of lava up to 3 m away. A partially drained lava tube containing incandescent but stagnant lava was seen 50 m downslope from the vents. The output was estimated at 1-3 m³/s. The SW ("diaframma") vent in the Voragine produced loud explosions every 2-10 minutes that ejected incandescent bombs above the vent.

Activity during July 1999. Another summit visit by Behncke on 1 July benefitted from perfect viewing conditions and very little wind. The generally flat floor of NEC had changed little since 5 October 1998, but now contained a large pit emitting a high-pressure gas plume charged with SO₂. There were periods lasting a few minutes when the noise level increased notably, and the plume became much denser; one time it contained brownish ash. BN had its usual two large eruptive centers, one in its NW part and the other at the base of its SE rim. While the latter periodically emitted plumes of grayish-brown ash, the former was the site of alternating ash emission and magmatic degassing.

The Voragine, according to a guide, had intensified its activity on 26 May. On the morning of 1 July explosions occurred at the SW vent every 1-10 minutes. Explosions at the SW vent started with a noise followed by large bombs that rose tens of meters above the vent, and sometimes even tens of meters above the crater rim itself, and then by a brownish ash plume. A few fresh vesicular bombs were found on the outer SW slope of the Voragine.

Claude Grandpey (LAVE) visited the eruptive fissure on 2 July and observed vigorous lava emission. The next day, lava emission had decreased. Activity was intense at the SW vent of the Voragine, with explosions ejecting bombs outside the crater on the northern side. Many bombs also fell into BN. The central vent in the Voragine had periodic gas and ash emissions. In the BN, noisy activity occurred in the SE vents (which during the 1 July visit only emitted ash), while the NW vent was relatively quiet.

The summit area was visited on 6 and 7 July by Behncke, Peter Ippach, and Eduard Harms (German Volcano Museum, Mayen, Germany). During the first of these two visits there was strong gas emission from the central pit of the NEC, and every 10-45 minutes there were explosive ejections of rocks and ash emissions. In the Voragine, explosive activity at the SW vent had decreased, and only one explosion was observed during two hours. However, the central vent was the site of Strombolian eruptions every 1-10 minutes. Incandescent bombs were ejected but only in one case rose as high as the rim of the vent, which was estimated to be at least 35-40 m deep and had a pit about 5 m wide in its floor. Recently ejected bombs up to 1.5 m long littered most of the Voragine floor.

The 7 July visit to the fissure disclosed continuing activity from two major effusive vents, one located in the area of the hornitos that formed in the past few weeks, while the other lay ~100 m downslope at the end of a lava tube. During four hours of observations, explosion sounds coming from the Voragine (and maybe also from BN) were heard every 5 to 45 minutes.

On 9 and 10 July, Behncke, Ippach, and Harms visited the summit area again, and additional information about the activity on 10-11 July was provided by Scarpinati and Charles Rivière (of Tremblay-en-France, France). Observations were restricted to the area of the 4 February fissure, but Rivière visited the summit craters early on 10 July. At the fissure, three vents were active at the tumulus ~150 m downslope from the uppermost February-March hornitos. Several lava flows were active during 9-10 July, and incandescent lava was seen in many places on the lava field. Lava also issued from several vents along the N margin of the flow-field.

Rivière, who visited the summit craters during the forenoon of 10 July, reported continuous pyroclastic activity deep within the pit of the NEC. In the Voragine, Strombolian activity occurred from the central andSW vents, with bombs at times rising high above the crater rim; Rivière noted that explosions occurred about every two minutes.

Scarpinati and Alain Catté (LAVE) observed the activity from the late afternoon of 10 July through the next morning. Shortly after 1800 on the 10th, the tumulus where the main vent had been emitting lava was seen to "inflate rapidly, and then lava came down on all its sides, forming three lava rivers." On the next morning, none of the vents on the tumulus were active, but a new vent had formed 30 m SE, burying the tourist path to the vent area; lava effusion diminished later that morning. Between 13 and 24 July lava continued to flow from the 4 February fissure, but the amount was relatively small, and short-lived flows extended only a few hundred meters downslope.

On 16 July Grandpey noted clouds of brownish ash from NEC. The Voragine was quiet, but Grandpey learned that the SW vent was active earlier during the week (around 12 or 13 July) with explosions, while lava was visible at the bottom. The NW vent inside BN was quiet, and parts of it had collapsed. Strong explosions heard every few minutes in the SE vent had been audible throughout the night.

Activity was particularly intense in the Voragine on 18 July when Rivière filmed the SW vent. Lava had again risen to ~20 m below the rim, and a small, dome-shaped mound of lava produced numerous small explosions. The mound was partly incandescent and was blown to pieces in some of the larger explosions, then rose again. During the days preceding 24 July, however, Rivière observed a diminution of activity in the Voragine, but there was explosive activity within BN.

The summit craters were visited again on 28 July by Behncke, Carmelo Monaco and Angelita Rigano (DSGUC), and others. Deep within the central pit of the NEC there were near-continuous detonations. Within the BN, explosive activity occurred deep within the two main vents. The SE vent produced near-continuous emissions of brownish ash. The Voragine central vent produced powerful explosions and at times prolonged fountains of incandescent bombs, some of them up to 1 m across. Some of the explosions ejected bombs to ~100 m above the crater rim. Many eruptions were accompanied by high-pitched roaring noises indicating high-pressure gas emission from the top of the magma column in the vent, which had risen by tens of meters since last observed directly by Behncke and others on 6 July. At the 4 February fissure, lava emission continued at a low rate. One area of effusive activity lay on the NE side of a large tumulus ~100 m downslope from the upper hornito cluster. The effusion rate was ~1-2 m³/s, and the volume of lava emitted since 4 February was estimated to exceed 35 x 10⁶ m³.

1 August-3 September 1999. Axel Timm from Germany visited on 15 and 16 August and made the following observations. There was little activity in the BN on 15 August, with quiet degassing at the NW vent, while dilute ash clouds were emitted at intervals of several hours from the SE vent. In the Voragine there was only gas emission from the SW vent, but minor eruptions occurred at intervals of 5-60 minutes from the central vent. Rumbling noises and dense gas emissions came from deep within NEC. Several small lava flows issued from the hornito area at the upper end of the 4 February fissure.

On 16 August the SE vent continued to quietly emit ash to 50-100 m above the vent at intervals of about 30 minutes. Voragine eruptions every 10-30 minutes from the central vent varied from noisy gas emissions to explosions that ejected bombs and scoriae far beyond the rim of the vent.

Grandpey reported that lava effusion from the 4 February fissure decreased notably around 20 August. Activity ceased on 25 August, and no effusive activity occurred thereafter for two days. Grandpey noted that the end of the effusive activity corresponded to a increased activity inside the Voragine. On 24 August he saw explosions from two small vents on the N rim of the SW vent. On 26 August Grandpey observed the central part of the Voragine inflate over a surface ~50 m in diameter, followed by an explosion that disrupted about half of that area, ejecting large pyroclasts. A few minutes later a much stronger explosion sent bombs as far as the center of BN and all over the W slope of the Voragine. Similar explosions followed through the next day. When Grandpey returned on 27 August, a new "cavity" had formed at the center of the Voragine and explosions were occurring near the SW vent.

The cessation of activity from the 4 February fissure on 25 August was followed two days later by the opening of a ~50 m long fissure located 40-50 m N of the hornitos. Mild Strombolian activity occurred during the following days and a small lava flow moved along the rim of the lava field.

4 September 1999 eruption from the Voragine and SEC activity. Scarpinati was observing the effusive activity at the new vents at the SE base of the SEC cone at around 1700 on 4 September and noted a hissing sound at around 1745, which gradually increased until it was "like a jumbo jet taking off." Guides at the Torre del Filosofo hut heard a loud detonation at about 1810, and saw intense red glow above the main summit cone ("the BN was incandescent all over"). Strong continuous incandescence between the Voragine and NEC suggested that lava was flowing down the E side of the main summit cone. At about the same time, Scarpinati saw through a gap in the clouds that gas and ash were rising from the summit area. Shortly afterwards he heard the crashing of impacting blocks and bombs, and retreated to the Piccolo Rifugio at about 2,500 m elevation. The climax of the eruption probably occurred between 1900 and 1930, judging from the audible detonations.

Bad weather during most of 4 September precluded observations, but a relatively clear view from Piano Provenzana (on the N flank, ~6 km from the Voragine) revealed the sudden uprise of a dark, ash-laden column that was bent eastwards. Observers at the Piano delle Concazze, about 2,600 m elevation on the N flank and ~2.5 km from the Voragine, enjoyed a splendid view of the eruption. By the time of their arrival, probably between 1830 and 1900, a huge lava fountain was rising hundreds of meters above the Voragine, and a pitch-black, tephra-laden eruption column rose ~2 km high before being blown E by winds. Large bombs fell onto the upper slopes of the NEC, which continuously emitted a dense brown ash plume, and onto the W side of the fountain. At the climax of the activity, the fountain roared to at least 1,500 m above the Voragine, an unprecedented height in the recent history of Etna.

At 1945 the cloud cover lifted, and the group at Piccolo Rifugio saw "an awesome spectacle of gigantic explosions" occurring at intervals of about 2 minutes, one of which was described by Scarpinati as "the biggest I have ever seen" (he has climbed Etna more than 500 times in the past 35 years), and which showered the main summit cone with meter-sized bombs. Some of this late activity may have come from the BN.

By 2045 all activity on the main summit cone had ended, but explosive activity began from the SEC summit vent consisting of dark "smoke" emissions mixed with incandescent pyroclasts. Ten minutes later the activity became purely Strombolian with 20-25 explosions per minute. Observations from the Piccolo Rifugio continued until about 2200 and were curtailed by bad weather; later that evening lava began to spill from the lower part of the fissure on the SE flank of the SEC cone. Lava supply increased at the vents that had become active on 27 August, and on early 5 September, a lava flow ~1 km long was observed by J.-C. Tanguy and local guides.

Effects of the 4 September 1999 eruptions. Soon after the beginning of the eruption, loud detonations were audible in villages and towns around the volcano. This was followed by a fall of scoriaceous lapilli on the E flank, extending to the coast near the town of Giarre, more than 15 km from the summit (figure 81). Many of the lapilli were walnut-sized, and some, in the area of Fornazzo, were up to 10 cm long (observation by J.-C. Tanguy). Eyewitnesses reported that some of the larger fragments were still hot when falling near the villages of Milo, Fornazzo, and Sant'Alfio, but not hot enough to set vegetation afire. Larger clasts broke windshields and seriously damaged vineyards and fruit gardens. In a narrow sector from the Milo-Fornazzo area towards the coastal strip near Giarre the pyroclastic deposit was several centimeters thick, and traffic was disrupted due to scoriae on roads. On the beach of the Ionian Sea between Riposto and Fondachello, scoriae 5-6 cm in diameter were not rare. Press reports put the damage to agriculture and infrastructure at several tens of billions of Lire (several tens of millions of US $). According to the Catania-based newspaper "La Sicilia," ~1 x 10⁶ m³ of pyroclasts fell on Giarre alone, while the full volume of pyroclasts was given as 5 x 10⁶ m³, a value that fits well with observations by Behncke and others.

Figure 81. Sketch map showing the distribution of pyroclasts from the 4 September 1999 eruption of the Voragine, based on field work during the week following the eruption. Courtesy of Boris Behncke.

Field investigations were made by Behncke and Werner Keller (Proyecto de Observación Villarrica/Internet) in the area of Milo, Fornazzo, and Giarre on 6-8 September, and during a summit visit on 7 September. Measurements were made of the thickness of the deposit in various locations before heavy rainfall swept part of it away, and when the cleaning of roads was still in an initial stage. During the afternoon of 7 September visibility was hampered by clouds, but the effects of the eruption were striking. The cones of the summit craters were hit by countless bombs up to 5 m in largest dimension and lithic blocks up to 1 m across. Many bombs and some blocks had fragmented upon impact, and others were found up to 10 m outside the craters created by their impact. Projectiles had arrived on both fairly flat and vertical trajectories. Some of the larger bombs were still warm about 60 hours after their emplacement.

On the S flank of the main summit cone the accumulation of juvenile scoriaceous pyroclasts had apparently been so rapid that the deposit began to slide down the steep flank, forming something like a dry debris flow that extended ~500 m down the slope to its base. In its distal portion the flow ended in two distinct lobes ~1 m thick. About 80% of this deposit consisted of juvenile clasts 10-30 cm in diameter whose edges were rounded while sliding down the slope, the other 20% were older, slightly smaller clasts (reddish scoriae and gray lithic blocks).

Brief glimpses through the clouds permitted a view on the Voragine from ~500 m W of the crater rim. The heavy fallout close to the crater almost healed the large scar cut into the S flank of the adjacent NEC cone during the 22 July 1998 Voragine eruption (BGVN 23:11). On the SW crater rim, the rapid accumulation of fluid ejecta formed a lava flow ~300 m wide and 250-300 m long. Two similar fountain-fed flows were emplaced on the E side of the Voragine, the longer of which traveled ~700 m towards the VdB. Guides on the N flank indicated that another fountain-fed lava flow cascaded into the Bocca Nuova.

On the lower E flank the lapilli deposit extended in a narrow strip E towards the coast near Giarre. Five communities (including Milo, Mascali, and Giarre) suffered heavy fallout. Going northwards from Zafferana, on the SE flank, the southern margin of the fall deposit was in the forests between Petrulli (~2 km N of the center of Zafferana) and Milo, where isolated scoriaceous lapilli with 1-3-cm diameters occurred. Closer to Milo (1.5 km farther N) the number of clasts per square meter increased as did their mean diameter, and on the southern margin of the village the deposit became continuous. Most of the deposit consisted of lapilli-size scoriae, with little ash mostly coating leaves and grass. The largest clasts found in the S part of Milo were 7 cm across, and many reached 5 cm. In the N part of Milo, the thickness of the deposit exceeded 5 cm, and many leaves were damaged. In the S part, ~1.5 km from Milo, the deposit was 5-6 cm thick, and the largest clasts were up to 10 cm across. Residents reported that larger clasts fragmented upon impact. Going north, the deposit thinned gradually and ended with a relatively sharp margin ~2 km N of Fornazzo. Downslope, near the town of Giarre, the area of fallout was ~5 km wide in N-S extension, and up to 5 cm thick in its central portion. Most of the deposit here was composed of fragments with diameters of a few millimeters to 3 cm. The N and S margins of the deposit were strikingly sharp, it seemed that only very little fine ash fell beyond the margins of the lapilli deposit.

Comparison with the (relatively poor) descriptions of the fall deposit produced by an eruption from the Voragine on 17 July 1960 allows the conclusion that the 4 September 1999 eruption was less voluminous but similarly violent, and therefore among the largest explosive eruptions at Etna's summit craters during the past 100 years. The 1960 eruption produced ~10 x 10⁶ m³ of pyroclasts, and clasts more than 5 cm in diameter were reported.

The activity at SEC on the evening of 4 September had many minor effects. The most impressive changes since 28 July were the presence of the new lava lobe that had issued from the lower part of the 4 February fissure, and the collapse of part of the E crater rim.

Activity after 4 September 1999. During the week following 4 September activity continued at the summit craters, but observations were hampered by bad weather. Intense explosive activity occurred each day at the BN, and at times bombs were ejected onto the outer slopes of the main summit cone. The Voragine remained active, and vigorous seismicity indicated that the most intense activity occurred between 0100 and 0400 on 9 September. During their summit visit on 7 September, Behncke and Keller reached the area of activity near SEC and saw two small lava flows issuing from vents 15 m below the spatter cone formed after 27 August that extended onto the W slope of the VdB after a few days. Mild Strombolian activity occurred from a new cluster of hornitos near the effusive vents.

During the evening of 11 September Scarpinati observed lava flowing from a vent ~200-250 m farther downslope to the E of the SEC effusive area. The next morning a new double spatter cone ~200-250 m E of the previous cone issued fluid lava, at an estimated rate of at least 1 m³/s, that moved along the margin of the flow-field. The new vents were on terrain not covered by lava during the previous months, and it appeared that this was a true new eruptive fissure.

Mild magmatic explosions were observed by guides every few minutes early on 18 September. On the next day, Rivière observed vigorous lava splashing from the NW cone of BN. Strombolian activity was relatively weak until early the next morning. At 0445, Tanguy observed the eruption from Trecastagni (on the SE flank). Continuous jets of incandescent material illuminated a gas plume rising more than 500 m above the crater rim. A bright glow in the area of the effusive vents at the ESE base of the SEC was noted, and weak incandescence was seen in the area of the Voragine. Tanguy arrived at the Piccolo Rifugio at about 0545, by which time the most energetic phase was over, although some incandescent bombs still rose up to 300 m above the crater rim. The activity had virtually ceased by 0630.

During the early morning hours of 20 September, vigorous lava fountaining occurred at the BN, mostly from the vents in the NW part of the crater where a broad cone had been the site of weak degassing for several weeks; previous reports noted that the area of this cone had remained virtually unchanged even during the 4 September Voragine eruption. The episode covered almost the entire floor of the BN with lava to thicknesses of several meters to tens of meters. A lava tongue invaded the depression that had previously hosted the SE vents, and only an irregularly shaped depression was left at the site of the NW vents. Explosive activity was again observed on the evening of 20 September, and a brief surge of activity occurred on late 21 September, after which BN became silent for about two weeks.

Effusive activity from the vents on the ESE base of the SEC was intense on the morning of 20 September when visited by Tanguy; lava issued from a vent that had opened the previous afternoon near the large spatter cone built after 27 August, and mild spattering occurred from this cone itself. A new vent had also formed at the fissure that had become active on 12 September. Vigorous effusive activity was continuing at the 12 September vents.

During the week following the 20 September eruptive episode at BN, the most persistently active summit crater was NEC, which had Strombolian activity in its central pit. A visit by Behncke on 28 September revealed that NEC cone had received heavy fallout of bombs on 4 September, and the footpath on its W side had vanished under a continuous cover of bombs, some up to 1.5 m in diameter. While the collapse scar on the SW flank of the cone had been largely healed by bomb fallout, a portion of the cone's flank farther to the ESE had collapsed, leaving a similar scar. Activity within the central pit consisted of near-continuous expulsions of dark ash. Good views obtained by Rivière on 25 September showed that the pit continued to a depth of several hundred meters with vertical walls.

On 28 September, good panoramic views of the Voragine from the S rim of NEC revealed that the former SW and central vents had merged into one large ~200-m-wide crater, but it appeared that there were still two eruptive centers. On the SW rim a wide U-shaped gap had formed in the former "diaframma" (septum) through which the floor of BN could be seen. Eruptive activity within the Voragine on 28 September consisted of frequent loud explosions.

Sub-concentric fractures were present on the outer ENE and E rim of the Voragine and on a ridge which now constitutes both the SE flank of the NEC cone and the NE rim of the Voragine. A fountain-fed lava flow that had formed during the 4 September eruption on the W side of the Voragine was up to 150 m wide in its upper part but narrowed to ~30 m in its distal portion where it formed a lobe along the N side of the 22 July 1998 flow; the new lobe, however, was shorter than its predecessor. Two fountain-fed lava flows also formed on the E side of the Voragine. The longer of these flows extended about halfway to the W rim of the Valle del Bove.

Rivière visited SEC on 24 September and reported that discontinuous effusive activity continued from the new vents (first seen by Scarpinati on the morning of 11 September) near the 4 February fissure. Lava flows extended ~1 km and spilled down the W face of the VdB.

Vigorous eruptive activity resumed in the BN on 30 September, ejecting large bombs hundreds of meters beyond the crater rim. At the same time, activity increased at the NEC. On 29-30 September, near-continuous Strombolian activity ejected bombs tens of meters above the crater rim, and larger bursts reached heights of up to 150 m, dropping bombs all over the crater floor and onto the flanks of the NEC cone.

Information Contacts: Boris Behncke and Jean-Claude Tanguy, Dipartimento di Scienze Geologiche, Palazzo delle Scienze, Università di Catania, Corso Italia 55, 95129 Catania, Italy.

November 1999 (BGVN 24:11) Cite this Report

Vigorous eruptions at Bocca Nuova send lava flows 5 km down the W flank

Following the gradual reactivation of the summit craters since June 1999 and eruptive episodes at the Voragine on 4 September and at the Bocca Nuova (BN) on 20 September, the activity shifted to the Northeast Crater (NEC) and then to the BN in early October. During the second half of October, the BN crater produced spectacular Strombolian activity, episodes of high lava fountaining, and lava overflows onto the W flank of the volcano, the first flows in that area since 1964. Lava flows on the W flank interrupted two dirt roads and burned a small portion of forest, but presented no threat to inhabited areas downslope. After 3 November, the activity declined to low levels.

The information for the following report, covering October-November 1999, was compiled by Boris Behncke at the University of Catania (DSGUC), Marco Fulle, Roberto Carniel, and Jürg Alean. Additional information was provided by Jean-Claude Tanguy. The compilation is based on personal visits to the summit, observations from Catania, and many other sources cited in the text.

Vigorous Strombolian activity occurred at the NEC during the first week of October. When the summit area was visited by Behncke, Roberto Scandone and Lisetta Giacomelli (Dipartimento di Fisica, Università "Roma Tre"), and Angelo Amara (Catania University) on 1 October, strong explosions ejected bombs up to 100 m above the crater rim, and ash emissions were frequent. Similar activity was observed during a summit visit by Behncke and others on 6 October. Brownish-gray ash plumes were frequent, and some of the Strombolian bursts were densely charged with small bombs.

Eruptive activity resumed within the BN on the afternoon of 5 October, after about two weeks of relative calm. After nightfall, Giuseppe Scarpinati (Italian correspondent of L'Association Volcanologique Européenne, LAVE) observed strong explosions from his home in Acireale (~18 km SE from the summit). Huge incandescent bombs were ejected to halfway down the S flank of the main summit cone. Scarpinati noted fluctuating glow at the NEC and increased effusion at the ESE base of the Southeast Crater (SEC) cone. Powerful explosions from the BN were continuing the next morning as Behncke and two students from the University of Trier visited Piano Provenzana on the N flank (~6 km from the BN). Explosions occurred at intervals of ~10 minutes, with minor activity between the explosions. Many bombs were ejected far beyond the crater rim. The source of this activity was probably at the SE eruptive center, which had been buried under lava on 20-21 September.

Vigorous eruptive activity continued at NEC and BN through 11 October. Dark ash-laden plumes commonly rose every few minutes from the NEC. Bombs were ejected from the BN to a distance of several hundred meters, and some bursts rose more than 300 m above the crater. Eruptive activity resumed within the Voragine and continued at least through the following day (information from Sandro Privitera, DSGUC, and Jean-Claude Tanguy).

On the afternoon of 12 October Behncke and Amara were ~250 m from the W rim of the BN, where activity was vigorous, with ejections of dense jets of bombs to hundreds of meters above the crater rim. Eruptive activity occurred from at least four locations within the crater. At 1830 there was the first in a series of powerful detonations that ejected abundant lithics along with incandescent bombs and a tephra-laden plume to ~500 m above the crater rim. The explosions initiated about 30 minutes of more intense activity from three locations in the W and NW part of the crater.

NEC emitted dark dense ash plumes almost continuously. After nightfall only ~10 percent of the emissions ejected incandescent bombs; other emissions appeared to eject mainly lithics. While near the front of the 22 July 1998 lava flow on the dirt road that connects the N and S routes to the summit (named "summit road" in the following paragraphs), several explosions from the Voragine were heard. At the ESE base of SEC cone lava was still issuing quietly after more than 8 months. The effusion rate was estimated at ~1 m³/s; during the previous four weeks, ~2.5 x 10⁶ m³ had been added to the more than 40 x 10⁶ m³ of lava emitted between 4 February and early September 1999.

Strong ash emission from the NEC on the morning of 13 October continued in a pulsating manner into the early afternoon of the following day. At the BN, however, near-continuous ejections of incandescent bombs caused rapid filling of the crater. On the evening of 15 October, vigorous eruptive activity occurred at the Voragine and loud detonations were audible as far as Catania.

Lava was fountaining in BN on the evening of 16 October, but strong explosions resumed the next morning (17 October). Fulle watched the activity from the summit road and reported that continuous lava jetting to several hundred meters above the crater rim occurred from several vents, and bombs dropped onto the outer flanks of the main summit cone. Sometime around 2015 a small portion of the W rim collapsed, allowing lava to move rapidly down the steep slope, crossing the summit road. On the early morning of 18 October, the farthest flow front had reached ~1,900 m elevation and stopped before reaching the Forestale dirt road (figure 82). Lava was reported to flow vigorously through the breach on the W side of the BN on the evening of 18 October, but the fronts did not extend as far downslope as the first major flows.

Figure 82. Sketch map of the lava flows emitted from the Bocca Nuova during October-November 1999, based on photographs taken after the end of the activity from various locations. Main vents of the Bocca Nova (BN) are shown as dots. The other summit craters are the Northeast Crater (NE), Voragine (V), and Southeast Crater (SE). Inset at upper left shows the entire Etna area with the location of the new lavas and the towns of Bronte and Catania. VDB in the inset is Valle del Bove. Courtesy of Boris Behncke.

At about noon on 19 October, Behncke and Scarpinati reached the summit area and observed near-continuous ejections of large bombs high above the rim of the BN. Movement of the lava flow on the W flank had slowed significantly, and only the central portion of the flow was moving. The lava field had many overlapping flow units with a total width of ~100 m at the summit road crossing. Between 1200 and 1230 activity increased until fountaining from the more southerly of the two vents became virtually continuous; frequent large blasts from the other vent dropped bombs up to 150 m beyond the crater rim. A short time later a new flow with a front ~3 m high advanced rapidly through the central flow channel, on top of the still-moving earlier lava. From points along the N margin of the lava field the summit of a pyroclastic cone growing within the BN could be seen rising above the crater rim. Explosive activity consisted of only a few ash-rich emissions between 1630 and 1730. After sunset the active flows were brightly incandescent over their entire length, and BN produced bursts of huge incandescent bombs every 2-10 seconds.

After continuing vigorously until the early morning of 20 October, the activity from the eruptive vents in the W and NW part of the BN ceased, and the lava overflow through the notch in the W crater rim stopped. Sometime near dawn, forceful expulsions of ash began from the SE vent, which had shown little activity the previous week. The low levels of activity permitted volcanologists from the U.K. to reach the rim of the BN and observe at least three vents with mild Strombolian activity and sizeable pyroclastic cones around them. On 21 October at 0300, intense eruptive activity apparently resumed, with renewed lava overflow onto the W flank. A new lobe on the S margin of the flow-field covered more of the summit road and extended to ~2,400 m elevation.

On the morning of 22 October, Scarpinati, from his home in Acireale, observed mild Strombolian activity (one explosion every 15-20 seconds) at the BN and more vigorous spattering at the vents on the ESE base of the SEC cone. By 1130 another episode of high lava fountaining and overflow from BN was in progress. From Catania jets of incandescent material to several hundred meters above the crater rim were visible, and a dense, ash-poor column of yellowish gas rose at least 4 km above the summit. Fulle witnessed the activity from a distance of a few hundred meters, and reported that a N-S fissure ~200 m long in the W part of the BN ejected a virtually continuous sheet of very fluid lava with jets rising up to 500 m high. A torrent of lava ran halfway down the W flank of the main summit cone at a speed of ~50 m/minute, carrying incandescent blocks more than 10 m across. An overflow may have also occurred on the NNW side of the BN. After 1230 the activity and the volume of overflowing lava diminished, but sporadic explosions threw large bombs hundreds of meters beyond the crater rim until 1700. Between 2000 and 2100 Behncke and Scarpinati visited the ESE base of the SEC cone where lava emission from at least three vents continued, and incandescent gas was emitted forcefully from two large hornitos that had grown earlier that day. Flowing lava was seen ~500 m NE and E from the active vents.

On 23 October another episode of high lava fountaining at the BN and overflow onto the W flank began at about 1000. This activity culminated at about 1045 but was less intense than the episode of the previous day. Relatively mild Strombolian activity persisted through the evening of 24 October, and small volumes of lava flowed onto the W flank. During the afternoon, Fulle and Carniel observed explosions (mostly ash) from four vents on the fissure in BN, and from a vent in the SE sector of the BN. During the night loud explosions at intervals of several minutes rattled windows and doors in towns 24 and 28 km NE.

On the morning of 25 October ash was emitted sporadically from BN until by about 1130 continuous fountaining was in progress. Broad jets of lava generally rose 100-200 m above the crater rim, but occasional jets soared to 500 m height. Lava again descended the W flank. A large pyroclastic cone near the vent that produced most of the fountaining (in the NW part of the BN) was ~30 m above the NW crater rim. Fulle and Carniel observed that the activity occurred from a number of vents along a N-S trending fissure in the W part of the BN. At 1145 Fulle observed that lava was overflowing the rim near the SW vent, covering the southern edge of the previous lava field.

From 1235 to 1300 the flank of the BN was affected by intense deformation, with the opening of several fractures and a series of collapses. Within a few minutes (peaking around 1320) a wide sector of the WNW crater rim was pushed up and out by lava within the crater. Minor collapses occurred for about 30 minutes while vigorous lava fountaining continued. The avalanches resulting from the collapses spilled several hundred meters down the W flank and produced brownish plumes. Movie clips taken by Carniel of the deformation and avalanches are available at Stromboli On-line. Lava flowing through the new breach was repeatedly covered with debris but continued to flow, carrying boulders up to 20 m in diameter. On the N side of the BN the mass of fluid bombs transformed into a rootless lava flow that advanced along the flow emplaced on 22 October, but extended farther downslope. The episode ended by about 1630, but was followed by a series of strong isolated explosions. By 1900, the main vent in the BN produced frequent Strombolian bursts, and lava flow through the breach in the crater rim continued at a reduced rate.

Observations made that evening revealed that a new lava flow with at least seven active branches had descended the W flank, and the farthest flow front had extended to ~1,900 m elevation. By about 1810 the front of the longest branch began moving through a small patch of forest a few hundred meters above the Forestale Road. The new lava flow was slightly N of the flows produced during the preceding week, with the longest branch extending almost 5 km from the BN, thus being one of the longest flows ever produced by a summit eruption.

On the morning of 26 October, the activity consisted mostly of isolated ash-rich explosions from the southernmost fissure vent in the W part of the BN. Towards the evening the activity became more continuous and there was mild Strombolian activity. Fulle and Carniel reported that up to five vents along the fissure were active. Explosions also occurred from two vents in the SE part of the BN where little activity had been observed the previous week.

On 27 October jets of lava rose tens of meters above two main vents in the W part of the BN, and a new large pyroclastic cone was growing around the northernmost vent. Lava continued to overflow on the W side of the crater, with active flow fronts to ~2,600 m elevation. Between 0015 and 1045, Fulle, Carniel, and Tom Pfeiffer (University of Arhus) observed intense activity, mostly in the NW sector of the BN. From 1230 onwards the explosions of the NW vent of the BN became increasingly stronger. Between 1400 and 1415 some of the largest explosions showered bombs over the whole main summit cone, and a scoria fall was noticed at the Torre del Filosofo mountain hut. At 1433 strong explosions of dark ash occurred at the NEC. The activity of the BN remained strong all afternoon. New lava spilled down the W flank, and at about 1700, the farthest flow front cut the Forestale road at about 1,800 m elevation, immediately S of Monte Nunziata (the main scoria cone of the 1843 eruption), and entered a patch of dense forest. Early the next morning the front of the main flow had extended ~200 m below the Forestale road, to ~1,730 m elevation; by 29 October the flow had stopped.

Vigorous lava jetting from the BN was observed at about 0600 on 29 October by Giovanni Sturiale (DSGUC). Activity observed by Sturiale, Behncke, Pfeiffer, and Vincenzo Polizotto (University of Catania) later that day included incandescent bombs from the NW vent, forceful ejections of dark gray ash and blocks from the SE vents, and vigorous Strombolian activity at the NW vent where the top of the new pyroclastic cone was projecting a few tens of meters above the crater rim. A variety of lava flows were seen on the W flank. Vigorous pulsating lava jetting from the NW vent was continuing at about 2230.

On 30 October, Pfeiffer revisited the summit area and reported that relatively mild Strombolian activity continued throughout the day. The entire Voragine area was covered with bombs, and the Voragine itself "had ceased to exist" because the 4 September 1999 crater was filled to within ~40 m of its rim. The active cone at the NW vent in the BN was very close to the location of the former "diaframma," of which no trace was visible. Emission of blocks and ash from the SE vents in the BN continued. During an overflight by Tanguy at about 1300, a bright red vent lay in the middle of the NW-trending BN fissure. Small lava flows were seen on the upper W slopes and a scoria cone was being built around the NW vent. NEC and SEC emitted a moderate white plume. After sunset a large red glow on the W flank indicated renewed strong effusive activity.

On the evening of 31 October, Scarpinati observed from Acireale that vigorous lava spattering had resumed at the ESE base of the SEC cone, while Strombolian activity at the BN was continuing. Scarpinati visited the area on 1 November and described voluminous lava flows running towards the Valle del Bove, and spattering from a group of hornitos. Effusive activity at the ESE base of the SEC cone showed a marked decrease after 2 November. On the 6th, Scarpinati observed trickles of lava flowing from these vents, but none thereafter.

On 1 November, Behncke and others climbed to the SW side of the BN where vigorous Strombolian activity continued from the NW vent, and occasional weak Strombolian bursts occurred from a vent farther S. Lava again extruded from below the uplifted block of 25 October. The southernmost of the three active lava lobes ran along the S margin of the lava field, cutting another 10 m of the summit road. Explosive activity at the NW vent produced jets up to 300 m high, but ~90 percent of the bombs fell back into the crater, enlarging the pyroclastic cone. On the evening of 3 November BN produced continuous jets of lava up to 300 m high, the last major eruptive episode of the sequence initiated on 5 October. Activity ceased after 0400 on 4 November, and after that the BN produced only weak intermittent Strombolian activity through about 15 November.

The volume of lava erupted from the BN between 17 October and 3 November is probably in the range of 15-20 x 10⁶ m³. Tanguy estimated that the lava flows of 27 October alone amounted to ~5 x 10⁶ m³, and similar flows were erupted on at least three other occasions. This places the October-November activity from the BN among the largest summit eruptions recorded at Etna during the past 200 years. The BN, which had been a 400-m-diameter pit about 150 m deep in 1995, was completely filled, and a sizeable pyroclastic cone was built in its N part, partly burying the "diaframma," the former wall separating this crater from the Voragine. Post-eruption collapse and subsidence caused the partial destruction of this cone and the formation of two pits at the main NW and SE vents of the BN, and the lava-covered plateau filling the former crater subsided by several meters towards its center. On the W side of the main summit cone, the accumulation of new lava caused a considerable buildup of this flank. The Voragine was largely filled by pyroclastics from the NW vent of the BN, with only a shallow depression remaining in its central part.

Information Contacts: Boris Behncke, Dipartimento di Scienze Geologiche, Palazzo delle Scienze, Università di Catania (DSGUC), Corso Italia 55, 95129 Catania, Italy; Roberto Carniel, Dipartimento di Georisorse e Territorio, Università di Udine, Via Cotonificio 114, 33100 Udine, Italy (URL: http://www.swisseduc.ch/stromboli/); Jürg Alean, Kantonsschule Zürcher Unterland, CH-8180 Bülach, Switzerland; Marco Fulle, Osservatorio Astronomico di Trieste, Via Tiepolo 11, 34131 Trieste, Italy; Jean-Claude Tanguy, Université Paris 6 and IPGP, Observatoire de Saint-Maur, 4, avenue de Neptune, 94107 Saint-Maur des Fossés Cedex, France.

March 2000 (BGVN 25:03) Cite this Report

Frequent eruptions in early 2000 discharging lava flows at new vents and fissures

Etna showed relatively low levels of activity during December 1999 and through 25 January 2000. In contrast, on 26 January, Southeast Crater (SEC) started a new series of strong eruptive episodes, and from then until the end of March, 46 episodes occurred at that crater (table 7). Episodic eruptive activity continued into April. The information for the following report, covering December 1999 to March 2000, was compiled by Boris Behncke at the University of Catania, with additional information from Marco Fulle, Roberto Carniel, and Jürg Alean of Stromboli On-Line. The compilation is based on personal visits to the summit, observations from Catania, and other sources cited in the text.

Table 7. Chronology of eruptive episodes from the Southeast Crater at Etna, 26 January-24 March 2000. Courtesy of Boris Behncke.

Episode Number	Date	Approximate Time	Comment
1	26 Jan 2000	0100-1300	Lava flows until late evening, flow about 2.5 km long.
2	29 Jan 2000	0845-0900	Lava flows until nightfall; less voluminous than 1st episode.
3	01 Feb 2000	0900-1000	Light ashfall on Catania.
4	02 Feb 2000	0800-0830	--
5	03 Feb 2000	0800-0900	--
6	04 Feb 2000	0950-1020	--
7	05 Feb 2000	0010-0030	Lava emission from N flank fracture heralds this episode.
8	05 Feb 2000	1200-1230	--
9	06 Feb 2000	0430-0500	--
10	06 Feb 2000	2300-2330	--
11	07 Feb 2000	1650-1710	Spectacular fountains from multiple vents at SEC summit, and eruption column ~5 km high.
12	08 Feb 2000	1130-1145	Observed from 3 km distance.
13	08 Feb 2000	2000-2015	--
14	09 Feb 2000	0700-0800	--
15	10 Feb 2000	0020-0100	--
16	10 Feb 2000	1330-1345	--
17	10 Feb 2000	2130-2300	--
18	11 Feb 2000	0530-0550	Four spectacular 400-m-high fire-fountains from the summit of SEC, and eruptive fracture on N flank.
19	11 Feb 2000	2200-2220	--
20	12 Feb 2000	0350-0430	--
21	12 Feb 2000	0945-1030	Strong ash emission from upper N flank at end of episode.
22	13 Feb 2000	0030-0050	Occurred during very bad weather and poor visibility.
23	13 Feb 2000	1240-1300	--
24	14 Feb 2000	0300-0330	--
25	14 Feb 2000	1600-1630	Oblique cauliflower-shaped plume; ashfall 50 km away. Observed from 900 m distance.
26	15 Feb 2000	1800-1820	The most violent episode of the sequence, with fountains to 800 m. Observed from ~1 km distance.
27	16 Feb 2000	0640-0700	--
28	16 Feb 2000	1605-1615	Observed from 1 km distance.
29	17 Feb 2000	0500-0530	--
30	17 Feb 2000	1310-1330	--
31	17 Feb 2000	2130-2200	--
32	18 Feb 2000	0730-0800	--
33	18 Feb 2000	1640-1700	--
34	19 Feb 2000	0900-0945	--
35	20 Feb 2000	1700-1820	--
36	23 Feb 2000	0245-0435	Activity less violent than during earlier paroxysms; buildup phase lasts much longer than in previous events.
37	27 Feb 2000	0645-0950	--
38	28 Feb 2000	1630-1730	Activity begins to concentrate at eruptive center S of the SEC ("Sudestino").
39	04 Mar 2000	0400-0450	--
40	08 Mar 2000	0745-1030	--
41	12 Mar 2000	1300-1415	Activity mainly concentrated at the Sudestino. Lava flows pass close to Torre del Filosofo.
42	14 Mar 2000	0710-0740	Activity at the Sudestino. Lava reaches Torre del Filosofo and piles up on two sides of the building to about two-thirds of its height, burns wooden hut.
43	19 Mar 2000	0100-0330	Activity at the Sudestino. Ashfall in Catania.
44	22 Mar 2000	1945-2100	Activity returns to SEC; lava emitted from fissures on S and N flanks of the SEC cone.
45	24 Mar 2000	1940-2035	Very similar to episode 44.

Activity at Southeast Crater, 26 January-29 February 2000. Eruptive activity resumed early on 26 January at the summit vent of SEC (figure 83), after 4.5 months of quiet, and 2.5 months after the cessation of lava emission from fissures at its SE base. Initially the activity was Strombolian, but at about 0500 the activity changed to fire-fountaining, followed by the opening of a fissure on the S flank of the cone. Fountaining continued intermittently until about noon, but lava continued to flow from the lower end of the fissure until the late evening, advancing ~2.5 km into the Valle del Bove along the S margin of the 1999 lava field. Field inspections later revealed that numerous blocks of older lava and welded scoriae from the upper part of the cone fell up to 500 m from the summit of the cone.

Figure 83. Map of the summit area of Etna showing the approximate extent of lavas erupted from the Southeast Crater (SEC) between late January and March 2000. Flows terminating in arrows indicate the flow direction rather than its length. Lavas erupted from fissures near SEC between February and November 1999 and from Bocca Nuova in October-November 1999 are shown for comparison. The broken line extending from TDF (Torre del Filosofo) to the W is the margin of the Piano caldera, presumably formed during a powerful explosive eruption in 122 BC. V is the Voragine and BN is the Bocca Nuova. Courtesy of Boris Behncke.

The second eruptive episode, on the morning of 29 January, lasted about 15 minutes. As during the preceding episode, the cone fractured on the S side, and lava flowed for a few hundred meters to the SSE and SE. After the cessation of lava fountaining, lava continued to trickle from the fissure until the evening.

Beginning on 1 February, eruptive episodes occurred at ever shorter intervals. For the next four days, these events were separated by quiet intervals of 20-24 hours. They essentially resembled the second episode, with initial mild Strombolian activity followed by lava fountaining at the summit vent. Fountaining continued for a few minutes before the S flank of the cone fractured and small fountains rose along the fracture, while lava flowed from its lower end. Activity continued for up to 10 minutes and then ceased.

During these days intermittent minor lava effusion occurred from vents on the lower N flank of the SEC cone, feeding short flows. On the evening of 4 February the lava output gradually increased. Mild Strombolian activity began sometime before 2330 from a vent high on the SSW flank. By this time lava apparently spilled over the N rim of the crater. The volume of lava running down the N flank increased, and explosive activity at the summit vent (and possibly at the SSW flank vent) became increasingly vigorous. Shortly after 0010 on 5 February the activity culminated with lava fountains and voluminous lava emission. After only ten minutes the activity began to diminish.

Between 5 and 18 February, eruptive episodes occurred at a rate of 2-3 events/day, separated by quiet intervals of 5.5-26 hours. During the first ten days of this period, lava slowly issued from the vents on the N flank of the SEC cone. Before each episode the volume of lava output gradually increased, followed by the onset of lava spattering at the same vents and increasing gas emission from the summit vent. The spattering soon graded into a continuous fountain of very fluid lava, jetting obliquely from the N-flank vents, and then the activity would extend to one or more vents at and near the SEC summit. At the height of the activity, an eruption column mainly consisting of white vapor rose several kilometers, and ash fell up to 40 km downwind. Towns at the base of the volcano, mostly in the E and SE sectors, received light rains of ash and lapilli.

During several episodes a fracture opened progressively across the N flank from the base up to the summit vent, with small fountains, while Strombolian bursts began at the summit vent. This activity rapidly culminated in high lava fountains from one or more summit vents. During an eruption late on 11 February, four fountains rose up to 400 m high, while a continuous line of smaller fountains played along the N-flank fracture. Lava flowed copiously from the lower end of that fracture, while a new vent high on the S flank fed a lava flow which reached the base of the cone. The activity became intermittent after 10 minutes of fountaining and ended shortly thereafter, while lava continued to flow at diminishing rate from the lower end of the N-flank fissure.

An eruptive episode on the afternoon of 14 February was observed from less than 1 km away by Behncke and Giuseppe Scarpinati (Italian delegate of the Association Européenne Volcanologique), who had arrived shortly before the onset at a spot SE of the cone. Like on other occasions, the activity started with increasing gas emission from the vents on the lower N flank. By 1600 a broad, dull red fountain roared to a height of ~100 m, and gas emissions increased rapidly on the upper N flank. Small rockfalls occurred on the SE flank.

Soon after 1605 a huge jet of glowing bombs from the summit formed a rapidly expanding eruption column. Shortly thereafter, a densely tephra-charged, cauliflower-shaped plume burst obliquely upwards from the S side of the summit. At the same time, incandescent pyroclastics fell far beyond the base of the cone, but none hit the area from where Behncke and Scarpinati were located. Instead, the curtain of falling ash and scoriae rapidly extended southwards, towards Torre del Filosofo, a mountain hut ~1 km S of the SEC. Scoria clasts up to 30 cm long fell around the building. Lapilli-sized scoriae fell abundantly up to 5 km to the S, and ash fell up to 50 km away. The continuous loud rumbling of the fountains mixed with the pattering noise of large clasts impacting the snow near Torre del Filosofo. Lava could be seen flowing down the S flank in a broad stream a few minutes after the onset of explosive activity. At about 1620, the activity began to wane, although lava trickled from a vent high on the S flank for several hours.

The next day, after 26 hours of quiet, the most powerful episode of the sequence was observed from Torre del Filosofo by a group including Marco Fulle of the Astronomical Observatory of Trieste, Italy. The event was heralded by increased gas emission from the summit vent shortly before 1800, followed by mild Strombolian activity. For about 10 minutes there was a gradual buildup of the activity, with Strombolian bursts from at least two vents. As the activity became more continuous, incandescent pyroclastics were thrown to ever greater distances, mainly onto the E flank. Shortly after 1800, a glowing spot appeared immediately below the S lip of the summit vent in a deep notch. A small pulsating fountain from this new vent gained rapidly in height and vigor. Eruption noises began to change from the intermittent gushing of the Strombolian activity to a continuous loud noise similar to heavy surf.

Within 1-2 minutes after the appearance of the S-flank vent, huge jets of fluid lava rose from that vent and from vents at the summit. The volume of lava from the S vent increased rapidly, at times generating surges overriding earlier flows. The upper part of the cone was soon covered by incandescent pyroclastics; most fallout occurred on the E side due to a strong wind from the W. Activity escalated when a huge incandescent jet burst obliquely from the S vent in the direction of the Torre del Filosofo, and within a few seconds it rose to a height of ~1,000 m. The noise soon became dominated by thousands of bombs crashing on the ground at rapidly growing distance from the cone. The observers fled under a side roof of the Torre del Filosofo building a few seconds before bombs began falling around and beyond the building. Some of them had diameters of tens of centimeters, and many were seen bouncing and bursting into fragments. This rain of bombs lasted about 20 seconds, after which activity stabilized with lava jetting vertically from S-flank and the summit vents.

As was evident from video filmed by British cameraman David Bryant, the largest fountain came from the summit, and from the video as well as from estimates made by other observers, including Behncke (in Catania) and Scarpinati (in Acireale), the fountain height was consistently 500-600 m with bursts reaching 800 m above the summit. The entire cone was covered with incandescent material, some of which developed secondary flowage, while a broad lava flow ran down the S flank.

About 10 minutes after the onset of violent fountaining, the fountains from the cone appeared slightly weaker, although the continuous uprush continued for some time. Then the fountains stopped abruptly, while thousands of incandescent projectiles continued to fall onto the cone. After a few seconds, new lava jets appeared that were short-lived and much weaker. At the end of the activity, dense ash from the summit vent blew E as far as Acireale. Lava continued to run out of a fracture on the S flank, and the gradual sinking of the lava level in the fracture indicated that the conduit was subsiding.

On the afternoon of 16 February, Fulle observed another eruptive episode from the Torre del Filosofo. This event included lava fountaining from a vent about halfway down the S flank of the SEC cone. The activity then extended to the summit vent, continued vigorously for about 10 minutes and ended abruptly.

Eruptive episodes began to diminish in frequency and intensity after 18 February. The near-continuous effusive activity at the N-flank vents stopped. During the last 10 days of the month, five episodes occurred. On the early morning of 23 February, an episode lasted more than 1 hour, but consisted mainly of strong Strombolian explosions. The last two episodes of February, on the 27th and 28th, involved significant activity from vents near the S base of the cone. In both events the activity lasted for several hours, and erupted more lava from the S vents than during earlier episodes. During some of the episodes lava was apparently also produced from N-flank vents.

Activity at Southeast Crater during March. Episodic eruptive activity at the SEC continued in March and became more focused at the vents at the S base of the SEC cone, where a cone began to grow. This cone was informally named "Sudestino" (little Southeast), following the example of the "Nordestino," a lava shield crowned by a large hornito that formed in 1970 at the NE base of the Northeast Crater. In late March, the main focus of activity returned to the SEC, and episodes became very similar to those of early- to mid-February, with lava emission mostly from fractures on the N and S flanks of the SEC cone.

The initial March activity began on the late afternoon of 3 March. At first the activity consisted of slow lava effusion from Sudestino. Loud detonations became audible in Acireale and other towns in the SE and E sectors around 0400 on 4 March, marking the period of strongest explosive activity. Scarpinati, who observed the activity from his home in Acireale, noted that even in the moments of strongest activity, no sustained lava fountaining occurred, but all activity consisted of discrete powerful explosions. When the activity began to diminish (at about 0430), a fountain of very fluid lava in the area of the Sudestino rose ~30 m. The episode ended at about 0500, but after 0430 most activity appears to have come from Sudestino. Minor outflow of lava continued for about two days from Sudestino. Another episode on 8 March was preceded by slow lava effusion from Sudestino. During a summit visit by Behncke and others on 11 March, the SEC and Sudestino were quiet.

Sudestino erupted again shortly after noon on 12 March. The activity began with increased gas emission, and by about 1300 a lava fountain rose to a height of several tens of meters. Ash was expelled from the crater lying a short distance further up the S flank. Later a densely ash-laden plume was emitted from the summit. Lava flowed abundantly from Sudestino, mainly to the S and SW. A lava flow passed only a few tens of meters W of the Torre del Filosofo and extended ~100 m down the steep slope, burying a section of the dirt road that leads to the building.

The Sudestino vent erupted once more on 14 March with a brightly incandescent lava fountain and emission of a voluminous lava flow that advanced to the S with a front hundreds of meters wide, reaching Torre del Filosofo sometime after 1100. Eyewitnesses reported that by about 1100 the lava front was still ~50 m from the building, but presumably the lava reached and encircled it on two sides shortly afterwards. The wooden shack next to the building, used as a souvenir shop by mountain guides during the summer, was burnt by the lava, melting the snow which had covered the shack. Lava flowed ~100 m further down the slope to the W of Torre del Filosofo. A new dirt road built on this flow two days later allowed monitoring and communication equipment to be salvaged prior to the building's destruction.

Lava fountains were visible at the Sudestino around 0130 on 19 March, by which time lava had already begun extending down the flanks. The activity continued vigorously until about 0300, and generated significant ash that fell in Catania and surrounding areas. A large volume of lava was emplaced on the plain SW of the SEC, and several flow lobes extended as far as the N base of Monte Frumento Supino, a prehistoric cinder cone (figure 83).

Sometime after 1800 on 22 March, mild Strombolian activity began at the summit vent, and by 1945 there was a pulsating lava fountain. A new vent burst open high on the SSW flank at about 2010, emitting a lava flow and producing a small fountain. The activity progressively increased at both vents until another vent opened at about 2025 near the NE base of the cone. At this vent, a lava fountain rapidly began to rise several tens of meters high, while two lava flows spilled into the adjacent Valle del Bove. The lava fountain from the summit began to diminish, and ceased shortly before 2100. Lava continued for some time from the flank vents. The southern flow rapidly reached the WSW base of the cone and turned W or WSW, in the direction of the 1971 "Observatory cone." About 500 m NW of Torre del Filosofo the flow turned SW and reached the slope near Monte Frumento Supino, where it advanced up to 100 m. On the NE side of the SEC cone, the two lava flows advanced several hundred meters into the Valle del Bove.

Lava effusion from the vents on the NE side of the SEC cone increased during the late afternoon of 24 March. Mild spattering and intermittent glow at the summit indicated the onset of Strombolian activity. This activity graded into a lava fountain shortly before the new year (2000), and a second, smaller fountain played at the effusive vent on the NE side of the cone. Lava flowed into the Valle del Bove, reaching a length of possibly more than 1 km. Sometime after the new year began, a vent opened on the upper S flank of the SEC cone, feeding a minor flow. The activity was still vigorous at around 2030, when loud rumbling noises could be heard in Catania, and windows were vibrating in Acireale and other towns nearer to the volcano. The strongest activity apparently ceased by 2100, but at 2230 there was still vigorous effusive activity.

The last significant activity of the reporting period occurred on the evening of 29 March, after five days of quiet, the longest repose period of the eruptive sequence. Lava effusion from vents on the NE side of the cone became evident after nightfall and gradually increased, accompanied by the weak Strombolian activity at the summit vent. By 2000, the Strombolian bursts had become more frequent, and soon blended into a continuous pulsating fountain. A new vent high on the S flank emitted a lava flow that rapidly spilled to the base of the cone, then was deflected to the SW by the Sudestino. During the following 30 minutes, at least three smaller vents opened at progressively lower elevations on the S flank in the direction of Sudestino. After the opening of the first S-flank vent, activity at the summit became weaker and discontinuous. Sometime around 2120 large fountains from vents on the N flank sent lava flows NE towards the Valle del Leone. Fountaining ceased at around 2200, but lava continued to flow from the N vents, feeding several lobes, the longest of which advanced ~2 km into the Valle del Leone. On the S side, lava extended ~1-1.5 km SW to the N base of Monte Frumento Supino.

Activity at Bocca Nuova, Voragine, and Northeast Crater. During December 1999-25 January 2000 Bocca Nuova produced intermittent mild Strombolian activity that at times ejected bombs outside the crater. Ash emissions were frequent in late December and early January.

Activity at Bocca Nuova during the eruptive episodes at SEC continued at relatively low levels. During a summit visit on 2 February, Behncke and Scarpinati observed frequent small explosions from the E part of the crater, but all ejecta fell back into the vent. Six days later, Behncke and Scarpinati entered the crater from the SW – this had become possible due to the filling of the crater in October-November 1999 – and approached the vent which was the source of intermittent night glow for most of February. Activity consisted of vigorous gas emission, punctuated by strong blasts of incandescent gas, but no pyroclastic ejections. When standing on the edge of the vent, Behncke and Scarpinati saw an incandescent hole ~2 m across on the floor of the funnel-shaped vent which was the source of the gas ejections. Scarpinati noted that the activity was similar to that observed during the first year of the life of the Bocca Nuova, when it was only a small vent ~8 m wide.

The same activity was observed in early March by Charles Rivière (from Tremblay-en-France, France). In late March activity was the same as in early February, consisting of jets of incandescent gas without pyroclastic ejections. A small amount of strongly altered, fine-grained lithics were sometimes contained in the gas jet. It appeared that no ejections of fresh magmatic material had occurred within the Bocca Nuova since at least early February.

The other two summit craters remained essentially quiet during the reporting period. Northeast Crater occasionally produced emissions of thick gas plumes, at times charged with a little lithic ash. No eruptive activity is known to have occurred at the Voragine. When seen by Behncke on 8 February, the crater emitted only wisps of vapor from the large pit formed during the 4 September 1999 eruption.

Information Contacts: Boris Behncke, Dipartimento di Scienze Geologiche, Palazzo delle Scienze, Universitá di Catania, Corso Italia 55, 95129 Catania, Italy; Roberto Carniel, Dipartimento di Georisorse e Territorio, Universitá di Udine, Via Cotonificio 114, 33100 Udine (URL: http://www.swisseduc.ch/stromboli/); Jürg Alean, Kantonsschule Zürcher Unterland, CH-8180 Bülach, Switzerland; Marco Fulle, Osservatorio Astronomico di Trieste, Via Tiepolo 11, 34131 Trieste, Italy.

June 2000 (BGVN 25:06) Cite this Report

Frequent Strombolian eruptions and high gas emissions March-June 2000

Between March and June 2000, Etna's activity was characterized by several Strombolian eruptions and high gas emissions predominantly at the Southeast Crater (SEC). Sixty-four strong eruptive episodes have occurred since the new eruptive series began on 26 January 2000 (BGVN 25:03), with 19 episodes between March and June. The information for the following report is based on official weekly monitoring reports posted on the Poseidon website.

Activity during 29 March-April. Through March lava flows and ash emissions occurred frequently, and on 29 March at about 1900, lava flows were generated on the S sector of the SEC. Shortly after 0730 on 1 April intermittent ash emissions rose to ~3 km and fell on the E flank. An episode on 3 April produced strong rumblings that were felt in the area of Zafferana Etnea, with ashfall in the area of Giardini (NE sector). On 6 April, between 1010 and 1130, explosive activity produced a lava fountain and lava flows. Over the following days the only activity at the volcano was abundant emissions of steam from Bocca Nuova (BN).

On 10 and 11 April, modest Strombolian activity was observed at BN, which became more sporadic in the following days then quieted on the evening of 14 April. On 15 April, at about 1700, weak effusive activity resumed from the vent at the S foot of SEC. At 0928 explosive activity recommenced with abundant lava emission. Ash also erupted from SEC's summit and reached 2 km altitude. Intense but irregular explosive activity was also present at the BN. Activity peaked at 1235 with an eruptive column that enveloped the SEC and rose to an estimated height of 6 km; the column produced abundant fall of ash and lapilli on the E slope. The episode ended abruptly at 1250. During this time Voragine (VOR) exhibited slow steam emission.

At 0545 on 26 April, intense Strombolian activity began and was followed at 0637 by an ash emission that rose several kilometers. In addition, a series of lava flows occurred from the SEC. Beginning at 0723, explosive activity diminished and had ended by 0740. In the following days there were no further eruptive events except for occasional, and sometimes intense, gas emissions from the BN.

Activity during May 2000. During 1-7 May, there was strong gas emission. On 5 May, a strong new gas emission phase began at the SEC, representing the 52nd episode since 26 January 2000. A dense eruptive column rose several kilometers over the volcano's summit and deposited several centimeters of ash on local villages to the SE. At about 1800 the volcanic tremors and eruptive column waned, leaving weak Strombolian activity that ended around 1824. After 5 May, the SEC returned to a state of quiet. The Northeast Crater (NEC) showed intense gas emission, with varied ash content. Weak Strombolian activity persisted at the BN.

Eruptive activity during 8-14 May consisted of abundant steam emissions, mainly from BN and NEC. The BN was the most active crater, emitting copious amounts of steam from at least two vents. The NEC also had abundant steam emissions with varied ash content. Meanwhile, VOR emitted modest amounts of gas and SEC virtually nothing.

During 15-21 May there were four strong gas emissions from the SEC. During the first strong episode, on 15 May, tephra covered the E flank of the volcano. A second episode during the night of 15-16 May consisted of a violent emission of tephra from 2100-2150 that covered the SE flank. The third episode began with Strombolian activity at the SEC then changed rapidly to well-developed lava fountains between 2240 and 2300. Activity abruptly decreased and ended completely within the space of a few minutes. A fourth strong episode occurred about 2145 on 19 May with increased activity from the lava flow on the N flank of the SEC. Violent gas emissions occurred shortly after 2200 and ended within an hour. Significant eruptive activity continued from the NEC, though more discontinuous than during the preceding weeks. The abundant emissions of ash increased significantly beginning 17 May, continuing for several hours. The ash emissions from the NEC were independent of the concurrent increase of volcanic tremors and activity of the SEC, except for occasional temporal coincidence. Steam emissions from the BN were also intense, sometimes associated with weak Strombolian intracrater activity. Slow gas emissions appeared from the VOR.

Two strong episodes occurred at SEC on 23 and 27 May. Activity at the other craters consisted of above normal ash emissions from NEC, intense gas emissions at BN, and weak fumarolic activity at VOR. The 57th eruptive episode of the series began on 23 May with strong explosive activity between 0301 and 0329 accompanied by lava flows down the S flank of the volcano. An episode on 27 May was obscured by poor meteorological conditions.

Activity through June 2000. Two eruptive episodes occurred at SEC on 1 June. First, at 0814, sustained lava fountains began, with some reaching an altitude of 600-700 m before ending around 0832. The column of ash and steam rose for several thousands of meters over the summit and produced a fall of fine pyroclastic material over much of the countryside on Etna's S slope, as far as Catania. At 1930 on 1 June another episode began with a considerable increase in the flow of lava.

On 5 June a strong gas emission at SEC went on for about thirty minutes, during which an ash-and-steam cloud rose to ~3-4 km. The ashfall covered an ample sector of the SE and S region, extending to the Plain of Catania and creating difficulties in air traffic to and from Fonatanrossa and Sigonella airports. As with preceding episodes, the gas emissions were associated with lava flows, primarily on the N slope of the SEC. Just after 1230 on 8 June, an increase in this same lava flow announced another strong gas emission phase beginning with a Strombolian eruption. There was a progressive increase in the explosive activity which reached its peak between 1356 and 1426. The fallout from the eruptive cloud was distributed toward the N.

Another strong gas emission began on 14 June at about 0700 with Strombolian characteristics. Ash emissions reached a climax between 0920 and 0940. On 24 June the 64th episode of activity at SEC occurred when a strong gas emission issued from NEC and VOR. This episode began with an increase of lava flow activity from the fracture on the N flank of the SEC. Later, Strombolian activity at the SEC's summit crater made a transition at about 2130 to a more violent, continuous gas emission phase which reached a peak about 2144, before ending shortly thereafter. After the 24 June activity there were no eruptions the rest of the month, but sporadic ash emissions occurred at all summit craters, particularly at BN and VOR.

Information Contacts: Sistema Poseidon, a cooperative project supported by both the Italian Government and the Sicilian Regional Government, and operated by several scientific institutions (URL: http://www.ct.ingv.it/en/chi-siamo/la-sezione.html).

September 2000 (BGVN 25:09) Cite this Report

Additional descriptions of April-May eruptions and an aircraft damaged by tephra-fall

Activity at Etna during March-June 2000 was previously reported with a focus on the overall eruptive pattern (BGVN 25:06). Additional details about the eruptions on 16 April, 26 April, 5 May, and 15 May provided here by J-C. Tanguy and colleagues present a different perspective on the activity. Following the 26 April eruption a commercial aircraft encountered fallout from the plume; Boris Behncke compiled a summary of this event based on local observers and news sources.

Southeast Crater eruption on16 April. In the late afternoon of 15 April, Etna guides noticed increased fumes, and at 1920 observed a small lava flow from the Sudestino, the large spatter cone at the southern base of the SE cone. Views of the upper S flank from the summit craters were obscured by heavy fumes, but by about 2300 the lava flow could be seen barely extending to a few tens of meters E. It increased during the night to an approximate length of 500-600 m, without explosive activity at the vent. On 16 April, fumes from Sudestino continued to increase, becoming thicker with a very dense, whitish color. At about 1115 a brilliant red lava fountain 20-30 m high supplied lava flows that traveled W and E. A calm wind allowed the bluish fumes of the lava flows and the white plumes from the Sudestino and Bocca Nuova to rise more than 1,000 m above the summit. At 1255 the Sudestino lava fountain stopped, although the lava outflow continued, and loud rumblings from the SEC main vent were accompanied by the crashing of bombs.

At 1305 a strong detonation and column of brownish ash (probably old material) rose ~1,500 m above the SE cone. Shortly afterwards the Sudestino lava fountain reappeared with a considerable increase of effusive activity. Lava flows spread rapidly W and E, and the whole summit zone became obscured by bluish fumes, as well as the increasing amount of dust rising from the flanks of the main SE cone from the impact of falling bombs and detritus. During the following hour there was a succession of increasing explosions at the SEC with dark jets of pyroclasts accompanied by loud rumblings, and periods of lower, though still significant, explosive activity. A sustained lava fountain rose 30-40 m high at the Sudestino.

At about 1430 the culmination began, which lasted less than 20 minutes. Some powerful jets of cinders and large bombs from the SEC shot obliquely to the SW while a large eruption column rose ~5 km above the summit. At one point, a small pyroclastic surge extended very rapidly toward the 1971 cone but stopped before reaching it, and the whole central cone suffered a heavy rain of large bombs, some of which reached the Torre del Filosofo building, forcing several bystanders to retreat hastily. At probably the same time, the SEC opened on its NE side (concealed by ashfall and dust), where still larger pyroclastic surges and lava flows were seen (also observed by the guide Alfio Carbonaro). The climax seems to have been reached during the following ten minutes (figure 84), with larger pyroclasts hurled to a maximum of 1,000-1,500 m above the vent. At 1450 explosive activity decreased and ceased within a few minutes. Lava flows continued to spread as large tongues several tens of meters across and 30-40 cm thick, notably to the S and the SW (a flow to the NE could not be observed). These flows were still advancing at a fast rate around 1600 (0.5-1.0 m/minute), but had stopped by nightfall. Activity at that time consisted of very small rare lava bursts at the Sudestino and a continuously glowing point near the E summit of the SE cone, probably fumaroles.

Figure 84. Eruption column from the Southeast Crater of Etna at about 1437 on 16 April 2000. White plumes are coming from Bocca Nuova on the left and the Sudestino spatter cone in the middle foreground. The Southeast Crater cone is completely obscured by the dark eruption plume. Photo courtesy of Jean-Claude Tanguy.

Southeast Crater eruption on 26 April. On the morning of 25 April, whitish fumes occurred intermittently at the SEC, changing after 1340 to small emissions of brownish ash. At nightfall a small glow was seen at the N foot of the SE cone, heralding a sluggish lava flow that had slightly increased after midnight. At 0615 on 26 April the SEC showed strong emissions of white vapors and brownish ash, and a new eruption began at 0655. It culminated towards 0705 with lava fountains several hundred meters high, and ended at 0720. Although the jet of material was apparently vertical, bombs up to 0.5-1.0 m in diameter fell S of the Torre del Filosofo refuge. The fissure on the S flank of the SE cone reopened and emitted a fast lava flow that rapidly reached the area around the 1971 cone and was still active at 0845, but the Sudestino vent remained inactive. A large plume of cinders and juvenile ash drifted towards Monterosso and Fleri on the SE flank.

Aircraft encounters tephra-fall on 26 April. Additional information about this eruption was furnished by Charles Rivière and Robert Clocchiatti, who witnessed the event from a small distance, Giuseppe Scarpinati, who lives in Acireale on the SE flank, and other sources. According to Rivière, the strongest portion of the eruption began at 0655, when lava fountains rose hundreds of meters. A tall eruption column rapidly rose several kilometers above the summit, forming a dark mushroom-shaped cloud of gas and ash. The plume was then carried to the SE, in the direction of Viagrande (which received a heavy shower of scoriaceous lapilli) and Acireale (where abundant pea-sized lapilli fell). From Catania the plume passing just slightly to the N filled about half the sky and blotted out the rising sun.

At 0739 on 26 April, shortly after the end of the main eruptive phase, an Air Europa Airbus 320, which had departed from the Fontanarossa International Airport of Catania in the direction of Milan, entered the fallout zone of the plume at an altitude of ~1,000 m. Apparently the aircraft received windshield damage (scratches but no breaks) caused by impacts of scoriaceous lapilli and was forced to return immediately to the airport in Catania. Passengers told news reporters that it seemed that the airplane entered a zone of turbulence, causing it to vibrate strongly, and then it seemed as though something was scratching one of the side windows, "as if it were hit by a sharp object." According to some news reports the pilot soon informed the passengers about a "technical problem" and told them everything was under control, and that they were to return to Catania. Other sources reported that the passengers did not note anything unusual until the pilot advised them of the return. It is not clear why the airliner ended up under the plume. The eruption had been visible from the airport as well as from all over eastern Sicily, and it occurred quite some time before departure. The pilot said that he did not see the plume ("It was invisible, certainly not a black cloud"), and to his knowledge it had been drifting in the opposite direction. However, the plume was reportedly quite dark as seen from Catania by residents.

This incident is the first of its kind reported at Etna, which is mainly known for low-explosivity emission of voluminous lava flows during flank eruptions. Summit activity on the other hand, is often much more explosive, and this has been the case particularly during the past five years, a period of intense summit activity. In this period nearly 100 episodes of powerful explosive activity generating significant tephra columns have occurred at all four summit craters. SEC generated 51 in the previous three months.

Southeast Crater eruption on 5 May. In the early morning of 5 May, the gaseous emissions of the SEC occurred in pulses similar to those preceding the previous emission. After a small brownish cloud erupted at 1050, weak Strombolian explosions began deep within the SEC main vent, throwing bombs 30-40 m above the crater rim. Soon after 1700 the explosions gradually increased in strength, sending bombs 100 m high. Lava fountains rose to more than 600 m between 1940 and 1955, burying the entire cone under a layer of incandescent material. The eruption stopped abruptly a few minutes later. Lava flows appear to have erupted only on the N side. The tephra fall covered a large sector of the SE part of the mountain. Most of the largest bombs, up to 1 m across, fell in a direction 120° from the SE cone as revealed by a field study of impacts of ballistic projectiles. The Belvedere zone on the rim of the Valle del Bove depression, at 2,760 m elevation and 2 km away from the SEC, was covered by a 10-cm-thick layer of lapilli, cinders, and bombs up to 30-40 cm in diameter. According to R. Basile, bystanders near Monte Zoccolaro, ~7 km from the SEC, had to protect their heads from scoriae, some of which exceeded 10 cm in diameter.

Southeast Crater eruptions on 15 May. According to Etna guide Alfio Ponte, lava began again to flow from the N side of the SE cone late in the evening of 14 May, while Northeast Crater (NEC) displayed Strombolian activity. A fissure seemed to have opened between the NEC and SEC in the early morning of 15 May. At about 1200 the SEC erupted lava fountains for 20 minutes. In the meantime and afterwards the NEC continued its Strombolian explosions mixed with brown ash clouds. Later on 15 May the SEC erupted again at about 2200, with activity culminating about 2315 and then decreasing during the following hours. Lava fountains and flows occurred on the N side. As of 23 May, other eruptions were known to have occurred during the nights of 17-18 May (about 2300-2400), 19-20 May (2200-0300), and 22-23 May (0300-0535), with lava mainly flowing N from the SE cone (observations by Boris Behncke and Giuseppe Scarpinati).

Information Contacts: Jean-Claude Tanguy, Université de Paris 6 and IPGP, Observatoire de Saint-Maur, 4, avenue de Neptune, 94107 Saint-Maur des Fossés Cedex, France; Giuseppe Patané and Santo La Delfa, Università di Catania, Corso Italia 55, 95129 Catania, Italy; Roberto Clocchiatti, Lab. Pierre Sue, C.E.N., Saclay, France; Charles Rivière, C.G.E., France; Boris Behncke, Dipartimento di Scienze Geologiche, Palazzo delle Scienze, Università di Catania (DSGUC), Corso Italia 55, 95129 Catania, Italy.

December 2000 (BGVN 25:12) Cite this Report

Summary of July to November 2000 notes small lava flows, Strombolian eruptions

This summary of Sistema Poseidon reports covers the period from July to November 2000. The summit craters discharged several minor lava flows, some Strombolian eruptions, and frequent degassing. The Bocca Nuova (BN) vent was particularly active.

During July and well into August the summit craters displayed comparatively low activity. During July at BN three different vents were degassing. During July at NEC emissions came from one primary vent. Emissions were robust on 18 August, and commonly bore light-brown ash.

During late August, Southeast Crater (SEC) renewed emission of a weak lava flow from a fracture on the N side. The lava stream, which flowed into the Valle de Bove, persisted throughout 27 August, and increased progressively on the night of 27-28 August.

At 0135 on 28 August fairly sustained degassing occurred at SEC with initially violent Strombolian emissions. Beginning at about 0600, the explosive Strombolian activity changed rapidly to violent lava fountains, which generated an eruptive cloud rising thousands of meters above the summit. Ash and lapilli fell on the Etna's E slopes. This phase lasted about one hour, and was analogous to what had been observed during episodes in the first half of 2000.

The lava flow, despite appearing larger during the more violent degassing phase, moved little on its farthest-advanced fronts, which along the W face of the Valle del Bove reached to about 2,200-2,300 m elevation. Rather, the flow tended to widen in the zone between 2,800 and 2,700 m. The lava emission rate at the vent appeared to be drastically reduced at the end of this degassing phase.

A new degassing episode was confirmed on 29 August. This was characterized by its brevity and by the way in which it manifested itself, producing explosive Strombolian blasts (rhythmic expulsion of pyroclastics) rather than true lava fountains.

As frequently observed for the last episode, this one also started with a glimmer of light on the N flank of the SEC announcing the beginning of a new lava emission. Eruptive activity increased between 22 and 28 August, while the volcanic tremor first showed a modest increase at 0339 on 29 August, when sporadic explosions from the SEC summit crater began. Only after 0530 did the explosive activity reach a continuous intensity. It concluded at about 0610. Peak activity did not reach the same levels as the preceding phase, but ejected pyroclastics ~200 m above the crater rim. The finer portions were carried several hundred meters and dispersed E, without reaching residential areas.

Observations at the conclusion of the late-August explosive phase showed the new lava flow still spreading over the N flank of the SEC, but new lava had ceased venting. This new flow overrode the one from 28 August, and descended to ~2,100 m on the W face of the Valle del Bove.

The other craters in the volcano's summit area chiefly slowly emitted gas vapors, with the exception of one of BN's vents, which frequently ejected brown ash. The emission of ash from this vent intensified during the week. As September began, BN continued to produce abundant steam and ash emissions, which at times seemed aided by elevated atmospheric humidity and by infiltration of recent precipitation. This effect continued later into September.

In mid-September, BN produced generally mild degassing. During 19, 22, and 23 September nearly continuous ash emission took place. Primarily dark gray and sometimes brownish colored plumes were visible for many kilometers. For the preceding weeks these plumes had vented at two distinct crater cavities on the inside of the BN. The larger cavity lies in BN's center and discharged gaseous blue-white emissions. The smaller cavity lay near BN's internal SW wall, and it expelled ash. During this same time, as in past weeks during the month, the Voragine and Northeast Crater continued to emit abundant steam. The SEC weakly degassed from fumaroles.

October activity continued as in past months with ash emissions at the BN. These were particularly visible on 3-6 October. At night it was possible to observe light coming from the crater cavity on the inside of the BN, suggesting weak Strombolian activity. Mid-October behavior included explosive Strombolian eruptions from both crater cavities; incandescent bombs occasionally fell outside of the crater. Milder episodes occurred on 17 and 21 October. Between 24 and 29 October two stronger episodes took place.

At the Voragine and the NEC, the early days of October showed rather sustained steam emissions, in part accentuated by the first snowfalls and by the elevated humidity on the summit. The SEC displayed mostly fumarolic activity. Later, the Voragine gave off copious steam, but at the SEC and NEC weak degassing occurred.

The last days of October and the early days of November were distinguished by a decline of the explosive Strombolian activity from the two emission points within BN. Strombolian activity sent tephra ~100-150 m high, which still frequently fell outside of the BN crater.

During November, BN continued to produce modest explosive Strombolian activity that sometime spewed incandescent material of moderate size outside the crater walls. Observers continued to note two distinct cavities in BN.

In the early hours of 29 November observers noted the presence of a small lava flow at the base of the SEC. Upon close viewing, observers found that the flow gushed from the base of a fracture on the N sector of the cone at the SEC and continued downslope for ~200 m. Although lava continued to flow in the succeeding days, atmospheric conditions obscured later views of this area. No relevant activity aside from a constant steam emission occurred either at the Voragine or at the NEC during this time.

May 2001 (BGVN 26:05) Cite this Report

Strombolian activity and lava flows during January-April 2001

As reported by Sistema Poseidon, activity at Etna (figure 85) during December 2000-8 April 2001 was characterized by episodic Strombolian blasts, steam and ash emissions, and lava flows.

Figure 85. Aerial photograph of Etna looking E towards the Bocca Nuova vent within the central crater on 6 December 2000. Northeast Crater is also partially visible (in the left background), as well as Southeast Crater (right). Courtesy of Sistema Poseidon.

Minor activity during December 2000 through mid-January 2001. Low-intensity gas emissions dominated activity during this period. Observations on 6 December revealed three distinct cavities in the interior of the Bocca Nuova (BN) vent. The two near the center of the crater trended NW, were deep and full of material, and were delineated by pit-craters. The smaller cavity to the SE was encircled by a high wall of scoria; it weakly emitted light brown ash, possibly due to internal collapse. White steam emissions from BN in early January were visible during the early morning hours, and became more evident as each day progressed due to increased humidity. Sporadic ash ejections also occurred.

At the end of December, adverse atmospheric conditions prevented detailed observations, but during rare periods of visibility observers saw snow covering the W flanks of the central crater and Southeast Crater (SEC). A weak intermittent fumarolic emission emerged from the base of the fracture that runs from the SEC to the lava cairn at its base. The SEC also produced weak fumarolic emissions in early January from the W edge of the crater's summit. On the evening of 14 January a weak, diffused illumination was observed at SEC, likely coming from the E edge of the crater, where during recent months there was visible night incandescence.

Increased activity during mid-late January 2001. The BN vent produced abundant steam during the middle of January. Brown ash was weakly emitted on 16 and 19 January; darker ash ejections occurred on the 18th and 21st. Ash fell on the E flank of the volcano for five hours during the morning of the 18th, and weak illumination was visible for 30 minutes that night coming from BN. Ash-and-gas emissions increased toward the end of January. Isolated night glow suggested weak explosive Strombolian activity confined to inside the central crater. Activity alternated between visible degassing and intense phases of ash emission; one particularly acute phase occurred on 31 January.

New activity initiated from SEC on the evening of 15 January. Low-energy Strombolian eruptions were seen at night by distant observers. Activity increased in frequency during 16-17 January, reaching a maximum on 18 January when explosions occurred every 3-4 minutes, interspersed with high-energy episodes that repeated at variable intervals of ~1-2 hours. Ejected material from these events reached ~50 m high on the edge of the SEC, falling back into the crater. Strombolian activity continued through 19 January. Lava began to flow from the radial fracture cutting the N flank of the SEC beginning during the day on 21 January and persisting discontinuously until the end of the month. Intermittent flows formed several finger-like fronts. The flow reached down to ~2,800 m elevation, and remained confined to the Valle del Leone.

Strombolian explosions at Bocca Nuova during February-April 2001. During the nights of 1 and 4 February, frequent illumination was observed in the BN vent. Strombolian activity continued from BN throughout February. As during January, strong degassing and dark gray ash emissions were sporadic. High ambient humidity during morning hours made gas plumes distinct, especially on 10 February; activity was particularly consistent during 20-22 February. The fixed Montagnola camera captured images of frequent flashes from the crater interior, but activity did not extend beyond the crater area.

The BN vent produced increased explosive activity during March from two vents (W and E) inside the depression. The W vent exhibited Strombolian explosions; during some periods these were continuous and sent incandescent material just above the crater rim. A small number of lava fragments fell outside of the crater and rolled down its flanks. Explosive activity at the E vent did not eject material above the crater rim. Alternating degassing and dark gray ash emission continued as in February. Fine-grained material blown by wind fell as far as 2 km from the summit. Activity was more intense on 6 and 28 March when BN emitted copious amounts of ash from the NW and SE sectors of the crater. The Montagnola camera detected almost continuous night illumination of the crater, suggesting Strombolian activity from multiple vents. Strombolian activity also occurred from Northeast Crater, although it was rarely visible.

Strombolian activity and ash emission from BN continued throughout April. On the evening of 4 April an intense phase at the S zone of the central crater included ejection of some incandescent material above the crater rim. During 7-8 April, a slight increase in the frequency of ash emissions was observed, while night-time incandescence was sporadic.

Lava flows from Southeast Crater during February-April 2001. Early in February lava emission from the N-flank of SEC diminished; it produced modest regular lava flows for the rest of the month. On 4 February observers saw intense flashes that indicated explosive lava ejection from the fracture. Flashes and illumination visible in camera footage evidenced erratic SEC effusive activity throughout February. One early February lava flow from a vent at 3,100 m continued for several days. Bubbles frequently burst from the lava, indicating high gas content within the magma. The lava flow was ~2 m wide near the source, grew to 5 m wide toward the base, and reached an elevation of 2,900 m. During mid-February a vent at 3,150 m elevation produced a flow down a 2-m-wide canal. The flow ran N initially, but ~100 m downslope it headed E and formed a lava tube about 20-25 m wide. The flow moved toward the Valle del Bove, in the direction of Monte Sinome; it continued through the end of the month and reached 2,600 m elevation.

Through mid-March lava continued to flow from the fracture at 3,080 m elevation on the SEC's N flank. Near the vent the flow was ~1 m wide and ~80 cm deep. After having flowed less than 2 m it divided into two forks that ran roughly parallel to each other. The principal flow retained a width of ~1 m and headed N for ~100 m before deviating toward the NE and reaching an elevation of ~2,800 m. The secondary flow was about half a meter in width; it traveled at ~4 m/s near the fork and ~2 m/hour near the flow front where it spread to ~5 m across at an elevation of about 2,970 m. Effusive activity appeared to diminish on 23 March. The vent observed three days before was no longer active. A single flow was fed by a new vent about 5 m below the previous vent. A steep slope at the vent's mouth produced flow velocities of ~6 m/minute. This flow reached down to an elevation of 2,950 m, where it traveled at 1 m/hour over the flows of three days before. The flow front measured 5 m wide and 1 m high. On 30 March conspicuous white vapor issued from the SEC.

A 4 April survey of the flows revealed a moderate flow from the N flank of SEC. The vent had built up a small cone ~6 m tall at 3,095 m elevation. Two flows, each ~1 m wide and 1-2 m deep, traveled away from the cone and joined together 20-25 m away, flowing E. The flows in the two channels moved at a speed of ~0.1 m/s and an estimated 0.2-0.4 m³ of molten material emerged each second. The maximum length of the overall flow was ~350 m. During the evening of 8 April strong, persistent illumination from the E base of SEC probably indicated a new lava flow. The incandescence was distinctly visible as it reflected off of a steam plume from the summit crater.

June 2001 (BGVN 26:06) Cite this Report

9 April-13 May activity punctuated by Strombolian eruption on 9 May

As reported by Sistema Poseidon, activity at Etna during 9 April-13 May 2001 was chiefly characterized by typical episodic Strombolian blasts, ash emissions, and modest lava flows. The larger lava flows that emerged from new vents and grew during June and July will be discussed in later reports.

Activity during mid- to late-April 2001. During this time interval ash escaped at the Bocca Nuova (BN) vent. The weather thwarted direct observations of summit activity; however, later information was obtained through outings to intermediate elevations and from La Montagnola surveillance camera.

Lava continued to flow from a vent low on the NNE flank of the Southeast Crater (SEC) cone, as it has since approximately 20 January 2001. This lava flowed down the SEC's NE flank. During the nights of 18 and 21 April observers noted that the SEC produced flashing, denoting effusive activity. The SEC also continued to give off gray-colored gas from both the fumarole on the crater's edge and from the pit-crater in the crater's interior. Later in April the SEC's N flank vent continued to emit lava variably, but generally weakly, and beginning 26 April, the flow became visible principally from the volcano's NE quadrant. During 26-28 April degassing increased at SEC, yielding abundant clouds of white steam that diminished on 29 April.

Observations on 27 April revealed two hornitos (at 3,085 m, ~3 m high, and aligned N-S). They produced steady emissions, sounds of pressurized gas, and discontinuous expulsion of vitreous and blistering lava fragments which fell within a few meters of the vents. The more northerly hornito produced a lava flow within a confined channel. At about 3,000 m elevation, this lava river divided into two branches before rejoining just above 2,900 m. In late April, the flow rate was estimated at 2-3 m³/s.

A party viewing the base of BN's crater saw two prominent, steep-sided fissures that were ~100 m in length and at least 30-50 m deep. At a shelf inside the N fissure a small pyroclastic cone gave off dense brown and reddish clouds visible from the slopes of the volcano. The fissure in the SW quadrant also degassed intensely, and both fissures gave off almost continuous noise associated with magma inferred to reside at depth. A field of semi-circular fissures was observed nearby running S and W from this depression. Observers also noted fumaroles emitting bluish gas. Until at least early May, Voragine and Northeast craters continued weak degassing.

When seen on 3 May SEC's N hornitos had grown by almost 1.5 m compared with the preceding week. The lava canal had also widened to about 2 m, corresponding to a significantly increased flow rate, 5-10 m³/s. Two small lava flows developed on the E and W sides of the hornitos.

Strombolian eruptions starting on 7 May. Strombolian activity began again at the SEC late on the morning of 7 May. When seen on 9 May these eruptions were almost continuous, as frequent as about 45-50 explosions per minute, including some strong ones that sent lava fragments 20-30 m above the crater. Lava fragments as big as a meter in diameter were thrown up to 50 m above the crater rim.

Beginning at 1400, along with a new increase in tremor, the Strombolian activity evolved into a more violent phase at 1520-1540. Ballistics landed at elevations as low as ~3,000 m, reaching the spatter rampart at the S base of the cone. At about 1630 modest lava fountaining was observed from the fracture on the N flank of the SEC. Jets of magma reached ~100 m high. The fragments emitted from the lava fountain fell mostly in the SW sector of the volcano.

At the same time, the Montagnola camera began to register frequent ash emissions from the cone's summit; Strombolian activity and ash emissions continued until midnight in a discontinuous manner and with variable intensity. Observations on 10 May showed a substantial decrease in the activity at the SEC summit. Weak explosive activity was observed from the N fracture.

The lava emission from the fracture cutting the N flank of SEC continued with more or less intense phases. On 9 May, the cessation of lava fountaining was followed by a repeat of effusive activity, still within the same area of emission, which gave rise to finger-like flows ~1.5-2 km long. On 10 and 13 May, short lengths of the active branches of the flows were observed. The outburst led to a considerable plume that impacted local air traffic.

Bocca Nuova continued to issue brown-reddish ash emissions, presumably ongoing ash-bearing eruptions from one of the fissures described above. On 9 May a new fumarolic field was seen in the S part of the Bocca Nuova, extending from the rim to half way down the cone.

August 2001 (BGVN 26:08) Cite this Report

Strombolian activity during May and June 2001

During 14-20 May 2000, lava emission continued from the N fissure of the Southeast Crater (SEC). At about 1900 on 17 May there was an increase in the intensity of Strombolian activity and lava began to flow in several directions, forming two sub-parallel tongues toward the E. On 18 May observers noted that the lava flow emerged from a single vent at 3,156 m elevation, with an effusion rate of 2.5-4.5 m³/s. A short distance below the effusive vent, the flow divided into three branches: one to the NE, whose front flowed at about 2,700 m and reached a distance of about 1 km from the vent; the central branch flowing to the E, widest of the three with some points wider than 20 m; and one to the S, flowing below 3,000 m elevation at about 700 m from the vent. The farthest lava front was estimated to reach ~2,700 m elevation, 1.2 km from the vent. During this period, the Bocca Nuova (BN) crater continued to degas, accompanied by occasional emissions of brown ash. Also noted were a further deepening and widening of the internal crater in the BN's SE quadrant.

During 21-27 May, lava flows from the N fissure of SEC continued intermittent and variably intense Strombolian activity. Sporadic emissions of brownish-reddish ash came from the N crater of BN. Problems with surveillance cameras precluded continuous observation of the summit craters; however, on the morning of 24 May, renewed explosive activity was seen. Observations from Belevedere showed three hornitos on the N flank of the SEC, which emitted pulsing pressurized gas. The lava flow was active and well fed, with branches of ~1.5-2 km in length.

Activity at SEC increased considerably during 28 May-3 June. On 28 May, the presence of a small cinder cone, possibly having formed slowly over recent months, was discovered at the base of Northeast Crater (NEC), occupying about 2/3 of the crater floor and at least 20 m high.

At SEC, evidence of Strombolian activity was masked by discrete flows of gas and steam. The active lava field on the N flank, emerged from a main vent at about 3155 m elevation, which fed two principal flows, one to the E and one to the NE (then turning E). The latter flow formed a lava tube and then re-emerged ~100 m downstream from a small tumulus from which spewed other lava flows, the longest of which extended more than 1.5 km. The S-most branch also initially flowed partly inside a lava tube.

During the evening of 28 May, between 2222 and 2242, Strombolian activity at SEC rose sharply, with ejecta reaching as high as 50 m above the crater rim and with materials occasionally falling on other flanks of the cone. Lava flow rates on 29 and 30 May were estimated at 6-8 m³/s. Temperatures measured using a K-type (Cr/Al) thermocouple showed a maximum temperature on the inside of an expansion bulb to be of 1,065°C at 5 cm depth. Intense degassing continued at SEC for the next several days.

On the evening of 3 June two sub-parallel lava flows descended to the E, of which the northernmost was the longest and reached at least 2,600 m elevation. A few hundred meters ahead of its front, a small branch flowed N but stopped soon after. The other flow was directed toward the Valle del Bove and its advances were discontinuous. Further deepening of the two interior Voragine vents was observed. Eruptive activity was not continuous.

The W rim of BN had a very warm fissure that ran to the N. The N vent was much widened, but it was not possible to observe the base. During observations, gas explosions occurred about every 15 minutes, but it was not possible to observe the fall of ejecta. The S vent had also widened and deepened. On its SE flank, a small semi-circular vent emitted rumbling explosions every 3-10 minutes, accompanied by mostly blue-colored gas mixed with brown ash.

Although intense degassing did not permit views of the interior of the NEC, an apparently recent fissure on the N side of the cone was very warm.

During 4-10 June, two episodes of lava fountaining occurred at the SEC. The first began during the night of 5-6 June, with modest Strombolian activity at the SEC's secondary vent. At 2136 on 6 June, Strombolian activity at the secondary vent reached a frequency of about one explosion per minute, which in successive hours included the main vent as well. The activity eventually climaxed at 0145 on 7 June, when the secondary vent produced a lava fountain whose altitude reached 50 m. Falling to the ground, the stream of lava formed a primary lava flow, which immediately divided into three branches and stopped at about 3,000 m elevation. A second stream flowed to the N before turning E, reaching 2,600 m and superimposing in part on earlier lava flows. The eruptive episode concluded about 0340, with copious ash emissions from the SEC and the BN.

On the night of 8-9 June, a new eruptive episode occurred at the SEC, also beginning with Strombolian activity at 2011 at the principal and secondary vents. The activity evolved into lava fountains which reached a maximum altitude of about 200 m at the principal vent and about 80 m at the secondary vent. The strong activity continued until about 0322 and was accompanied by sustained lava emissions from the secondary vent, which gave rise to two flows which spread to the E and N respectively, superimposing themselves over preceding lava flows.

Activity at the other craters during this period was characterized by continuous degassing at the Voragine and NEC, accompanied, as in the case of the BN, by frequent ash emissions in the SE sector of the crater.

September 2001 (BGVN 26:09) Cite this Report

Strong June eruptions, a M 3.9 earthquake, copious July-August flank lavas, and a new cone

Although Etna's early June 2001 eruptions were unusually vigorous (BGVN 26:08), still more energetic behavior followed. An earthquake swarm took place in mid-July, and large SSE-flank eruptions vented lavas in late July and early August on a scale not seen since 1983.

This report covers mid-June through early August 2001. During this interval, the highest cited lava fountains reached heights of ~ 0.7 km; ash plumes rose 3 km; lava flows stretched ~ 6 km from their source vents (largely, though not exclusively traveling due S); and people constructed earthen berms to constrain lava flows. Etna repeatedly made international news during this period. Outstanding photographs appeared widely; some may be seen on the website of Tom Pfeiffer, who graciously provided several for this report.

The text of this report came from two key sources: 1) reports by Sistema Poseidon covered the interval from 11 June-8 July; 2) a report by Jean-Claude Tanguy, Roberto Clocchiatti, Santo La Delfa, and Giuseppe Patanè for 17 July-early August. The latter group acknowledged the valuable insights from Giovanni Frazzetta of Sistema Poseidon and from local guides, particularly Alfio Mazzaglia, Antonio and Orazio Nicoloso, Alfio Carbonaro, and Giuseppe Mazzaglia. The group also received valuable contributions from Charles Rivière and Giuseppe Scarpinati.

Activity during 11 June-8 July. In the weeks of middle to late June the N-flank of the secondary vent at Southeast Crater (SEC) was very active. There were four eruptive events there during 11-17 June. Between these episodes volcanism was limited to degassing at all of the summit vents and lava outpourings from the SEC N-flank vent. Lava flows reached a length of just over 2 km, descending to elevations of 2,600 m or lower. Some lava fountains were accompanied by brown ash emissions for periods of 10 minutes to several hours. Each fountaining episode commenced with 5-11 hours of buildup, followed by more intense events lasting ~1 hour. Observers in a helicopter on 17 June saw a widening of the interior of Bocca Nuova (BN), primarily in the W sector extending ~20 m back from the former crater rim.

During 18-24 June SEC's N-flank vent produced three vigorous eruptive episodes. The first episode began about 1700 on 19 June and increased gradually in intensity. At 2040 the lava fountains reached ~ 700 m high; these diminished at about 2110, and after 2130 the episode ended.

A second N-flank SEC episode began at about 1700 on 22 June. At 1730 lava fountaining reached a height of ~ 200 m accompanied by brown ash, possibly indicating that the vent had widened. At about 1750, the lava fountain at the secondary vent produced jets up to 10-20 m and lava spattering from the N base, which ultimately widened the lava field. During this time the lava fountain from SEC increased to 300-400 m high. The associated reddish ash plume rose 1-2 km above SEC. At 1800 on 22 June lava fountaining became almost continuous, but without a continuous ash column. At 1810 the ash plume rose to over 3 km, with the quantity of ash in the plume increasing gradually; lava emissions from the secondary vent increased simultaneously. The event diminished rapidly after 1835.

The third episode began on 24 June with a small lava emission at the base of SEC. Unlike the preceding two episodes, this one began with consistent ash emissions from Northeast Crater (NEC), beginning about 1654 on 24 June with pressurized pulses that formed a plume ~1 km high at about 1700. Ash emissions continued for the next few hours and at 1815 Strombolian eruptions began again at SEC. At 1930 explosive activity began at the secondary vent on the N flank of SEC. At 2000 the explosive activity spread to the whole fissure. Lava emissions increased rapidly, and at 2015 lava fountains reached 200 m high. Lava flows at 2045 reached a length of ~ 2-3 km. The episode peaked at about 2030, diminished visibly at 2115, and had ended completely by about 2250.

SEC generated its tenth eruptive episode of the month on 27 June. The strongest part of that event took place during 2120-2200, with Strombolian activity becoming more intense and lava fountains at the summit reaching 400-500 m high. This event ended about 2300. Another event at SEC took place on 29 June, with flashes coming from the NE flank. At NEC, mixed ash and gas emissions continued. A continuous plume was produced over the summit of the volcano, variable according to the wind intensity and extending for a few hundred meters.

During 2-8 July, explosive Strombolian episodes continued at SEC. The periods between events were calm. An eruptive episode on 4 July began with slow lava emission from the N-flank secondary vent, followed by increased Strombolian activity at the summit. Explosions were discontinuous but violent, with fragments of incandescent magma ejected 150-200 m above the crater rim. The secondary N-flank vent produced less explosive activity. The intensity peaked at about 2100 when lava emerging from the summit vent of SEC reached a height of 50-60 m, and explosions sent ejecta to a height of ~400 m. At this time, a lava flow reached a length of ~2 km to the E, heading toward the Valle del Bove. Beginning at 2150 on 4 July, the Strombolian explosions became progressively less frequent although at that time the lava flow was being vigorously fed.

A few days later, tall ash plumes appeared. Activity began on 6 July with the reactivation of the then slow-moving lava flow emerging from SEC's N-flank secondary vent. At about 0600 copious degassing was seen at the SEC, accompanied by sporadic Strombolian explosions. At 0745 an ash-rich eruptive cloud containing lapilli rose 500-600 m. The plume blew E and SE and continued to ascend to 1.5-2.0 km above the crater area. One of the larger outbursts during the reporting interval, the eruption produced widespread ashfalls in the areas of Milo and Zafferana Etnea to Aci Castello and the northern limits of Catania. At about 1000 the explosions became progressively less frequent and strong. The lava flow continued to be well-fed and reached a maximum length of more than 2.5 km. The lava front reached nearly to the base of the W face of the Valle del Bove, not far from Monti Centenari. From 1050 on, the explosive phase diminished, although the lava flow was well-fed until about 0700 on 7 July.

Early on 13 July the 14th SEC event was accompanied by an impressive earthquake swarm, which included a M 3.9 shock felt to the SE, particularly in the coastal town of Acireale. More than 2,000 shocks were recorded during the following two days. Meanwhile, fissures appeared and gradually enlarged on the upper S flank along the 1989-91 fracture zone, a place where unusual fumarolic activity had previously been observed.

Activity during July-August 2001: S-flank fissures. On 17 July another strong eruption from the SEC was followed by lava venting from a fissure near 3,000 m elevation. This spot lay just below the "Sudestino," a small parasitic vent that had appeared last year at the S base of the SE cone, and where incandescence had persisted at a depth of a few tens of centimeters. Weak explosive activity quickly formed small hornitos, and lava flows proceeded SE towards the Valle del Bove depression. In the afternoon of the same day new vents appeared between 2,800 and 2,700 m elevation, along a trend oriented SSW. These vents emitted lava fragments and moderate lava flows that began to invade the area of the upper cable-way station at 2,500 m elevation.

On 18 July at 0120 another new vent opened to the S at 2,100 m elevation. This vent appeared just beside the Sapienza refuge and the lower cable-way station, ~ 200 m upslope from the famous Mt. Silvestri (cinder cones born in 1892 and subsequently visited by millions of tourists). This vent produced a low lava fountain. A sluggish lava flow gradually grew and traveled W of Mt. Silvestri, threatening a restaurant and cutting the SP 92 road. This became the main lava flow that headed S in the direction of Nicolosi, a village 10 km away at 700 m elevation.

On 19 July at about 1800 an explosive vent appeared near 2,600 m elevation above the Montagnola (a large cinder cone born in 1763, which still dominates the landscape and towers over the Sapienza tourist complex). The Montagnola vent area sometimes contains a small ephemeral crater lake that is variously called "Cono del Lago," "Cratere del Lago," and "Montagnola 2" (M2). M2 is ~3 km S of SEC. On 19 July the M2 vent released dense clouds of fine ash that disturbed people on Etna's E and S sides.

On 20 July the fracture zone extended northward, cutting across and beyond the SEC summit. Where it descended the other side of the mountain, it formed a strange, curved fissure that opened at 2,650 m elevation, forming a vent. The fissure followed the northern base of the Valle del Leone depression. This vent emitted a moderate lava flow and built a small hornito.

The climax of the eruption was reached on 21-23 July when phreatomagmatic activity from the M2 vent fed an impressive and continuous ash plume (figure 86). The plume interrupted air traffic at Catania airport and caused disruptions as far away as Syracuse, 100 km S of Etna. By this time the main lava flow from the 2,100-m vent (figures 87 and 88) had reached 1,030 m elevation, ~ 6 km from its source and 4 km from Nicolosi. However, no concern was raised for the little town as the lava fronts had practically stopped advancing on the gentle slope and the effusion rate remained moderate (5-10 m³/s).

Figure 86. An overview of the scene at Etna during the 2001-eruption climax, which took place on 21-23 July. The upper ash column rises from M2 at the far side of Montagnola. The lower, smaller series of plumes rise from the 2,100-m vents and associated lava flow. This shot was taken on 23 July from astride the 1983 lava flow (foreground) and the Sapienza tourist complex, a facility that sits at ~ 1,900 m elevation on the S flank (buildings on the right). The camera was aimed towards the N to NE. Courtesy of J.C. Tanguy.

Figure 87. A fissure vent erupting at Etna after sunset on 23 July. The venting occurred at 2,100 m elevation and remained moderate. The scale can be appreciated by noting the row of photographers silhouetted by the plume in the photo's lower right corner. View is towards the E. Courtesy of J.C. Tanguy.

Figure 88. The main lava flow from Etna's 2,100-m vents. Montagnola lies in the background. The photo was taken from Mount Silvestri with the camera pointed N. Courtesy of J.C. Tanguy.

The Sapienza complex at 1,900 m elevation was more seriously threatened by lava flows. Some of these flows had originated at the 2,700 m vents, and later from effusive vents at the lower base of M2 (near 2,580 m elevation on 26 and 31 July). Earthen barriers protected the buildings; however, the complex was left in a vulnerable hollow between the new lava flows on the E and the 1983 flows on the W.

The highly explosive M2 vent at 2,600 m elevation created a big show beginning with black ash mixed with a few incandescent materials forming jets with the elongate shapes of Cypress trees (figure 89). On 25 July the activity turned magmatic, quickly building a scoria cone ~ 97 m high (based on post-eruption range-finder and altimeter measurements that yielded summit and lower SW base elevations of 2,674 ± 3 m at 2,577 ± 5 m, respectively).

Figure 89. This scene of a ~ 200-m-tall fountain of lava and associated plumes appeared at Etna at about 1600 local time on 24 July 2001. The fountain emerged from a 150-m-wide crater formed along a fissure at ~ 2,500 m elevation near the summit of the new cone called "Cono del Lago" or "Montagnola 2" (M2). The viewpoint was the cable car station at 2,600 m elevation that was destroyed in an earlier eruption. The photographer was ~ 400 m SE of M2; he used a 90 mm lens. Copyrighted photo provided courtesy of Tom Pfeiffer.

A second climax was reached on 28 July when powerful explosions hurled car-sized lava lumps in a radius of over 500 m. These seriously damaged the upper cable-way station and rattled windows all around the volcano (figure 90).

Figure 90. At Etna, a photo taken on 28 July captured the newly formed M2 cone discharging molten material from two vents. One vent was at the summit; the other was on M2's NW flank. The next day, Tom Pfeiffer and other photographers saw at least five points of simultaneous discharge. Copyrighted photo provided courtesy of Tom Pfeiffer.

The eruption's waning stages began 1 August. Ash became more and more abundant from the M2 vent, but was driven by considerably decreased pressure. Effusive activity had practically stopped at the 2,580-m-elevation vents. On 2 August both explosive and effusive activity ceased at the 3,000-m-elevation hornitos, and activity began to decrease along the 2,700-m-elevation fissure, except for the lava flow, which remained well fed and headed SW. At the M2 vent ash emissions practically ceased on 6 August and at the 2,100 m vents the last lava flow was observed on 8 August.

This eruption appeared quite unusual in a number of ways. The flank fissure always remained active throughout its entire length, from 2,100 m to 3,000 m elevation and above (small lava flows were seen several times on the NE side of the SEC at 3,100 m elevation, for example, on 24 August. The explosivity of the M2 vent was exceptionally high for Etna. The lavas emitted in the upper region are almost aphyric, whereas products from the M2 and 2,100 m vents are rich in large phenocrysts, including amphibole, and contain numerous inclusions from the sedimentary basement (sandstones). Although further detailed study is needed, this fact led several scientists to suggest that the 2,600-2,100 m part of the fissure represents a separate eruption triggered by upslope activity.

Information Contacts: Sistema Poseidon, a cooperative project supported by both the Italian and the Sicilian regional governments, and operated by several scientific institutions (URL: http://www.ct.ingv.it/en/chi-siamo/la-sezione.html); Jean-Claude Tanguy, University of Paris 6 and IPGP, 94107 St. Maur des Fossés Cedex, France; Roberto Clocchiatti, CNRS and CEN Saclay, 91191 Gif sur Yvette Cedex, France; Santo La Delfa and Giuseppe Patanè, University of Catania, 55 Corso Italia, 95129 Catania, Italy; Tom Pfeiffer, Department of Earth Sciences, University of Aarhus, C.F. Møllers Allé 120, DK-8000 Aarhus C, Denmark (URL: http://geo.au.dk/).

October 2001 (BGVN 26:10) Cite this Report

Amphibole megacrysts from the 2001 S-flank eruption

On 18 July a new vent opened on the S flank at 2,100 m elevation (BGVN 26:09). Lava from that vent contained exceptionally large crystals of amphibole (Pargasite-kaersutite) reaching to 6-8 cm along the c axis and less than 1 cm along the b axis (figure 91). These megacrysts, apparently blown loose by Strombolian explosions, were weakly adhering to the scoriaceous part of the flow, most of them found as isolated crystals practically free of lava. More rarely, amphibole is not elongated and may be confused with pyroxene.

Figure 91. Photograph of amphibole megacrysts found in the lavas emitted during the July 2001 S-flank eruption at Etna. Courtesy of Roberto Clocchiatti.

Acicular amphibole crystals 2 or 3 cm long were also common. In thin section, their central part contains spherical voids, which seems to indicate that the mineral grew in contact with gas bubbles. Gas present in fluid inclusions probably consists of water vapor at low density. The crystals often occur in areas with elevated silica. We presume that these areas resulted from siliceous inclusions, perhaps from sandstones, which clearly occur as inclusions elsewhere in the host lava. Other minerals included within amphibole consist of plagioclase (An85-76), olivine (Fo75), pyroxene (Wo45-En42-Fs13), Fe-Ti oxides, and numerous iron and copper sulfides. These sulfides do not resemble those from immiscible sulfur liquids within silicate melts, but are aggregates or trapped within fluid inclusions, and their compositions, mostly pyrite or copper pyrite, suggest an origin from magma cooling in a shallow reservoir.

The amphibole megacrysts are practically unzoned. They sometimes show a thin reaction rim of rhonite and fassaite within a melt strongly enriched in Si, Al, and alkalis. Microprobe analyses show that their composition is roughly that of a kaersutite close to pargasite or ferropargasite (table 8). Although kaersutite is occasionally found in ancient Etnean products, it has never been observed as phenocrysts in lavas during the past 2,000 years, let alone as such large crystals. The 2001 host lava is a K-trachybasalt whose chemical composition is practically identical to that of the lava with elevated K, Rb, and Cs content that first appeared in 1974 and started a period of stronger activity, probably linked to selective assimilation of rocks from the sedimentary and metamorphic basement (Tanguy and Kieffer, 1976, Clocchiatti and others, 1988).

Table 8. Amphibole microprobe analysis for megacrysts of the July 2001 S-flank eruption at Etna. Number of analyses was 60; oxide total was 98.79 wt. %. Courtesy of Roberto Clocchiatti.

Amphibole	SiO₂	TiO₂	Al₂O₃	FeO	MgO	CaO	Na₂O	K₂O
Oxide Percentage	39.59	3.76	14.07	11.15	13.50	12.17	2.36	1.09
Std Deviation	0.36	0.29	0.29	0.31	0.20	0.16	0.07	0.08

In the present case, the amphibole megacrysts are closely linked to the early products of the 2,100 m vent, which also display numerous white sandstone inclusions sometimes reaching the size of a human head. Amphibole as well as sandstone inclusions are less frequent in the products from the 2,600-m vent and are not found in lavas from the upper vents (2,700-3,000 m elevation). Although investigations are still in progress, it may be hypothesized that the amphibole developed under high water pressure at a later stage of crystallization, probably near the sandstone roof of a small, shallow magma chamber. The recent origin of the amphibole megacrysts is also testified by their K-content, which reflects the higher K contents of magmas from the past 30 years (figure 92).

Figure 92. A plot of K₂O versus Na₂O for various amphiboles found at Etna. Courtesy of Jean-Claude Tanguy and Roberto Clocchiatti.

References. Tanguy, J.C., and Kieffer, G., 1976, The 1974 eruption at Mount Etna: Bulletin of Volcanology, v. 40, no. 4, p. 239-253.

Clocchiatti, R., Joron, J.L., and Treuil, M., 1988, The role of selective alkali contamination in the evolution of recent historic lavas of Mt. Etna: Journal of Volcanological and Geothermal Research, v. 34, p. 241-249.

Information Contacts: Roberto Clocchiatti, CNRS and CEN Saclay,91191 Gif s/ Yvette cedex, France; Jean-Claude Tanguy, University of Paris 6 and IPGP, 94107 St. Maur des Fossés cedex, France.

March 2002 (BGVN 27:03) Cite this Report

Overview of Etna's much-photographed July-August 2001 flank eruption

The last flank eruption at Etna occurred in 1993, but eruptive activity has been nearly continuous in the summit area since late July 1995. Unusually vigorous eruptions in early June 2001 (BGVN 26:08) were followed by still more energetic behavior. An earthquake swarm took place in mid-July, and large SSE-flank eruptions vented lavas in late July and early August on a scale not seen since 1983 (BGVN 26:09). Though this activity has been reported in previous Bulletin reports, what follows is a more detailed description of the summer 2001 activity.

Precursory phases. During the first half of 2001 most activity occurred at the Southeast Crater (SEC), starting with very slow lava extrusion from a vent on the NNE flank of its cone in late January. During the next three months the lava emission rate progressively increased and, in late April, weak ejections of lava fragments began to build small spatter cones (also known as hornitos) in the vent area. Strombolian activity resumed at the SEC's summit vent on 7 May, followed by an episode of vigorous Strombolian activity and lava fountaining two days later.

The activity then returned to lower levels, but for the next two months the SEC was the site of very picturesque continuous and persistent activity, with mild, discontinuous Strombolian explosions from the summit vent and vigorous lava emission (at times accompanied by lava spattering) from vent(s) on the NNE flank. At this spot, a large, steep-sided cone consisting of overlapping lava flows and spatter began to grow, and it was informally named "Levantino." From Levantino (figure 93, upper part), lava flowed NE (toward the Valle del Leone), E, and SE (toward the Valle del Bove), forming a composite lava field with numerous overlapping flow lobes. The longest flows extended up to 2 km from the vent(s). From late May to early June the continuous and relatively harmless activity attracted many visitors.

Figure 93. Inset map (upper left) and sketch map showing Etna's July-August 2001 lava flows, fissures, and related features. The 1983 lava flow-field on the S flank (lighter shading) is shown for comparison. The legend is also linked to numbers near the vents and fissures, as a way to indicate the sequence of activity. The pattern of activity lacked a simple spatial progression. For the time citations, note that the eruption occurred during daylight saving time (UTC + 2 hours). The sketch map is preliminary; it is a composite based on both fieldwork by Behnke and others, and already available maps appearing on the web, including those on the site of INGV-Sezione di Catania. Courtesy of Boris Behnke and Marco Neri, INGV.

The prelude to the main eruption began in early June, with the first strong phase on 7 June, which was mostly confined to lava fountaining at the Levantino, whereas only mild Strombolian activity occurred at the SEC summit vent. During the following six weeks the vigor of the eruptive episodes gradually increased and at times culminated in true lava fountaining from the summit vent. Fourteen such episodes occurred between 7 June and 13 July (7, 9, 11, 13, 15, 17, 19, 22, 24, 27-28 and 30 June; 4, 7 and 13 July), ending with the most violent outburst of the series. Immediately after its cessation, vigorous seismicity began, including shocks that were felt as far as the cities of Acireale and Catania (figure 93 index map).

Between the early mornings of 13 and 17 July, about 2,600 tremors, mostly unfelt, were recorded instrumentally. During this same time interval, severe ground cracking and faulting occurred in various places on the W rim of the Valle del Bove and near the "Cisternazza" pit crater on the Piano del Lago ("PDL," figure 3), a flat area at ~2,500 m elevation to the N of the Montagnola. Press sources cited local volcanologists saying that magma was rising through a dike and stagnating about 1 km below the surface. Steaming was observed at some of the new fractures, but as of the late evening of 16 July no magma had reached the surface. Seismicity continued at a slightly decreased rate.

Shortly after midnight on 17 July, yet another paroxysmal episode occurred at the SEC. This was similar to its 13 July predecessor, with vigorous lava fountaining from the summit vent and the Levantino. It was the last event that could be considered part of the prelude to the main eruption. Figure 93 shows a sketch map of the lava flows that ultimately resulted from the July-August 2001 eruption. The inset at upper left shows the 2001 lavas and locations of various towns on Etna's S, SE, and E flanks.

Eruption of 17 July-9 August 2001. As defined here, the main eruption lasted nearly 24 days, from early 17 July to late 9 August 2001. It began a few hours after the last paroxysmal eruptive episode at the SEC.

An eruptive fissure opened at about 0700 on 17 July at the SSE base of the SEC at ~ 2,950 m elevation (point 1 on figure 93). Vigorous lava spattering occurred at a number of vents, while lava flows advanced toward SE, in the direction of the Valle del Bove rim. Several hours later, at 2200, another fissure opened at an elevation of ~ 2,700 m (point 2 on figure 93), a bit to the W of a panoramic point on the W rim of the Valle del Bove known as "Belvedere," and lava began to extend S from there, across the Piano del Lago, and in the direction of the cable car and ski lifts (shown by the vertical dotted line just beneath PDL on figure 93).

At 0120 on 18 July, a third eruptive fissure became active on the S flank of the Montagnola at ~ 2,100 m elevation, slightly uphill of the Monti Calcarazzi (point 3 on figure 93). Activity at this fissure was initially weak, and a sluggish lava flow began to move from the lower end of the fissure toward the Monte Silvestri superiore, a large complex cinder cone formed in 1892. During the day, the activity gradually increased; lava flowed around the W side of the Monte Silvestri, crossed the road (which connected the Rifugio Sapienza-cable car area with the town of Zafferana) and passed close to buildings. By late evening on 18 July the flow front was at 1,800 m elevation. On 19 July, the lava flow fed by the vents at 2,100 m elevation continued to pass between numerous older cinder cones along the E margin of the 1983 lava flow-field. At the same time eruptive activity continued unabated at all eruptive fissures.

On the evening of 19 July at about 1900, a new vent opened on the Piano del Lago at ~2,570 m elevation, ~ 500 m N of the Montagnola (point 4 on figure 93; "Montagnola 2", "Monte del Lago" or "Cono del Laghetto", unfortunately, all three names are in common usage). The activity was characterized by violent phreatomagmatic explosions that produced a black, ash-laden column and ejected large blocks of older volcanic rocks. This phreatomagmatic activity might have been the result of magma-water interactions with shallow ground water. (The name, Piano del Lago, the "plain of the lake," derives from the fact that frequently during the spring snow-melt a small meltwater lake had formed in that area.) To observers familiar with footage of the 1963 Surtsey (Iceland) eruption, the steam-and-ash columns rising from the new vent appeared strikingly similar. After nightfall spectacular lightning flashed through the plume and ash fell over inhabited areas including the NE, E, SE, and S flanks. Close observation of the vent at 2,570 m elevation revealed a simple, though constantly eroding, pit. Rumors spread that the pit would eventually "make the Montagnola cave in;" however, it remained intact.

The front of the lava flow emitted at 2,100 m elevation (point 3 on figure 93) was at 1,350 m late on the evening of 19 July. It still advanced vigorously, though at reduced speed (~45 m/hour). Soon after, authorities declared a state of emergency.

By the evening of 20 July the front of the lava flow had reached 1,220 m elevation, but it had slowed in a gently sloping area. Nonetheless, the threat to Nicolosi had become international news. The main risk now came from forest and bush fires. Helicopters began to drop large quantities of water onto the burning forest (not onto the lava flow, as was widely reported). Fortunately, no fires broke out. By late 21 July the lava flow's front had reached 1,050 m elevation.

During the night of 19-20 July, the SEC reactivated, and lava began to issue from the NNE side of the Levantino, forming a small flow that advanced in the direction of the Valle del Bove.

At about 1100 on 21 July, yet another eruptive fissure formed (point 5 on figure 93). It emerged on the NE flank, far away from the earlier fissures (below the Pizzi Deneri on the floor of the Valle del Leone). Figure 93 portrays the impressive arcuate fracture system that developed. The lava first issued from the fissure's uppermost portion at ~ 2,700 m elevation, then from its eastern extension ~50 m further downslope. A fracture system formed between this northeasternmost fissure and the E side of the summit crater area, and fissures up to 1 m wide opened on the slope between the Bocca Nuova and the SEC, and began emitting dense vapor plumes.

The large pit crater on the Piano del Lago at 2,570 m elevation continued to produce dense, ash-laden plumes. In late July ash fell over the area between Zafferana and Acireale (inset, figure 93).

On 21 July, the eruption continued with unabated vigor at all eruptive fissures. Late that day, the lava from the vents at 2,700 m had not further advanced on the steep slope above the tourist complex of the Rifugio Sapienza area (shown as Rif. Sapienza, figure 93).

The next day, 22 July, a shift in the wind direction drove the dense ash plume produced by the phreatomagmatic vent at 2,570 m elevation directly over the Catania area, paralyzing the city's Fontanarossa International Airport, and dropping large amounts of fine, black, sand-sized tephra over streets and buildings. Eruptive activity continued without significant variations at all fissures, although the main lava flow directed toward Nicolosi had slowed significantly and advanced only a few meters per hour, still 4 km from the outskirts of the town. That evening, minor, though fast-moving lava tongues fed by the vents at 2,700 m elevation spilled down the steep slope above the tourist complex, destroying part of the ski lifts and threatening to overwhelm some of the poles of the cable car. However, none of these flows made it further than about halfway down that slope. Vigorous Strombolian activity continued at the fissure at 2,100 m elevation, and a cone about 20-30 m high had formed around the largest of its vents, while minor lava spattering from four vents in the lower part of the fissure was building a low-spatter rampart. The lava flow from this fissure moved as a single, broad unit (point 6 on figure 93). Throughout 23 July the activity showed little variation.

On 24 July it became clear that something was changing at the Piano del Lago crater, which until then had displayed only phreatomagmatic activity. Loud detonations came from the Piano del Lago vent on the morning of 25 July, as the activity there had now become purely magmatic.

A new cone was growing on the former Piano del Lago on 26 July produced near-continuous explosions accompanied by loud detonations that could be heard ten's of kilometers away. The cone received bombs ejected from at least three vents within it. Lava began flowing from vents on its S and N sides, spilling around the N and NW sides of the Montagnola and down the steep slope on the W side of that cone toward the Rifugio Sapienza. The new lava flow passed E of the lower cable car station, covered another portion of the road and advanced a few hundred meters further. Vigorous eruptive activity continued on 26 July at the eruptive fissure at 2,950 m elevation, while the fissure at 2,700 m elevation continued to emit lava but pyroclastic activity there had ended. Weak activity continued at the Valle del Leone fissure, with lava flowing toward Monte Simone (in the N part of the Valle del Bove), and the fissure at 2,100 m elevation showed no significant changes in its activity with respect to the previous days.

During 27-30 July the eruption produced some outstanding displays (figures 94 and 95) and caused the greatest impact on human structures. While the fissure in the Valle del Leone showed ever-lower levels of activity and the fissures at 2,900, 2,700, and 2,100 m elevation continued to erupt in a manner almost identical to the previous days, the Montagnola 2 cone and several nearby vents not only provided a show, but vents on its N and S flanks delivered vigorous lava flows that spilled down the steep slope to the W of the Montagnola in surges, presenting a continuous threat to the Rifugio Sapienza area.

Figure 94. At Etna, a night view taken from high on the S flanks near Torre del Filosofo documenting the erupting vents at 2,700 m elevation (left) and a lava fountain at the Piano del Lago cone (right), probably taken on 30 July 2001. The camera was aimed SE. Lights of towns between Acireale and Giarre are visible in the background. Photo was published in the 1 August 2001 issue of the "La Sicilia" newspaper.

Figure 95. Spectacular aerial view of the largest cone formed in Etna's eruption during July-August 2001, built on what used to be the "Piano del Lago" at ~ 2,500 m elevation on the S flank. View is to the SW. Most of the cone grew in a few days in late July; this photo shows the waning phase around 2 August when only ash was emitted. After the end of the activity the summit of the cone stood nearly 100 m higher than its base, but then partially collapsed leaving the cone ~ 80 m higher. To the left of the cone is the 1763 Montagnola crater. Between the two lies a fuming vent; it emitted one of the latest lava flows in the area (black ribbon extending to the left margin of the photo). Other lava flows that were emitted from vents at ~ 2,700 m elevation (out of the photo to the right) can be seen in the right foreground. Yet another lava lobe extends toward the lower left corner of the photo; it emerged at the E base of the Piano del Lago cone. Photograph by volcanologists of the INGV (National Institute of Geophysics and Volcanology); published on 6 August 2001 in the "La Sicilia" newspaper.

A lava flow from the southern base of the Piana del Lago cone on 27 July remained active for about 2 days (point 7 of figure 93). This cone produced three distinct lava flow units from three different vents on its SW, S, and NW sides; those from the SW vent were the most damaging. On the evening of 30 July, the eruption claimed the upper cable car station, which burst into flames as a tongue of lava invaded its interior. Behind it, the rapidly growing cone of the Piano del Lago sent its lava fountains hundreds of meters into the sky, producing ground-shaking detonations.

During late July, the rate of lava emission in the direction of the Rifugio Sapienza area diminished as a new vent opened on the S side of the Piano del Lago cone, from which a lava flow spilled over the crest of the Valle del Bove and flowed to the bottom of the Valle, covering a portion of lava erupted in 1991-1993. The Valle del Leone fissure ceased emitting lava. The Montagnola 2 had become a large cone. It again shifted from magmatic to phreatomagmatic activity. Although the level of activity at this cone was decreasing, ash columns developed, and the wind carried the ash again in the direction of Catania, again closing the Fontanarossa airport. Vigorous eruptive activity continued during the first days of August at the fissure at 2,100 m elevation, but the lava effusion rate had dropped, and only the central portion of the original flow remained active, feeding a flow that advanced on top of the larger earlier flow from the same fissure. Strong phreatomagmatic explosions occurred from time to time at the upper vents on this fissure. Lava also continued to pour from the fissure at 2,700 m elevation, and numerous active flow lobes extended SE toward Monte Nero.

Beginning on 3 August the activity at the fissure at 2,100 m elevation showed a marked decrease. During the last week of the eruption (4-10 August) lava continued to flow from that fissure at a rapidly diminishing rate, explosive activity ended, and the fissures at 2,950 and 2,700 m elevation ceased erupting. Ash emission from the Piano del Lago cone ended around 6 August. Lava was last seen flowing from the fissure at 2,100 m elevation on late 9 or early 10 August. The eruption ended after almost 24 days, much earlier than its vigorous onset had suggested.

Products of the eruption and morphological changes. The July-August 2001 eruption emitted at least eight distinct lava flows which mostly affected the S and SSW flanks of Etna. The most damaging flows came from vents near the Piano del Lago cone at 2,570 m elevation. This cone produced most of the pyroclastic material, of which the most fine-grained portion (ash) caused widespread distress.

Petrographically, the lavas fall into two main groups, one of which is essentially similar to the historical products of Etna (porphyric hawaiites with phenocrysts of plagioclase, clinopyroxene and olivine), while the other shows characteristics not seen in any Etnean lavas during the past millennia (alkalic basalts).

Several major pyroclastic edifices grew during the eruption. The largest, the Piano del Lago cone at ~2,570 m elevation, is a nearly symmetrical cone, ~80 m high, which grew mostly between 25 and 31 July. It is crowned by a large crater ~150 m across and 50-60 m deep with near-vertical walls. During a visit on 30 August a few fumaroles located on the SEC walls emitted vapor and gas without forming a visible plume. A spectacular dike was exposed at the base of the E crater wall, and a less conspicuous dike was visible at the base of the WNW crater wall. Several faults or groups of faults were visible in the E and NE crater walls; a narrow graben developed on top of the E crater wall dike. The second-largest pyroclastic edifice lies in the upper part of the fissure at 2,100 m elevation.

Extensive (non-eruptive) fracture systems formed between the various eruptive fissures. Some of them began to form before the eruption, others developed during its first week. Many of these fractures are arranged in an en echelon pattern, which is especially notable in the Valle del Leone, between the northeastern (2,600 m) vents and the SEC. Other spectacular fractures opened between the Piano del Lago cone and the eruptive fissure at 2,100 m elevation. However, the most impressive fractures developed on the E side of the former Central Crater (now occupied by the Voragine and the Bocca Nuova), where they attained widths of more than 1 m. These fractures were vigorously steaming when visited in late-August and mid-September 2001. Fracturing also affected the southern face of the SEC cone.

About 5.5 km² of Etna's upper and middle slopes were covered with new lava (compared to 7.6 km² in the 1991-1993 flank eruption). The total volume of lavas and pyroclastics emitted during the eruption is ~ 30-35 x 10⁶ m³ (25 x 10⁶ m³ of lava and 5-10 x 10⁶ m³ of pyroclastics, all calculated as dense rock equivalent), which makes this eruption a relatively modest-sized one for Etna (the 1991-1993 eruption had produced ~ 235 x 10⁶ m³ of lava). Yet the fairly high proportion of pyroclastic material distinguishes this eruption from most other recent Etnean flank eruptions.

The most productive vents were those at 2,100 m elevation, which produced the longest (~ 7 km) and most voluminous (slightly less than 14 x 10⁶ m³) single lava flow. The average combined effusion rate at all eruptive fissures throughout the eruption was ~11 m³/s, with peak rates of 14-16 m³/s. It is assumed that much of the magma that accumulated in one or more reservoirs below the base of the volcano in the years preceding the eruption was not erupted and remains available for future eruptions.

Information Contacts: Boris Behncke, Dipartimento di Scienze Geologiche (Sezione di Geologia e Geofisica), Palazzo delle Scienze, Corso Italia 55, 95129 Catania, Italy.

April 2002 (BGVN 27:04) Cite this Report

Nine months of relative quiet follow mid-2001 flank eruption

This report discusses Etna following the July-August 2001 eruption and through 25 April 2002. According to Boris Behncke, the chief source for this report, this 9-month interval was an unusually quiet one and marked the longest quiet interval since 1995.

A visit to the summit craters on 30 January 2002 revealed low levels of activity and no evidence of energetic outbursts. Loud explosions occurred at intervals of 5-30 minutes within the NW pit of Bocca Nuova, but no solid material was ejected. The rims of the pit were covered with brown lithic ash (which had been emitted in December-January) but there were no blocks or fresh scoriae indicating recent ejections. The pit appeared much the same as in September 2001, with a crescent-shaped flat terrace surrounding a deep, degassing vent in the SE part of the pit.

Most of the present degassing at the summit craters is occurring from a vent in the SW part of the Voragine, which had been much less active during the past 1.5 years. Northeast Crater emitted a fairly dilute plume, and at Southeast Crater, fumarolic activity was concentrated at its W rim where numerous degassing vents lie in a fracture. Mechanized access remained limited after the demise of the cable car and the ski lifts on the S flank during the July-August 2001 eruption (BGVN 26:08 and 27:03). In order to access the summit area one has to hike from ~1,900 m elevation, a trip that takes several hours and leads across the July-August 2001 lava fields.

Numerous small earthquakes, some of which were felt by the local population, were recorded on the S flank (in the area of the largest of the July-August 2001 lava flows), and were interpreted to result from the cooling of the lava. Near-continuous, pulsating emissions of reddish-brown lithic ash began around 9 March at the NW vent of Bocca Nuova, generating a plume that trailed for dozens of kilometers downwind. The same source vent has been the site of deep-seated explosions during the past six months. The emissions may have been caused by collapse within the conduit, which occurred repeatedly after the end of the July-August 2001 eruption, and does not necessarily indicate an intensification of eruptive activity or uprise of fresh magma. On the other hand, the volcano had been quiet for some 8 months at this time, and renewed magmatic activity at the summit was to be expected in the near future.

During the third week of March, emissions of lithic, pink-colored ash continued at Bocca Nuova. These were accompanied by voluminous degassing from Northeast Crater and minor fumarolic activity from Voragine and Southeast Crater. During days without strong wind, these emissions rose vertically to form a spectacular plume that might easily create the impression of true eruptive activity at the summit. However, there is no evidence that fresh magma has risen to near the surface, because no incandescence can be seen at night.

A mid-March summit visit by Giovanni Tomarchio, a cameraman of the Italian television RAI (who is responsible for much of the television footage of Etna in recent years), revealed frequent loud explosions at the SW vent of Bocca Nuova. Although the floor of this vent was not visible, it seemed that the explosions originated somewhere immediately below the visible part of the pit. All recent ejecta were fine lithic ash, which accumulated to form a thick, soft deposit in the summit area. Similar emissions occurred for months at Bocca Nuova during the spring and summer of 1999, prior to the vigorous eruptions at Voragine and Bocca Nuova during September-November of that year.

In late March, after nearly three weeks of ash emissions from Bocca Nuova, Northeast Crater began to emit dark brown to gray ash. The emissions appeared to follow a series of small SE-flank earthquakes during 24-25 March. At least three of the shocks were felt by the local population. On 27 and 28 March the ash emissions from both Bocca Nuova and Northeast Crater rose as distinct puffs to several hundred meters above the summit and seemed more energetic, denser, and darker than during the previous weeks. To a passing airplane pilot they appeared so spectacular that he sent out a warning of an eruption. On 28 March, light ash fell over the S flank as far as Catania (~25 km SSE).

Whether Etna is back in magmatic eruption is the subject of debate. The ash that came from the two craters consisted of fine-grained fragments of rock and was derived from the conduit walls and thus contained no new magmatic material. The ash that fell in Catania on 28 March was distinctly darker than the ash that fell in the summit area during the previous weeks and may contain a certain proportion of juvenile magmatic material, although microscopic examination has not been conducted to confirm this. No glow has been seen so far at the summit during night observations, so it seems unlikely that magma has reached the surface. On 29 March two impressive columns bearing dark ash rose nearly continuously from the two craters to several hundreds of meters (~800 m at one point) above the summit. Shifting winds carried the plume E, S, and W.

During late March through 2 April ash emission continued without interruption from Bocca Nuova, while at Northeast Crater it had apparently stopped. Light ashfalls occurred in downwind areas, at times extending as far as Catania. The emissions took the form of billowing brown plumes, which at times rose several hundred meters above the summit. No incandescence was seen at night. Weather prevented observations after the afternoon of 2 April.

The summit became visible again on 6 April. Bocca Nuova continued to produce weak expulsions of brown-colored (probably lithic) ash, while Northeast Crater emitted only white vapor. Two small (M ~3) earthquakes occurred under the SE flank on 4 April. On 13 April two earthquakes (M 2.7-3) were felt by residents on the SE flank (between the towns of Zafferana and Santa Venerina), their epicenters lying in an area named "Salto della Giumenta," located ~5 km NW of Zafferana. Press sources citing scientists of the Istituto Nazionale di Geofisica e Vulcanologia of Catania gave focal depths of ~4 km below the surface. Numerous earthquakes had occurred within the past few weeks in this area, although their correlation with magma movement within the volcano remained unclear.

Ash emissions continued almost constantly at Bocca Nuova. On 14 April these appeared to be dark gray, and at times were emitted forcefully enough to form plumes several hundred meters high. No incandescence was seen during night observations. A dense plume of brownish-gray ash drifted from Etna's summit across the E sky of Catania as Bocca Nuova emitted pulverized rock from its SE vent. Voragine and Northeast craters gave off dense steamy plumes.

In late April heavy snow fell on Etna; snow-cover reached down to ~1,400 m elevation and access to the summit area was reduced. The snow provided a good opportunity to observe the hot areas at the summit and to confirm that no recent lava outflows have taken place. Snow was melting rapidly on the cones of the summit craters and along the fracture that extends NNE from Southeast Crater. Since 23 April, Bocca Nuova's ash emissions, which had been nearly continuous since early March, decreased markedly. The only visible summit activity during 24-25 April consisted of apparently ash-free gas emissions, mostly from Bocca Nuova and Northeast Crater. Nine months after the climax of its most recent flank eruption, Etna continues its unquiet slumber.

Information Contacts: Boris Behncke, Dipartimento di Scienze Geologiche (Sezione di Geologia e Geofisica), Palazzo delle Scienze, Corso Italia 55, 95129 Catania, Italy.

August 2002 (BGVN 27:08) Cite this Report

Generally weak activity at summit craters during mid-May through July 2002

This report discusses activity at Etna during mid-May through July 2002.

Northeast Crater (NEC). During mid-May, weak degassing continued at NEC with sporadic mass wasting along the inner crater walls. There were abundant fumaroles on the crater floor and Strombolian activity was also confirmed. Intermittent degassing occurred during 3-9 June and, during the following week emissions of ash continued with intervening brief periods of light-colored gas emission. Ash emission ceased on 23 June and observations by the thermal telecamera from the Civil Protection helicopter indicated that the NEC's intracrater-floor fumaroles reached temperatures of 200-250°C. Unusually high temperatures (max. 50°C) of emitted ash were seen, suggestive of Strombolian activity. The 23 June observations indicated higher temperatures than earlier results in April 2002.

On 26 June, observers again confirmed emissions from deep within the NEC. The base of the crater was not visible, but was believed to be ~100-150 m below the rim of the intracrater floor. During one of the more vigorous outbursts, tephra spattered over the internal rim of the crater, allowing visitors to take a sample. Outbursts on 1 July threw fragments of incandescent lava outside of the crater walls. Similar ejections occurred at NEC again on 5, 6, and 7 July and continuing into the following week. The most intense explosions could be heard at the base of the cone and were accompanied by pulsing clouds of fine ash. On 9 July, ash emissions diminished significantly. On 11 July there were puffs of ash at the NEC. The rim of the crater and the high outer western slope of the cone was littered with bombs. Some bombs close to the crater rim reached dimensions of ~50 cm across. The steam and ash hindered visibility of NEC's interior. During the third week of July, ash emission stopped for the first two days of the week. Helicopter observations on 20 July found that NEC contained copious fresh ash. During the last week of July, continuous and sometimes intense white steam emissions occurred.

Bocca Nuova (BN). During mid-May, BN degassed normally, in a pattern that continued intermittently through mid-June and later. At times, emissions were dark-ochre colored. While the S vent degassed, the N vent emitted ash. On 26 June, ash emissions interfered with visibility of the two internal craters as well as the crater floor, but the activity was not accompanied by audible gas releases. During the first week of July there was an almost continuous and significant increase in the amount of ash emitted but again no rumbling. On 9 July, ash emissions diminished significantly, and remained at these levels, albeit with oscillations. Two days later, at the W crater, degassing was accompanied by a weak emission of ash. The crater had a diameter of 150-200 m and was more than 180 m deep, dropping the initial 70 m from the rim in a steep step. Fresh material could not be found near BN's rim. The E crater had a diameter of ~150 m and a depth of more than 160 m. On the same day, thermal measurements of the fumaroles on the rim between the Voragine and BN's E crater saw temperatures oscillating at ~450°C. During the third week of July, ash emission stopped for the first two days of the week but returned by 20 July.

Voragine. During mid-May, the two interior vents, one central and the other on the rocky division between Voragine and BN, degassed in a continuous and pulsating way and the Voragine's crater rim showed more intense fumarolic activity in the NW and S. During 3-9 June, Voragine's emissions were weaker than NEC and BN, consisting of steam, with rarer darker emissions of fine ochre- and black-colored ash. In mid-June, the two vents showed continuous and pulsating degassing. The rim of the crater displayed more intense fumarolic activity in the NW and S sectors. Snow-covered areas were still present inside Voragine through late June.

Discontinuous ash emissions occurred during the first week of July. On 9 July, ash emissions diminished significantly, and remained at these levels, albeit with oscillations. During the second week of July, the Voragine continued to degas while accompanied by a pulsating emission of ash from the vent in the most depressed part of the crater. Minor ash emissions were observed through 20 July, but by the last week of July, no Voragine emissions were visible from the Milo telecamera.

Southeast Crater (SEC). SEC, the origin of the strong eruptive episodes of July and August 2001, showed virtually no activity during the current reporting period; the interior was reported to be completely obstructed. In early June, there were localized fumaroles with white emissions on the rim of the crater. Otherwise, there was no degassing, except for some weak fumaroles in the NW portion of the crater rim noted in mid-June. In late June, weak fumarolic activity persisted at the edge of the crater summit and along the fracture running N-S on the flanks of the pyroclastic cone of the SEC. In the last week of July, the Milo telecamera revealed only weak gas emission from the SEC's border fumaroles.

Thermal images of summit craters. Thermal images registered at dawn on 20 July by helicopter surveillance without solar radiation interference showed a midbase temperature (max. 100°C) at all the fractures surrounding the summit craters. The field of the fracture that extended S from the NEC, skirting the Voragine before reaching the SEC, appeared enlarged and extended also to the N flank of the NEC. However, no significant thermal anomalies were noted in this field.

Information Contacts: Istituto Nazionale di Geofisica e Vulcanologia, Sezione di Catania, (INGV-Catania), Piazza Roma, 2, 95125 Catania, Italy.

October 2002 (BGVN 27:10) Cite this Report

A flank eruption started on 27 October; lava vented at N- and S-flank fissures

At 2225 on 26 October 2002 a swarm of earthquakes was recorded by the seismic network of the National Institute of Geophysics and Volcanology (INGV) in the Catania sector. Three hours after the swarm began, Etna started a new flank eruption. Until 1 November, ~500 shocks registered. The seismic swarm preceded and accompanied explosive activity in the summit area.

A survey at 0400 on 27 October found that two eruptive fissures had opened on Etna's N and S flanks; they were still propagating up- and down-slope when observed. Fire fountains escaped at both fissures.

At that time, lava flows started to pour from the lower part of the N-flank fissure, causing concern on Etna's N flank around Piano Provenzana. At the lower end of this fissure, two major flows spread NE and E. The NE flow stopped on 31 October after having traveled 2 km, behavior congruent with an observed decline in the effusion rate.

The E flow slowed down until 1 November, but it continued moving and crusting over in the middle portion of the flow field until 3 November. Scientists from INGV-CT conducted a helicopter-based aerial survey, using helicopters from the Civil Protection, and deploying a FLIR TM 695 thermal camera. Survey results showed a few sectors of solid crust and suggested the initial formation of a lava tube on this lava flow, which completely stopped on 5 November. The ski station and tourist shops on Piano Provenzana were first destroyed by the earthquakes, and then surrounded by lava flows. The flows also caused fire that engulfed parts of the pine forest. Flow mapping (shown on the INGV website) was limited by both the presence of fire around the flow fronts and ash clouds masking most of the flow field, and only the use of the FLIR TM 695 thermal camera allowed views of the active lava flows.

The N fissure opened between 2,500 and 2,350 m elevation, an area close to the fissure developed in the year 1809. The current N-flank fissure is a few kilometers long and expanded NE following the NE Rift Zone.

A lava flow from the S-flank fissure started ~12 hours after the N one. It spread SW and split in two branches around Monte Nero, following the same path as one of the 2001 lava branches. The S flows stopped on 31 October, having reached a total length of about 2 km. Fire fountains and phreatomagmatic activity decreased in intensity with time and disappeared at the N fissure, but were still continuing on the S fissure.

The S fissure, which opened at 2700 m elevation, traveled N20°W, and occurred a few hundred meters W of the 2001 S-fissure field, between Monte Frumento Supino and Cisternazza (a map appears at the INGV website, see below). Spatter falling around the S-fissure's vents formed two cinder cones at about 2,030 m elevation. Fire fountains from these vents were initially 100-300 m high, producing an ash plume and abundant ashfall on Etna's S flank. In 3 days the city of Catania received ~2.5 kg/m² of ash due to strong winds from the N. This disrupted the local airport and caused problems with travel.

The high amount of gas released by the summit vents and at the 2,750-m cone (up to 25,000 tons/day), and the continuing explosive activity at the S vent, suggest a long duration for this eruptive event (figure 96).

Figure 96. SO₂ released from Etna during January 2001-1 December 2002. Courtesy INGV.

Editor's note: Summaries of Etna activity from recent issues of the Bulletin have been prepared by our staff without the benefit of crafted summaries in English. As such, the contributors found them deficient in clarity of translation. For greater clarity and more technical details consult journal publications and the INGV website.

Information Contacts: Sonia Calvari, Istituto Nazionale di Geofisica e Vulcanologia Sezione di Catania, Piazza Roma 2, 95123 Catania (URL: http://www.ct.ingv.it/).

November 2002 (BGVN 27:11) Cite this Report

Witnesses saw N- and S-flank eruptions begin at around 0200 on 27 October

After the violent flank eruption of July-August 2001, Mount Etna was rather calm for more than 10 months, except for usual fumes from the four summit craters [and minor ash emissions]. In the first days of July 2002 weak magmatic activity resumed sporadically at the NE Crater with ejection of bombs that fell on the outer slopes of the cone. On 12 September explosions occurred every 2 or 3 minutes and were violent enough to throw large spatter as far as the northern rim of the Voragine (Central Crater). However, there were many days without explosive activity and, at other times, the NE Crater emitted large clouds of brownish ash. Although a magnitude 3.7 earthquake had struck the northern flank of the volcano on 22 September, subsequent days were so calm that, to these contributors, the following events came as quite a surprise.

As the National Institute of Geophysics and Volcanology (INGV) previously reported (BGVN 27:10), a seismic swarm began to shake Etna late during the evening of 26 October 2002. One observer, Maurice Aubert, happened to be in a hotel on the northern flank (at Piano Provenzana, 1,816 m elevation). There the seismic shocks were distinctly felt after midnight and rapidly reached hazardous levels. Hours later, at 0205 on 27 October, lava fountains began to play along a fissure 1-2 km up slope, but decreased at 0220 when lava flows expanded downwards.

The seismic intensity of earthquakes felt the night of the 26th ranged from II to VII or perhaps VIII. The approximate timing and seismic intensity was recorded as follows at 0030, II; at 0140, VI; at 0200, VI; at 0320, VII; and at 0343, VII or VIII. Maurice Aubert and his group hastily retreated shortly after 0320, exiting while cracks were developing through the mountain road. The last of the above-reported intensities was felt during their departure, when a strong earthquake shook their car.

Vents at ~2,700 m elevation on the southern flank (on the Piano del Lago) are here called the S2700 vents. These new S-flank vents lay just SE of the ancient cone of Monte Frumento Supino and ~800 m NW of the Laghetto cone, which appeared in 2001.

Watching the S2700 vents, Giuseppe Scarpinati saw two lava fountains develop after 0200, together with a large ash plume that drifted S. The eruptive phenomena were accompanied by strong detonations and rumblings together with continuous earthquakes that were felt in Acireale, a town at Etna's southeastern foot.

Lava flows from the northern vents invaded and over ran the flat area containing tourist facilities at Piano Provenzana and proceeded as two branches downwards through the pine trees towards Linguaglossa, a village ~10 km to the NE. The greatest damage was not the loss of all tourist facilities at Piano Provenzana, but was instead due to heavy ashfall S of the volcano, which led to closing of the Catania airport on the afternoon of 27 October.

On the morning of 28 October the S fissure had developed at least three explosive vents. A 100-to-200-m-high lava fountain, ~200 m downslope, fed lava flows that extended by more than 2 km toward the uninhabited area of Monte Nero degli Zappini (figures 97 and 98). During the day, however, the effusive activity significantly decreased, and on 29 October the lava fronts virtually stopped on the southern side, although violent degassing at the upper end of the fissure continued unabated. Sustained release of high pressure gas fed a voluminous SE-directed ash plume that reached to more than 5 km altitude. At the same time on the 29th, a large plume of white vapor was emitted at the summit from the central crater vents (Bocca Nuova, Voragine) and the NE Crater. The SE crater, the main site of the 2001 eruption, remained entirely calm.

Figure 97. Southern vents of Etna at 2,700 m elevation as seen during daylight on the morning of 28 October 2002 (taken from 2,500 m elevation looking N). The white plume on the right comes from the lava vent, and the plume in the left background is from the summit craters. Courtesy of J.C. Tanguy.

Figure 98. Southern vents of Etna as photographed from the SW in the early afternoon of 28 October 2002. From left to right the image shows the summit craters emitting white vapor, the cone of Mt. Frumento Supino, the S2700 explosive vents giving off a dark column, the lower lava vent emitting a faint white plume, new lava flows (dark narrow band), 2001 cone, and Montagnola cone. Courtesy of J.C. Tanguy.

Strong earthquakes on 29 October caused damage on the lower E flank of the mountain, particularly at Santa Venerina where some 1,000 people were left homeless. The main shock was recorded by Jean-Claude Tanguy in the SE region of the volcano (Trecastagni) at 17 seconds after 1102 (± 5 sec). Horizontal ground motions there lasted 7 to 8 seconds. The INGV reported the seismic event as M 4.4, located 8-9 km beneath Santa Venerina. Other strong shocks at 1739 and 1814 (M 4.0 and 4.1) caused walls to collapse along the road between Zafferana and Milo.

On 30 October soon after midday the Bocca Nuova vent began to emit large clouds of brownish ash. This activity culminated between 1310 and 1320, and the ash cloud merged into the still large, dark ash plume from the southern lateral vents. However, Strombolian explosive activity was still vigorous at the main explosive center, which included a group of about six vents near 2,000 m elevation (called the N2000 vents). These vents, which produced photogenic activity into the night (figure 99), lie just to the E of an old cinder cone known as Monte Ponte di Ferro (at 2,040 m elevation). Here the accumulation of pyroclasts had built a spatter rampart ~200 m long and 30 to 40 m high, the upper part of which reached 2,035 m elevation (± 5 m, measured from Mt. Ponte di Ferro using both altimeter and inclinometer).

Figure 99. A night photograph of Etna's N2000 vents showing the brilliant glow of lava fountains and associated spatter. Taken on 30 October 2002 from Mt. Ponte di Ferro looking E. Courtesy of J.C. Tanguy.

On 31 October the wind gradually shifted from the N to the W and then SW, so that ashfall from S2700 vents affected localities NE of the volcano including Reggio di Calabria, whose airport also had to be closed. At the northern vents the lava effusion was on a waning stage, but violent explosions from the two upper vents of the N2000 group threw blocks of ancient material amid juvenile tephra (figure 100).

Figure 100. Outbursts began to wane at Etna's N2000 vents on the evening of 31 October 2002, but substantial explosions continued at the upper two N2000 vents. The photograph was taken looking southward, towards Etna's summit, from the lower NE rift zone at the eastern base of the northern Monte Nero (crater of the 1646 eruption at 2,049 m elevation; but easily confused with the S-flank feature of the same name). On the photo's right-center area lies a more brightly lit uplands region that leads to the summit of NE Crater, which is emitting a dense plume of white smoke. From left to right in the darker foreground lie the new spatter ramparts, with incandescent lava lumps at the middle vent, and dark ash and block explosions at the two upper vents, and the upper part of the eruptive fissure (small white fumes, far right) located between about 2200 and 2500 m elevation. Courtesy of J.C. Tanguy.

On 1 November all activity ceased on the northern side except for very small residual lava flows, but the S2700 upper vent appeared to enter a phase of sustained explosive activity resembling a small subplinian column that continued to cause disruptions around the volcano. It was not until 12 November at 1340 that the activity abruptly changed to typical Strombolian explosions of liquid lava clots with loud detonations. On 13 November at about 1600 a small lava flow began to trickle from the lower base of the S2700 cone. The lava effusion increased on 14 November, expanding downwards along the 27-28 October flows. Meanwhile ash emission recommenced at the S2700 crater.

This kind of eruption style is quite unusual at Mount Etna. The authors suggest that it could indicate that a considerable amount of magma has intruded into the S rift zone, which would account for strong degassing without any significant lava effusion between 2 and 13 November.

Information Contacts: Jean-Claude Tanguy, University of Paris 6 & Institut de Physique du Globe, 94107 St. Maur des Fossés, France; Maurice Aubert, University of Clermont-Ferrand, Department of Geology, 63038 Clermont-Ferrand, France; Roberto Clocchiatti, CNRS-CEN Saclay, Lab. Pierre Süe, 91191 Gif sur Yvette, France; Santo La Delfa and Giuseppe Patané, University of Catania, Department of Geological Sciences, Corso Italia 55, 95129 Catania, Italy; Giuseppe Scarpinati,via Muggia 7, 95024 Acireale, Italy.

December 2002 (BGVN 27:12) Cite this Report

Late October 2002 earthquake swarm signals start of new flank eruption

On 26 October 2002 at 2225 a swarm of earthquakes was recorded by the seismic network of the Catania Section of the National Institute of Geophysics and Volcanology (INGV-CT). This signaled the start of a new flank eruption that has formed fissures on the N and S sides of the volcano.

The lava supply from the main vents were cut off by 3 November. At that time both the N and S fissues stopped producing lava flows, although the S fissure continued to discharge fire fountains. After that, 20 m of downslope movement was observed at the most advanced flow front near Piano Provenzana on 5 November. This late movement was caused by channel emptying, and occurred when lava emerging at the main vent, ~5 km upstream, was completely crusted over. No further advancement of the lava flows was observed on the S or N flanks of the volcano after this date. However, while explosive and effusive activity stopped at the N fissure by 5 November, as of 11 November fire fountaining continued at the S vent located at 2,750 m elevation, near Torre del Filosofo. All data (gas emission, volcanic tremor, composition of the ash) suggested a steady state at this vent. Ash fallout caused intermittent disruption at the Catania airport and damage to buildings.

The eruption continued into December 2002. Lava flows and Strombolian activity continued on the S flank from vents at 2,750 m elevation. Ash emission from the 2,750 m cinder cone significantly declined on 17 December, allowing the local airport of Catania to reopen.

The two vents, which opened at the SE base of the 2,750 m cinder cone on 9-10 December, fed four major lava flows spreading S and SW. A lava flow spreading S on 13 December approached the Rifugio Sapienza and eventually crossed a road on 17 December. An overflow from the main lava channel covered a building and caused a strong explosion in the Rifugio Sapienza area during the night of 17 December, injuring 32 people. The explosion was not directly caused by the eruption, but by vaporization of oil or water inside the building while it was covered by the expanding lava flow. The effusion rate from the two vents gradually decreased, eventually causing the closure of the western vent and then the lack of supply to the lava flows spreading SW towards Monte Nero.

A new vent opened on 17 December at the S base of the 2,750 m cinder cone, a few meters W of the previous vents. A lava flow soon started from this vent, spreading SW towards Monte Nero. The new vent cut supply to the flows expanding S towards Rifugio Sapienza and formed a fan of thin lava flows spreading S, SSW and SW. The lower lava output produced shorter flows, which spread up to 2.5 km from the vent, without threatening the tourist facilities at Rifugio Sapienza. Lava flows spreading from the 17 December vent slowed down and crusted over on 22 December, when a new vent opened at the SW base of the 2,750 m cinder cone. A flow, again directed SW towards Monte Nero, originated from this vent and was expanding in this direction on 23 December.

SO₂ emission measured daily during the eruption had significantly decreased as of 1 December, when the previous values of about 20,000 tons per day decreased to about 7,000 tons per day (figure 101). The lower gas output, the decrease in effusion rate, and the lower emission of ash from the summit, suggested a declining stage of the eruption.

Figure 101. A plot of SO₂ flux at Etna during September-December 2002. Courtesy of INGV-CT.

Updated maps of the lava flows, and reports of the eruptive activity, gas emission and ash composition (in Italian), can be found on the INGV-CT website.

Information Contacts: Sonia Calvari, Istituto Nazionale di Geofisica e Vulcanologia (INGV), Sezione di Catania, Piazza Roma 2, 95123 Catania (URL: http://www.ct.ingv.it/).

January 2003 (BGVN 28:01) Cite this Report

Flank eruption that began in October ends on 28 January

After three months of activity, the flank eruption at Etna that began on 27 October 2002 finished on 28 January 2003. Lava flows and Strombolian explosions in January were confined to the S-flank vent located at 2,750 m elevation. Lava flows formed a fan and covered the previous lava flow field. A decrease in effusion during January was suggested by the shorter lava flow lengths of less than 2 km, which formed a complex flow field with small lava tubes. Strombolian activity from the 2,750-m cinder cone significantly declined on 27 January and disappeared on 29 January. Lava flows slowed on 27 January, and were no longer fed by the 29th, and thus cooled down. At this time SO₂ output decreased significantly, reaching the lowest value of 2,000 tons/day on 29 January 2003. Volcanic tremor amplitude showed a marked decrease on 27 January, and on 28 January at 2240 it returned to background levels, signaling the end of the eruption.

Information Contacts: Istituto Nazionale di Geofisica e Vulcanologia (INGV), Sezione di Catania Piazza Roma 2, 95123 Catania (URL: http://www.ct.ingv.it/).

February 2003 (BGVN 28:02) Cite this Report

Petrographic and geochemical comparison of 2001 and 2002 lavas

On 27 October 2002 Mount Etna opened on both its northern and southern sides (BGVN 27:10-27:12), erupting lava from vents about 2,500-1,800 m elevation on the NNE flank and 2,800-2,700 m on the S flank. The N vents emitted two flows that stopped after a few days, the longer of which stretched ~5 km. The S vents erupted lighter intermittent lava flows, but showed much stronger and sustained explosive activity that developed two large cinder cones at 2,750 and 2,850 m elevation.

The northern lavas are similar to the tephra erupted from Northeast Crater during the summer of 2002 and, more generally, to the trachybasalts that characterized Etna's activity during the past centuries (Tanguy and others 1997, and references therein). They are typically porphyritic (30-40% phenocryts), containing numerous millimeter-sized crystals of plagioclase (An 86-65/Or 0.4-2.1), clinopyroxene (En 42.3-37/Fs 11.7-15.5), and fewer ones of olivine (Fo 76-71) and titanomagnetite (Usp 35-43). The silica content is about 47-48% with a "normal" MgO content of about 5% and "low" CaO/Al₂O₃.

The southern lavas are significantly higher in MgO (~6.5%) and CaO/Al₂O₃ with fewer phenocrysts that comprise barely 10% of the rock. Olivine crystals are decidedly more magnesian (Fo 82-76), although other minerals are much like those described above, with plagioclase An 80.8-63.8/Or 0.8-1.3, clinopyroxene En 42-34/Fs 12-15.7, and titanomagnetite Usp 37-42.7. It must be pointed out, however, that plagioclase and titanomagnetite are here almost entirely confined within the groundmass, a characteristic that is uncommon in Etnean lavas and characterizes some of the most basaltic samples.

A particularity of the southern 2002 lavas is the presence of destabilized amphibole crystals, together with quartz-bearing inclusions (sandstones) surrounded by a reaction rim of pyroxene and embedded in a rhyolitic matrix. These characteristics are quite similar to those already found in the 2001 lavas emitted at 2,100 m elevation on this same flank (BGVN 26:10). The 2002 amphibole is present in rarer and smaller "megacrysts" that do not exceed 2 cm in length and display a reaction rim composed of rhonite, anorthitic plagioclase, and olivine within a silicic and potassic glass. Its chemical composition is similar to that of the 2001 amphibole.

Orthopyroxene was found in a southern flow emitted at the very beginning of the eruption (27 October). The average of 16 microprobe analyses is as follows (Centre de microanalyse Camparis, University of Paris 6): SiO₂, 53.18; TiO₂, 0.23; Al₂O₃, 0.79; Cr₂O₃, 0.04; FeO, 19.43; MnO, 0.80; MgO, 23.52; CaO, 1.72; Na₂O, 0.05; Total, 99.75. The composition is thus hypersthene close to bronzite, typical of basalts or basaltic andesites. Hypersthene here occurs as crystals 0.5-0.7 mm in length, always surrounded by clinopyroxene. The two minerals are not in equilibrium as indicated by their different Mg values (0.69 for Opx, 0.71 to 0.78 for Cpx). This is the first time that such large crystals of orthopyroxene have been observed in lavas of the last tens of thousand years. Orthopyroxene is very rare at Etna, being previously found on only two or three occasions in pre-Etnean basalts about 200,000 years old.

Olivine separates from both N and S lavas (~100 crystals each) were microprobed, showing a single distribution for the N flank of Fo 69-70 for 65% of the crystals. The S lavas have a twofold behavior with Fo 78-81 for 37% of the crystals and Fo 73-75 for 45% of them. These results are similar to what was found between the upper southern 2001 lavas (including the NE flank below Pizzi Deneri) and those emitted at lower elevation (S 2,600 m and S 2,100 m). It is worth noting that the 2,600 m S vent of the 2001 eruption is close (~1 km) to the 2,700 m S vent of the 2002 eruption.

Based on these preliminary results, the low porphyritic index added to the whole rock chemical composition and that of the olivine crystals, a common origin is suggested for the southern 2002 lavas and those emitted low on the S flank during the 2001 eruption.

Reference. Tanguy, J.C., Condomines, M., and Kieffer, G., 1997, Evolution of the Mount Etna magma: Constraints on the present feeding system and eruptive mechanism: Journal of Volcanology and Geothermal Research, v. 75, p. 221-250.

Information Contacts: Roberto Clocchiatti, CNRS-CEN Saclay, Lab. Pierre Süe, 91191 Gif sur Yvette, France; Jean-Claude Tanguy, Univ. Paris 6 & Institut de Physique du Globe de Paris, Observatoire de St. Maur, 94107 St. Maur des Fossés, France.

August 2003 (BGVN 28:08) Cite this Report

Ash emissions during April from Bocca Nuova; volcanic seismicity and ash puff on 11 August

Activity at Etna since the end of the last flank eruption on 28 January 2003 (BGVN 28:01) was characterized by intense degassing at the Northeast Crater (NEC). In April, ash emission was observed from Bocca Nuova crater (BN), and ash fell for about 1 hour on E-flank villages. On 17 April a helicopter survey, aided by use of a thermal camera, revealed a cinder cone within the S pit of BN with a hot vent at its top. However, no degassing was taking place from this vent, and the pit appeared mostly obstructed by debris from the crater walls. Rare explosions from the vent caused little emission of juvenile material on the crater floor. Another helicopter-borne thermal survey in May showed that the summit craters were mostly obstructed.

Only a hot crack within the S pit of BN was observed during a June field survey. A new vent on the N rim of the Voragine (VOR), detected during a June field survey, was ~0.5 m wide, and the temperature measured through a thermal camera was ~500°C, much higher than the two vents within the crater. Given the presence of hot features within the summit craters and the obstructions observed inside BN, Southeast Crater (SEC), and VOR, it is possible that renewal of explosive activity at these summit craters could be accompanied by sudden, unpredictable gas explosions.

On the afternoon of 11 August an increase in volcanic tremor at the summit seismic stations lasted about 15 minutes and was followed by about 30 minutes of strong explosion earthquakes recorded at all summit stations of the INGV-CT seismic network. This was the first such event recorded at Etna since the end of the flank eruption. The INGV-CT web camera at Milo (~11 km from the summit) showed a puff of red ash from the summit of NEC. Red glows from the same crater were reported that night. A field survey on 14 August did not reveal any explosive activity or sounds of explosions from the crater. There were no explosion earthquakes or increased volcanic tremor between 11 and 16 August.

Periodic measurements of the gas plume from the summit using both COSPEC (SO₂ flux) and FTIR (SO₂/HCl and HCl/HF ratios) showed decreases in all three values since the end of the flank eruption. This suggests a general decreasing trend in gas output from Etna's summit craters.

Information Contacts: Sonia Calvari, Istituto Nazionale di Geofisica e Vulcanologia, Piazza Roma 2, 95123 Catania, Italy (URL: http://www.ct.ingv.it/).

December 2003 (BGVN 28:12) Cite this Report

September-November 2003 volcanism low; web camera and satellites depict small plumes

BGVN 28:08 reported ash emission at Etna during April 2003, and seismicity and ash emission during August 2003. A 12 September 2003 report noted that volcanic activity remained low at Etna's summit, with abundant SO₂ and steam emissions at the NE and Bocca Nuova craters. An M 3.3 earthquake occurred on 14 September. It struck beneath the Ionian sea well offshore of Sicily's southeastern-most point. The reported epicenter (36.74°N, 15.60°E) was ~ 120 km SSE of Etna's summit. A Volcanic Ash Advisory noted activity depicted by web camera starting at 0500 on 25 September, with an ash-and-steam plume drifting to the W and visible below 4.5 km altitude. No ash cloud was visible on satellite imagery at 0530.

On 9 November, aviation sources and web camera observations detected an ash-and-steam plume moving S from Etna. The plume rose to ~ 4 km altitude.

Information Contacts: Sonia Calvari, Istituto Nazionale di Geofisica e Vulcanologia (INGV) Sezione di Catania, Piazza Roma 2, 95123 Catania, Italy (URL: http://www.ct.ingv.it/); Toulouse Volcanic Ash Advisory Center (VAAC), Météo-France, 42 Avenue G. Coriolis, 31057 Toulouse, France (URL: http://www.meteo.fr/).

January 2004 (BGVN 29:01) Cite this Report

Additional details and interpretation of the 2002-03 eruption; space-based photographs

Although Etna's 2002-3 eruption was previously discussed in BGVN 27:10-27:12 and 28:01, Boris Behncke subsequently posted a report to his website highlighting some further observations and interpretations. His report presented many photos, including two taken by astronauts aboard the International Space Station (figures 102 and 103). His report drew on published or soon-to-be published material (Acocella and others, 2003; Behncke and Neri, 2003; Branca and others, 2003; and Dellino and Kyriakopoulos, 2003). Extracts from Behncke's summary follow.

Figure 102. A photo of Etna during the 2002-2003 eruption looking SE and downward from ~ 400 km altitude on 30 October 2002 from the International Space Station (ISS-5). A large dark tephra column appears in the top center, rising from the upper S flank and then blowing toward the left (E). A much smaller gray-white plume rose just in front of the tephra column; it discharged from the summit craters. Appearing in the central foreground are two distinct white plumes that issued from along the NE Rift, and some lower, dispersed, low-density plumes. Smaller, lower plumes towards the photo's lower-left center came from forest fires. On the ground surface, the youngest lava flows appear darkest; some pyroclastic cones on the outer flanks are also visible. Future studies may disclose whether the brown-colored region beneath the tephra column in the upper-left quadrant of the photo was due to factors such as diffuse clouds, camera angle, and lighting geometry, or due to falling tephra descending from the plume. (Image ISS005-E-19024.) Courtesy of Earth Sciences and Image Analysis, NASA-Johnson Space Center (on their website see "Earth Sciences and Image Analysis Photographic Highlights").

Figure 103. A broader view of Etna's 30 October ash plume taken looking SE and downward from the International Space Station at ~ 400 km altitude, showing large portions of Sicily in the middle to foreground. According to the NASA Earth Sciences and Image Analysis team, the plume followed a curved path from Etna, first blowing SE, and then blowing S towards Africa at higher altitudes. They also noted that ashfall was reported in Libya, more than 560 km distance from Etna. Note the fainter, lighter-colored plumes from the NE Rift vents, which were also seen in the previous figure. (Image ISS005-E-19016.) Courtesy of Earth Sciences and Image Analysis, NASA-Johnson Space Center (on their website see "Earth Sciences and Image Analysis Photographic Highlights").

Behncke puts the eruption's start date a few hours earlier than previously reported, enough to shift the start date from early 27 October to late on 26 October. While mountain guides who visited the craters on Saturday 26 October noted nothing unusual, an intense earthquake swarm at shallow depth within the volcano began at about 2125 that day. Tremors woke hikers at the Hotel "Le Betulle" at Piano Provenzana, a spot at about 1800 m elevation on the NE flank; they abandoned the seriously damaged building. At dawn on 27 October those who still remained at Piano Provenzana noted large E-W trending fractures cutting across the paved parking lot of the tourist complex. According to Behncke, the first eruptive vents to become active during this eruption opened at 2345 h on 26 October, on the upper southern flank, and immediately began to produce intense explosive activity.

Italy ended daylight saving time at 0100 UTC on Sunday 27 October (0200 local time). The change moved the clock back one hour, from 0200 to 0100 local time. Few if any important events were noted during the 60-minute interval of the time change. Later, however, at approximately 0230 h on 27 October a few persons watching the summit of Etna noted the sudden onset of high lava fountaining from the northern base of the Northeast Crater. The fountaining lasted only a few minutes.

Etna's 2002-2003 eruptions have been described as unusual, differing in four key respects. First, this was one of the most explosive eruptions in recent times. Pyroclastic material comprised more than half of the total volume of erupted products, contrasting with Etna's most recent eruptions, which mainly extruded lava.

Second, the 2002-2003 eruption discharged two different types of magma. The fissures on the NE rift produced magma of the sort normally produced by Etna over the past few centuries, while the vents on the S flank produced a magma rich in amphibole, a water-bearing mineral relatively rare in Etna's recent products. Amphibole also clearly appeared in the 2001 lavas (BGVN 26:10), and in products erupted in 1892 at Monti Silvestri, and 1763 at Montagnola. All of these vented on the S flank.

Third, some scientists have correlated large-scale flank slip and magma uprise. Specifically, on 22 September, the E flank of the volcano began to slip toward the Ionian Sea, with movement occurring mainly on the Pernicana fault system (Neri et al., 2003). This displacement is thought to have allowed magma to migrate from the central conduit system into the NE Rift, although a second, larger flank slip event was necessary to permit magma uprise to the surface. This occurred not only on the NE rift, but also on the S flank, where magma came from the eccentric reservoir previously active in 2001. Thus, the eruption can be interpreted as having been triggered by the flank slip, in contrast with the 2001 eruption, which was preceded by the forceful uprise of a dike from the eccentric reservoir, and possibly was triggered by regional tectonic compression (Acocella et al., 2003). One of the most important discoveries during the events of late 2002 and early 2003 was that the Pernicana fault system is not only 9 km long, as previously believed, but extends from the NE rift down to the Ionian Sea, and possibly continues offshore, over a distance of at least 18 km (Neri and others, 2003).

Fourth, N flank lava flows invaded a tourist complex and adjacent forest for the first time in the historic record. An important landmark in this region is the northern Monte Nero, which sits ~ 6 km N of Etna's summit, includes a crater of the 1646 eruption, and is a local high at 2,049 m elevation. It is easily confused with S- and SE-flank features bearing identical or similar names. The northern Monte Nero lies ~ 2 km W of Piano Provenzana and the surrounding forest called Ragabo. These latter environs had not been invaded by lava flows for many centuries. Eruptions on the NE Rift, which looms above the Provenzana plain, had occurred as recently as 1911, 1923, and 1947, but their lava flows had taken a more westerly course, leaving Piano Provenzana and the forest unharmed.

Tourist facilities were constructed at Piano Provenzana during the late 1960s to early 1970s. The associated ski area became popular among locals because, lying on the northern flank of the volcano, it received and preserved more snow than its southern-flank counterpart, and owing to wind patterns, it received fewer tephra falls. On Christmas 1985 an earthquake along the Pernicana fault (a few kilometers to the northeast of Piano Provenzana) destroyed the Hotel "Le Betulle," killing one person. That earthquake accompanied an eruption in the Valle del Bove, but the latter was very small and did no damage. Hotel "Le Betulle" was rebuilt to sustain higher seismic loads and it became the hub of Etna's N-flank tourism.

The 2002-3 eruption produced a number of small scoria cones along the fissure on the NE Rift and a cluster of huge cones at the vents on the S flank. The latter have completely changed the topography of what was once known as the "Piano del Lago" ("Plain of the Lake", indicated as "PDF" on the map in BGVN 26:10). Until 27 October 2002 this area bore the scars of the 2001 eruption, most of it being covered with virtually inaccessible lava flows and various pyroclastic cones. In early November 2002 the formerly rugged surface was transformed into a rolling plain of ash, which facilitated excursions on foot. The area was subsequently covered by rugged new lava flows. Etna's old abandoned cable car station (partially destroyed by an eruption in 1983) was buried by the lowermost of the new cones. A new souvenir shop and bar erected by mountain guides early in 2002 at 2,760 m elevation vanished under the cover of pyroclastics, although the Torre del Filosofo mountain hut at 2,900 m elevation is still standing. In the past, the Piano del Lago offered a splendid panorama of the summit cone complex, but this view became largely concealed by the new cones along the fissure at 2,700 m elevation. The largest of these cones, formed at a spot that was 2,750 m in elevation prior to the eruption, now stands about 200 m higher, and a second cone slightly up slope is nearly as tall. The sheer size of these new cones dwarfs that of Monte Josemaria Escrivà, which formed in 2001 and had been a prominent feature.

Behncke and Neri (2002) presented initial estimates for the volume of products emitted during the 2002 eruption. They indicated ~ 30 million cubic meters of lava, nearly two-thirds of which was emitted on the S flank. They also indicated that 40 million cubic meters of pyroclastics, were nearly exclusively emitted from the S-flank vents. In terms of magma volume, this is not an enormous eruption for Etna, but it ranks among the more significant of recent decades.

Outlook and interpretations. The 2002-2003 eruption came 1.27 years after the beginning of the 2001 eruption. Between 1971 and 1993 flank eruptions occurred at a mean interval of 1.7 years (Behncke and Neri, 2003). Etna's historical eruptive behavior has undergone significant fluctuations during the 400 years of reasonably complete documentation. It seems that flank eruptions tend to occur in series, and the 2001 eruption could be interpreted as the first in a new eruptive series, analogous to the sequence of 13 flank eruptions witnessed between 1971 and 1993. According to this interpretation, more such eruptions will occur at relatively brief intervals over a period of 10-20 years. By this model, the 2002-2003 eruption was the second in the new series, implying a third in the not too distant future.

The volcano was extensively fractured during both eruptions, which may allow magma to rise much more easily under the flanks of the edifice, and has grown progressively more active during the past 50 years. It is erupting more frequently and more vigorously than during the 280 years before 1950, and its productivity, or output, is increasing. Flank eruptions must thus be expected to occur at intervals ranging from 1 to 3 years, and some of them might be much more voluminous and potentially hazardous than the latest two eruptions.

The 2002-2003 eruption was one of the most explosive flank eruptions in the past 150 years, and it shows that Etna is a potentially explosive volcano, as it has been historically. Nearly all of the flank eruptions of the past 100 years have been relatively benign with mostly lava emissions; thus the local population has been lured into the belief that Etna is a "good volcano." But a short look at the record of its historically documented eruptions shows that the rather effusive, non-explosive behavior of the 20th century was, in fact, unusual.

Part of the explosivity of the 2002-2003 eruption might be due to the water-rich nature of the magma rising from a reservoir located below the S flank. This magma was comparatively gas rich, in contrast to the magma erupted from the central conduit system (and on the NE flank), which had degassed to some degree during the months before the eruption. The fact that this magma has appeared for the second consecutive time might be taken as an indicator that future eruptions will be fed from the same reservoir and therefore could be as explosive. However, an additional factor controlling the explosivity of an eruption is the interaction of magma with external water, such as a shallow aquifer. This was the case during the 2001 eruption (at Monte Josemaria Escrivà), and it was probably again the case at the new cones at 2750 and 2800 m elevation on the S flank. In fact, ash from the first day of the 2002-2003 eruption that arrived on the Greek island of Cefalonia during the following 24 hours was determined to be of phreatomagmatic origin (Dellino and Kyriakopoulos, 2003)

Eruptive activity at Etna quieted on 28 January, but in terms of seismicity, the volcano remained restless. Some of the continuing seismic activity was due perhaps to the adjustment of the edifice to the major displacements at the beginning of the eruption, or it may have started to recharge for its next eruption. Seismicity dropped to relatively low levels in the spring of 2003, but since mid-June 2003 was again slightly elevated.

References. Acocella, V., Behncke, B., D'Amico, S., Maiolino, V., Neri, M., Ursino, A., and Velardita, R., 2003, The 2001 and 2002-2003 eruptions of Mount Etna (Italy): Evidence for different triggering mechanisms: Abstract presented at the Annual Workshop 2003, Pantelleria, Sicily (23-28 September 2003) on Seismic phenomena associated with volcanic activity.

Behncke, B., and Neri, M., 2003, Cycles and trends in the recent eruptive behaviour of Mount Etna (Italy): Canadian Journal of Earth Sciences, v. 40, p. 1-7.

Behncke, B., and Neri, M., 2003, The July-August 2001 eruption of Mt. Etna (Sicily): Bulletin of Volcanology, v. 65, p. 461-476.

Branca, S., Carbone, D., and Greco, F., 2003, Intrusive mechanism of the 2002 NE-Rift eruption at Mt. Etna (Italy) inferred through continuous microgravity data and volcanological evidence: Geophysical Research Letters, v. 30, p. 2077.

Dellino, P., and Kyriakopoulos, K., 2003, Phreatomagmatic ash from the ongoing eruption of Etna reaching the Greek island of Cefalonia: Journal of Volcanology and Geothermal Research, v. 126, p. 341-345.

Neri, M., Acocella, V., and Behncke, B., 2003, The role of the Pernicana Fault System in the spreading of Mt. Etna (Italy) during the 2002-2003 eruption: Bulletin of Volcanology (in press but published on-line 5 November 2003).

Information Contacts: Boris Behncke, Dipartimento di Scienze Geologiche (Sezione di Geologia e Geofisica), Palazzo delle Scienze, Corso Italia 55, 95129 Catania, Italy; Earth Sciences and Image Analysis, NASA-Johnson Space Center (URL: http://eol.jsc.nasa.gov/).

March 2004 (BGVN 29:03) Cite this Report

Ashfall with juvenile components, emitted gases, and seismic patterns imply magma ascent

Since the cessation of the last eruption of Mount Etna on 28 January 2003, no further eruptive activity has been observed. Summit activity has been limited to pulsating gas emissions from the Northeast Crater (NEC) and from one of the two vents within Bocca Nuova (BN). The other central crater vents and the Southeast Crater (SEC) were essentially blocked and only producing extremely weak gas emissions.

The first significant variation from this very low level of activity was seen between 12 and 14 February 2004, when a weak ash emission was observed within the summit crater plume. A fresh ash sample was collected in Pedara, a village about 10 km SE from the summit. Del Carlo and Andronico (2004) reported that the sample was made up of material with a grain-size less than 0.125 mm. Components comprising the sample consisted of sideromelane (41.5%), tachylite (24.7%), loose crystals of clinopyroxene, olivine, and plagioclase (4%), and lithics (29.7%). The clasts of sideromelane were very vesiculated and made of light-brown, transparent and shiny glass. There were also a few strands of Pele's hair. Tachylites were black or gray, shiny, sub-angular clasts. Lithics comprised fragments of weathered scoria, lavas, or secondary minerals. The high amount of juvenile components within the ash were taken to suggests an uprise of magma into the summit feeder conduit, the first to occur since the end of the 2002-2003 flank eruption.

The INGV-CT Geochemistry group performed regular remote-sensing measurements of volcanic gas flux and chemical composition on Etna using COSPEC and FTIR instruments. Such measurements demonstrated that the upper conduit system of Mt Etna has been weakly supplied with magma since the end of the 2002-2003 eruption, an observation supported both by relatively low fluxes of SO₂ and low molar ratios of SO₂/HCl. Occasional discrete injections of magma into the upper conduit system have been observed, however, as sharp increases in both SO₂ flux and SO₂/HCl ratios. These inputs occurred in August 2003, December 2003, and in late January 2004.

The INGV-CT permanent seismic network consisted of ~ 40 stations, 10 of which were installed in October 2003 and have broad-band, 40-second-period sensors. After the end of the 2002-2003 flank eruption, seismicity was mainly concentrated along Etna's E and NE flanks, appearing in two main phases. Until the end of May 2003, earthquakes were localized along the same structures that were activated during the 2002-2003 eruption, suggesting a relaxation phase. During this phase, several swarms occurred mainly between 3 and 7 km depth, showing a progressive decrease in seismic energy. After June 2003, several shallow earthquakes were recorded along the upper eastern part of the volcanic edifice near Zafferana, and along the Pernicana fault on the NE flank. This second phase was characterized by a renewal of seismic activity, with several seismic swarms characterized by progressive release of seismic energy. In particular, during the last two months, the Pernicana Fault has been very active (UFS Weekly Reports, 2003 and 2004).

References. Del Carlo, P., and Andronico, D., 2004, Rapporto cenere Etna del 13-14/02/04: INGV-CT Internal Report, Prot. Int. no. UFVG2004/024, p 1. UFS INGV-CT Weekly Internal Reports, 2003 and 2004.

Information Contacts: Sonia Calvari, Istituto Nazionale di Geofisica e Vulcanologia, Piazza Roma 2, 95123 Catania, Italy (URL: http://www.ct.ingv.it/).

September 2004 (BGVN 29:09) Cite this Report

New effusive eruption begins on 7 September and spreads to several fissure vents

At about 1030 on 7 September 2004 a new effusive eruption started from the summit of Mount Etna. A N110°E-trending eruptive fissure about 230 m long opened at the base of the SE Crater without any significant seismic activity. A degassed lava flow poured from the base of the fissure, spreading towards the Valle del Bove. The lava flow had very low output rate (between 0.2 and 0.5 m³/s), and was ~ 1 m thick, 10 m wide, and up to 250 m long. On the morning of 8 September the lava flow appeared to lack new input from its source, but the eruptive fissure continued to advance down slope. These events were not accompanied by seismicity or explosive activity.

After two days of slow expansion of the fracture field, a new effusive vent opened at a lower elevation, 2,650 m, on the upper western flank of the Valle del Bove. This occurred between 0600 and 0700 on 10 September. Lava poured from this vent, spreading over the upper wall of the Valle del Bove. No explosive activity accompanied the emission of lava, but some phreatic explosions were triggered by lava intersecting a thick cover of snow. The lava flow was degassed and flowed out at a rate of about 2-4 m³/s. It spread E to the Serra Giannicola Piccola before splitting in two branches. At about 0930 the longest branch was about 300 m long and 50 m wide. Due to the high slope-angle, the front of the N lava flow breached. Hot blocks rolled down slope, causing the flow front to expand due to the collapse of hot debris rather than by flowage. At 1400 the lowest elevation of the lava flow front was about 2,250 m elevation within the upper Valle del Bove. At that time, no villages were threatened by the lava flows since they had spread out over a deserted zone at least 10 km away from the nearest village.

Activity appeared similar on 14-15 September 2004, when Mike Burton, Enza Longo, and Margherita Polacci had clear views of the Valle Del Bove in fair weather. Their first observations were carried out at the Southeast Crater (SEC), where the team saw a conspicuous plume emitted from a fumarole field on the SEC's SE rim. This activity, not seen prior to the eruption, had been consistently observed during the previous 3-4 days.

A visit to a vent at 2,830 m elevation revealed behavior similar to previous days, consisting of continuous high-pressure degassing in the absence of explosive activity (figure 104). At this vent, in contrast to the one at 2,630 m (which emitted lava), incandescence was limited to a circular zone at the vent area. No recent scoria were observed near the degassing vent. At this degassing vent the peak temperature, measured with a thermal camera, was ~ 900°C (see thermal image, figure 8).

Figure 104. A vent emitting high-pressure gas at 2,830 m on Etna, 15 September 2004, with thermal image of the vent's mouth (at right). Courtesy of Mike Burton, Enza Longo, and Margherita Polacci.

The team also visited the lava flow at 2,630 m (figure 105). Fresh scoria had fallen along the path leading to the lava flow, and samples were collected. The estimated flux rate of the lava flow was between 2 and 4 m³/s, using an estimated flow velocity of 1 m/s, a width of 2 m, and a depth of 1-2 m. Estimates were obtained by observing the lava flow just above the rock island seen in figure 9. This flux was roughly equal to that seen on 13 September.

Figure 105. Lava flow witnessed at 2,630 m elevation on Etna on 15 September 2004. The image at right is a closer view of the indicated area taken with a thermal camera. The thermal image shows the lava flow splitting and skirting around a small rock island. Courtesy of Mike Burton, Enza Longo, and Margherita Polacci.

A pair of hornitos lay up slope of the lava flow originating at 2,630 m elevation. One hornito sat just behind the spot where lava was first observed on the surface. The second hornito was larger and resided about 20-30 m farther up slope (figure 106). It released gas at high pressure, creating noise. No scoria were emitted during their observation.

Figure 106. A hornito seen at Etna on 14-15 September up slope from the lava flow at 2,630 m elevation. The indicated area appears in an enlarged thermal image at right. Courtesy Mike Burton, Enza Longo, and Margherita Polacci.

Polacci and Burton then walked down to the lava flow that began on 13 September (figure 107). The lava flow's flux rate was low. The team estimated an outflow rate of ~ 1 m³/s, using a width of 2 m, a flow velocity of 0.5 m/s, and a depth of 1 m, dimensions noted near the lava flow's source. The lava flow emanated from a small depression; no scoria deposits were seen nearby. GPS established the flow's source at 2,340 m elevation. The team observed several distinct overflows escaping from the principal lava flow, which originated at 2,630 m elevation (figure 108).

Figure 107. The source of an Etna lava flow at 2,340 m elevation, as seen in two photographs taken on 14 or 15 September. Courtesy of Mike Burton, Enza Longo, and Margherita Polacci.

Figure 108. The lava flow that originated at 2,630 m elevation as seen in a thermal image on 14 or 15 September. The advancing lava flow broke into a series of branches. Courtesy of Mike Burton, Enza Longo, and Margherita Polacci.

Information Contacts: Sonia Calvari, Mike Burton, Enza Longo, and Margherita Polacci, Istituto Nazionale di Geofisica e Vulcanologia (INGV), Piazza Roma 2, 95123 Catania, Italy.

January 2005 (BGVN 30:01) Cite this Report

7 September eruption continues on W wall of Valle del Bove, includes lava tubes, multiple vents

The effusive eruption that started on 7 September 2004 on the W wall of the Valle del Bove continued. Lava escaped at a very low effusion rate from two main vents at 2,620 and 2,320 m elevation. Lava tubes developed downslope of these vents, forming a complex lava-flow field with ephemeral vents at the base of the W wall of the Valle del Bove. After December 2004, effusive vents were mainly located at the lower end of the tube network below 2,000 m elevation. Lava flows were up to 2.5 km long, and the lava-flow field did not change significantly since the end of October 2004 (figure 109).

Figure 109. A map of Etna emphasizing features associated with the lava flow field as they appeared 4 October 2004. Courtesy of INGV.

On 8 January 2005 an ash plume formed above the summit of SE crater and lasted a few hours. Analysis of the ash components revealed that it consisted of lithic material. This episodic ash emission was probably caused by collapse within the crater into the void left after three months of lava output.

On 18 January the INGV-CT web camera located 27 km S of the summit craters revealed a dense, pulsating gas plume rising above the summit of NE crater and lasting a few minutes. This was probably caused by snow vaporization due to hot gas emission from the main crater vent.

During the afternoon of 18 January a new lava flow formed upslope along the 2,620-m-long eruptive fissure, at ~ 2,450 m elevation. The lava flow spread for about 200 m SE on the snow and along the middle wall of the western Valle del Bove. This flow front moved slowly and completely stopped after about 24 hours. The emission of lava from the ephemeral vents below 2,000 m stopped during the effusion from the 2,450-m vent. The lower ephemeral vents again started to emit lava on 19 January. During the afternoon of 22 January two new lava flows erupted from vents at 2,400 m elevation, along the same tube system fed by the 2,620-m-elevation vent. Two parallel, fast-moving flows spread E. They were still evident on 27 January from the images recorded by the INGV-CT webcam at Milo, together with a number of ephemeral vents and small lava flows at the lower end of the lava tube.

The opening of effusive vents upslope along the tube system of a complex lava-flow field has usually indicated the final stages of expansion, an effect observed several times at lava-flow fields on Etna and Stromboli. Decreased effusion from the main vent causes the tube system to drain, so the lava tube walls collapse. Obstruction at the lower end of the tube then causes accumulation of lava farther upslope and the opening of new vents at higher elevations.

Since the start of the eruption on 7 September 2004 (BGVN 29:09), there has been no significant explosive activity at the summit craters or the eruptive fissures.

Information Contacts: Sonia Calvari, Istituto Nazionale di Geofisica e Vulcanologia, Piazza Roma 2, 95123 Catania, Italy (URL: http://www.ct.ingv.it/).

December 2005 (BGVN 30:12) Cite this Report

Late degassing, summit explosion and ash release in December 2005

The previous report on Mount Etna (BGVN 30:01) described what turned out to be the final activity of the 2004-05 eruption, which ended by March (Burton and others, 2005). From March 2005 until November there was only a low and quiet degassing at the summit craters. Between the end of November and early December 2005 a significant increase in the SO₂ output was accompanied by an increase of volcanic tremor and a minor deformation of the summit part of the volcanic cone.

On 16 December 2005 an explosive sequence was recorded by the INGV-CT seismic network, localized at the summit. This was accompanied by an increase in SO₂ emission, which reached peaks 10 times the background flux levels. On 22 December the increase in gas pressure was accompanied by a dilute emission of juvenile ash from the Bocca Nuova crater. This vent had been blocked since the end of the previous summit eruption. However, the very fine-grained nature of the ash suggested a deep level of the magma column within the conduit.

Reference. Burton, M., Neri, M., Andronico, D., Branca, S., Caltabiano, T., Calvari, S., Corsaro, R.A., Del Carlo, P., Lanzafame, G., Lodato, L., Miraglia, L., Muré, F., Salerno, G., and Spampinato, L., 2005, Etna 2004-05: an archetype for geodynamically-controlled effusive eruptions: Geophysical Research Letters, v. 32, L09303, doi:10.1029/2005GL022527.

Information Contacts: Sonia Calvari, Istituto Nazionale di Geofisica e Vulcanologia Sezione di Catania, Piazza Roma 2, 95123 Catania, Italy (URL: http://www.ct.ingv.it/).

July 2006 (BGVN 31:07) Cite this Report

An upper E-flank fissure eruption lasting from 14 to 24 July 2006

This report covers the new eruption from an E-flank fissure during mid July 2006. Previously, on 7 September 2004, an eruptive period began that lasted until March 2005 (BGVN 29:09, 30:01). From March 2005 until November quiet degassing took place at the summit craters; on 16 December 2005 an explosive sequence at the summit was accompanied by an ash emission from the Bocca Nuova crater (BGVN 30:12). This report is from Sonia Calvari of the Istituto Nazionale di Geofisica e Vulcanologia (INGV) and covers the interval through 26 July. Brief mention is made at the end of the report about another episode starting on 31 August and going into at least mid-September.

On 14 July 2006 at 2330 a fissure opened on the E flank of the Southeast Crater (SEC) summit cone. Two vents along the fissure produced a lava flow spreading E to the Valle del Bove (figure 110). A helicopter survey carried out on 16 July at 0730 showed a braided lava flow field up to 1.7 km long. Based on the surface area and approximate volume of this lava flow field, workers estimated a mean output rate of ~ 2.6 m³/s during the first 32 hours of eruption. During the opening phase of the eruptive fissure, moderate strombolian emissions occurred at a third upper vent, located at about 3,100 m on the E flank of the SEC, just below the wide depression that cuts its eastern flank. It produced minor ash fallout on Catania. The composition of the ash was 80% juvenile, with small amount of lithics probably due to the opening phase of the vents.

Figure 110. Lava flows descending from vents near Etna's summit cone. Reuters photo.

On 17 July, the lava flow field was situated on the W wall of the Valle del Bove, and the two main flow fronts reached about 2,100 m elevation, spreading N of the Serra Giannicola Piccola ridge. The lava discharge peaked on 20 July (figure 111), when an effusion rate of ~ 10 m³/s drove the lava flow advance to a maximum distance of ~3 km within the Valle del Bove. The lava flow front widened at the base of Monte Centenari, at 1,800 m elevation, located at least 15 km from the closest villages. The effusion rate on 23 July decreased to ~3 m³/s. At that time the lava channels had narrowed and levees had partially collapsed. The eruption appeared to end on 24 July.

Figure 111. On 21 July 2006, the Moderate Resolution Imaging Spectroradiometer (MODIS) flying onboard NASA's Terra satellite captured this image as Etna emitted a faint ash plume that blew SW. MODIS also detected a hotspot near the summit, where surface temperatures were much higher than in the surrounding area (red outline). Courtesy the MODIS Rapid Response Team, NASA GSFC.

On 26 July, observers on the rim of the NE Crater heard strong explosions, and saw lapilli fall. This crater, together with the south pit within Bocca Nuova, showed significant thermal anomalies during a helicopter survey carried out on 24 July.

In the early morning of 31 August, Strombolian activity resumed at SEC's summit. In the next two weeks SEC was the scene of a series of dramatic events. By 11 September, lava from the SE flank of the SEC had advanced to reach ~3 km ESE. The resulting ribbon of lava was in places over 200 m wide. More details will follow in a subsequent report.

Information Contacts: Sonia Calvari, Istituto Nazionale di Geofisica e Vulcanologia Sezione di Catania, Piazza Roma 2, 95123 Catania, Italy (URL: http://www.ct.ingv.it/); Reuters (URL: http://today.reuters.com/).

August 2006 (BGVN 31:08) Cite this Report

Changes in morphology of SE Crater and the emission of lava flows to the SSE

Strombolian eruptions, which had resumed in late August 2006, continued into September and took place in conjunction with lava flows escaping towards the ESE and reaching over 1 km in length by mid-September. A large circular depression had grown along the SE side of the cone at Southeast Crater (SEC) during 2004-5. The wall between the depression and the SEC's established central crater became increasingly eroded. On 10 September 2006 that weak zone failed. Lava erupted in the SEC's central crater soon filled the depression and then moved SSE.

The following report was supplied by Sonia Calvari and other members of the Istituto Nazionale di Geofisica e Vulcanologia (INGV). The INGV website featured several reports on this time interval (including Lodato and Consoli, 2006; and Neri and others, 2006).

After the short eruptive phase of 14-24 July 2006 (BGVN 31:07) and the renewal of explosive activity at the Northeast Crater at the end of July, Strombolian activity resumed at SEC's summit in the early morning of 31 August. This activity was mild, with fallout of lapilli and bombs mainly within the crater. The ejecta eventually filled the SEC, and between 1900 and 2000 on 5 September an overflow from the summit formed spectacular lava falls along the breached E side. The descending lava accumulated within the prominent circular depression (figure 112) on the SEC's eastern flank.

Figure 112. A view of the E side of Etna's SEC with Bocca Nuova (crater) in the background, 5 September 2006. The frame is drawn around the area that failed on 10 September. The depression, larger in diameter than the central SEC crater, had carved away material backing the eventual zone of failure. Photo taken from the report of Lodato and Consoli (2006).

Figure 113 presents plan views of Etna's SEC and vicinity, indicating the large depression that grew on the cone's SE side. The scene during July 2006 (left panel) provides a size comparison between the SEC's established central crater and the recent depression immediately to its SE. The 12 September 2006 scene (figure 113, right) shows the lava's eventual path. After lava flows escaped the central crater, they ponded in the adjacent depression. They later crossed the rim of the depression, and went on to advance over 1 km E.

Figure 113. (Left) 2005 digital elevation map at Etna, including two key features: the established SEC crater and the adjacent (larger, circular) depression that grew to its SE during the 2004-05 eruption. This was the scene prior to the collapse of the wall between the two features. (Right) A schematic map discussing eruptive activity during July through 12 September 2006. Base map from M.T. Pareschi (INGV- Sezione di Pisa) and right-hand panel from Neri and others (2006).

The overflow from the SEC's central crater that began on 5 September continued to spread within the depression until about 0645 on 7 September, when it overflowed the SEC's eastern rim and started to spread on the outer E flank and from there towards the Valle del Bove rim. The flow was extremely viscous, slow, thin, and cold, mainly propagating through collapses and breaching of the `a`a flow front. Explosive activity continued at the SEC summit with variable intensity and lava blocks falling as far down as the base of the SEC's cone.

The failure of the SEC's upper wall (figure 112) took place late in the evening of 10 September, due to the pressure of magma accumulating within the summit crater. A new rock fall occurred at the wall dividing the SEC summit crater from the eastern depression, and was suddenly covered by the lava flow spilling from the summit crater. An ash plume rose from the failed material and blew W. No significant ash fallout was observed on the ground, but a lava flow spread E, advancing slowly towards the Valle del Bove rim. After the wall had fallen Strombolian emissions continued at the SEC (figure 114).

Figure 114. Etna's SEC seen during the evening of 11 September 2006. Note the large breach of the SE side of the SEC's wall, permitting a direct view of strombolian eruptions within the summit crater in the SEC and channeling of the lava flow toward the SSE (towards the viewer and in the direction of the observatory). From the report by Neri and others (2006).

On 12 September the lava-flow length reached ~1.5 km E of the vent at SEC's crater. Both lava effusion and explosive Strombolian activity continued until 27 September, when both stopped following a sudden decrease in volcanic tremor.

References. Neri, M., Behncke, B., and Norini, G., 12 September 2006, Forma e strutture del Cratere Sud-Est (Etna) tra l'eruzione di luglio 2006 e l'attivit? eruttiva in corso, aggiornata al 12 settembre 2006 ['Forms and structures of the SEC from the eruption of July 2006 and ongoing eruptive activity, updated 12 September 2006']: Prot. int., WKRVGFTR20060913.pdf [UFVG2006/107].

Lodato, L., and Consoli, O., 11 September 2006, Aggiornamento attivit? Etna ['Etna activity update']: INGV, Catania, U.F. Vulcanologia e Geochimica, 20060911.pdf [UFVG2006/107].

Information Contacts: Sonia Calvari, Marco Neri, Luigi Lodato, Boris Behncke, Gianluca Norini, and Orazio Consoli, Istituto Nazionale di Geofisica e Vulcanologia (INGV), Sezione di Catania, Piazza Roma 2, 95123 Catania, Italy.

October 2006 (BGVN 31:10) Cite this Report

Lava flows from multiple vents during 22 September to 4 November

The following Etna report from Sonia Calvari and Boris Behncke is based on daily observations by numerous staff members of the Istituto Nazionale di Geofisica e Vulcanologia (INGV). As previously reported here (BGVN 31:08), a 10-day-long eruption vented from the base of the Southeast Crater (SEC) in mid-July 2006. Eruptive activity then shifted to the crater's summit vent during 31 August-15 September, leading to lava overflows and repeated collapse on the SEC cone (BGVN 31:08).

This report discusses the time period 22 September to 4 November, an interval with multiple episodes of eruptive activity (roughly eight in all, seven of which involved a return of activity at the SEC summit). The activity typically included lava flows and Strombolian eruptions. In general, the eruptive episodes became increasingly brief and vigorous. Eruptions came from the SEC's summit as well as from multiple vents along fractures on the SEC's sides or adjacent to it that developed during the reporting interval.

As mentioned above, in general, during the reporting interval, the renowned SEC summit area was only episodically active. Since the SEC's collapse of September 2006, it has had a breached E wall. During this reporting interval, lava flows escaped the crater through the breach to form narrow rivulets down the steep upper SE flank. Ash from SEC fell on Catania on 30 October.

On 12 October a fissure opened at ~ 2,800-m elevation on the ESE base of the SEC cone, ~ 1 km from SEC's summit. Lava from this vent traveled SE, and a map showing the vents and pattern of flows through 20 November indicated lava extending ~ 2 km from the 2,800-m vent (Behncke and Neri, 2006). The 2,800-m vent also sits along the path of some of the SEC lavas from the summit crater. By late November, a complex flow field from both SEC summit and the 2,800-m vents lay on the SE side of the SEC. The field extended from the summit ~ 3 km, and its distal ends reached the W wall of the Valle del Bove.

Two other important vents began erupting in late October. One was on the SEC's upper S flank. The other, at 3,050 m elevation, stood ~ 1 km SW of the SEC's crater and at a spot ~ 0.5 km from the nearest margin of Bocca Nuova's crater. Although lava emissions from this vent at 3050-m elevation stopped, they later restarted and by 20 November the vent had created a large SW-trending field of lava flows roughly the size of those from the SEC summit and 2800-m vent.

Eruptive behavior 22 September-4 November. During this time interval, the seven episodes determined by eruptive activity at the SEC occurred as follows.

The first episode, which was five days long, started late 22 September from the summit of the SEC. Activity during the first two days was limited to mild Strombolian explosions, but lava began to overflow the SEC's crater on 24 September, spilling onto the cone's SE flank. This activity ceased sometime on 27 September.

The 2nd episode began late the afternoon of 3 October with Strombolian explosions from the SEC summit, which increased in vigor during the following hours. Late that evening lava began to spill down the SE side of the SEC cone adjacent to flows of the previous two episodes. Following a sharp decline in tremor amplitude on the afternoon of 5 October, the activity ended sometime between midnight and the early morning of 6 October.

The 3rd eruptive episode occurred between the evening of 10 October and the evening of the following day. The SEC's summit produced vigorous Strombolian activity and lava again descended the SEC cone's SE flank. A sharp drop in tremor amplitude on the afternoon of 11 October indicated the eruptions imminent cessation.

At the tail end of the 3rd episode, a short eruptive fissure opened with vents at ~ 2,800-m elevation. Monitoring cameras fixed the start of this activity at 2328 on 12 October. The SEC's summit was quiet throughout the following eight days, leaving this burst to be considered as activity late in the 3rd episode, rather than representing the start of the 4th episode in the SEC's sporadic on-and-off behavior.

Trending N90°E-N100°E, the new fissure resided on the ESE flank at the base of SEC, a spot also on the Valle del Bove's W wall. For the first few days, lava was emitted non-explosively, quietly spreading in the upper Valle del Bove and advancing a few hundred meters downslope. Mild spattering on 17 October resulted in the growth of three hornitos on the upper end of the eruptive fissure.

Summit SEC activity marked the 4th episode since 22 September. As lava effusion continued from the fissure vents at 2,800 m elevation, the SEC started a powerful eruption at 0600 on 20 October. Accompanied by a rapid increase in tremor amplitude, vigorous Strombolian eruptions occurred in the central portion of the SEC's summit. A vent near the E rim of the SEC's crater, in the notch created by the collapse events of early September, produced large explosions every few minutes and quickly built a new pyroclastic cone. Lava once more flowed down the SEC's SE side, stopping N of the 2,800-m fissure. At that fissure vent, lava emission continued but appeared reduced compared to the previous days. The SEC ceased issuing lava the same day it began, 20 October.

The 5th episode involving the SEC was preceded on 22 October with a few isolated bursts of ash from the SEC. The episode began with strong activity at 0700 the next day, when the SEC's summit generated vigorous Strombolian discharges and pulsating lava fountains from two vents. The new pyroclastic cone grew rapidly. Lava spilled down the ESE flank of the cone, to the N of the flows formed in the previous episodes.

Coincident with the above eruptions, INGV researchers noted an increased lava emission from the 2,800-m vents. This led to several lava overflows (in an area adjacent to the hornitos formed 17 October).

Although Strombolian activity and fountaining at the SEC diminished on the afternoon of 23 October, strong ash emissions began at around 1700, producing an ESE-drifting plume. Pulsating ash emissions and occasional bursts of glowing tephra continued and, at about 1750, the SEC cone's S flank fractured. Lava escaped from the fracture's lower end, forming two small lobes. The longer lobe reached the base of the cone and then traveled SE, ultimately to reach ~ 1 km from their source at the new fissure. The smaller lobe took a path down the cone slightly to the W, but halted before reaching the base of the cone. The new fissure's lava supply diminished early on 24 October, stopping around noon.

Coincident with the above events, effusive activity continued without significant variations at the 2,800-m vents. The farthest flow fronts reached an elevation of ~ 2,000 m to the NW of Monte Centenari, and extended ~ 2.5 km from their source.

Field observations made on 24 October revealed that part of the new pyroclastic cone had subsided and a new collapse pit, ~ 50 m wide, had opened on the SE flank of the SEC cone, roughly in the center of the largely obliterated collapse pit of 2004-2005.

The 6th episode of SEC activity began in the late afternoon on 25 October. Initially there was an increase in tremor amplitude, as well as both ash emissions and weak Strombolian activity from the SEC's summit. Both the tremor and Strombolian discharges decreased late that evening, but at 0054 on 26 November lava was emitted from a new fissure. This fissure, on the SEC cone's SSE flank, was active only for a few hours and produced a very small lava flow. As has often been the case during the reporting interval, the 2800-m vents continued to discharge lava toward the Valle del Bove.

What was to later become another important effusive vent opened at 0231 on 26 October. The vent developed at ~ 3,050 m elevation in an area ~ 700 m S of the center of Bocca Nuova's crater and ~ 500 m SW of the center of SEC's crater. This spot sits at the S base of the central summit cone below the Bocca Nuova, and ~ 700 m to the W of the fissure that had erupted 2 hours earlier.

Fieldwork carried out on 26 October by INGV researchers revealed that the vent at 3,050 m elevation had formed at the southern end of a fracture field. That field extended across the SE flank of Etna's central summit cone to the W flank of the SEC cone. Lava extruding at the 3050-m vent poured out at a decreasing rate before a pause began on the evening of 26 October.

The 7th episode, 27 October and into early November, was first associated with a new increase in tremor amplitude and corresponding SEC ash emissions on the afternoon of the 27th. These emissions were followed at 0206 on the 28th by the reactivation of the vent at 3050-m elevation. Ash emissions and Strombolian activity occurred from the SEC between 0830 and 1100, but no lava overflows were produced. On the evening of 28 October, both effusive vents at 3,050 and 2,800 m were active.

29 October ash emissions from the SEC became more vigorous during the early morning of the 30th and fine ash fell over inhabited areas to the S, including Catania (27 km from the SEC). Intermittent bursts of glowing tephra were recorded by INGV-CT surveillance cameras, although later analysis revealed that most of the tephra was lithic rather than juvenile. Ash emissions gradually diminished and ceased at around 0800 on 29 October.

Ash was again emitted from the SEC shortly before 1300 on 31 October, and in minor quantities at least once per day through 5 November. No incandescent ejections occurred from this crater after 28 October until the evening of 4 November (during 1830-2005) when weak Strombolian explosions were recorded by the INGV-CT surveillance cameras.

The vent at 3050-m elevation continued to emit lava on 29 October. The effusion rate was estimated as 1 to 5 m³ per second. Emitted lava descended SW to ~ 2,400 m elevation.

Lava also continued to flow from the 2,800-m vents on the 29th, but the associated lava flow front advancing from these vents had moved little since 24 October. Lava continued to flow from both vents during the first days of November, but the effusion rate had clearly dropped by the 3rd when active flows had retreated upslope from the distal fronts. Similarly, a helicopter overflight on the morning of 5 November disclosed actively flowing lava confined to the uppermost parts of the lava flow fields.

References. Behncke, B., and Neri, M., 2006, Mappa delle colate laviche aggiornata al 20 Novembre 2006 (PDF file on the INGV website).

Information Contacts: Sonia Calvari and Boris Behncke, Istituto Nazionale di Geofisica e Vulcanologia (INGV), Sezione di Catania, Piazza Roma 2, 95123 Catania, Italy (URL: http://www.ct.ingv.it/).

December 2006 (BGVN 31:12) Cite this Report

Changing lava chemistry after 24 October 2006

Roberto Clocchiatti and colleagues have provided information on the chemical composition of Etna lavas discharged during the recent eruptive period. Results of 18 major-element analyses on lavas erupted beginning 24 October 2006 are presented below.

The violent 2001 and 2002-2003 flank eruptions were fed by both trachybasaltic ("hawaiite") and basaltic magmas from various erupting vents (e.g. Clocchiatti and others, 2004). Conversely, the summit activity resuming from September 2004 to March 2005 produced only trachybasalt, which came from the upper levels of the magmatic system (Corsaro and Miraglia, 2005). After 16 months of calm characterized by mild gas venting, new lava emission began on 14 July 2006 at the summit SE Crater (SEC), lasting 10 days (BGVN 31:07). Since 31 August the SEC area exhibited a number of Strombolian episodes and lava flows, either from the SEC cone itself or from fissure vents which opened eastward at 2,800 m elevation (13 October), then southward at 3,000 m (23, 25 October), and finally westward at 3,050 m (26 October) and 3,180 m (8 November, internal reports from the INGV-Catania and the Omega-Acireale observatory) (figure 115).

Figure 115. Location and elevation of various fissure vents that appeared in the area of Etna's SE Crater during October and November 2006. Samples were collected from the SEC flow on 14-23 July and 1 September, the 2,800-m flow on 24 October, 3,180-m flow on 8 November, and the 3,050-m flow on 9 November 2006. Courtesy of Roberto Clocchiatti and colleagues.

Whole-rock analyses from 24 October onward show a significant increase of the MgO content and of the CaO/Al₂O₃ ratio (figure 116). The higher MgO and CaO, as compared to lower Al₂O₃ and alkalis, indicate a larger content of olivine and Ca-rich clinopyroxene at the expense of less plagioclase, so that the last analyzed lava is very close to a basalt composition (5.7% MgO, 10.7% CaO, 11.6% total Fe as Fe₂O₃, and 5.8% Na₂O + K₂O).

Figure 116. Plots showing increases through time of the MgO content and the ratio of CaO to Al2O3 at Etna beginning on 24 October 2006. Courtesy of Roberto Clocchiatti and colleagues.

References. Clocchiatti, R., Condomines, M., Guénot, N., and Tanguy, J.C., 2004, Magma changes at Mount Etna: the 2001 and 2002-2003 eruptions: Earth Planet. Sci. Lett. 226, p. 397-414.

Corsaro, R.A., and Miraglia, L., 2005, Dynamics of the 2004-2005 Mt. Etna effusive eruption as inferred from petrologic monitoring: Geophys. Res. Lett. vol. 32, L13302.

Information Contacts: Roberto Clocchiatti, CEN Saclay, 91191 Gif-sur-Yvette Cedex, France; Gilles Chazot, Observatoire de Physique du Globe Clermont, 63038 Clermont Ferrand, France; Jean-Claude Tanguy, IPGP, Observatoire de St. Maur, 94107 St. Maur des Fossés, France; Giovanni Tringali, Osservatorio Meteorologico, Geodinamico e Ambientale (Omega), 95024 Acireale, Italy.

February 2007 (BGVN 32:02) Cite this Report

Episodes of eruptions continue between 4 November and 14 December 2006

The 10-day-long eruption of Etna's Southeast Crater (SEC) in mid-July 2006 (BGVN 31:08 and 31:10) was considered by scientists at the Istituto Nazionale di Geofisica e Vulcanologia (INGV) to represent a distinct phase of 2006 activity for Etna. They identified a very different phase when eruptive activity shifted to SEC's summit vent between 31 August and early 15 September 2006. The latter activity led to lava overflows and repeated collapse on SEC's E side. The seven eruptive activity episodes previously described (BGVN 31:10) have since been renumbered slightly, with Episode 1 taking place between 31 August and 16 September.

The following report was compiled from recent reports by Boris Behncke and Sonia Calvari, based on daily observations by numerous staff members of the INGV Catania (INGV-CT). This issue overlaps with our previous Bulletin reports and then goes on through the end of 2006.

Overview of the 31 August to 14 December eruption. Figure 117 indicates key vents and lava flows during the period 4 September-7 December 2006. It excludes lavas emitted during the short but intense final episode (Episode 20, 11-14 December 2006), but they did not significantly extend beyond flow margins shown here. The longest lava flows of the reporting interval reached ~ 4.7 km SE from their source vent (figure 117).

Figure 117. Map Etna showing lava flows and their corresponding periods of activity: (1) lavas from the summit and flanks of the SEC, 4 September-3 December 2006; (2) lavas from the 2,800-m vent, 13 October-7 December 2006; (3) lavas from the 3,050-m vent, 27 October-27 November 2006; and (4) lavas from 3,180-m vent, 8-27 November 2006. The capital letters indicate the most persistent eruption sources: (A) SEC summit; (B) 2,800?m vent; (C) 3,050-m vent; (D) 3,180-m vent; (E) 3,100-m vent (active between 30 November and 3 December 2006); and (F) the foundation crater of the 23 October 2006 activity (which developed a pit that was also active between 24 November and 7 December 2006). Courtesy of INGV-CT; Behncke, Branca, Neri, and Norini (2006).

Table 9 summarizes the 20 episodes of recent eruptive activity, as currently identified by the INGV staff. Note, however, that episode numbers have changed since discussed in BGVN 31:10. One earlier episode has been added (31 August-15 September). Former Episodes 1-7 as listed in BGVN 31:10 based on earlier INGV reports, have been renumbered to Episodes 2-8. Subsequent episodes (9 through 20) are the main subject of this report.

Table 9. List of eruptive episodes (1-20) at Etna as reported by INGV-CT for the interval 31 August-December 2006. "Former number" refers to the episode numbers stated in BGVN 31:10 but here revised. Geberal morning and afternoon times are indicated by am and pm, respectively. Courtesy of INGV-CT.

Episode (former number)	Dates (2006)	Comments on onset of episode
1 (new)	31 Aug-15 Sep 2006	Eruptive activity shifted to SEC's summit vent (see BGVN 31:10).
2 (1)	22 Sep (pm)-27 Sep (am)	Mild Strombolian explosions for first 2 days.
3 (2)	03 Oct (pm)-6 Oct (am)	Started with Strombolian explosions from SEC summit, increasing in vigor during the following hours.
4 (3)	10 Oct (late pm)-11 Oct (late pm)	Vigorous Strombolian activity and lava descending SE flank of SEC cone.
5 (4)	20 Oct (0500-late)	Rapid increase in tremor amplitude, vigorous Strombolian activity in the central SEC summit and isolated large explosions from a vent near the E rim.
6 (5)	23 Oct (0600-?)	Vigorous Strombolian activity and pulsating lava fountained from two vents at the summit of the SEC.
7 (6)	25 Oct (late pm)-26 Oct (late pm)	Marked increase in tremor amplitude and ash emissions from the summit of the SEC, which produced only weak Strombolian activity.
8 (7)	27 Oct (pm)	Increase in tremor amplitude and ash emissions from the SEC (see text for 26 Oct-4 Nov).
9	29-30 Oct	Pulse of activity.
10	05 Nov (2004)-06 Nov (am)	Strong eruptive episode started at SEC summit vent and continued with some fluctuations and intermittent ash emissions.
11	08 Nov (until 2200)	Ash emissions from summit of SEC, followed by vigorous Strombolian activity.
12	10 Nov (2100)-11 Nov (1100)	Tremor amplitude rapidly increased, bad weather hampered visual observations.
13	16 Nov (0500-late pm)	Lava issued from the 3,180-m vent, sharp increase in tremor amplitude, vigorous ash emissions at the SEC summit, these gradually replaced by intense Strombolian bursts.
14	19 Nov (0400)-20 Nov (am)	Strombolian activity at SEC occurred from two vents at the summit, lava flowed through the 16 November trench.
15	21 Nov (1200)-23 Nov (0000)	Inclement weather, a black ash plume rose to 1.5 km above the summit.
16	24 Nov (0219-1530)	Ash emissions mixed with Strombolian explosions at the SEC.
17	27 Nov (0410-pm)	SEC monitoring camera recorded thermal anomaly and an ash plume.
18	31 Nov (1600)-03 Dec (am)	Rising lava fountains followed 2 hours later by the '23 October pit' emitting dense ash and Strombolian explosions.
19	06 Dec	Increased tremor implied weak Strombolian activity and ash emission at SEC.
20	11 Dec (0330)-14 Dec (pm)	Strombolian explosions and voluminous lava flows from 2,800-m vent, ash from '23 October pit'.

Episode 9. Although there were no real paroxysms of Strombolian activity or lava fountaining at the SEC during 26 October-4 November, clear pulses of activity occurred at the effusive vents at 2,800 and 3,050 m elevation, accompanied by ash emission or weak Strombolian explosions at the SEC. These events defined Episode 8, on 27 October, and Episode 29, which took place during 29-30 October. The clear pattern of distinct paroxysms from the SEC finally returned on 5 November and lasted through late that month, before the activity became again more continuous early in December.

Episode 10. Following one week of intermittent ash emissions and weak Strombolian activity on late 4 November, a new strong eruptive episode started at the SEC summit vent at 2004 on 5 November and continued with some fluctuations and intermittent ash emissions for the next 9.5 hours. Light ashfalls occurred over populated areas to the SE. At about 2147 on 5 November, the effusion rate increased at a vent at 3,050 m elevation at the S base of the central summit cone (C on figure 117) which had been continuously active since 27 October. A new lobe of lava traveled S of the summit cone complex across a flat area known as the Cratere del Piano.

An apparent increase in the effusion rate was also noted at the effusive fissure at 2,800 m elevation on the ESE flank (B on figure 117), with active lava lobes extending downslope. Lava effusion from the 3,050-m vent ended during the morning of 6 November, and for the following 48 hours, lava emission continued only at the 2,800-m vent.

Episode 11. Ash emissions from the summit of the SEC occurred on 8 November 2006, followed by vigorous Strombolian activity that continued until about 2200. Around 1600, lava started to flow from a new vent located in the saddle between the SEC cone and the adjacent main summit cone, at an elevation of ~ 3,180 m (D on figure 117). The lava reached the SW base of the SEC cone in a few minutes, where it bifurcated into several short lobes, the largest and westernmost lobe stopping at the E margin of the lava flow field from the 3,050-m vent. Lava from the 3,180-m vent had ceased flowing by about 1845, whereas spattering and lava effusion continued at the 3,050-m vent for some time. Spattering ended at that vent around 1930, but lava continued to flow for another 24 hours.

Episode 12. At 2100 on 10 November 2006, tremor amplitude rapidly increased. Bad weather hampered visual observations until 11 November, when it became evident that this episode was quite similar to its predecessor, with lava emission occurring from both the 3,050-m and 3,180-m vents. Strombolian activity from the SEC summit ceased at 1100 on 11 November. Lava emission from the 3,050-m vent continued until the following night, and the associated lava flow field grew mainly on its W side, with flow fronts descending to ~ 2,800 m. For the next five days, lava emission continued unabated from the 2,800-m-vent, whereas the SEC and all other vents remained inactive.

Episode 13. Following a sharp increase in tremor amplitude at 0500 on 16 November, vigorous ash emissions started at the SEC summit at 0507 and were gradually replaced by intense Strombolian bursts, marking the onset of this eruptive episode.

Very early during the episode, lava issued from the 3,180-m vent, forming a lobe ~ 100 m long before activity at this vent ceased.

Lava effusion from the summit started at 0615 on 16 November and triggered a series of rockfalls down the SE flank of the SEC cone, before the lava descended on the same flank. At 0626, brownish ash was emitted from a spot next to the effusive vent, and major rockfalls and avalanches started shortly thereafter. These originated at the S rim of what remained of the 2004/2005 collapse pit on the E flank of the SEC (see BGVN 30:01 and 30:12). Plumes rising from the descending avalanches contained both brownish ash and white steam. Avalanching was most intense between 0631 and 0640, after which the new lava flow rapidly descended the lower SE flank of the cone and began to extend beyond its base toward the area of the 2,800-m vent. At the same time, strong emissions of black ash marked the opening of another explosive vent next to the summit, and a third explosive vent became active in the same area. For the next several hours, the vents continued to eject ash and occasionally bombs, and to produce vigorous Strombolian activity.

At 0700 on 16 November emissions of white vapor occurred from the SE flank of the SEC cone; a few minutes later large rock avalanches started to descend that flank. Simultaneously a fissure began to open near the summit to downslope on the SSE flank, triggering local rockfalls and dust avalanches. This fissure initially propagated ~ 100 m downslope, then it temporarily stopped; but at 0720, it propagated another 150 m downslope. During the following 15 minutes, another fissure perpendicular to the earlier one cut SE across the flank, generating more rockfalls and dust avalanches. The resulting fissure system had the form of an inverted Y delimiting a block that was actively pushed outward by magma intruding into the cone's flank.

Lava began to issue from the lower end of the W branch of the fissure system at about 0810 on 16 November. At approximately the same time, the 3,050-m vent started to emit lava. By this time, the upper portion of the fissure cutting the SSE flank of the SEC cone had significantly enlarged and became a deep trench. Dense volumes of steam were emitted from this trench at 0831 and were followed a few minutes later by another series of rockfalls and avalanches. Direct observation from ~ 700 m showed that the most energetic of these avalanches resulted from the collapse of low fountains of gas and tephra at the lower end of the large trench. The avalanches and rockfalls lasted about 15 minutes, then a voluminous surge of lava issued from the lower end of the opening trench.

Over the next few hours this sequence of events (vapor emission?rockfalls and avalanches?lava emission) was repeated several times as the trench widened and propagated further downslope. During the few moments when steam and dust clouds cleared and the interior of the trench became visible, a cascade of very fluid lava was seen in the center of the trench. Apparently, the lava issued from a source high in the head wall of the trench, and at times spurted from the vent like a firehose.

At 1100 on 16 November, white steam plumes, rockfalls, and dust avalanches appeared high on the SE flank of the SEC cone, in the area where the summit lava flow was emitted. These phenomena marked a major collapse of the E wall of the trench, which eventually cut into the descending summit lava flow, diverting it into the trench. The original flow, which had descended immediately S of the 2,800-m vent down to ~ 2,600 m elevation, rapidly stopped, although lava continued to drain from the main flow channel and accumulated in a thickening lobe at the cone's base.

At about 1425 on 16 November, several vertical jets of black tephra shot upward from an area at ~ 150 m distance from the cone's base. These emissions were very distinct in color from the brownish dust clouds, which at the same time descended from the trench. The activity at the new site appeared to migrate rapidly both toward the SEC as dark plumes began to rise closer to the cone, while a ground-hugging plume of white vapor shot in the opposite direction. A few ten's of seconds later, very dense clouds of dark brown material began to appear at the base of the surging white cloud and formed a distinct flow that rapidly overtook the front of the white cloud while speeding toward SE. At the slope break along the W rim of the Valle del Bove (~ 2,800 m elevation), both clouds disappeared from view in weather clouds, but at the site where the activity had originated, a huge plume of white vapor soared skyward. White vapor continued to rise from the area and from the path of the white and dark brown clouds for more than 15 minutes.

Another explosive emission of white steam and dark brown plumes occurred at about 1455. Like the 1425 event, it generated ground-hugging clouds of steam and dark brown material, the latter again traveling faster. During the following hours, activity at the SEC gradually decreased, with several spectacular cascades of lava descending through the trench on the cone's SSE side. Steam explosions and rock avalanches occurred at the lower termination of the trench at 1525. Strombolian activity ceased at 1500 on 16 November, but lava emission continued until about midnight. This lava does not seem to have extended far from the base of the SEC cone, since investigation during the following day failed to reveal any fresh lava on top of the debris deposits emplaced during the major explosive events at 1425 and 1455. A minor lava flow was also fed from a new short fissure ~ 80 m E of the 3,050-m vent. During the evening a small lobe of lava was emitted from the accumulation at the SEC cone's base.

Fieldwork and aerial surveys during the two days following 16 November revealed that the 1425 and 1455 explosions and related volcaniclastic density currents (figure 118) had left two main types of deposit. One was of lobate shape and extended a few hundred meters from the source of the explosions to the SE, covering a footpath established by mountain guides to allow tourists to approach the persistently active 2,800-m vent.

Figure 118. One of the peculiar density currents at Etna that occurred during Episode 13, 16 November 2006. The photo was taken from the N side of the large 2002-2003 cone complex, ~ 1.3 km S of the SEC. Seen in the photo are strong emissions of dark gray ash from two vents at the summit (a third caused intense Strombolian activity, but not in the moment shown in the photo). A huge gash carved out of the near right side of the cone emitted a lot of white vapor, with lava flowing from its lower end, and a ground-hugging brownish ash cloud spilling downslope on top of the flowing lava. Photo courtesy of INGV-CT.

On the ground the deposit consisted of very fine grained reddish-brown ash made up almost exclusively of lithic fragments. To the N the deposit gradually thickened and larger clasts were found on its surface, some of which represented fresh magmatic material. Close to the 2,800-m vent, the deposit abruptly graded into a sort of debris flow rich in lithics but with up to 25% of fresh magmatic clasts. These latter showed a peculiar flattened-out morphology. Where this deposit overlay the tourist path near the 2,800-m vent it was 1.52 m thick. In one place the flow had surrounded a plastic-coated sign warning tourists to stay on the path. The plastic lacked evidence of strong heating, indicating that the flow was relatively cool at this point along its path.

Volcanic tremor amplitude began to increase during the late afternoon of 18 November and, during a helicopter flight at 1800, the 2,800-m vent showed vigorous spattering. Active lava from the vent traveled ~ 3 km to Monte Centenari. Bright incandescence was also noted within the 3,180-m vent during this overflight.

Episode 14. At 0400 on 19 November, Strombolian activity at the SEC occurred from 2 vents at the summit while lava flowed through the 16 November trench and divided into numerous braiding lobes on top of the debris deposited 3 days earlier. The longest lobe traveled along the prominent channel in the main debris flow, passing immediately to the S of the 2,800-m vent and extending to an elevation of ~ 2,600 m. This episode was much less violent than its predecessor and lacked the explosions, surges, and flows characteristic of that event. Strombolian activity continued until the late evening, while lava effusion ended early on 20 November. As during previous episodes, lava had also briefly issued from the 3,050-m and 3,180-m vents. In addition, a flow of a few meters in length started from another fissure that opened at ~ 3,200 m, on the saddle between Bocca Nuova and SEC. This upper flow merged with the flow coming out from the 3,180-m vent.

Episode 15. This eruptive episode at the SEC started at 1200 on 21 November 2006, but direct observations were thwarted by inclement weather through nightfall. At about 1500, a black ash plume was seen rising above the cloud cover to ~ 1.5 km above the summit. Light ashfalls occurred along the Ionian coast near Giarre and further N, while at Rifugio Citelli (~ 6 km NE of the SEC), ash deposition was nearly continuous.

After 1900, the cloud cover gradually opened, allowing direct views of the strong Strombolian explosions generating jets sometimes over 300 m high. Lava once more flowed through the 16 November trench on the cone's SSE flank toward the 2,800-m vent. Likewise, the 3,050-m and 3,180-m-vents reactivated, although the latter apparently ceased erupting early during the episode. Lava flowed from the trench until shortly after midnight on 22 November. Bad weather precluded observations until the evening, when all activity was again limited to the 2,800-m vent.

Episode 16. At 0219 on 24 November, there began ash emissions mixed with Strombolian explosions. These were recorded by the INGV-CT thermal camera in Nicolosi (~ 15 km S of the SEC) with a significant anomaly occurring at the SEC summit. Strombolian activity at 0320 was accompanied by voluminous ash emission, which formed a plume that rose ~ 2 km above the summit before being blown to SE.

Two particularly powerful explosions occurred at 0452 and 0455. The latter was followed by lava extruding from a vent presumably located within the 16-November trench. At around 0535, lava began to issue from the 3,050-m vent, forming a small flow on the W side of the lava flow field emplaced since 26 October. A second minor flow issued from another vent located ~ 80 m SE of the 3,050-m vent. Vigorous ash emission from the summit of the SEC caused light ashfalls over populated areas between Zafferana and Acireale (figure 119).

Figure 119. Dark ash plume rising from Etna's SEC during eruptive Episode 16 on the morning of 24 November, photographed from a helicopter provided by the Italian Department of Civil Protection (Dipartimento di Protezione Civile) during that day's particularly explosive episode. A small steam plume at left rises from the area of the 2,800-m vent. More diffuse gas emitted from active lava flows engulfs the photo's extreme left. Etna's other summit craters (Northeast Crater foremost, with Voragine and Bocca Nuova behind) are in the lower right corner of the image, showing normal degassing activity. View is approximately to the S. Courtesy of INGV-CT.

A fracture opened at about 0817 at the SSE base of the SEC cone, producing a violent explosion and a rock avalanche that descended at a speed of several ten's of km/h toward the Valle del Bove, following the path of similar avalanches that had occurred on 16 November. Lava effusion continued from vents at the cone's base, where mild spattering was observed. Upslope from the effusive vent at 2,800 m elevation, a second fracture formed and commenced spattering and lava emission.

During the early afternoon a change in the wind direction drew the plume from its earlier SE-ward course toward Catania and adjacent areas, forcing the closure of the Fontanarossa International airport of Catania. The activity began to diminish, and by 1530 all explosive phenomena ceased. For several more hours lava continued to issue from two vents at the SEC cone's base.

Late in the afternoon of 24 November, weak sporadic Strombolian explosions occurred from a pit located on the E flank of the SEC cone, which had formed during the 23 October eruptive episode (hereafter, '23 October pit' identified as F on figure 117). On 25 November this vent produced pulsating ash emissions that continued intermittently for the next two days.

Episode 17. At around 0410 on 27 November, eruptive activity occurred at the SEC and the thermal monitoring camera at Nicolosi began to record a significant thermal anomaly at the crater and a W-drifting ash plume. Visual observations were hampered by inclement weather. Around 0730, the thermal camera at Nicolosi disclosed lava emission on the W side of the SEC cone, possibly from the vent at 3,180 m elevation in the saddle between the SEC and the Bocca Nuova. About 45 min later, lava emission became evident at the cone's SE base. No further visual observations were available after 0845, but the tremor amplitude remained high until the afternoon, when a sharp drop indicated the end of this eruptive episode.

Bad weather persisted until early on 29 November when observers saw ash emissions from the '23 October pit.' These emissions became more intense after 0545, and the tremor amplitude began to increase rapidly during the late morning. Intermittent, weak Strombolian activity from the '23 October pit' was visible after nightfall; this became notably stronger shortly after 0100 on 30 November and reached its highest intensity around 0130, after which there was a notable decrease. Ash emissions occurred from the same pit at dawn and again from 1240 onward, producing low ash plumes.

Episode 18. At around 1600 on 30 November 2006, lava fountains began to rise from the 2,800-m vent. Two hours later the '23 October pit' emitted a dense ash plume, and Strombolian explosions reached up to 150 m above the vent. At 2045, a fissure opened at ~ 3,100 m elevation, venting spatter several ten's of meters high and releasing a short lava flow towards the 2,800-m vent. After about 10 min the effusion rate at this new fissure diminished, but lava continued to escape at a decreasing rate for ~ 1 hour. The '23 October pit' remained vigorously active for the next 5 hours, producing incandescent jets and a dense tephra plume.

The new fissure at 3,100 m elevation revived around 0115 on 1 December, with vigorous spattering and a new surge of similarly directed lava. At the same time, the '23 October pit' emissions strongly increased. Like on the evening before, the new fissure at 3,100 m elevation remained active only for a short time; lava emission ceased by 0200 on 1 December.

The 2800-m vent produced the largest lava flows during the entire period of activity, in this episode extending lava flows to ~ 1,500 m elevation on the Valle del Bove floor, to a distance of ~ 4.7 km from their source.

Between 1-3 December, the '23 October pit' remained active with nearly continuous emissions of ash interspersed with Strombolian activity. This was accompanied by the 3,100-m fissure emitting low fountaining and lava; lava flows from that fissure were generally short and did not extend far beyond the 2,800-m vent. The last observed activity at the 3,100-m vent occurred during the morning of 3 December. Ash emissions from the '23 October pit' continued for another few days but became progressively weaker; likewise the lava emission at the 2,800-m vent diminished gradually.

Episode 19. Weak Strombolian activity and ash emission occurred at the SEC on the afternoon of 6 December, evidenced by increased tremor, but the amplitude dropped rapidly to very low levels implying that the SEC ceased erupting late on 6 December. Minor lava emissions continued from the 2,800-m vent. On the morning of 8 December, no eruptive activity was visible at any of the numerous vents of the previous weeks. Following several days of very low tremor amplitude, it began to increase again late on 10 December.

Episode 20. Eruptive activity resumed around 0330 on 11 December 2006 from the '23 October pit' on the SEC, with Strombolian explosions documented by INGV-CT's monitoring cameras. Simultaneously, lava emission started from the area of the 2,800-m vent, forming a flow that slowly descended toward the Valle del Bove. Bad weather hampered observations during the following days, but occasional clear views revealed ash emissions from the '23 October pit.' In addition, there were voluminous lava emissions from the 2,800-m vents, feeding a broad lava flow adjacent the N margin of the lava flowfield produced from the same vent between mid-October and early December. The 2,800-m vents generated vigorous Strombolian explosions from two vents that built up a pair of large hornitos, and lava emissions came from a third vent located on the lower E flank of the larger, more easterly of the hornitos. No activity occurred from any other of the numerous vents that had been active during the previous weeks at the summit and in the vicinity of the SEC. Late in the afternoon of 14 December, a sharp drop in tremor amplitude indicated that the end of this final eruptive episode was imminent, and field observations made on the following morning revealed the absence of eruptive activity.

INGV considered Etna's 2006 summit eruptions during 14 July-14 December and made a rough estimate of erupted lava volumes. The total volume produced during those 5 months amounted to ~ 15-20 x 10⁶ m³.

There was a single, relatively small ash emission from Bocca Nuova on 19 March 2007, discharged without an associated seismic signal. This was followed ten days later by a brief episode of violent lava fountaining and tephra emission from the SEC. Details on that and subsequent activity will be reported in a future Bulletin.

References. Behncke, B., and Neri, M., 2006, Mappa delle colate laviche aggiornata al 20 Novembre 2006 (1 page PDF file on the INGV website) and Carta delle colate laviche emesse dall'Etna dal 4 Settembre al 7 Dicembre 2006 (Map of lava flow emissions at Etna from 4 September to 7 December 2006).

Behncke, B., Branca, S., Neri, M., and Norini, G., 2006, Rapporto eruzione Etna: mappatura dei campi lavici aggiornata al 7 Dicembre 2006 (Report of Etna eruption: map of lava flows up to 7 December 2006): INGV report WKRVGALT20061215.pdf.

Information Contacts: Sonia Calvari and Boris Behncke, Istituto Nazionale di Geofisica e Vulcanologia-Catania (INGV-CT), Sezione di Catania, Piazza Roma 2, 95123 Catania, Italy (URL: http://www.ct.ingv.it/).

March 2007 (BGVN 32:03) Cite this Report

Eruptions continue in April 2007

Recent eruptive episodes occurred between 4 November and 14 December 2006, with small eruptions on 19 and 29 March 2007 (BGVN 32:02). According to the Istituto Nazionale di Geofisica e Vulcanologia Sezione di Catania (INGV), there were other noteworthy eruptions on 11 and 29 April 2007.

The eruption of 19 March was captured on video as well as a thermal monitoring system. The thermal data appear on figure 120, which also includes data from a reference site away from the eruption (lower panel). Both sites underwent similar diurnal variations due to solar warming and night-cooling effects. The 19 April 2007 eruption appears as a 37°C upward spike in apparent temperature (computed from the sensor system).

Figure 120. Time-series plot showing the apparent temperatures (in degrees C) at Etna recorded by the NEW SARATER monitoring system during the explosive event at the Bocca Nuova on 19 March 2007. The upper graph shows the thermal data from the summit crater zone (rectangular inset), where the increase in temperature related to the explosive event stands out boldly. The lower graph shows the thermal data for the same period but from a region outside of the summit crater area and notes solely the daily oscillation of apparent air temperature tied to solar warming. Time shown is UTC. Courtesy of INGV.

The INGV reported that the 29 March eruption took place at Bocca Nuova. Two new lava streams emerged near the summit, one at 3,180 m elevation, and the other at 3,050 m elevation. The lava flows advanced initially but ultimately halted after related emissions only lasted several hours (ceasing at 1500 local time).

INGV's report on the 11 April event noted an increase in volcanic tremor, followed by lava fountaining. That eruption lasted about 5 hours. A resultant ash plume drifted E with ashfall reported as far as Zafferana, about 10 km E. Two lava flows were observed at the summit of Etna, one to the E within the large depression on the side of the volcano known as the Valle del Bove and the second to the S. The E lava flow stopped 3 km away at the base of the Serra Giannicola Grande, within the W Valle del Bove. The second flow stopped near Mt. Frumento Supino (less than 1 km S of the summit).

A new summit eruption began on 29 April 2007 with a general increase in tremor followed by fire fountaining and a vertical ash cloud. The INGV-CT monitoring webcams showed the evolution of this eruptive phase that lasted about 8-9 hours. At 1600 the thermal webcam at Nicolosi registered a thermal anomaly at the Southeast Crater (SEC); there were also reports of rumbling from the summit craters. At 1834, explosions of lapilli and ash were observed almost continuously, together with lava emission very near the explosive vent (figures 121 and 122). A lava flow followed the fissure on the SE flank of the SEC, which had opened during November 2006. Another flow moved E within the Valle del Bove.

Figure 121. Activity at Etna's Southeast Crater at 1834 on 29 April 2007, seen from the S at Torre del Filosofo. Courtesy of INGV.

Figure 122. Etna in eruption on 29 April 2007. Arrows denote strong explosive Strombolian activity (1), spattering (2), and lapilli and ashfall (3). The spattering and related extrusions fed a lava flow descending as an incandescent ribbon. Courtesy of INGV.

Information Contacts: Sonia Calvari, Istituto Nazionale di Geofisica e Vulcanologia, Sezione di Catania, Piazza Roma 2, 95123 Catania, Italy (URL: http://www.ct.ingv.it/).

July 2007 (BGVN 32:07) Cite this Report

Ash emissions started 15 August and built a small cinder cone on SEC's E flank

According to Sonia Calvari of the Istituto Nazionale di Geofisica e Vulcanologia Sezione di Catania (INGV-CT), on 15 August the Southeast Crater (SEC) at the summit of Mount Etna began to produce ash emissions. They emerged at the depression that cuts the SEC's E flank. The ash cloud was very diffuse, rising for just a few ten's of meters above the source, and it was quickly dispersed by the wind. Reddish-colored ashfall deposits were observed only on the flanks of the SEC cone.

During the night of 21 August the summit web-camera of INGV-CT recorded incandescent blocks erupted during the most energetic emissions. A field survey on 22 August observed few very energetic events (about 20% of the total), cases where the ejection of hot, lithic blocks fell on the E flank of the cone. On 24 August, researchers from INGV on the summit with a thermal camera recorded the first short Strombolian sequence. Strombolian explosions increased in intensity and became more common through August, slowly amassing material to create a cinder cone within the depression on the SEC's E flank. Etna's emissions continued through August (figure 123) and into at least early September. Later INGV reports noted a strong eruption during 4-5 September.

Figure 123. Cropped images from the INGV-CT webcamera of a night eruption at Etna at 0300 on 31 August 2007 showing a Strombolian eruption (left) and a daylight photo five hours later (0800 on 31 August) of the same region (right). The arrow indicates the point of emission. Courtesy of INGV-CT.

Information Contacts: Sonia Calvari, Istituto Nazionale di Geofisica e Vulcanologia Sezione di Catania, Piazza Roma 2, 95123 Catania, Italy (URL: http://www.ct.ingv.it/).

August 2007 (BGVN 32:08) Cite this Report

Explosive activity and lava fountains during 4-5 September 2007

A report by members of the Istituto Nazionale di Geofisica e Volcanologia di Sezione Catania (INGV-CT), Behncke and Neri (2007), discussed Etna's 4-5 September eruption. On 6 September field work on the eastern zone of the Southeast Crater (SEC) revealed profound morphologic changes. The SEC's eastern pit crater was the source of lava flows.

The erupted material was distributed mostly to the E, covering the plateau between the base of the SEC and the western rim of the Valle del Bove with a thickness ranging from a few meters to more than 25 m (figure 124). The accumulation of welded scoria formed a mound more than 700 m long.

Figure 124. The Southeast Crater cone at Etna seen from the SSE. The white dotted line shows the eruption topography before the 4-5 September 2007 eruption. The photo highlights significant new material over the old topography. From Behncke and Neri (2007).

The scoria mound, which formed by falling material, was composed primarily of extremely light and vesicular scoria, of varying size, from less than a centimeter to meters, oxidized and reddish in color. The thickness of the scoria deposits varied from over 25 m at the base of the SEC to about 8 m in the area around the western rim of the Valle del Bove, behind hornitos at ~ 2,800 m elevation, which formed during the 2006 eruption.

The scoria appeared to have moved after landing. In addition, localized movement also occurred along some wide-opening fracturing.

During the formation of the scoria mound, lava descended as three principal streams. The streams emerged from the SE sector of the eruptive crater (venting at the Eastern pit crater) (figure 125).

Figure 125. Lava flows and pyroclastic materials on the E flank of Etna's Southeast Crater from the 4-5 September 2007 eruption. Labels indicate lithologies. The observer (right) is on the mound of larger scoria, about 150 m from the crater. Photo from Behncke and Neri (2007).

The field observers saw the southern rim of the eruptive crater and the zone beneath it. To an elevation of about 2,800 m, these rocks emitted fumarolic vapors and contained hot fractures. The position of this fissure field appeared to coincide, at least in part, with what had already been identified by thermal telecamera during the helicopter survey carried out by the governmental Regional Civil Protection. Inside the 4-5 September eruptive vent (Eastern pit crater seen in figures 125 and 126), the team also saw a point of continuous and pulsating gas emissions.

Figure 126. At Etna's SEC, this photo shows the degassing vent inside the active crater. Courtesy of INGV.

Reference. Behncke, B. and Neri, M., 2007, L'eruzione del 4-5 settembre 2007 al Cratere di Sud-Est (Etna): osservazioni di terreno in prossimit? della bocca eruttiva; copyrighted report of the INGV-CT (posted on their website and accessed October 2007).

Information Contacts: Sonia Calvari, Boris Behncke, and Marco Neri, Istituto Nazionale di Geofisica e Vulcanologia (INGV), Sezione di Catania, Piazza Roma 2, 95123 Catania, Italy.

September 2007 (BGVN 32:09) Cite this Report

4-5 September eruption emitted long-duration fountains; lava flows extend 4.6 km

Although BGVN 32:08 discussed the eruption of 4-5 September 2007, this report goes on to more fully describe Etna's lava fountaining at the Southeast Crater (SEC) observed during that eruption, and also adds other details such as a map of the resulting lava flow. The fountain associated with the eruption was spectacular, though by far not the tallest seen on Etna (that was 8 years earlier, on 4 September 1999, at the Voragine, when a fountain rose over 2 km high). The fountaining lasted a full 10 hours, whereas most other recent fountains on Etna only lasted 15-20 minutes.

As background, Etna became active on 15 August 2007 following four eruptive episodes on these dates: 29 March 2007, 11 April, 29 April, and 6-7 May 2007. At the end of August, ash emissions were nearly entirely replaced by Strombolian activity.

The header at the top of this report contains a new summit elevation corrected to the latest LIDAR (light detection and ranging) data, which was acquired in the Spring of 2007. It revises an older estimate of 3,350 m to 3,330 m.

A significant increase in tremor amplitude took place at ~ 1600 on 4 September. After that, a sustained lava fountain rose from the SEC's August-September vent, jetting to 400-600 m above the vent for the next ~ 10 hours (figure 127). A dense tephra plume blew E toward the Ionian Sea. Lava flowed over the vent's E and SE rims, initially forming three branches that coalesced at a short distance from the SEC and descended as a single flow toward the Valle del Bove, to a distance of 4.6 km (figure 128).

Figure 127. Lava fountain and flow emitted at the SEC on 4 September 2007. The photo was taken from the Acireale in Catania, ~ 20 km SE of Etna. Courtesy of INGV-CT and Alfio Amantia (credit on the photo).

Figure 128. Preliminary map of Etna's lava flow emitted during the 4-5 September 2007 lava fountain of the Southeast Crater. The eruptive August-September vent is indicated on the eastern slope of the Southeast Crater cone. Courtesy of Boris Behncke and Marco Neri (INGV).

Heavy showering of tephra occurred on the E flank in the areas between the towns of Fornazzo, Milo, and Giarre. As a precaution, the International Airport of Catania was closed for a few hours early on 5 September.

Renewed activity at Etna in late September and early October was similar to that seen in mid-August; incandescence was noted in some of the emissions in early-mid October. Observations were frequently hampered by bad weather, but as of 22 October, sporadic emissions continued without significant variations in their intensity.

References. Behncke, B., and Neri, M., 2007, L'eruzione del 4-5 settembre 2007 al Cratere di Sud-Est (Etna): osservazioni di terreno in prossimit? della bocca eruttiva. Report published on-line at: http://www.ct.ingv.it/Report/RPTVGSTR20070906.pdf.

Calvari, S., and Behncke, B., 2007, Rapporto sull'attivit? eruttiva dell'Etna. Aggiornamento del 26 agosto 2007. Report published on-line at: http://www.ct.ingv.it/Report/RPTVGREP20070826.pdf.

Information Contacts: Boris Behncke and Marco Neri, Istituto Nazionale di Geofisica e Vulcanologia (INGV), Sezione di Catania, Piazza Roma 2, 95123 Catania, Italy.

January 2008 (BGVN 33:01) Cite this Report

Tall sustained lava fountains, lava flows, and tephra blanket on 22-24 November 2007

After the 10-hour-long episode of sustained lava fountaining from the Southeast Crater (SEC) on 4-5 September 2007 (BGVN 32:09), Etna remained quiescent for about three weeks. Ash emissions then resumed from the vent on the eastern flank of the SEC cone, which had been the main focus of activity since mid-August 2007. During October, ash emissions occurred intermittently, at times with minor incandescent ejections. This activity persisted until mid-November, after which there was a week-long pause until the early morning of 22 November. That day around 0500, weak Strombolian activity and ash emission started from the vent on the E flank of the SEC and continued with increasing strength for the following 36 hours.

A series of explosions occurred at the Bocca Nuova between 1658 and 1705 on 23 November, ejecting dark gray ash plumes, and producing strong seismic signals on nearby stations. During the following hours, Strombolian explosions occurred from the SEC vent, ejecting incandescent bombs to several tens of meters high.

After 2020, the vigor increased, with bursts of bombs rising to 100 m high, accompanied by a sharp rise in tremor amplitude. By 2130, a broad, pulsating lava fountain rose from the vent. Then, 15 min later, observers saw sustained fountaining up to 600 m high. The fountains discharged from what appeared to be two closely spaced sources within the depression, often making a V-shape.

Lava spilled over the vent's rim in at least three locations (figure 129), feeding three narrow branches of lava that ran E and coalesced, before spreading down the steep W slope of the Valle del Bove. A fourth lava flow started from an area ~ 150 m NE of the active vent, where fountain-fed spatter rapidly accumulated and ultimately began to flow. This flow joined the main lava flow toward the Valle del Bove at about 2,500 m elevation.

Figure 129. Preliminary map of the lava flows emitted during Etna's lava-fountaining episodes of and 4-5 September 2007 and 23-24 November 2007. Both sets of flows discharged from the active vent on the E flanks of Southeast Crater (SEC). Courtesy of INGV-Catania.

The November lava flowed mostly on top of, or immediately adjacent to, the lava emitted during the eruption of early September 2007 (figure 129). At the base of the Valle del Bove slope, the November eruption's lava fanned out to form several minor lobes, the longest of which advanced to 1,670 m elevation, 4.2 km from the vent (figure 130; Burton and Neri, 2007).

Figure 130. Aerial view, taken on 25 November 2007 from a helicopter of the Italian Civil Protection, of the lava flows erupted at Etna during 23-24 November 2007. View is from SE across the Valle del Bove (foreground). From Burton and Neri (2007), courtesy of INGV-Catania.

The explosive activity fed a dense tephra plume. It blew NE and caused ash and lapilli falls as far as 80 km away in southern Calabria, (Andronico and Cristaldi, 2007). At Piano Provenzana (~ 6.5 km NNE of the summit), the deposit was about 3 cm thick. Coarse scoriae, up to 5 cm across, fell ~ 10 km NNE from the SEC (in Linguaglossa) during the first hour of the eruption. During the following hours, finer ash fell in areas adjacent Etna and to the W.

Shortly after 0300 on 24 November, the eruptive activity and volcanic tremor amplitude began to diminish gradually, and during the next 20 min the fountain height dropped from ~ 600 m to under 200 m. Subsequently, the fountaining gave way to a series of powerful explosions, which showered the entire SEC cone with meter-sized bombs. The last of these explosions occurred at 0338, and for another 45 min after this, only minor explosive ejections occurred from the vent.

During the following hours, material continued to crumble and collapse on the steep slopes around the vent, exposing incandescent rock in countless spots. By 0600, the tremor amplitude had dropped to background levels, and no further eruptive activity was noted at the vent.

For several days after the eruption, gravitational instability of the new pyroclastic deposit, which had accumulated to thicknesses of several tens of meters, especially on the N side of the vent, caused occasional slides of material, exposing the still-incandescent interior of the deposit. A particularly large collapse from the overhanging W rim of the vent at 1713 on 27 November may have been accompanied by minor explosive activity, with incandescent material rolling to the base of the SEC cone (Calvari, 2007).

Ash emissions from the same vent occurred on 10 January 2008 and again on 1-3 February (figure 131). In mid-February such emissions became more frequent; some produced plumes several hundreds of meters high.

Figure 131. Ash plume rising about 1 km high above the active vent on the eastern slope of Etna's Southeast Crater cone, on the morning of 10 January 2008. View is from Trecastagni, ~ 16 km SSE of the active vent. Courtesy of INGV-Catania.

References. Andronico, D. and Cristaldi, A., 2007, Il parossismo del 23-24 novembre 2007 al Cratere di SE: caratteristiche del deposito di caduta. Report published on-line at: http://www.ct.ingv.it/Report/RPTVETCEN20071123.pdf

Burton, M. and Neri, M., 2007, Stato attuale e osservazione dell'Etna 25 novembre 2007. Report published on-line at: http://www.ct.ingv.it/Report/WKRVGREP20071125.pdf

Calvari, S., 2007, Rapporto sull'attivit? dell'Etna del 27 novembre 2007. Report published on-line at: http://www.ct.ingv.it/Report/WKRVGREP20071127.pdf

Information Contacts: Boris Behncke, Sonia Calvari, and Marco Neri, Istituto Nazionale di Geofisica e Vulcanologia (INGV), Sezione di Catania, Piazza Roma 2, 95123 Catania, Italy.

May 2008 (BGVN 33:05) Cite this Report

6-km-long lava flow; ash emissions; 13 May 2008 opening of a new eruptive fissure

After several months of eruptive activity at the summit craters, on 13 May a new eruptive fissure opened between 3,050 and 2,650 m elevation on Etna's upper E side, feeding lava flows into the Valle del Bove (figure 132). This took place without threatening inhabited areas. It was preceded by several months of sporadic ash emissions, a brief period of Strombolian activity, and a powerful eruptive phase from Southeast Crater (SEC) on 10 May. As of 20 June, modest Strombolian activity continued from two vents along the fissure at approximately 2,800 m elevation, accompanied by lava emission from a third vent, with lava advancing ~ 5 km to the E.

Figure 132. Map showing extent of lava flows from Mount Etna, 2006-2008, including the lava flow field of the 2008 flank eruption as of 21 June 2008. Summit craters are Northeast Crater (NEC), Voragine (VOR), Bocca Nuova (BN), and Southeast Crater (SEC), whose recently active vent on the E flank is labelled SEC-E. The upper E flank fissure system is distinguished by two segments: one (A) active on 13 May morning; and the other (B) starting on the afternoon of 13 May and continuing through June. Courtesy of INGV-CT.

This report was compiled from contributions by the staff of the Istituto Nazionale di Geofisica e Vulcanologia, sezione di Catania (INGV-CT), which are available as pdf files on the Institute's website (see Information Contacts).

Activity during January-April 2008. During this time interval, periodic emissions of ash occurred from a vent located on the E flank of the SEC cone (hereafter named SEC-E), which had been the site of two strong eruptive episodes on 4-5 September and 23-24 November 2007 (see BGVN 32:08, 32:09 and 33:01). This activity apparently ejected mostly lithic ash, and no incandescence was seen through mid-April. A period of weak Strombolian activity occurred between 23 and 28 April (figure 133), when explosions ejected incandescent bombs up to 100 m above the vent, and some material fell to the base of the SEC cone. The area was quiet between 29 April and 10 May.

Figure 133. Thermal camera image of a Strombolian explosion from the active eastern vent of the Southeast Crater (SEC-E) on 23 April 2008. Courtesy of INGV-CT.

Event of 10 May 2008. A sharp increase in the volcanic tremor amplitude at 1400 UTC on 10 May announced the onset of a new paroxysmal eruptive episode at the SEC. Observation was difficult, due to inclement weather conditions. During the first stages of activity, eyewitnesses in the summit area observed explosive activity at several locations within and around SEC-E, and lava overflows feeding several branches of lava toward the Valle del Bove (figure 134). While lava descended very rapidly into the Valle del Bove, explosive interaction with patches of remaining snow repeatedly occurred along the path of the lava flows. The lava advanced across the Valle del Bove floor toward Monte Calanna down to an elevation of ~ 1,370 m, reaching a total length of 6.4 km from its source. This is one of the longest lava flows fed by a summit eruption of Etna in recorded history. A preliminary estimate of the lava volume yields ~ 4.5 x 10⁶ m³, which was emitted at peak rates exceeding 300 m³/s (in comparison, peak eruption rates calculated for the violent fire-fountaining episodes at the SEC in 2000 were consistently below 200 m³/s; Behncke et al. 2006). Tephra fallout occurred mostly to the N and later to the NE (Andronico et al. 2008). The activity came to an abrupt halt at about 1800, after which no appreciable activity occurred for the following 2.5 days. Figure 134 is an aerial view of the SEC with its SEC-E vent, taken during a period of complete quiescence on 28 May.

Figure 134. Oblique aerial view of the Southeast Crater and its E flank vent (SEC-E, in the foreground) in a state of total quiescence, taken from a helicopter of the Italian Civil Protection Department on 28 May 2008. Courtesy of INGV-CT.

Start of flank eruption, 13 May 2008. The intrusion of a dike into the upper portions of the Etna's edifice was marked by a seismic swarm starting at 0840 UTC (Unit? Funzionale Sismologia, 2008). Eruptive activity started from a fissure segment ("A" in figures 132 and 136 and shown close-up in figure 135) located roughly at 3,000 m elevation at the E base of the Northeast Crater (NEC) cone, where fire-fountaining produced a thick scoria deposit and generated sheet flows 2.5 km E toward Monte Simone. This activity probably lasted only a few hours and was followed by the propagation of new fissures to the SE ("B" in figures 132 and 136), down to an elevation of ~ 2,650 m, into the Valle del Leone, in the opposite direction of the initial dike intrusion, which apparently came to a halt during the early afternoon.

Figure 135. Close-up aerial view of fissure segment "A," formed on the morning of 13 May 2008, and its rheomorphic lavas, taken from a helicopter of the Italian Civil Protection Department on 15 May 2008. Lava fountaining from this fissure segment lasted only for a few hours at the start of the eruption, but weak ash emissions continued for several days. Note fracture pattern created by the dragging along of freshly fallen tephra deposits along the margins of moving lava flows. Courtesy of INGV-CT.

Figure 136. Photomosaic composed of about 10 frames taken from a helicopter of the Italian Civil Protection Department on 15 May 2008, showing eastern sector of Etna with the active eruptive fissure just below the summit craters at right, and extent of active lava flows in the Valle del Bove, in the center and at left. Courtesy of INGV-CT.

Visual observations were severely hampered by poor weather conditions, but heavy scoria falls were noted on the N flank during the early afternoon, and satellite imagery showed a narrow plume extending NNE (Coltelli et al. 2008). INGV staff visiting the summit area later that day stated that explosive activity occurred from multiple vents along an eruptive fracture to the E of the summit, and lava was flowing toward the Valle del Bove. Fieldwork carried out during the following days revealed that an extensive fracture field had formed around the NEC and beyond toward the upper N flank of Etna (Neri, 2008).

Continuing activity, 14 May to present. Improved weather conditions on 14 and 15 May permitted the first overviews of the eruption area (figure 136), and revealed that lava flows from the still active fissure segment at ~ 2,700-2,800 m elevation had descended approximately 6 km to 1,300 m elevation, but movement of the lava flow fronts had slowed significantly. Intense Strombolian activity occurred from a number of vents, and lava issued from at least two main locations. The uppermost fissure segment, first active on the morning of 13 May, showed little activity except for degassing and occasional emissions of dilute ash plumes. Ash was also emitted periodically from SEC-E.

On 16 and 17 June, ash emissions from that vent became more vigorous, and ash was also emitted from several vents in the upper portion of the still-active fissure segment on the upper E flank. The active lava flows, however, showed a significant reduction in their length compared to the first few days of eruption. During the following days, the ash emissions at the SEC stopped, and activity at the E flank fissure showed a marked diminution. Throughout late May and into early June, Strombolian activity was confined to one or two vents at about 2,800 m elevation, and lava emission from a single vent located a few tens of meters downslope fed small flow lobes that advanced to ever decreasing distances, reaching a minimum of ~ 0.4 km on 4 June.

A gradual but clear increase in the volcanic tremor amplitude and changes in the gas geochemistry heralded a revival of both the explosive and effusive activity on 8 June, which created a fresh surge of lava into the Valle del Bove. On 18 June, little more than one month after the start of the flank eruption, the lava fronts reached an elevation of about 1,350 m between Rocca Musarra and Rocca Capra (figure 132) and a distance of 5 km from the vents. Mild Strombolian activity continued from two vents located at ~ 2,800 m elevation.

After extending 5 km down through the Valle del Bove in mid-June, lava flows remained much shorter until the last few days of the month, when a new lobe advanced 4.8 km E, somewhat southward of the mid-June lava lobe. The late-June lobe was seen stagnant on 1 July. On the afternoon of 4 July, ash emissions from a point of the eruptive fissure upslope from the recently active vents (at 2,800 m elevation) marked the reactivation of a vent that had been inactive since mid-May. Vigorous Strombolian activity occurred from this vent during the following days, alternating with periods of ash emission. As of 6 July, lava was traveling further S, extending less than 4 km from the vents.

References. Andronico, D., Coltelli, M., Cristaldi, A., Lo Castro, D., and Scollo, S., 2008, Il parossismo del 10 maggio 2008 al Cratere di SE: caratteristiche del deposito di caduta (URL: http://www.ct.ingv.it/Report/RPTVETCEN20080510.pdf).

Behncke, B., Neri, M., Pecora, E., and Zanon, V., 2006, The exceptional activity and growth of the Southeast Crater, Mount Etna (Italy), between 1996 and 2001: Bulletin of Volcanology, v. 69, p. 149-173.

Budetta, G., Ciraudo, A., Currenti, G., Del Negro, C., Ganci, G., Greco, F., Herault, A., Napoli, R., Scandura, D., Sicali, A., and Vicari, A., 2008, Aggiornamento dello stato di attivit? dell'Etna: Osservazioni gravimetriche e magnetiche, (URL: http://www.ct.ingv.it/Report/UFGMET20080513.pdf ).

Coltelli, M., Prestifilippo, M., Scollo, S., and Spata, G., 2008, Rapporto tecnico del 13 Maggio 2008 ? Osservazione da satellite e simulazione dell'emissione di cenere (URL: http://www.ct.ingv.it/Report/Rapporto_UPNV_CT_ 20080513.pdf )

Neri, M., 2008, Eruzione dell'Etna: Fratture non eruttive sul fianco settentrionale del Cratere di Nord-Est; Aggiornamento al 28 Maggio 2008 (URL: http://www.ct.ingv.it/Report/RPTVGSTR20080528.pdf ).

Puglisi, G., Gambino, S., Mattia, M., and Aloisi, M., 2008, Monitoraggio Geodetico delle Deformazioni del suolo all'Etna: Aggiornamento 14 maggio 2008 ? 09:00 (URL: http://www.ct.ingv.it/Report/UFDG-RA_2008-08.pdf ).

Unit?Funzionale Sismologia (edited by D. Patanè), 2008, Quadro di sintesi e aggiornamento al 19 Maggio 2008 sullo stato di attivit?sismica dell'Etna (URL: http://www.ct.ingv.it/Report/REPUFS20080519.pdf ).

Information Contacts: Boris Behncke and Sonia Calvari, Istituto Nazionale di Geofisica e Vulcanologia, Sezione di Catania, Piazza Roma 2, 95123 Catania, Italy (URL: http://www.ct.ingv.it/).

May 2011 (BGVN 36:05) Cite this Report

Ongoing effusive fissure eruption that began on 13 May 2008 ends on 4 July 2009

A new eruptive fissure opened on W flank at ~2,800 m elevation on 13 May 2008 (BGVN 33:05)). Effusive eruptions there continued until 4 July 2009. There was some degassing at some of the summit craters degassed, while others were quiet. Figure 137 presents a map made in 2009 showing summit craters and the eruptive fissure. The following account was compiled from reports of the Istituto Nazionale di Geofisica e Vulcanologia, Sezione di Catania (INGV-CT) surrounding events from 16 July 2008 through 10 November 2009.

Figure 137. Schematic map of the eruptive fissure at Etna that opened on 13 May 2008, as updated on 22 May 2009, showing the lava field that emanated from it. In colored versions of this Bulletin, the fissure is a thin blue line, the lava field appears in yellow, and red arrows show some of the near-source flow directions. Summit crater abbreviations (SEC, NEC, and BN) defined in text. From the 25-31 May 2009 report by INGV-CT's Marco Neri (with reference to report WKRVG20090526).

2008. On 15 July 2008 INGV-CT scientists inspected the summit craters at 2,800 m and found degassing from the Northeast Crater (NEC) and to a lesser degree from the Bocca Nuova (BN) crater BN-1. Eruptions issued from Vent 2 of the active NW-trending fissure located E of the summit craters. The activity consisted mainly of weak Strombolian and diffuse ash emissions.

During 15 and 17 July lava flows occurred in the Valle del Bove. During 11-17 August, there was less intense activity and reduced emissions. During 18-24 August NEC and, to lesser degree, one of two craters at the BN degassed. The other summit craters, many obstructed with eroded debris, degassed from the walls and fumaroles along fissures. Although the Southeast Crater (SEC) appeared obstructed with debris, it emitted both diffuse and occasionally intense fumarolic emissions from its walls and crater floor. During 25-31 August the eruptive activity at the fissure at 2,800 m elevation showed little change, with only weak degassing.

A lull in activity ended in mid-October. On 13-20 October, observers saw increased degassing on the NW flanks, including at NEC and BN-1. During 27 October-2 November, the NEC continued with intense degassing. The other summit craters, all obstructed by detritus, showed degassing diffused from the walls and localized fumarolic fields along fissures. The SEC showed diffused and occasionally intense fumarolic activity from its walls and the crater floor.

During 17-23 November, the fissure at 2,800 m continued to show modest effusive activity, producing a small lava flow along the high part of the western wall of the Valle del Bove. On 19 November the lava flow front had reached the elevation of ~2,500-2,600 m.

During 1-7 December the degassing at summit craters was particularly intense at NEC, while at SEC, fumarolic degassing was observed along the flanks of the cone and the crater rim. Observations on 5 December showed small sporadic ash emissions at the upper portion of the eruptive fissure at 2,800 m. Images recorded on 5 December near Mt. Zoccolaro revealed two lava flows trending parallel to the eruptive fissure to the W of the Valle del Bove. Between 29 December 2008 and 19 January 2009 weak degassing continued.

2009. During 19-25 January lava flows from the fissure at 2,800 m fanned out at elevations between ~2,600 m and ~2,450 m. During the same week, the SO₂ flux increased. During 26 January-2 February effusive activity at the eruptive vents along the W rim of the Valle del Bove continued in the lava field that has been active since May 2008. During 16-22 March eruptive activity continued along the high flanks of the volcano. At times observers saw intense degassing at the NEC and BN (figure 137).

During 6-12 April the level of activity remained constant and unchanged from the preceding time period.

During 18-31 May and 29 June-5 July 2009 the level of activity remained substantially unchanged, although in the earlier interval there were at least three lava flows, the foremost of which reached ~2,400 m elevation. The SO₂ fluxes increased and on 27 and 28 May became particularly elevated, to 8,000 and 6,000 metric tons per day (t/d), respectively. For the later interval, the SO₂ fluxes often remained more modest, ~2,900 t/d, with a maximum of ~3,500 t/d recorded 30 June. On 1, 3 and 5 July instruments measured higher peaks, to 7,000 t/d.

Although the explosive eruptive phases ceased in early July, ongoing degassing continued. Throughout August, the activity level remained unchanged, although roaring sounds emerged at SEC. Activity during 28 September-4 October showed little variance, but elevated SO₂ fluxes became elevated, with average values ranging between 1,500 and 4,500 t/d, with a peak on 4 October 2009 at 8,000 t/d.

A 10 November message from INGV's Sonia Calvari explained that the effusive fissure eruption that began on 13 May 2008 ended 4 July 2009. There was thereafter an absence of significant explosive activity at the summit craters for a few months before deep explosive activity resumed once again at SEC on 6 November. The INGV monitoring web cameras detected pulsating red glowing from SEC's eastern floor, venting within the depression that cuts its E flank. However, as late as 10 November, no ejecta were found on the summit's snow cover.

Information Contacts: Istituto Nazionale di Geofisica e Vulcanologia, Sezione di Catania (INGV-CT), Piazza Roma 2, 95123 Catania, Italy (URL: http://www.ct.ingv.it/).

February 2012 (BGVN 37:02) Cite this Report

Sporadic summit activity and pit crater collapse in late-2009 and 2010

This report, summarized by the Istituto Nazionale de Geofisica e Vulcanologia - Osservatorio Etneo, Catania (INGV-OE), covers the time interval from 10 November 2009 through 31 December 2010 and discusses activity at Etna since our last Bulletin report (BGVN 36:05), which covered activity through 10 November 2009.

For six months following the end of the May 2008 to July 2009 flank eruption, Etna passively degassed from the summit craters. Beginning in the evening of 6 November 2009, a pulsating red glow was observed from a small pit that had opened at the eastern base of the South-East Crater (SEC) at 3,050 m elevation. This continued for several months, visible only at night from the INGV web camera, and was interpreted as being related to Strombolian activity entirely confined to the interior of the pit (and thus not directly visible). The incandescence was sometimes accompanied by small lithic ash emissions from the pit, probably associated with inner collapses.

For about 30 minutes during the afternoon of 8 April 2010, the stations of the Permanent Seismic Network recorded 12 large low-frequency events located at Etna's summit. At the same time, the pit crater at the eastern base of the SEC collapsed, producing a dark-colored plume of volcanic ash that rose to ~1 km and dispersed to the NE. Mainly lithic ash fell at distances of up to 6 km from the volcano, and the pit widened from ~40 m to ~80 m in diameter. An explosive component in this event was evidenced by a small pyroclastic density current that moved a few hundred meters to the NE from the pit. All other summit craters of Etna displayed only passive degassing.

At about 1840 on the same day, dark emissions were also observed at the central crater, the location of two active vents, Bocca Nuova and La Voragine ("The Chasm"). The phenomenon was observed by INGV-OE staff in the Pernicana-Linguaglossa area of the volcano, who also reported the fallout of ash in the Rocca Campana area, between Milo and Fornazzo. Photos taken by R. Azzaro showed an initial ash emission from the pit crater at Etna's SEC at 1800 (figure 138a), followed at about 1840 by emissions also from the central crater, and ash fallout on the NE flank.

Figure 138. An initial emission of ash from the pit crater at Etna's SEC: (a) at about 1800; and (b) at 1842 on 8 April 2010. Both photographs were taken from the NE (the area of Linguaglossa). Courtesy Raffaele Azzaro, Istituto Nazionale de Geofisica e Vulcanologia - Osservatorio Etneo (INGV-OE).

On 9 April intense gas emissions were noted at the pit crater, but without ash emission.

INGV-OE reported a series of landslides on 19 June from the NW rim of the pit crater located on the lower E side of the SEC. The collapses generated small ash clouds that drifted NE and changed the pit crater's morphology. Data from a fixed thermal monitoring camera showed thermal anomalies over 180°C, indicating that the landslide material was hot. Fumarolic activity was seen in the landslide source area during an inspection on the previous day. The events on 19 June also formed a large gap on the NW side of the crater rim.

INGV-OE reported that at 1509 on 25 August 2010 a powerful explosion occurred at the Bocca Nuova. This explosion initiated a period of ash emission that continued, at diminishing strength, for about 20 minutes. As seen in figure 139, the onset of the explosion was characterized by the emission of hot material, which was recorded as a thermal anomaly up to 170°C by the new thermal camera on La Montagnola, ~3 km S of Etna's summit craters. The visible camera on La Montagnola recorded the rapid uprise of a cauliflower-shaped, dark gray ash plume that rose to ~1 km before being blown to the E.

Figure 139. Views from video (a, b) and thermal (c) monitoring cameras at La Montagnola, taken 3 km S of the summit craters, during the beginning of the explosive events of 25 August 2010. Courtesy of INGV-OE.

The explosion on 25 August 2010 was the strongest in a series of similar explosions of the western vent of the Bocca Nuova forming a sequence that began on 5 July 2010. There was no evident change in the activity of the other summit craters; deep explosions within the active pit of the NEC had been occurring continuously for several months.

The 25 August events led to ashfall reported in areas SE of Etna, including the town of Catania (27 km S). An inspection the next morning revealed that the W wall of the BN-1 crater of Bocca Nuova had collapsed. During 25-29 August 2010, a total of seven explosions were recorded.

During the first days of October 2010, INGV-OE reported that Etna's activity levels remained fairly stable. Explosions continued deep inside the NEC, but with significant fluctuations. The western depression at the Bocca Nuova was the source of an explosive event that occurred at 1127 on 7 October and generated a small ash emission. Ashfall was observed shortly thereafter at the Rifugio Sapienza, on the high southern flank of the volcano at ~1,900 m a.s.l. The event was of short duration and formed a discontinuous deposit of very fine ash. The depression crater on the lower E flank of the SEC cone emitted gas more or less continuously, sometimes in a pulsating manner. There were no significant changes at La Voragine, the E vent of the central crater.

A field inspection on the morning of 8 October revealed a low level of gas emissions without explosive activity at the NEC, the Voragine and the Bocca Nuova. In contrast, the pit crater on the E flank of the SEC cone showed dramatic degassing from an open vent on its floor, which had opened during the first half of September. The degassing took place in a pulsating manner and was accompanied by loud hissing sounds, possibly produced by deep explosive activity. The walls of the pit crater were seen to be highly unstable, and small landslides were observed during the inspection, generating small red ash clouds. There were no "fresh" juvenile products either outside or inside the crater depression, however, on the crater floor there was clearly visible coarse material (meter-sized blocks) from areas that had collapsed in recent weeks.

Following several days of minor ash emissions at the NEC, on the morning of 14 November 2010 there was a significant increase in both the frequency and the volume of ash emissions (figure 140). These emissions generated narrow plumes to a few hundred meters high, which were then dispersed by the wind to the SW on 14 November, then NE on the night of 14-15 November, and finally E on 15 November. The ash emissions occurred intermittently, alternating with periods of white gas and vapor emissions.

Figure 140. Aerial view of Etna's Northeast Crater taken about 1200 on 14 November 2010. A dilute ash plume can be seen rising from the crater, and patches of snow on crater rims are covered with thin ash deposits. Photo courtesy of Alfio Amantia, INGV-OE.

On 15 November INGV-OE staff visited the NEC and observed that near the cone, particularly to the S, in the northern portion of La Voragine, a few millimeters of brown ash were present on the ground. On the rim of the NEC, the deposit was up to 1 cm thick and thickest on the eastern side. The NEC's ash emissions were then rather modest, and were accompanied by nearly continuous deep rumblings, which sometimes increased.

For more than a year there had been an open degassing vent on the NEC's crater floor, which up until the previous visit to the NEC in October had a diameter of ~25 m. On 15 November, this vent was seen to be much larger, with a diameter of at least 75 m. Ash emissions from this vent were often minor, but at other times more vigorous. The NEC's inner walls were covered by reddish brown ash deposits. No coarse-grained material was observed, either in the deposits, or in the emissions. Microscopic analysis revealed much of the ash to consist of juvenile glass shards.

After more than one month of relative quiet at Etna, at 0446 GMT on 22 December, a strong explosion occurred at the western vent of the Bocca Nuova. This event generated an ash plume a few hundred meters high that blew NE, resulting in light ash falls more than 10 km away, as far as the town of Linguaglossa. Video recorded by the thermal cameras of the Montagnola (EMOT) and Nicolosi (ENT) clearly showed the emission of hot material with temperatures exceeding 60°C (figure 141a, b). A thermal anomaly was also evident in the footage recorded by the thermal camera of Nicolosi (ENT; figure 141c, d). The visible-light footage recorded by other INGV monitoring cameras did not reveal any incandescent material.

Figure 141. Explosion from the Bocca Nuova on 22 December 2010, seen in frames recorded by the thermal video cameras of the Montagnola (EMOT; a, b), and Nicolosi (ENT; c, d). The emission of hot - though non-incandescent - expanding material is well evident as a thermal anomaly in the images, which also show the subsequent evolution of the ash plume rising a few hundred meters above the summit of Etna, and drifting NE. Courtesy of INGV-OE.

The 22 December 2010 explosion at the Bocca Nuova was probably less powerful than the one on 25 August 2010, but certainly stronger than the numerous subsequent events between late-August and late-October. Smaller emissions of reddish-brown ash continued to occur during the forenoon of 22 December.

On 23 December 2010, an intense glow from the pit crater on the E flank of the SEC cone was recorded by the visible-light monitoring camera at the Schiena dell'Asino (6 km SE of the summit craters) during a brief interval of partial visibility amidst weather clouds. At the same time, the volcanic tremor amplitude recorded by the summit seismic network of the INGV-OE showed a brief, but sharp increase. Very small and brief emissions of hot material from the pit crater were again noted on 29 December and continued for the next few days.

Information Contacts: Boris Behncke, Istituto Nazionale di Geofisica e Vulcanologia (INGV), Sezione di Catania, Piazza Roma 2, 95123 Catania, Italy (URL: http://www.ct.ingv.it/).

September 2013 (BGVN 38:09) Cite this Report

46 paroxysms and birth of the New Southeast Crater (NSEC)

Since our last report on Etna (BGVN 36:05), which covered activity through 29 December 2010, intervals of vigorous activity (paroxysms) have continued, with 18 paroxysms in 2011, 7 in 2012, and 21 in 2013. During this reporting interval, 30 December 2010-31 December 2013, the activity can be viewed as a series of paroxysms detailed in a chronology shown below. Activity at the Northeast Crater (NEC) remained minor during the reporting interval. The Bocca Nuova produced activity in July and December 2011, and then in January 2013 where two episodes of intense Strombolian activity occurred on the evenings of 16 and 18 January.

In addition, during this reporting interval, there emerged a "New" Southeast crater (NSEC). The "old" SEC was last active in May 2007. NSEC formed at a large pyroclastic cone that grew alongside the SEC's active crater. The cone's early growth took place during seven paroxysmal episodes between January and July 2011, and continued to grow though the end of 2013.

Paroxysms at Etna. The term paroxysm, and its use in the phrase 'paroxysmal episode,' has become common in describing Etna's eruptive outbursts, particularly in the past few decades. INGV's Boris Behncke has described the behavior associated with these terms, employing both photos and videos widely available online. Paroxysm is a short-hand for Etna's often intense Strombolian discharges that frequently include lava fountaining, lava flow emission, and tephra columns, which erupted at the summit craters.

Behncke notes that Etna's typical paroxysm consists of three main phases: (1) prelude and waxing, (2) climax, and (3) waning and cessation. The climactic phase 2 part of the behavior represents the true paroxysm. To describe a collective set of all three phases at Etna, Behncke prefers that they be called "paroxysmal episode," "paroxysmal eruptive episode" or "eruptive episode."

Summary and chronology. Table 10 contains a 2011-2013 chronology of Etna's paroxysmal episodes at the NSEC as reported by INGV. There were 46 such episodes during the interval shown in the table. There are clear cases where the description of a single paroxysm glosses over complexities of the eruptive process (see, for example, the 30 July discussion in the next section).

Table 10. A list of NSEC paroxysmal episodes from Etna's New Southeast Crater and their numbering for 2011- 2013. The column at far right contains occasional notations of interesting or extraordinary events taken from INGV reporting. In some cases there are minor variations in dates and numbering.

Paroxysm number	Date	Notes
2011
1	13 Jan 2011	1-7 correspond to strong growth of NSEC; At irregular intervals small landslides occurred within the crater depression
2	18 Feb 2011	--
3	10 Apr 2011	--
4	12 May 2011	--
5	09 Jul 2011	A dense eruptive plume rose several kilometers and drifted S and SE, causing ash-and-lapilli fall in populated areas and forcing the closure of the Fontanarossa international airport in Catania.
6	19 Jul 2011	--
7	25 Jul 2011	--
8	30/31 Jul 2011	See figure 142 (30 July 2011) The event was essentially a repetition of the previous paroxysms, with the emission of a lava flow W toward the Valle del Bove, lava fountains rising to maximum heights of 450-500 m, and an ash plume that was blown E by the wind.
9	08 Aug 2011	--
10	12 Aug 2011	--
11	20 Aug 2011	--
12	29 Aug 2011	--
13	08 Sep 2011	--
14	19 Sep 2011	This event, which occurred during rather poor weather conditions, produced lava fountains from various vents within the crater and on its southeastern flank, lava flows that descended the western slope of the Valle del Bove, and an ash cloud that was bent by the strong wind to the NE.
15	28 Sep 2011	--
16	08 Oct 2011	--
17	23 Oct 2011	--
18	15 Nov 2011	This episode has in nearly all details been a repetition of its predecessors, though with a few minor variations; the culminating phase lasted about one hour and terminated rather abruptly. Ash-and-lapilli falls affected the SE flank, including the towns of Zafferana, Etnea and Acireale.
2012
1 / 19	05 Jan 2012	--
2 / 20	09 Feb 2012	This event was less violent than its predecessors, but lasted more than 5 hours. A lava flow descended toward the Valle del Bove, stagnating before it reached the valley floor.
3 / 21	04 Mar 2012	--
4 / 22	18 Mar 2012	Tall lava fountains, a tephra and vapor column several kilometers high (leading to ash and lapilli falls over the E sector of the volcano), and lava flows that descended into the Valle del Bove, locally interacting explosively with thick snow cover on the ground.
5 / 23	01 Apr 2012	--
6 / 24	12 Apr 2012	--
7 / 25	24 Apr 2012	This event, which occurred after a relatively quiet interval of 11.5 days, repeated in virtually all details the preceding episodes, with lava fountains, copious emission of ash and lapilli, and lava flows that descended into the Valle del Bove.
2013
1 / 26	20 Jan 2013	The two episodes of Strombolian activity at the New Southeast Crater during 20 and 22-23 January represented the first emission of new magmatic products after a quiet interval of nearly nine months.
2 / 27	22-23 Jan 2013	--
3 / 28	19-20 Feb 2013	Starting the morning on 19 February, with 3 more paroxysms during the next 54 hours. Pronounced cone growth at NSEC. Lava flows emitted from base of NSEC ongoing between paroxysms.
4 / 29	21 Feb 2013	--
5 / 30	23 Feb 2013	Very active event. See figure 143 (23 Feb). Ash plume trending ESE, lava flows from the fissure cutting the SE crater rim and also from a new eruptive fissure, and small lahars. The second paroxysm of the day produced an ash cloud that drifted E; new lava flows descended toward the Valle del Bove, following the paths of their predecessors. The rapid succession of three paroxysmal eruptive episodes in less than 36 hours is quite notable; the only known historic precedent of three paroxysms occurring in such a short time interval at Etna was the series of eruptive episodes in 2000
6 / 31	28 Feb 2013	--
7 / 32	5/6 Mar 2013	--
8 / 33	16 Mar 2013	This event, one of the most intense of the current series of paroxysms, was preceded by a long "prelude" (Strombolian activity) that started on the afternoon of 15 March, and was followed by weak, discontinuous activity at the Voragine.
9 / 34	3 Apr 2013	--
10 / 35	12 April 2013	Lava fountaining; high column of pyroclastic material; The eruption formed a pyroclastic cloud directed to the SE, initially producing lapilli and ash, which fell mostly near the inhabited centers of Zafferana Etnea, Santa Venerina e Acireale; later including the communities of Giarre and Milo situated slightly to the N.
11 / 36	18 Apr 2013	--
12 / 37	20 Apr 2013	Very powerful episode: lava fountains reached heights of 800-1000 m above the crater, whereas the cloud of pyroclastic material expanded toward ESE, leading to heavy fall of ash and lapilli over the areas of Zafferana Etnea, Milo, Santa Venerina and further downslope, in the area of Giarre.
13 / 38	27 Apr 2013	--
14 / 39	26 Oct 2013	A gas plume laden with pyroclastic material rose several kilometers above the summit and drifted SW, affecting population centers as far as the Caltanissetta area. Activity caused the closure of airspace near Catania airport before dawn through the early morning.
15 / 40	11 Nov 2013	--
16 / 41	17 Nov 2013	--
17 / 42	23 November 2013	Very powerful episode: rapid evolution from Strombolian activity to lava fountains. The eruption column, several kilometers high, was charged with pyroclastic material that was dispersed by the wind to the NE.
18 / 43	28 Nov 2013	–
19 / 44	02 Dec 2013	See Figure 144 (2 December) This event produced tall lava fountains, lava flows, and an eruption column charged with pyroclastic material, which drifted NNW, causing ash and lapilli to fall in the area of Bronte. Several lava flows were emitted to the SSE, SE, NE and S. The flow traveled SE and reached the base of the W headwall of the Valle del Bove.
20 / 45	14-16 Dec 2013	Ash emissions caused the cancellation of more than 20 flights in and out of the Catania airport on 15 December.
21 / 46	29-31 Dec 2013	--

Figure 142. A photo of NSEC in eruption during a paroxysm on the evening of 30 July 2011. The photo shows lava fountaining activity, ash plume, and lava flow from the new and actively growing cone on the E flank of Etna's old Southeast Crater (barely discernible at extreme left). The photo was taken from a point about 1 km to the SE of SEC but the height of the lava fountains were undisclosed. Photo taken by Marco Neri, INGV-Catania.

Regarding paroxysm number 8 (30-31 July 2011), INGV featured photos (e.g., figure 142) and made comments such as the following.

"About 19.00 h local time (= UTC-1), the mean amplitude of the volcanic tremor started to increase again, and so did the Strombolian activity. At around 19.30, a dilute gas and ash plume was again blown eastward by the wind. The Strombolian activity progressively gained in intensity, quite more rapidly than during the morning's activity, and the incandescent jets became continuous around 21.30 local time. At the same time, renewed lava overflow toward east showed a rapid increase in effusion rate, forming a multilobate flow down the western slope of the Valle del Bove, which traveled approximately 3 km down reaching about 2,000 m elevation by 2300 local time. The ash plume became denser and was blown eastward by the wind, generating ash falls in the Ionian sector of the volcano.

"During the phase of maximum intensity, fragments of fluid lava were violently thrown to heights of about 450-500 m above the crater rim, causing heavy fallout onto the external flanks of the pyroclastic cone to a distance of 200-300 m. Lava fountains were jetting from at least two vents located within the crater and on its upper east flank, roughly aligned west-northwest - east-southeast."

2013. There were two main phases of activity during 2013. The first occurred during January-April; the second, after a 6-month quiescence, began on 26 October (table 10).

Figure 143 shows a view of the paroxysmal event of 23 February 2013. Of the events listed during the first phase of 2013 (table 10), this was a particularly active one.

Figure 143. View of the Pizzi Deneri area in the aftermath of incandescent bombs falling during the peak of the 23 February 2013 paroxysm at the NSEC. Photo taken from the Rifugio Citelli, on Etna's NE flank. Photo taken by Daniele Pennisi and taken from INGV report.

INGV reported that eight eruptive events occurred between 26 October and 31 December 2013. The largest of these events occurred on 23 November 2013 and stood out as a noteworthy event in terms of amplitude. Figure 144 shows a scene from the episode on 2 December 2013.

Figure 144. Strong explosions at the end of the lava fountaining during the paroxysm of 2 December 2013 at Etna's New Southeast Crater, and lava flow directed toward the SE (at left). Note also the beginning of the formation of a small lava flow toward the NW, more to the right, forming a more luminous point on the cone's flank. Ballistics rose hundreds of meters. Photo taken from Macchia di Giarre by Walter Contarino, and INGV report.

Paroxysmal activity at Etna caused significant disruptions regionally during the reporting period; the Catania airport cancelled flights in and out of the airport several times. On 9 July 2011, Strombolian explosions turned into a continuous lava fountain; a dense eruptive plume rose several kilometers and drifted S and SE. Ash and lapilli from the plume fell in populated areas including Trecastagni, Viagrande, and Acireale (SE), and between Nicolosi and Catania (S), forcing the closure of the Fontanarossa international airport in Catania. In 2013, according to a news article, a representative from Catania airport noted activity at Etna prompted the closure of nearby airspace from before dawn through the early morning of 26 October 2013. According to another news article, the ash emissions caused the cancellation of more than 20 flights in and out of the Catania airport on 15 December 2013.

The New SEC (NSEC). The old SEC cone was last active in May 2007. The NSEC cone grew substantially between 12 January and 25 July 2011 (episodes 1-7) (table 10) and thereafter. Figure 145 shows a photo of the NSEC taken on 29 July 2011.

Figure 145. A photo of Etna's Southeast Crater (SEC) taken on 29 July 2011 from 1 km S of the SEC. The photo shows the large pyroclastic cone that has grown around the active crater, located on the E flank of the old SEC cone, during the seven paroxysmal episodes between 12 January and 25 July 2011. Photo taken by Boris Behncke, INGV-Catania.

Since its emergence in 2011, the NSEC grew substantially, especially in 2013. The size of NSEC can be seen relative to the old SEC in figure 146. Smaller and farther left (E) is the low cone Sudestino ('little southeast'), which grew during several paroxysmal episodes during the spring of 2000 just beyond the SEC's S side (BGVN 25:03; 25:09). The right upper half of the image is dominated by the NSEC cone, which grew entirely during the previous 10 months. INGV noted that during 2013 the NSEC cone expanded both in height and width.

Figure 146. A view of the Southeast Crater (SEC) complex at Etna as seen from the S on 14 December 2011. The "old" SEC cone is in the center and contains the conspicuous light colored area with wisps of fumarolic vapor and yellow sulfur deposits. The right half of the image shows the New SEC cone, which grew entirely during the previous 10 months. The large bombs and blocks in the foreground, with some clasts 3-5 m in diameter, were deposited during the paroxysmal episode of 15 November 2011. Mosaic composed of 3 photos taken by Boris Behncke, INGV-Osservatorio Etneo (Catania).

The October -December phase of Etna's 2013 activity is summarized in an INGV report from 22 January 2014 (B. Behncke & E. De Beni). Figure 147 shows a map of lava flows emanating from the NSEC during this phase of activity (26 October - 31 December 2013).

Figure 147. Map of the lava flows emitted at the NSEC from 26 October to 31 December 2013 and morphology of the NSEC cone updated in January 2014 (base map, August 2007). BN=Bocca Nuova; SEC = Southeast Crater; NSEC = New South East Crater. Taken from UFGV Report of 22 January 2014, (INGV, by B. Behncke and E. De Beni).

Information Contacts: Boris Behncke, Istituto Nazionale di Geofisica e Vulcanologia (INGV), Sezione di Catania, Piazza Roma 2, 95123 Catania, Italy (URL: http://www.ct.ingv.it/).

November 2014 (BGVN 39:11) Cite this Report

January–13 June 2014: NSEC emits lava and 11 Feb landslide with ground-hugging reddish cloud

Our last report on Etna covered activity through 31 December 2013 (BGVN 38:09) and described activity in terms of a series of paroxysms, including the emergence of a new South East Crater (NSEC; see figure 147 in BGVN 38:09).

This report covers subsequent activity from 1 January-13 June 2014 and summarizes first-hand accounts by Istituto Nazionale di Geofisica e Vulcanologia (INGV-Catania). The key events of this reporting interval were ongoing emissions of E-directed lavas from a vent area on the lower E flank of the NSEC. That same vent area at NSEC generated an unusual, reddish, ground-hugging cloud associated with a landslide on 11 February. It left a swath of pyroclastic deposits mapped for over 2 km.

A sketch map shows lava and pyroclastic emissions from October 2013 through February 2014 (figure 148). It thus gives an overview of Etna's products during the first part of this reporting interval (January through February 2014). Flows on figure 148 emitted during 2013 were discussed in the previous report (see map, figure 147, in BGVN 38:09). During January-February 2014 lava flows vented in an area on the NSEC's lower E flank. That same general area was the source of a landslide and pyroclastic deposits emplaced on 11 February 2014 (shaded in light tan with triangles or dots conveying coarser and finer deposits). The deposits were laid down by fast-moving, reddish, ground-hugging emissions.

Figure 148. Map of Etna's summit area highlighting volcanic deposition during the interval October 2013 through 11 February 2014. Lavas of October 2013-December 2014 are shown in pale green; lavas of 14-16 December 2013, in light blue; lavas of 29 December 2013, in blue; lavas of 22 January-February 2014, in red. The 11 February 2014 pyroclastic deposits (tan) as mapped here stretch ~2.3 km W from their source at a depression (inside the hachured red line) on the lower E side of NSEC. These pyroclastic deposits are mapped into two adjacent map units on the basis of grain size. Both the pyroclastic deposits and the lava flows descended the steep W headwall of the broad valley called Valle del Bove. The valley's headwall area extends to ~2-3 km to the SE of NSEC before the slope gradient drops and the slope starts to make the transition to the valley floor. Courtesy of INGV (Etna Cartographic Laboratory).

Figure 148 also shows the important vent on NSEC's E flank (red hachured circle). Abbreviations for other summit vents: (SEC (Southeast crater), BN (Boca Nuova), VOR (Voragine), NEC (North East crater), as similarly defined in previous Bulletin reports). These other vents issued little in the way of deposits as late as the end of February 2014 (based on the map) and INGV reporting did not disclose much in the way of other deposits either.

Activity during January 2014. INGV reported that during 31 December 2013-1 January 2014 lava flows from a vent located on the NSEC continued to travel toward the N part of the Valle de Bove; the lava flows had been active since activity resumed on 29 December 2013. A 1 January web camera photo near midday showed a dense black plume emerging from NSEC. By 3 January 2014 the lava effusions stopped. Meanwhile at NEC during 4-13 January 2014 this vent released pulsating and almost continuous reddish ash emissions. Tremor remained at low amplitude into at least late January.

On the evening of 21 January after ~20 days absence (since an increase seen during 29-31 December 2013), strombolian emissions returned at NSEC. These emissions were weak. Sparse ash also discharged, barely rising over NSEC's rim.

Late on 22 January a small lava flow emerged from the vent on NSEC's upper E flank advancing over a few hundred meters in a few hours. This was the start of the lava flow shown in red on figure 148. Strombolian explosions ejected glowing pyroclasts onto NSEC's flanks. The explosions declined early on 23 January, and the lava flow stopped advancing. At 0105 that day a small puff emerging from the E base of the cone heralded the start of a new W-trending lava flow. On 26 January, strombolian emissions occurred and an ash plume drifted E. By evening the strombolian eruption declined in terms of both the amount of ash emitted and the eruptive intensity. The lava flow (red, figure 148) had by this time reached ~4 km long. Also, a new lava flow advanced on top of the earlier one.

Regarding NSEC, INGV reported that on 27-28 January it underwent a gradual but steady decrease of activity. Lava flows from two vents at the E base of the NSEC cone continued to effuse at a very low rate. Weather conditions almost entirely prevented visual and optical observations during early on 30 January until the evening of 3 February.

Activity during February 2014. Late on 3 February INGV noted a lava flow from one of the NSEC's vents along its E base remained active and had extended several hundred meters. Almost continuous ash emissions from NSEC began at about 1300 on 4 February and continued into the night; about 5-10 ash puffs were separated by steam emissions. Ash plumes drifted E. After sunset, jets of hot material were observed rising 100 m above the crater rim. At 2000 the ash emissions and injection of incandescent material ceased, but the lava flow continued and reached 1 km long. Into 5 February, lava escaped from one or two vents at the NSEC cone's E margin. Lava flows advanced several kilometers to the base of the Valle del Bove's W slope. On 6 February ash emissions ceased. Nevertheless, small Strombolian explosions ejected incandescent pyroclastic material 100 m above the crater. On 7 February Strombolian explosions ejected material onto the flanks of the NSEC; the next day ash puffs were observed.

INGV noted that the ongoing activity at NSEC that began 21 January 2014 represents a notable deviation from the behavior of the NSEC over the last three years. In the context of the last few decades of Etna activity, they viewed this as a completely normal eruptive occurrence. It is similar to emissive activity from January to March 2001 on the N flank of the old SEC, and other episodes of long duration observed in the past.

During 9-10, February activity continued to be characterized by Strombolian activity, periodic ash emissions, and advancing lava flows. On 9 February venting shifted to NSEC's W portion and included ash emissions. On 10 February at least one new eruptive vent opened upslope of the vents feeding the active flows.

At 0707 on 11 February a large, dense, reddish-brown ash cloud discharged from a lower E-flank vent area at NSEC (figure 149). Rather than rising much distance, the ash-charged cloud moved rapidly downslope. The cloud consisted of a dense hot avalanche or landslide that INGV also said looked very much like a pyroclastic flow. The ash laden cloud took about a minute to reach the base of the W wall of the Valle del Bove only stopping after it encountered less steep terrain. After this event, reddish brown ash emissions continued. The mapped portions of the 11 February pyroclastic deposits are shown on figure 148, but the ash cloud itself continued farther downslope (figure 149).

Figure 149. The reddish ash cloud generated the morning of 11 February 2014 associated with a landslide and related eruption in the active vent area on the NSEC's E flank (upper left). This is a view from ~11 km E of NSEC (at Sant'Alfio, located on the Valle del Bove floor ~5.5 km from the closest point to the coast). Photo taken from INGV reporting on the 11 February event. They credit the photo to Casa di paglia Felcerossa-Permacultura.

Prior to the 11 February 2014 eruption, the area of collapse at the NSEC vent had contained unstable heated rock. In the past weeks, multiple vents in this area had been active. One vent near the E rim of the vent area was hot enough to glow. The presence of molten rock (e.g., magma and lava), hot gases, and the glowing vent were interpreted by INGV to have contributed to destabilizing the area that failed during the eruption.

Although the mapped area is smaller, the reddish cloud of 11 February expanded as it advanced over the lava field of 2008-2009, covering it almost entirely, and reaching the Valle del Bove with a front about 1 km wide. Shortly after reaching the level ground at the base of the W wall of the Valle del Bove, the flow stopped in an area about 3.5-4 km away from source vent. A cloud of ash rose up and drifted NE.

Lava flows also continued to erupt on 11 February. Those were associated with bluish clouds. During and after the 11 February event, the NSEC still generated persistent strombolian eruptions accompanied by small ash emissions. At 1800 on February 11 this was in progress, showing no change compared to the activity of the last days. During 11-12 February the amplitude of tremor remained slightly higher than normal but it dropped back to normal levels after that, and the average amplitudes generally remained at modest levels through mid-March.

NSEC's strombolian emissions slightly intensified on 12 February. An unstable part of the lower E flank of the vent that collapsed on 11 February continued to produce small collapses and reddish ash clouds. Lava continued to flow from the cone towards the Valle del Bove, and by nightfall had reached the base of the steep W wall of the valley. It then advanced on the flat land to the N of Mount Centenari (figure 148).

Strombolian activity continued during 12-28 February. Lava emissions declined, but produced lava flows a few hundred meters long. Lava emissions continued also from an effusive vent from the interior of the portion of the recess formed 11 February, which continued through 17 February. On 15 February an explosion generated a vapor-and-ash plume, and was then followed by more explosions from the same area. Later on 15 February a small lava flow emerged from a new vent at the N base of the NSEC cone, which traveled 100 m towards the W wall of the Valle del Bove, and remained active the next day. During 16-17 February strombolian activity continued to produce small quantities of ash. Lava continued to flow from the vent at the base of the cone.

Activity during March 2014. During 1-10 March generally weak though persistent strombolian activity and diffuse ash emissions continued at NSEC. Tremor was generally low. An unstable part of the lower E flank of the cone that collapsed on 11 February (figure 150) continued to produce small collapses with reddish ash clouds, and thermal anomalies. Lava continued to flow from a vent on the lower part of the NSEC cone to the W wall of the Valle del Bove, and during 2-3 March the flows reached the base of the wall (figure 150).

Figure 150. Glowing Etna lava flows seen from the SE on the evening of 3 March 2014. The flows continued to vent from the lower flank of the NSEC cone. The vent was in the same area associated with the collapse of 11 February 2014. Photo credit Turi Caggegi.

After several days of lava emissions from a vent on the lower part of the NSEC cone, during 5-6 March lava flows originated only from a higher vent and traveled 1.5 km towards the lower part of the W wall of the Valle del Bove. The lava flow fed by the vent on the inside of the unstable lower portion of the lower E flank remained active on 5 March. A second flow was fed a few hundred meters downslope , with an active front on the upper margin of the 2008-2009 lava field (directly to the NE, in the direction of Monte Simone and following the lava flow of 30-31 December 2013). On 8 March BN (Bocca Nuova) issued sporadic emissions of hot material with small amounts of volcanic ash.

INGV reported that during 12-25 March strombolian activity with occasional diffuse ash emissions continued from one or two vents at the base of Etna's NSEC cone. Lava flows originating from a vent on the upper wall traveled towards the upper part of the W wall of the Valle del Bove. Strombolian activity intensified during 18-22 March, producing more ash, and then decreased; no ash was emitted on 23 March. Lava flows originating from a vent on the upper wall traveled towards the upper part of the W wall of the Valle del Bove and also NE in the direction of Monte Simone. Tremor amplitude rose slightly on 24 March but declined on 26 March to low values similar to those seen prior to the episode of persistent NSEC eruptions that began on 21 January.

Strombolian activity at the NSEC cone ceased during the night of 26-27 March, after 64 days of persistent activity. Lava emissions from the lower side of the NSEC significantly decreased; on the evening of 28 March a small lava flow continued to advance but had stopped and was cooling the next day.

Activity during April 2014. During the night of 1-2 April emissions of minor lava flows from the NE base at NSEC cone decreased. Strombolian activity gradually intensified during the evening of 2 April, along with tremor, and then both decreased. Some collapses from the E flank of the NSEC cone took place that morning. Poor weather conditions prevented views of Etna for a few days, but by 7 April the lava flows had ceased and strombolian activity had sharply declined. No activity was observed on 8 April.

No eruptive activity at Etna was observed thereafter until the early hours of 22 April, when sporadic and weak strombolian activity resumed at the NSEC and continued for the next few days. Some explosions ejected incandescent pyroclastic material out of the crater and onto the upper S and SE flanks of the cone. A few small collapses occurred on the cone's unstable E flank. Late in the evening on 30 April the frequency and intensity of Strombolian explosions slightly increased. Degassing at the NEC also increased and thermal anomalies were detected by a camera.

Activity during May-13 June 2014. During the night of 2-3 May INGV attributed incandescence to weak, high-temperature gas emissions or strombolian explosions or both. The activity intensified on 4 May; some of the explosions ejected incandescent pyroclastic material high onto NSEC's S and SE flanks. Although tremor amplitude generally remained at low levels since early April; tremor on 1 May registered in episodes (banded tremor). Weak strombolian activity at NSEC continued through at least 10 June and no noteworthy eruptions were highlighted through 13 June.

Information Contacts: Istituto Nazionale di Geofisica e Vulcanologia (INGV), Sezione di Catania, Piazza Roma 2, 95123 Catania, Italy (URL: http://www.ct.ingv.it).

February 2015 (BGVN 40:02) Cite this Report

Strombolian eruptions, ash emissions, and new effusive vents through February 2015

Our last report (BGVN 39:11) covered activity at Etna through 13 June 2014, which consisted primarily of ongoing emissions of E-directed lavas from a vent area on the lower E flank of the New South East Crater (NSEC). This report, summarizing first-hand accounts by the Istituto Nazionale di Geofisica e Vulcanologia (INGV-Catania), covers the subsequent interval from 14 June 2014 through 2 February 2015. INGV described several eruptive episodes, including strombolian eruptions, ash emissions, and the appearance of new effusive vents at the E base of the North East Cone (NEC) and on the high E flank of the NSEC cone.

Activity during June-December 2014. On 14 June a new eruptive episode began within the NSEC, with near-continuous strombolian explosions and lava fountaining. Fine ash emissions were concurrent with lava that began to overflow the edge of the South East Crater (SEC), forming a flow that continued downhill on the W wall of Valle del Bove. During the morning of 15 June the overflowing lava followed the fissure that had been formed on 28 November 2013. Explosive activity occurred from three vents inside the crater. A spatter cone also formed in the NSEC's E sector, partially filling the fissure formed on the high NE flank during eruptions of late December 2013, and January–March 2014. During 14-15 June tremor increased sharply and remained moderately high until 18 June, when it returned to normal levels.

INGV noted that this lively strombolian activity over the course of four days was similar to the episode of effusive lava emissions observed during 14-16 and 19-31 December 2013 in terms of duration and intensity.

After images of a thermal anomaly in webcam images from Monte Cagliato, located on the E flank of Etna, a new, small fissure (tens of meters long) at the E base of the North East Crater (NEC) was observed by INGV Etna observatory personnel during 5-6 July. The vent was located between 3,015 and 3,025 m elevation. Weak spattering from this vent fed a lava flow that extended ~100 m within the saddle of the NSEC and SEC cones. Weak and sporadic strombolian explosions and small ash emissions were observed during 6-7 July from NSEC, but by 11 July this activity had ceased. Activity from the new fissure continued through 11 July with frequent strombolian explosions that were audible in nearby towns. The lava flow diverged; the longer of the two branches extended ~1.5 km, reaching the bottom of Valle del Leone.

On the morning of 25 July about 1114 local time, a new eruptive vent opened near the same eruptive fissure. This new vent ("25 July vent"), located at a distance of about 150-200 m to the N of the one from 5 July, was a source of strombolian explosions, accompanied at times by modest quantities of ash. This activity continued through 31 July. The strombolian explosions occurred at intervals of about 2-5 seconds and were often accompanied by visible compression waves ("flashing arcs") and audible rumblings up to a few tens of meters away, mostly in the E and NE sectors of the volcano. As previously observed, for example during the paroxysmal episode at the NSEC during 14-16 December 2013, the rumblings were interpreted as the result of explosions of gas bubbles inside the eruptive vent. Emissions of bombs and scoria occasionally rose 200 m high and fell within a few hundred meter radius around the vent. In a few instances, the explosions were accompanied by small quantities of ash. The lava flows, which had reached ~1.8 km during the preceding week, (halting on the saddle between the Valle del Leone and the Valle del Bove), had in the recent days overlapped the earlier ones, with active fronts at least 1 km from the effusive vent.

On 9 August INGV reported a strong decrease in volcanic tremor. From the 25 July vent, there began a gradual increase in the ash emissions that formed an ash plume, which rose to 1 km above the vent area and renewed strong strombolian activity in the evening. Strombolian activity increased at NSEC and was accompanied by small emissions of black ash that remained within the crater.

With the intensification of activity at the NSEC, the eruptive activity at the E flank of the NEC diminished. At 0645 on 9 August an effusive vent opened on the high E flank of the NSEC cone, which caused a small landslide and emitted a lava flow that after an hour had reached the E base of the cone. During the first 24 hours of activity, a small pyroclastic cone in the W portion of the NSEC summit appeared, increasing the height of the NSEC structure that began to grow in 2011. On 13 August INGV reported continued strombolian explosions, accompanied by modest emissions of ash and lava from a single vent on the high E flank of the NSEC. The lava flows emitted from the effusive vent to the E had almost ceased to advance the evening before, but two new branches were overlapping the earlier flow. The longest flow changed direction to later descend about 3 km NE toward Monte Simone. INGV reported that the eruption at NSEC had ended on 15 August and that the lava flow activity had ceased by 16 August (figure 151).

Figure 151. This photo was taken on the morning of 16 August 2014 from the town of Tremestieri Etneo (from 20 km S of Etna). It shows Etna's NSEC (at right) with its new peak formed during the eruptive episode of 9-15 August. The old SEC cone (which appears lower) resides at left. Courtesy of Istituto Nazionale di Geofisica e Vulcanologia (INGV-Catania).

Beginning in the afternoon of 7 October through 16 October the NSEC produced weak and intermittent explosive activity; small ash puffs were rapidly dispersed by the wind. During some nights small strombolian explosions ejected incandescent material a few tens of meters above the crater rim.

Starting at 1850 on 28 December the NSEC produced a short but intense eruption characterized by lava fountains, lava flows, and an ash plume that drifted E, and caused ash and lapilli fall in the nearby towns of Milo, Fornazzo, Sant'Alfio, and Giarre. It was the first typically "paroxysmal" event at the NSEC since 2 December 2013. Inclement weather prevented observations of the summit area, so the erupting crater was not identifiable. Two lava flows traveled E and NE, towards the Valle del Bove. Tremor began to decrease at 2030, and indicated that the eruption was over at 2200 (figure 152).

Figure 152. Lava flows deposited associated with Etna's large 28 December 2014 eruption (red). N is towards the top. The NSEC vented on a fissure developed a few hundred meters to the SE of the SEC (NNW-trending dashed blue line). Courtesy of INGV.

On 29 December, cameras viewing Etna recorded small ash emissions from the NSEC and persistent glow from the saddle between the SEC and NSEC cones at dusk. INGV indicated that this paroxysmal episode occurred at a series of eruptive vents along a NE-SW fissure that cut across the NSEC and the southern flank of the old SEC. From the two extremities of this fissure lava flows emerged, traveling SW toward the area of Milia-Galvarina and NW toward the northern part of the Valle del Bove near Monte Simone, reaching lengths of about 4.5 and 3.3 km, respectively (figure 152).

Activity during January 2015. During the night on 1 and 2 January, cameras recorded intermittent flashes from Voragine Crater (one of four summit craters), indicating strombolian activity there for the first time in nearly two years. At 0730 on 2 January explosions at NSEC generated ash plumes that drifted SW. Emissions ejected pyroclastic materials up to ~150 m above the crater rim, which intensified during the evening of 3 January.

At night during 6-7 January the frequency of strombolian explosions at the Voragine Crater decreased; however, some of the explosions ejected incandescent pyroclastic material outside of the crater and onto the W and SW flanks. On 7 January many of the small explosions generated brown ash plumes that rose a few hundred meters above Etna's summit and quickly dissipated. Strombolian activity increased on 8 January, possibly from two vents within the crater. Pyroclastic material continued to be ejected out of the crater. Early on 9 January strombolian activity again decreased and gave way to ash emissions that rose several hundred meters. During the evening on the same day some ash emissions were accompanied by incandescent pyroclastic material that at times fell on the external flanks of the central summit. Ash emissions continued the next morning, decreased, and had almost completely ceased by late morning. Ash emissions rapidly resumed in the afternoon and were sometimes accompanied by strombolian explosions. During the morning of 13 January, new ash emissions began at the Voragine. For some hours, these emissions were continuous, but successively diminished in the afternoon to every 5-10 minutes. Marco Neri, of the INGV- Osservatorio Etneo, during a helicopter overflight on 14 January, captured a clear view of these emissions and of the summit crater area (figure 153).

Figure 153. Summit craters of Etna seen from helicopter on the morning of 14 January 2015, looking NW. In the foreground is the cone of the New South East Crater (NSEC), its summit vent being much enlarged after the 28 December 2014 paroxysm, and the old South East Crater (SEC), with an extensive fumarolic area on the saddle between the two cones. Note the two conspicuous eruptive fissures (labeled), one on the NE flank of the NSEC (in the lower right portion of the image), and the other on the S flank of the old SEC (which opened on 28 December 2014). In the background are the Bocca Nuova (at left), the Voragine (center, emitting a dense white vapor plume), and the North East Crater (NEC) (at right). The town visible in the distance at upper right is Randazzo, on the N-NW flank of Etna. Photo and caption courtesy of Marco Neri, INGV-Osservatorio Etneo.

In the evening on 14 January weak strombolian activity was recorded at the Voragine Crater and NEC. The next day, occasionally pulsating ash emissions rose from the NEC and drifted SE. Ash emissions continued through 17 January; cloud cover prevented observations of the summit area on 18 January.

A new eruptive episode began on 31 January and continued through the morning of 2 February. Poor meteorological conditions prevented views of the summit area during the first 36 hours of the eruption. During improved viewing conditions on the evening of 1 February, volcanologists observed lively strombolian activity from a single vent in the saddle between the SEC and NSEC cones. Explosions occurred every few seconds and ejected incandescent bombs 200 m high, which fell on the S flank of the SEC. At the same time, from a vent at the southern base SEC cone corresponding to the lowest part of the SE eruptive fissure from 28 December, a lava flow issued that traveled 2 km S, dividing into two branches. At dawn on 2 February the strombolian activity produced a dense ash cloud that drifted E. At about 0750 emissions stopped, and volcanic tremor suddenly decreased.

Information Contacts: Istituto Nazionale di Geofisica e Vulcanologia (INGV), Sezione di Catania, Piazza Roma 2, 95123 Catania, Italy (URL: http://www.ct.ingv.it/).

May 2017 (BGVN 42:05) Cite this Report

Major eruptions with lava fountains, ash plumes, and lava flows during January-February, May, and December 2015

Italy's Mount Etna on the island of Sicily has recorded eruptions for the past 3,500 years. Lava flows, and explosive eruptions with ash plumes and lava fountains, commonly occur from its four major summit crater areas, the North East Crater, the Voragine-Bocca Nuova complex, the South East Crater (formed in 1978), and the newest, the New South East Crater (formed in 2011). The Etna Observatory, which provides weekly reports and special updates on activity, is run by the Catania Branch of Italy's Istituo Nazionale di Geofisica e Vulcanologica (INGV). This report uses information from INGV to provide a brief summary of the major events during 2011-2014, and a detailed summary of events between January 2015 and March 2016. Major eruptions took place during 28 December 2014-2 January 2015, 31 January-2 February 2015, 11-16 May 2015, and 3-7 December 2015.

Summary of 2011-2014 activity. Most of the 44 eruptive episodes at Etna reported by INGV between 12 January 2011 and 2 December 2013 occurred at the New South Crater (NSEC) (figure 154) at the SE edge of the summit crater area. These eruptive events generally lasted for less than an hour and were characterized by sustained lava fountains accompanied by dense ash emissions and ejected pyroclastic material. Eruptive episodes occurred at Bocca Nuova (BN) in July 2011, July-August and October 2012, and January-February 2013. In addition, two weeks of intense Strombolian activity took place at Voragine (VOR) between late February and mid-March 2013. After an episode on 27 April 2013, Etna was quiet for six months until a large explosion on 26 October 2013 sent pyroclastic material several kilometers above the summit and caused a brief closure at the Catania airport. Two other episodes at NSEC during the middle and end of December 2013 were characterized by strong Strombolian activity, but without sustained lava fountains and fewer ash emissions.

Figure 154. DEM (Digital Elevation Model) of the summit crater area at Etna, August 2007, updated with GPS measurements at NSEC in January 2014, and annotated by INGV. The white hatched lines outline the crater rims. BN = Bocca Nuova; VOR = Voragine; NEC = North East Crater; SEC = South East Crater; NSEC = New South East Crater. Courtesy of INGV (Bollettino settimanale sul monitoraggio, volcanico, geochimico e sismico del volcano Etna, 6 January 2015, No. 2).

During 2014, major activity was characterized by four events: 1) modest Strombolian activity and lava flows from the NSEC between 21 January and around 7 April; 2) intense Strombolian activity at NSEC accompanied by a lava flow to the SE during 14-18 June; 3) strong Strombolian explosions and lava flows from several vents between NSEC and the E flank of the North East Crater (NEC) between 5 July and 10 August; and 4) intense Strombolian activity at NSEC accompanied by a lava flow during 10-15 August. Weak explosive activity was also reported from NSEC during the second week of October.

Summary of December 2014-March 2016 activity. Activity from NSEC during 28-29 December 2014 created two major lava flows and an ash plume. During 31 January-2 February 2015 NSEC produced a new lava flow and several ash plumes. A minor ash emission from the BN crater took place on 12 April 2015. A large Strombolian eruption began at NSEC during the night of 11-12 May 2015, followed by a lava flow down the E flank on 13 May. Activity continued until 16 May. Minor ash emissions were reported from the NEC on 20 May, and again during 16, 18, and 19 July 2015.

The VOR crater released minor ash emissions on 20 and 24 August 2015, and again on 18 September. Small amounts of ash were also observed in a plume from NEC on 4 October. This was followed the next week by sporadic ash emissions from VOR which grew into persistent Strombolian explosions by the end of October and continued into mid-November. Strombolian activity at a new crater on the E flank of NSEC began on 25 November; ash emissions began there on 2 December 2015.

A major lava fountaining event from VOR began on 3 December 2015 which generated an ash plume that dispersed ash 70 km NE. This was followed by a 7-km-high (over 10 km altitude) ash plume the next day that sent ash to the E. Three more lava-fountain episodes took place at VOR over the next two days. After this the activity decreased at VOR but increased at NSEC with a 3.5-km-long lava flow on 6 December, followed by ash emissions and Strombolian activity. Sporadic ash emissions continued from VOR, NSEC, and NEC during December 2015-March 2016.

Activity during December 2014-February 2015. After four and a half months of relative quiet, with only minor ash emissions during 7-16 October 2014, the NSEC began a new eruptive episode on 28 December 2014 (BGVN 40:02). This was the 45th major episode at Etna since January 2011, according to INGV, and was characterized by lava fountains, lava flows in two different directions from a NE-SW trending fissure that crossed the NSEC (see figure 152, BGVN 40:02), and a tephra plume that drifted to the E. INGV calculated a volume of lava from the 28-29 December event, based on a lava thickness of 1.5-2 m, of about 3 x 10⁶ m³. Coarse ash and lapilli as large as 4-5 cm were reported in Fornazzo (9 km E), and mostly coarse ash and fine lapilli were deposited in Giarre (15 km E). Fine ash was also reported in Linguaglossa 17 km NE.

Explosive activity at NSEC resumed on 2 January 2015 with dense continuous ash emissions lasting until the next day that dispersed SW (figure 155). During the night of 1-2 January, INGV also observed new Strombolian activity from VOR for the first time in two years. During the next week, incandescent pyroclastic material rose up to 150 m above the crater rim and occasionally fell outside the crater onto the W and SW flanks; this was accompanied by minor ash emissions rising a few hundred meters. MODVOLC thermal alerts were issued nine times between 5 and 10 January. Strombolian and ash plume activity resumed at the NEC on 14 January for a few days (figure 156), but clouds obscured the summit area for most of the rest of the month. Intense degassing and minor ash was seen during clear weather through 31 January.

Figure 155. Dense ash cloud from the New Southeast Crater (NSEC) at Etna that dispersed to the SW on 2 January 2015. A) taken from the webcam at La Montagnola (EMOV) 3 km S of the summit, and B) from the town of Tremestieri Etneo, 20 km S of Etna. Photo by Boris Behncke; courtesy of INGV (Il Parossismo dell'Etna del 28 Dicembre 2014 e la Susseguente Attivita al Crateri Sommitale, INGV).

Figure 156. The summit area of Etna on 14 January 2015, observed from a Coast Guard AW139 helicopter. Minor gray ash was emitting from the Northeast Crater (NEC) and the Voragine (VOR). Dense steam plumes are visible coming from Bocca Nuova (BN) and the fumarolic vents at Southeast (SEC) and NSEC. Photo by Marco Neri; courtesy of INGV (Bollettino settimanale sul monitoraggio, volcanico, geochimico e sismico del volcano Etna, 20 January 2015, No. 4).

A sudden increase in volcanic tremor amplitude in the early morning of 31 January 2015 indicated a new ash emission from the summit which was obscured from view by clouds. Later in the morning, fine ash fell over the snow in Rifugio Citelle (6 km NE). Strombolian activity was observed, along with a new lava flow moving to the SW, from the NSEC the next day. Sixteen MODVOLC thermal alerts were issued during 1-2 February while the lava flow was active. A field survey on 2 February determined that the lava front had stopped at 1,950 m elevation near the Monte Scavo area on the SW flank (figure 157). An ash emission occurred at NSEC in the early morning of 2 February; only persistent degassing was observed from the summit craters for the remainder of February.

Figure 157. The 1 February 2015 lava flow at Etna observed on 2 February from the base of the S flank of the New Southeast Crater (NSEC). BN = Bocca Nuova, SEC = South East Crater. The NSEC is at the top right of photo. Courtesy of INGV (Bollettino settimanale sul monitoraggio, volcanico, geochimico e sismico del volcano Etna, 10 February 2015, No. 7).

Activity during March-September 2015. Degassing continued from the summit craters through March 2015 as viewed during limited clear weather. A high-temperature fumarole was observed in an infrared camera image on the E edge of NSEC on 29 March. The next ash emission occurred on 12 April from Bocca Nuova; it produced a plume a few tens of meters high that drifted SE, leaving fallout of fine reddish ash on the snow covering the western wall of the Bove Valley above 2,000 m elevation. A second smaller emission later in the day quickly dissipated.

A visit to the summit on 29 April 2015 confirmed persistent degassing from the craters. INGV scientists noted that the narrow septum separating the BN and VOR craters was much lower in height and broken through at the base, compared with earlier visits (figure 158). A small brownish-red ash plume on 1 May rose from BN; it likely resulted from a collapse inside the NW crater wall.

Figure 158. A view from the SE rim looking into the Bocca Nuova (BN) crater at Etna on 29 April 2015. In the foreground (a) is the SE pit crater which is blocked with debris, and in the background (b), the NW pit crater is degassing. The red arrow indicates the portion of the septum (setto) between Bocca Nuova (BN) and Voragine (VOR) that has collapsed. Courtesy of INGV (Bollettino settimanale sul monitoraggio, volcanico, geochimico e sismico del volcano Etna, 5 May 2015, No. 19).

A Strombolian eruption began during the night of 11-12 May 2015 from the central part of NSEC. By midnight, the activity was strong enough to send tephra out of the crater and onto the flanks. A new lava flow appeared from a fracture just below the rim on the NE side early on 13 May; it generally followed the path of the 28 December 2014 flow to the NE. This was followed by increased ash emissions later in the day. The lava flow continued to advance NE during 14 May, into the Valle del Leone, and crossed near Monte Rittmann, flowing rapidly down the steep slope connecting the Valle del Leone with the Valle del Bove, headed towards Monte Simone (figure 159). By the end of the day it had traveled 3.5 km and was at 2,000 m elevation.

Figure 159. Early morning on 14 May 2015 reveals the lava flow on the NE flank of Etna from a fissure on the E flank. Photo by Emanuela/Volcano Discovery Italia; courtesy of Volcano Discovery.

Intense Strombolian activity continued the next day at NSEC along with intermittent ash emissions. The lava flow split and flowed down the central part of the Valle del Bove, travelling 4.5 km to just below 1,800 m elevation. During the morning of 15 May a series of strong ash emissions lasting 2-3 minutes each continued from BN for about two hours. By the evening, the lava flow had traveled about 5 km and was at 1,700 m elevation (figure 160). Between 12 and 16 May, MODVOLC issued 103 thermal alerts for Etna.

Figure 160. Images from the Monte Cagliato thermal camera (8.3 km ESE) taken on 14, 15, and 16 May 2015 at Etna show the summit from the E. The 13-16 May lava flow is seen progressively expanding into Valle del Bove until reaching the vicinity of Rocca Musarra and Serracozzo. Courtesy of INGV (Bollettino settimanale sul monitoraggio, volcanico, geochimico e sismico del volcano Etna, 19 May 2015, No. 21).

By the morning of 16 May, volcanic tremor had diminished and Strombolian activity had ceased, but magma was still feeding the lava flow until the afternoon, when it tapered off. During the morning of 20 May there were sporadic brown ash emissions from the NEC. After this, variable amounts of degassing continued at the summit craters for a few months, with the NEC being the most active. This period of relative quiet permitted INGV scientists to make several surveys of the summit during July to document the effects of the recent eruptions on the craters (figures 161 and 162).

Figure 161. The vent at the bottom of the Northeast Crater (NEC) at Etna is viewed with both visible (top) and thermal (bottom) images on 2 July 2015. Courtesy of INGV (Bollettino settimanale sul monitoraggio, volcanico, geochimico e sismico del volcano Etna, 7 July 2015, No. 28).

Figure 162. Views of the multiple vents at Etna's New Southeast Crater (NSEC) on 8 July 2015 showing changes caused by the 2014 and 2015 activity. Top: Vent on the S side of NSEC formed during the 31 January-2 February 2015 episode, looking SW. Bottom: The NSEC, looking SE at the main crater formed during the 28 December 2014 episode. Inside of this are several vents that were active during the 11-16 May 2015 episode. Photo by B. Behncke; courtesy of INGV (Bollettino settimanale sul monitoraggio, volcanico, geochimico e sismico del volcano Etna, 14 July 2015, No. 29).

During a field visit on 16 July 2015, INGV scientists witnessed intense pulsating gas emissions and loud noises at NEC; the gas often contained small amounts of reddish fine-grained ash. Increased gas emissions on 18 and 19 July rose a few hundred meters above the summit and occasionally released appreciable amounts of reddish ash that covered the W flank of the crater. Small puffs with minor ash were intermittent for the next several days. Only degassing from the summit craters was observed until 20 August when minor ash emissions were noted from VOR. The next day increased seismicity was recorded at the summit area, but there were no visible surface effects. Frequent gas emissions that included minor ash were observed at the summit during a visit on 24 August (figures 163 and 164).

Figure 163. Emissions from Etna's summit crater on 24 August 2015. Steam emissions from the Northeast Crater (NEC) viewed from the N edge of the crater (top) and a weak ash emission from the Voragine (bottom), seen from the NW edge of the crater. Photos by B. Behncke; courtesy of INGV (Bollettino settimanale sul monitoraggio, volcanico, geochimico e sismico del volcano Etna, 1 September 2015, No. 36).

Figure 164. Activity at the summit craters at Etna on 24 August 2015. Top: The Bocca Nuova seen from its E rim, with vapor emitting from the cone (conetto) that formed during 2011-2013 activity, and darker emissions of gas and small amounts of fine-grained ash from the pit located in the center of the crater floor (pozzo centrale). Bottom: fumarolic activity at the Southeast Crater (SEC) and New Southeast Crater (NSEC), viewed from the E edge of the Voragine. Photos by B. Behncke; courtesy of INGV (Bollettino settimanale sul monitoraggio, volcanico, geochimico e sismico del volcano Etna, 1 September 2015, No. 36).

Degassing continued at the summit craters during September. The Montagnola webcam captured a minor ash emission from VOR on 18 September 2015. A glowing fumarole was observed inside the NSEC during a summit visit on 23 September 2015 (figure 165).

Figure 165. A glowing fumarole inside Etna's New Southeast Crater (NSEC) observed on 23 September 2015. Photo by B. Behncke; courtesy of INGV (Bollettino settimanale sul monitoraggio, volcanico, geochimico e sismico del volcano Etna, 29 September 2015, No. 40).

Activity during October-November 2015. Small but appreciable amounts of reddish ash which quickly dissipated were contained in a gas plume from NEC on 4 October 2015. Activity the following week (12-18 October) was characterized by sporadic, minor ash emissions from VOR; they were brownish-red, and were ejected during pulsating events that lasted for a few tens of seconds, repeating for as long as a few hours. Explosive activity was witnessed by a field crew at the bottom of VOR on 19 October. Lithic fragments and ashes were ejected in the immediate area of the crater. Activity increased at VOR during the end of October. During an inspection on 27 October, Strombolian explosions every 5-10 minutes sent incandescent pyroclastic material around the crater and produced minor ash emissions. A few bombs fell along the NW crater rim (figure 166).

Figure 166. Activity at Etna's Voragine Crater on 27 October 2015. a) DEM of the summit crater area at Etna (DEM 2012, Aerogeophysical Laboratory - Section 2). The red circle indicates the position of the vent inside Voragine. BN = Bocca Nuova; VOR = Voragine; NEC = Northeast Crater; SEC = Southeast Crater; NSEC = New Southeast Crater. b) The vent on the N side of the Voragine; c) detail of a Strombolian explosion from the vent. Photo by B. Ragonese (Group Guide Etna Nord, 27 October 2015); courtesy of INGV (Bollettino settimanale sul monitoraggio, volcanico, geochimico e sismico del volcano Etna, 3 November 2015, No. 45).

On the morning of 2 November, after stormy weather conditions had blocked views of the summit for several days, volcanic ash was observed on the camera lens of the Montagnola (EMOV) webcam that was later washed away by rain. During a 4 November field survey, an ash deposit was discovered within layers of snow that fell between 31 October and 2 November on the upper part of the S flank (figure 167). The source of the ash remains unknown.

Figure 167. Ash deposit at Etna interlayered in the snow that fell between 31 October and 2 November 2015, exposed along the track leading from the cable car station at Torre del Filosofo, at an elevation of approximately 2,800 m. Photo taken on 4 November 2015. Courtesy of INGV (Bollettino settimanale sul monitoraggio, volcanico, geochimico e sismico del volcano Etna, 10 November 2015, No. 46).

Modest Strombolian activity continued from the bottom of VOR during November 2015. A single small explosion occurred at the NSEC in the early hours of 8 November. During a 14 November field visit, INGV scientists observed intracrater explosive activity continuing at VOR which included several explosions with abundant ash emissions, interspersed with periods of strong spattering. On the E rim of the crater, several fresh, large (40 cm) clasts of volcanic debris had fallen as far as 12 m from the edge of the rim (figure 168).

Figure 168. Explosive activity at the Voragine crater (VOR) at Etna on 14 November 2015. a and b) volcanic ash explosions; c) an episode of strong spattering of ejecta without ash emissions; d) a recent bomb from the eastern edge of the pit inside the crater. Courtesy of INGV (Bollettino settimanale sul monitoraggio, volcanico, geochimico e sismico del volcano Etna, 17 November 2015, No. 47).

By the third week in November 2015, ash emissions from VOR were more frequent and reached high enough levels to be visible from the webcams on the S slope. Lapilli and bombs rising more than 10 m above the northern edge of VOR were observed on a site visit on 19 November. During 20 and 21 November, a slow and gradual increase in the magnitude of volcanic tremor was noted, but there was no visible change at the summit. Weak Strombolian activity began at NSEC on 25 November and was observed in the Montagnola webcam. This led to the formation of a new "pit crater" located a few tens of meters below the E edge of the NSEC, with a diameter of 15-20 m.

Eruption of 2-8 December 2015. While on a site visit to VOR on 2 December 2015, INGV observed continuing Strombolian explosions with material ejected tens of meters above the crater rim; the cone at the bottom of the crater had continued to grow from the previous week. An explosion at the NSEC pit crater in the afternoon generated minor ash emissions, and Strombolian activity at VOR increased in the evening. A progressive increase in explosive activity began at VOR on 3 December. In the early morning, a lava fountain reached heights well over 1 km (figure 169) above the crater rim.

Figure 169. Eruption from the Voragine crater (VOR) at Etna during the early morning of 3 December 2015. Witnesses reported the lava fountain as over 1 km in height. Photo by Marco Restivo/Demotix/Corbis; courtesy of Erik Klemetti.

An ash plume from this eruption initially drifted NE; ashfall was reported in Linguaglossa (17 km NE), Francavilla di Sicilia (20 km NE), Milazzo, Messina (70 km NE) and Reggio Calabria (70 km NE) (figure 170). Weak and sporadic ash emissions also occurred from the NSEC pit crater. INGV reported this as one of the most intense and among the largest eruptions from Etna in the last twenty years, similar to events on 22 July 1998 and 4 September 1999. After about one hour, activity diminished and returned to less intense Strombolian activity.

Figure 170. The OLI instrument on Landsat 8 collected this natural-color view of the ash plume from Etna on 3 December 2015 drifting SE after initially drifting NE. The close-up image (bottom) reveals abundant fresh ashfall on the NE quadrant of the volcano. Courtesy of NASA Earth Observatory.

The explosive activity at VOR intensified again around 0900 UTC on 4 December, with renewed lava fountains and an ash plume that rose 7-8 km above the summit (10-11 km altitude); this episode lasted until about 1025 UTC (figure 171). Ash emissions continued throughout the day from the NSEC as well. Bombs and lapilli were deposited high on the SW slope above 2,000 m elevation. Ashfall was reported in the Giarre-Zafferana area 17 km E. Strombolian activity continued for much of the day at VOR until 2000 UTC, when the third lava fountain (since 3 December) erupted that lasted for about 90 minutes before subsiding again to less intense Strombolian activity.

Figure 171. Eruption at Etna from the Voragine crater (VOR) in the morning of 4 December 2015, viewed from Cesaro, province of Messina (27 km NW). Copyrighted photo by Giuseppe Famiani, used with permission.

A fourth episode of lava fountaining from VOR took place mid-afternoon on 5 December 2015 and lasted for about 60 minutes. After this, activity decreased (both ash emissions and Strombolian explosions) from VOR, but increased at the NSEC pit crater, which grew due to continuous activity. In the early morning the following day two pyroclastic flows descended a few hundred meters toward the Valle del Bove. Around 1700 UTC, INGV personnel observed two lava flows, fed from the NSEC, headed toward Valle del Bove; one headed E for 3.5 km and reached 2,100 m elevation, and the other advanced ENE a few hundred meters to 2,600-2,700 m elevation. The easternmost vent at NSEC began emitting dark ash plumes on 7 December along with Strombolian activity that evening (figure 172). Activity at NSEC lasted for about 48 hours, ending in the morning of 8 December.

Figure 172. Lava flows and Strombolian activity at Etna on the evening of 7 December 2015 from the new vent on the E side of the New Southeast Crater (NSEC) that formed in late November. Photo by B. Behncke, taken from Piano del Vescovo, on the SE flank. Courtesy of INGV (Etna Update, 8 December 2015).

Activity during December 2015-March 2016. Ash plumes accompanied by sporadic Strombolian activity were ejected from the NEC beginning on 7 December, and lasting intermittently through 14 December. Renewed explosions on 13 December at NSEC produced ash emissions, minor incandescence, and thermal anomalies. MODVOLC reported 84 thermal anomalies at Etna between 2 and 9 December.

INGV scientists observed on a 12 December visit that the BN and VOR craters were essentially joined into a larger, single crater after the early December explosions, similar to the former Central Crater at Etna. VOR was covered with tens of meters of pyroclastic debris. The debris also covered much of the rest of the summit area, including the lava flows from the previous winter. The parking lot of the visitor area, located 0.5-1 km W and NW of VOR, was marked with numerous impact craters several meters in diameter.

Two minor ash emissions occurred at VOR on 19 December. After that, only steam emissions were observed at the summit until 28 December when a new series of ash emissions with minor incandescence were ejected from the vent on the E flank of NSEC. They were sporadic over the next several days and had ceased by 8 January 2016. Trace amounts of ash were again reported from the E flank vent during the last days of January 2016 and on 6 February. During this time, emissions from NEC often contained trace amounts of ash. Modest amounts of brown ash were observed from the NEC in the morning of 9 February.

An explosive event at NEC on 23 February created an ash plume tens of meters high which drifted N and rapidly dissipated. Lightning was observed in the ash cloud. Ashfall was reported in Linguaglossa, Gaggi, and Santa Teresa Riva (40 km NE) from this event. A new emission on 25 February consisted of several pulses of medium-low intensity that produced a very dilute ash plume a few meters above the crater. During March 2016, sporadic ash emissions at NEC accompanied persistent degassing, but there were no reports of ashfall other than in the immediate area of the crater.

Sulfur dioxide data. Numerous images of SO₂ emissions from Etna during this period were captured by the Aura instrument on NASA's OMI satellite. Emissions during the four major eruptive events discussed in this report (28-29 December 2014, 31 January-2 February 2015, 11-16 May 2015, and 2-7 December 2015) were the largest (figure 173).

Figure 173. Sulfur dioxide plume data for Etna during the four major eruptive episodes covered in this report. Clockwise from top left: 29 December 2014, SO₂ plume drifts E; 1 February 2015, SO₂ plume drifts ENE; 15 May 2015 SO₂ plume drifts SW, E and NE; the largest, from 6 December 2015, shows a detached plume drifting NNE and another plume moving NW that is truncated by the row-anomaly shadow. Courtesy of NASA/GSFC.

Information Contacts: Sezione di Catania - Osservatorio Etneo, Istituto Nazionale di Geofisica e Vulcanologia (INGV), Sezione di Catania, Piazza Roma 2, 95123 Catania, Italy (URL: http://www.ct.ingv.it/it/); Hawai'i Institute of Geophysics and Planetology (HIGP), MODVOLC Thermal Alerts System, School of Ocean and Earth Science and Technology (SOEST), Univ. of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://modis.higp.hawaii.edu/); NASA Earth Observatory, EOS Project Science Office, NASA Goddard Space Flight Center, Goddard, Maryland, USA (URL: http://earthobservatory.nasa.gov/); NASA Goddard Space Flight Center (NASA/GSFC), Global Sulfur Dioxide Monitoring Page, Atmospheric Chemistry and Dynamics Laboratory, 8800 Greenbelt Road, Goddard, Maryland, USA (URL: https://so2.gsfc.nasa.gov/); Erik Klemetti Eruptions Blog, Wired (URL: https://www.wired.com/author/erikvolc/); Tom Pfeiffer, Volcano Discovery (URL: http://www.volcanodiscovery.com/).

September 2017 (BGVN 42:09) Cite this Report

Lava flows during May 2016 followed by new fracture zones and major subsidence at the summit craters

Italy's Mount Etna on the island of Sicily has had historically recorded eruptions for the past 3,500 years. Lava flows, explosive eruptions with ash plumes, and lava fountains commonly occur from its major summit crater areas, the North East Crater (NEC), the Voragine-Bocca Nuova complex (VOR-BN), the South East Crater (SEC) (formed in 1978), and the New South East Crater (NSEC) (formed in 2011). The Etna Observatory, which provides weekly reports and special updates on activity, is run by the Catania Branch of Italy's Istituo Nazionale di Geofisica e Vulcanologica (INGV). This report uses information from INGV to provide a detailed summary of events between April 2016 and January 2017.

Summary of April 2016-January 2017 activity. A new eruptive episode at Etna began on 15 May 2016 and included activity around all four major summit cones; Strombolian activity began at NSEC on 15-16 May, from a pit on the E flank of the cone. The following night, thermal webcams suggested Strombolian activity at NEC. This ceased on 18 May when Strombolian activity started at VOR that also produced a large ash plume. Lava then overflowed the W rim of BN and headed W multiple times during the next few days. A different flow emerged from a fracture on the SE side of VOR near SEC on 21 May. Activity from all of the active vents had ended by 26 May. New fracture zones trending N-S and NE-SW, and extensive subsidence within VOR were observed at the summit craters at the end of May after the episode ceased.

Intermittent weak ash emissions during late May and July and intense degassing from several craters were the primary activity until explosive activity at VOR began on 7 August and opened a new vent along the inner wall of the NE rim. Strong subsidence followed at VOR and BN during August and September, creating a single large crater that included both areas. Dense ash emissions from the vent on the upper E flank of NSEC in mid-October and a few modest ash emissions from VOR and NSEC were observed. There was also persistent incandescence from the new vent at VOR and its continued subsidence through early January 2017. After the spike in activity during May 2016, heat flow diminished, but was persistent throughout the period (figure 174).

Figure 174. MIROVA log radiative power thermal anomaly graph of activity at Etna from late May 2016 through early January 2017. A major effusive eruptive event with lava flows and Strombolian activity caused a spike in heat flow during late May 2016, but heat flow was persistent throughout the period. Courtesy of MIROVA.

Activity during March-April 2016. After the major lava fountains and ash plumes of the first week of December 2015 (BGVN 42:05), eruptive activity was lower through March 2016. Sporadic ash emissions and minor incandescence were reported a few times each month. The largest event was an explosion on 23 February 2016; it produced an ash plume that drifted NE and caused ashfall in communities as far as 40 km away.

Continuous degassing accompanied dense ash emissions from the North East Crater (NEC) and the New South East Crater (NSEC) during 31 March-1 April 2016. Winds sent material to the SW, and then changed direction to the N the following day, dispersing pyroclastic material around the crater area. Ash emissions continued to be weak but persistent for the rest of April from NEC and NSEC, while only minor degassing was observed from the Voragine-Bocca Nuova complex (VOR-BN). A new pit crater was observed near the center of BN from the gradual collapse of the crater between 19 February and 15 April 2016.

Activity during May 2016. Although visibility was limited due to weather in early May 2016, discontinuous explosive activity with minor ash emissions was observed over several days from NEC and NSEC near the top of Valle del Bove (a large valley SE of the summit crater area). Weak incandescence from NSEC was detected by the high-resolution webcam at Monte Cagliato for the first time in several months during the night of 16 May, and marked the beginning of a new eruptive episode that lasted until 25 May 2016, involving activity at all four summit crater areas (figure 175).

Figure 175. The four summit craters at Etna shown in a DEM from 2014 created and modified by INGV's Aerogeophysical Laboratory. The black hatched lines outline the rims of the craters. BN = Bocca Nuova, VOR = Voragine; they are delimited by a single crater rim after the explosive activity of December 2015; NEC = North East Crater; SEC = South East Crater with cone of the New South East Crater (NSEC) on its SE flank. Activity from the 17-25 May 2016 episode is shown in red and yellow and discussed in the text. Courtesy of INGV (Bollettino settimanale sul monitoraggio vulcanico, geochimico e sismico del vulcano Etna, 16/05/2016-22/05/2016, Reporte No. 21/2016).

Explosive activity first observed during the night of 15-16 May 2016 at NSEC came from a pit on the E flank of the cone. The following night, webcams also showed a thermal anomaly at NEC, interpreted by INGV as probable Strombolian activity. At first light on 17 May, intense degassing was observed from NEC which lasted throughout the day and included minor ash emissions. Strong explosions from NEC were heard about 10 km from the crater. Strombolian activity rising tens of meters above the rim was first observed around 2000 UTC. During the night of 17-18 May, intermittent flashes, likely from explosive activity, originated from the pit on the E flank of NSEC.

Continued explosions at NEC during the morning of 18 May produced an ash cloud that drifted ESE. This activity ceased around 1050 UTC, when Strombolian activity began at VOR that rapidly evolved into a lava fountain. The activity also created an ash plume that rose to an altitude of 7 km and drifted due E. The lava fountain continued until about 1430 UTC. Shortly after the Strombolian activity began at VOR (around 1100 UTC), lava overflowed the W rim of BN and headed W towards Monte Nunziata. It traveled for about 2 km and stopped at an elevation of around 2,100 m based on observations from the Bronte thermal webcam. Also at 1100 UTC, a small explosive vent opened at the base of the N side of NEC (Bocca 1 in red, figure 175) that spattered for a few minutes. Around 1530 UTC, an improvement in weather conditions permitted observation of a new lava flow in the Valle del Bove. The flow, fed by a vent at the base of the E side of NEC (Bocca 2 in red, figure 175), headed E towards Monte Simone, and stopped at an elevation of approximately 2,400 m.

By the morning of 19 May, although adverse weather conditions prevented observations, a sudden increase in the amplitude of tremor and loud explosions heard in communities E and S of the volcano suggested another explosive episode at VOR. A dense eruptive cloud drifted E. A new lava flow emerged from the W rim of BN, and headed W on top of the flow from the previous day. It divided into several arms, the longest of which flowed about 1,800 m, near Monte Nunziata, without reaching the nearby highway. Strombolian activity was again observed at VOR beginning around 1900 UTC on 20 May when weather conditions improved.

Beginning around 0140 UTC on 21 May 2016, a rapid escalation of the amplitude of volcanic tremor occurred together with increased explosions from VOR. Around 0200 a small lava flow was observed from a fracture at the base of the SE side of the cone of VOR near the base of SEC (the yellow flow marked on figure 175). The intense explosive activity at VOR generated a plume that drifted S. Tremor amplitude decreased suddenly around 0600. Lava was observed overflowing the W rim of BN around 0700, covering the flows of the previous days. Strombolian activity was again observed from VOR during the night of 21-22 May. Sporadic ash emissions from the pit on the E flank of NSEC during the early morning of 22 May quickly dissipated. That afternoon, renewed Strombolian activity began at NEC which intensified and then ended during the following night (figure 176).

Figure 176. Volcanic activity at Etna during 20-22 May 2016. a) intense explosive activity of 21 May at VOR, taken from the thermal webcam at Monte Cagliato; b) the lava flow from the fracture on the SE side of VOR during the explosive activity of 21 May, photo by Alessandro Lo Piccolo; c) intense degassing on 20 May from the fracture that fed the lava flow shown in (b) the following day, taken from the Piano delle Concazze; d) the overflow from the western edge of BN during 21 May, taken from Bronte's thermal webcam; e) Strombolian activity at VOR taken by the high definition camera of Monte Cagliato at 1845 UTC on 22 May; f) ash emission from the pit on the E flank of the NSEC, taken with the camera at Monte Cagliato on 22 May at 0630 UTC. Courtesy of INGV (Bollettino settimanale sul monitoraggio vulcanico, geochimico e sismico del vulcano Etna, 16/05/2016-22/05/2016, Reporte No. 21/2016).

A new round of weak Strombolian activity began at VOR around 1900 on 23 May 2016. Activity continued until 1750 on 24 May when explosive activity increased sharply. Vigorous Strombolian activity peaked during the night of 24-25 May. Incandescent material rose a few hundred meters into the air, and mostly fell back into the crater. It was not accompanied by a lava flow or ash plume. Activity began decreasing during the afternoon of 25 May, and ceased sometime during the following night. Both ground-based and aerial observations by INGV personnel on 26 and 27 May confirmed the end of the eruptive episode and documented its effects (figure 177).

Figure 177. The summit area of Etna seen from the north on 27 May 2016 after the eruptive episode of 15-25 May. At the North East Crater (NEC), the black dashed line shows the position of its rim prior to the eruptive phase that started on 15 May. Large areas of the crater rim collapsed on both the N and S sides. The S side of the collapsed NEC rim intersects a fracture zone that forms a graben (yellow arrows) that trends N-S and cuts across the E rim of the VOR. A second graben trends SE from the VOR. Fumarolic activity is visible in both structures. Degassing is also visible from a vent at the bottom of VOR (red arrow within VOR). The NW-SE trending graben that extends between VOR and SEC appears to terminate at the eruptive vent created on 21 May (red arrow between NSEC and SEC). However, slope failure on the N flank of the SEC cone (white arrows) suggests to INGV geologists that the structural zone continues SE towards NSEC. Inset photo is an image of NEC captured with the thermal camera by Sonia Calvari, showing the NEC crater bottom filled with the detritus from the collapse of the southern crater wall. Courtesy of INGV (Bollettino settimanale sul monitoraggio vulcanico, geochimico e sismico del vulcano Etna, 23/05/2016-29/05/2016, No. 22/2016).

A N-S trending fracture zone about 400 m wide and 1,300 m long was observed extending S beginning at the northern side of NEC, crossing the E rim of the Central Crater (the combined VOR-BN complex), where it changes direction and extends SE toward the SEC (figure 178). A vent at the base of the saddle between SEC and VOR fed weak effusive activity on 21 May. Tens of meters of collapse within the graben contributed to the destruction of the S rim of NEC, significantly changing its shape and filling it with debris.

Figure 178. The summit area of Etna seen from the SE on 27 May 2016. The yellow arrows highlight a new NW-SE trending fracture system that produced a near-symmetrical graben on the E side of the Central Crater (the combined VOR-BN complex). It then veers to the N and joins with another graben (the black arrow) that breaches the rim of the NEC. The dotted black line highlights the portion of collapsed NEC rim during the recent eruptive period. Courtesy of INGV (Bollettino settimanale sul monitoraggio vulcanico, geochimico e sismico del vulcano Etna, 23/05/2016-29/05/2016, No. 22/2016).

Major subsidence at VOR after the end of the Strombolian activity of 23-26 May 2016 created numerous sub-circular concentric fractures within the crater with a vent degassing at the base (figure 179). The BN area was filled with the eruptive material that had overflowed the W rim (figure 180).

Figure 179. Detail of the Central Crater (CC), comprising the VOR and BN craters at Etna. View is from the NW on 27 May 2016. The concentric subcircular fractures with a degassing vent located at the bottom of the crater (red arrow) formed during collapse immediately after the end of the Strombolian activity at VOR from 23 to 26 May 2016. The yellow arrows (above) show the position of the graben responsible for the collapse of part of the NEC. The white arrows (bottom) highlight the western portion of the N-S oriented fracture zone, which affects NEC, VOR, and BN. Courtesy of INGV (Bollettino settimanale sul monitoraggio vulcanico, geochimico e sismico del vulcano Etna, 23/05/2016-29/05/2016, No. 22/2016).

Figure 180. View of the summit of Etna from the WSW on 27 May 2016. In the foreground is the Central Crater, consisting of VOR and BN. The two white arrows point to the overflow area of the lava flows from the W edge of BN during 18-21 May. The yellow arrows highlight the main fractures bordering the E side of the crater area, extending from NEC to SEC. The dotted black line highlights the portion of collapsed NEC during the recent eruptive period. The three red arrows highlight the locations of the recent eruptive vents: north of NEC (far left), within the VOR, and at the base of the saddle between the Central Crater and the SEC. Courtesy of INGV (Bollettino settimanale sul monitoraggio vulcanico, geochimico e sismico del vulcano Etna, 23/05/2016-29/05/2016, No. 22/2016).

Activity during June 2016-January 2017.A weak ash emission from VOR on the morning of 31 May 2016 was the only additional eruptive activity during May. INGV volcanologists making ground observations on 3 June noted about 10 m of subsidence of the lava surface filling BN and continued collapse at the center of VOR. Intense degassing of mostly water vapor occurred from the fracture on the SE side of VOR. Strong degassing continued from all the new fracture zones at the summit during June and July. Ground-based thermal imagery recorded on 16 June indicated temperatures as high as 300°C around the fractures within the Central Crater. A helicopter overflight on 14 July showed few changes in the graben system first documented at the end of May, except for continued collapse near the S rim of NEC. Minor ash emissions resumed at NSEC; they were observed during 10-14, 19-21, and 26-28 July. Explosions were heard from the W side of BN during a visit by INGV scientists on 28 July.

Intense and persistent degassing continued during August 2016 from NEC and from the fractures between NEC and VOR (figure 181). Incandescence was observed within the fractures on 4 August. NSEC produced minor ash emissions again during 4-5 August. Low intensity explosive activity began at VOR on 7 August, but no material was ejected beyond the crater rim. An incandescent vent was observed within the collapsed inner wall of VOR on 10 August (figure 182). Explosive activity and incandescence was intermittent from this vent during 7-22 August. The apparent temperature at the vent as measured by thermal camera was greater than 580°C on 22 August. Weak and episodic ash emissions also occurred from a vent on the upper E side of NSEC on 27 and 29 August. Incandescent degassing continued at the 7 August VOR vent throughout September, along with persistent fumarolic emissions from the fracture zones.

Figure 181. Intense degassing within NEC and along the fractures between NEC and VOR at Etna on 3 August 2016. This view to the N shows the rim of NEC at the top and the new graben that breaches the rim. Photo by B. Behncke, courtesy of INGV (Bollettino settimanale sul monitoraggio vulcanico, geochimico e sismico del vulcano Etna, 01/08/2016 - 07/08/2016, No. 32/2016).

Figure 182. A new vent opened on 7 August 2016 from the collapse of the inner wall of VOR near its NE rim at Etna. Photo by B. Behncke on 10 August 2016, courtesy of INGV (Bollettino settimanale sul monitoraggio vulcanico, geochimico e sismico del vulcano Etna, 08/08/2016-14/08/2016, No. 33/2016).

A series of low-frequency seismic events were recorded at the summit on 10 October, some accompanied by explosive sounds. The strongest seismic event produced ash and hot gas that was recorded by two thermal cameras during the early afternoon. The ash rose from the W part of BN about 100 m above the rim and drifted rapidly E. During an inspection on 12 October, INGV scientists noted that subsidence of about 50 m had occurred within the BN, centered near the W crater wall, and was ongoing. They observed the sudden dropping of material along concentric fractures accompanied by reddish ash and modest steam emissions. One of these events exposed an incandescent area within the fresh lava (figure 183).

Figure 183. The bottom of the BN crater at Etna on 12 October 2016 during a collapse within the peak subsidence zone, showing incandescent material under the fresh lava. Photo by B. Behncke, courtesy of INGV (Bollettino settimanale sul monitoraggio vulcanico, geochimico e sismico del vulcano Etna, 10/10/2016-16/10/2016, No. 42/2016).

Dense ash emissions were produced on 17 October from the 25 November 2015 vent on the upper E flank of the NSEC (figure 184). A diffuse brown ash plume was observed the next day during a field inspection of the area. Intermittent diffuse brown ash emissions were again observed on 6 November. Persistent fumaroles from the vent at VOR and bottom subsidence at BN continued during November where two distinct areas of subsidence (BN-1 and BN-2) were visible (figure 185).

Figure 184. A Digital Elevation Map of the summit crater area at Etna (DEM 2014, Aerogeophysics Laboratory - Section 2 modified) showing the active degassing areas during August-December 2016. The yellow dot shows the position of the vent opened on 7 August 2016 in the upper part of the E wall of the VOR; the red dot indicates the location of the vent opened in November 2015 on the upper E flank of the NSEC, from which minor ash emitted during October and November 2016. Courtesy of INGV (Bollettino settimanale sul monitoraggio vulcanico, geochimico e sismico del vulcano Etna, 31/10/2016-06/11/2016, No. 45/2016).

Figure 185. An aerial view from the W of the summit crater area of Etna on 13 November 2016 annotated with areas of activity. The Central Crater (CC), highlighted by the dashed yellow line. Inside, the VOR and BN have coalesced; two depressions (BN-1 and BN-2) were undergoing constant, slow subsidence (especially BN-1) with enough heat released to prevent snow buildup. The subsidence of BN-1 and BN-2 began on 10 October 2016. Near the E edge of the VOR, gas emissions continued from the 7 August 2016 vent 'Bocca attiva dal 7 Agosto 2016'. Photo by Piero Berti, courtesy of INGV (Bollettino settimanale sul monitoraggio vulcanico, geochimico e sismico del vulcano Etna, 07/11/2016-13/11/2016, No. 46/2016).

Intermittent, low-intensity incandescence at the VOR vent appeared during the night of 28-29 November 2016. Sporadic, minor ash emissions occurred from the saddle area between SEC and NSEC during 15 December. Incandescence that evening from the VOR vent was also recorded on the webcams. A light coating of ash and a few lithic blocks appeared the next morning in the fresh snow on the flank of the SEC. Modest ash emissions from the same area continued intermittently through the end of December. On 31 December, a diffuse ash plume was also noted from the vent on the upper E flank of NSEC. Sporadic incandescence continued from the VOR vent during early January 2017.

October 2017 (BGVN 42:10) Cite this Report

Extensive lava flows during February-May 2017; new summit crater emerges

Italy's Mount Etna on the island of Sicily has had historically recorded eruptions for the past 3,500 years. Lava flows, explosive eruptions with ash plumes, and lava fountains commonly occur from its major summit crater areas, the North East Crater (NEC), the Voragine-Bocca Nuova (or Central) complex (VOR-BN), the South East Crater (SEC) (formed in 1978), and the New South East Crater (NSEC) (formed in 2011). A new crater, the SEC3 or "saddle cone" emerged during early 2017 from the saddle between SEC and NSEC.

After a major explosive event in December 2015 (BGVN 42:05), activity subsided for a few months before renewed Strombolian eruptions and lava flows affected all of the summit craters during late May 2016 (BGVN 42:09). These events were followed by a lengthy period of subsidence and intense fumarolic activity across the summit that lasted until a new eruptive episode began at the end of January 2017. The Osservatorio Etneo (OE), which provides weekly reports and special updates on activity, is run by the Catania Branch of Italy's Istituo Nazionale di Geofisica e Vulcanologica (INGV). This report uses information from INGV to provide a detailed summary of events between January and August 2017.

Summary of January-August 2017 Activity. Minor ash emissions began from a new vent in the saddle between NSEC and SEC on 20 January 2017, followed by Strombolian activity a few days later. Activity intensified at the end of February when the first of several lava flows emerged from this vent, and then from several other vents on the S flank of the new, rapidly growing cone during March and April. By mid-March 2017, Strombolian activity, ash emissions, and lava flows had created a cone higher than the adjacent NSEC and SEC cones. The last effusive episode at the end of April 2017 sent flows down both the N and S flanks of the new cone from multiple vents. Intermittent weak Strombolian activity at the new summit area was associated with abrupt tremor amplitude increases during May, but no additional flows were reported. During June-August, fumarolic activity persisted at several crater areas, and minor ash emissions were observed a few times, but no major eruptive activity took place. The sharp increase in heat flow resulting from the lava flows of March and April 2017 are clearly visible in the MIROVA thermal anomaly plot of log radiative power for the year ending on 12 October 2017 (figure 186).

Figure 186. Thermal anomalies at Etna (log radiative power) identified by the MIROVA system for the year ending on 12 October 2017. Major effusive eruptive events with lava flows and Strombolian activity occurred from late February through April 2017. Courtesy of MIROVA.

Activity during January-February 2017. Sporadic incandescence continued from the 7 August 2016 vent on the E side of VOR during January 2017, and minor ash plumes rose from the NSEC "saddle" vent on 20 January. Modest Strombolian activity began at the saddle vent that on 23 January and continued into February (figure 187). Small bombs were ejected onto the flank of NSEC and minor ash plumes quickly dissipated in the high winds near the summit. Also during February, steady subsidence continued at BN, especially in the BN-1 area (see figure 185, BGVN 42:09), where active degassing with minor amounts of ash was observed on 1 February (figure 187). Debris deposits from Strombolian activity at the saddle vent covered the S side of the pyroclastic cone and travelled to its base during the end of February.

Figure 187. Activity at Etna during the first week of February 2017. Left: Strombolian activity at the NSEC saddle vent; photo by B. Behncke. Right: degassing with minor ash emissions from the vent at the bottom of BN-1; photo by M. Ponte. Courtesy of INGV (Bollettino settimanale sul monitoraggio vulcanico, geochimico e sismico del vulcano Etna, 30/01/2017-05/02/2017, No. 6/2017).

During the late afternoon of 27 February, the Strombolian activity that began on 20 January from the saddle vent between SEC and NSEC rapidly intensified, and lava emerged from the vent and flowed down the S flank of SEC (figure 188). It slowed after reaching the flat ground at the base of the cone, and expanded slowly SE toward the older cones of Monte Frumento Supino. Intense activity that evening sent shards and bombs 200 m above the vent while the flow continued. Ash from the Strombolian activity dispersed NE, with minor ashfall reported in Linguaglossa and Zafferana. A new cone of pyroclastic material that formed around the saddle vent quickly grew to about the same elevation as the NSEC and SEC crater rims, approximately 3,290 m (figure 189). The lava continued to flow until 2 March 2017, when it stopped at about 2,750 m elevation with an overall length of 2,180 m, covering an area of 306 x 10³ m², for a total volume of slightly less than 1 x 10⁶ m³.

Figure 188. An outline of the new lava flow at Etna that emerged from the saddle vent located between NSEC and SEC on 27 February 2017. It rapidly advanced down the steep S flank of SEC. Base map is a DEM image created by the INGV Cartography Laboratory. Courtesy of INGV (Bollettino settimanale sul monitoraggio vulcanico, geochimico e sismico del vulcano Etna, 27/02/2017-05/03/2017, No. 10/2017).

Figure 189. Strombolian activity, the 27 February lava flow, and ash and vapor emissions from the new NSEC/SEC saddle vent at Etna on 28 February 2017 around 1730 local time. Photo by F. Ciancitto; courtesy of INGV (Bollettino settimanale sul monitoraggio vulcanico, geochimico e sismico del vulcano Etna, 27/02/2017-05/03/2017, No. 10/2017).

Activity during March 2017. Sporadic ash emissions continued from the new saddle vent during early March 2017, accompanied by weak Strombolian activity during the night of 12-13 March. Intense degassing continued from VOR during March as well, with incandescent bursts visible on many clear nights. On the morning of 15 March the Montagnola webcam recorded a lava overflow from the saddle vent down the S flank of NSEC, and an intensification of explosive activity that caused the flow to reach the base of the complex at about 3,000 m elevation. During the day, it advanced towards Monte Frumento Supino; it had reached elevation 2,800 m by the late evening, overlapping significantly with the earlier flow from 27 February. Strombolian eruptions were nearly constant until late afternoon, and continued intermittently, along with ash emissions, for several days.

Shortly before 2300 UTC on 15 March (0100 on 16 March local time), a second new flow emerged from a vent near the base of the S flank of the new NSEC/SEC cone (at about 3,200 m elevation) and travelled SE (figure 190), splitting into two lobes. INGV personnel in the summit area reported a series of phreato-magmatic explosions at 0043 (just after midnight) along the lava front at an elevation of approximately 2,700 m along the W edge of the Valle del Bove. The contact of the active flow with the underlying snow caused several explosions. An INGV volcanologist suffered minor injuries during one of the explosions. Increased emissions also caused minor ashfall in Adrano and Santa Maria di Licodia (both about 17 km SW).

Figure 190. Explosions at Etna from a vent at the base of the new NSEC/SEC cone complex during the early morning of 16 March 2017 viewed from the Torre del Filosofo, 1 km S. Courtesy of INGV (Bollettino settimanale sul monitoraggio vulcanico, geochimico e sismico del vulcano Etna, 13/03/2017-19/03/2017, No. 12/2017).

By the afternoon of 17 March 2017, the second flow had reached an elevation of about 2,600 m, near the base of the W slope of the Valle del Bove. INGV personnel at Monte Zoccolaro (1.5 km S) spotted a third flow on 18 March, located S of the other two (figure 191). The front had reached about 2,200 m elevation, and was responsible for some phreato-magmatic explosions during 18 and 19 March. Several avalanches of incandescent material reached the base of the slope at the edge of Valle del Bove as the flow fronts collapsed during 18 March. Two Landsat 8 Operational Land Imager images on 18 and 19 March captured evidence of the lava flows, an ash plume, and Strombolian activity during this episode (figure 192). By 19 March, the advance had slowed as the flows began to spread out over the valley floor. The flows into the Valle del Bove ceased on 20 March.

Figure 191. Thermal image of the W wall of the Valle del Bove at Etna on 18 March 2017, viewed from Monte Zoccolaro showing the activity of the three lava flows. Courtesy of INGV (Bollettino settimanale sul monitoraggio vulcanico, geochimico e sismico del vulcano Etna, 13/03/2017-19/03/2017, No. 12/2017).

Figure 192. The eruption from Etna's NSEC/SEC cone on 18 and 19 March 2017 as captured from space. The upper image was taken on 18 March by the Operational Land Imager (OLI) on Landsat 8 as a natural-color image, and shows an ash plume and two columns of gas and steam drifting SE. The more northerly steam and gas plume and the ash plume are rising from the summit vent of the new NSEC/SEC cone, and the more southerly steam and gas plume is rising from the effusive vent at the base of the S flank of the NSEC/SEC cone. The lower image shows the thermal glow of active lava flows on the SE flank on 19 March 2017, and the Strombolian activity at the summit of the new cone (the yellow spot directly below the Mt. Etna label) surrounded by the city lights of Catania and the surrounding communities. An astronaut aboard the International Space Station took this image. Courtesy of NASA Earth Observatory.

Strombolian activity and ash emissions ceased at the summit vent of the NSEC/SEC cone between 20 and 22 March 2017 leaving a new pyroclastic cone that rose above the adjacent NSEC and SEC cones (figure 193). Once the Strombolian activity had ended, yet another lava flow emerged from the base of the cone at an elevation of about 3,010-3,030 m, and spread into several segments, one of which flowed W around Monti Barbagallo (near the former Torre del Filosofo) and then turned SW following the valley between Monti Barbagallo and Monte Frumento Supino. By 26 March the front of this flow segment had reached an elevation of 2,300 m and travelled about 2.5 km from the vent. A second segment of the flow travelled E of Monti Barbagallo, following the earlier flows that had been active along the W slope of the Valle del Bove; it slowed and broke into several additional segments, reaching 1.3 km from the vent on 26 March, and advancing through the first week of April.

Figure 193. The new pyroclastic cone 'cono di scorie' between the SEC and NSEC rises above and between both older craters at Etna shortly after 22 March 2017. It first emerged during the eruption of 27 February to 1 March 2017, and then continued to increase in size until 22 March 2017 from extensive Strombolian activity. The dotted white line separates the South East Crater (SEC) from the New South East Crater (NSEC). "Bocca effusive" is the effusive vent that fed the lava flows beginning on 22 March, and the new lava is the dark material with fumarolic emissions in the foreground. Courtesy of INGV (Bollettino settimanale sul monitoraggio vulcanico, geochimico e sismico del vulcano Etna, 20/03/2017-26/03/2017, No. 13/2017).

Activity during April 2017. The active lava flow continued WSW towards the cones of the 2002-2003 eruption from the vent at the base of the NSEC/SEC cone until it stopped advancing sometime during the night between 8 and 9 April (figure 194). Another new flow then emerged from the same vent on 10 April and was active for just over 24 hours. This flow travelled SE to the W edge of the Valle del Bove and moved a few hundred meters along the edge before stopping during the day of 12 April.

Figure 194. The lava flow at Etna that emerged from the base of the NSEC/SEC cone complex on 22 March 2017 flows WSW towards the cones of the 2002-2003 eruption during the first week of April 2017. Courtesy of INGV (Bollettino settimanale sul monitoraggio vulcanico, geochimico e sismico del vulcano Etna, 27/03/2017-02/04/2017, No. 14/2017).

During the evening of 13 April 2017, Strombolian activity at the summit crater of the NSEC/SEC cone accompanied the emergence of flows from three vents along the S flank at elevations of approximately 3,200 m, 3,150 m, and 3,010 m which headed S and SE. The upper flows were active for only a few hours, but the lower flow continued SE towards the Valle del Bove and had overlapped the 10-11 April flow by the next day. The active front of the flow was at an elevation of 2,400 m on the western slope of the Valle del Bove, just north of the Serra Giannicola Grande. A flyover on 14 April revealed the extent of the fracture system on the flank of the NSEC/SEC complex from which the numerous flows emerged (figure 195). The flow rate diminished during the day of 15 April, and the flow stopped sometime during the next night.

Figure 195. Thermal images of the fracture system affecting the S flank of the NSEC/SEC cone at Etna on 14 April 2017 showing the pyroclastic cone 'Cono di scorie', a collapsed portion of the cone 'Porzione collassata', and the three eruptive vents 'Frattura eruttiva' that opened on 13 April (at 3,200 m, 3,150 m and 3,010 m elevation). Courtesy of INGV (Bollettino settimanale sul monitoraggio vulcanico, geochimico e sismico del vulcano Etna, 10/04/2017-16/04/2017, No 16/2017).

A thermal anomaly appeared at the S edge of the NSEC/SEC summit vent, which INGV began calling SEC3, on the morning of 19 April. Weak Strombolian activity from the vent was followed by the emergence of a lava flow from the S side of the crater rim that flowed down the S flank of the cone. Dense, brown ash emissions about an hour later accompanied the re-opening of three vents on the S flank from which new lava flows emerged (figure 196). Lava jets rose tens of meters above the crater rim for about an hour in the afternoon. The lava flows from the three vents formed into two branches moving down the S flank (figure 197), then turned E and spread over the W slope of the Valle del Bove; by 20 April they had reached an elevation of 1,950 m. Explosive activity ceased at SEC3 that afternoon, and the flows stopped advancing sometime during the night of 20-21 April. Observations of the summit of SEC3 on 22 April revealed a N-S trending graben formed in the S rim of the summit crater about 100 m long, 10 m wide, and several tens of meters deep.

Figure 196. The new SEC3 cone at Etna lies in the former saddle between SEC and NSEC. The red circles indicate the positions of the three eruptive vents (V1, V2, and V3) that opened on 19 April 2017 on the S flank of the cone. Lava from the vents is flowing E toward the Valle del Bove in this N-looking photo taken by Mauro Coltelli on 20 April 2017. Courtesy of INGV (Bollettino settimanale sul monitoraggio vulcanico, geochimico e sismico del vulcano Etna, 17/04/2017-23/04/2017, No. 17/2017).

Figure 197. Lava flows from the summit crater of the new cone (SEC3) at Etna on 20 April 2017. Photo by Salvatore Allegra/Anadolu Agency/Getty Images/CFP, published in Globaltimes, 20 April 2017.

The next eruptive episode began late in the day on 26 April 2017, with a slow-moving lava flow that emerged from the summit vent of SEC3. The flow made it part way down the S flank before another flow from the same vent covered it and reached the base of the flank. Strombolian activity began at the summit vent during the late evening while the flow continued to spread SE toward the Valle del Bove (figure 198). Strombolian activity intensified during the early hours of 27 April and a new vent opened at the summit immediately N of the first one. At around 0220, two new eruptive fractures opened on the N flank of SEC3, from which lava flowed N toward the Valle del Leone (figure 199). At daybreak, an ash plume was visible about 1.5 km above the summit drifting E. Phreato-magmatic explosions were observed in the Valle del Leone when the northern lava flow encountered snow on the ground. Strombolian activity ceased around noon and the flows on both the N and S flanks had ceased by the following morning.

Figure 198. Lava flows down the S flank of SEC3 at Etna during the early morning of 27 April 2017, heading SE towards the Valle del Bove. Strombolian activity occurred from both of the summit vents, and an ash plume rose from the summit. Photo taken from the roof of the INGV-Osservatorio Etneo located 27 km S of the volcano. Courtesy of INGV (Attivita' dell'Etna, 20 Aprile-14 Giugno 2017).

Figure 199. Lava flows from both the N and S flanks of SEC3 at Etna on 27 April 2017. a) the two lava flows are clearly visible from the Monte Cagliato thermal camera (EMCT) in this view looking W. b) a phreato-magmatic explosion in the Valle del Leone from the lava flow encountering snow on the N side of SEC3. Courtesy of INGV (Bollettino settimanale sul monitoraggio vulcanico, geochimico e sismico del vulcano Etna, 24/04/2017 - 30/04/2017, No. 18/2017).

Activity during May-August 2017. Intense degassing with incandescence at night continued from the vent at VOR throughout April and into May 2017. At NEC, degassing continued from the large fumarole field at the bottom of the summit crater. No further lava flows erupted during May 2017, however, there were several short, high-energy tremor episodes in the area around SEC3. During May, more than 35 episodes of transient increases in tremor amplitude were recorded by INGV seismic instruments (figure 200). During 15-18 May, there were 11 episodes of Strombolian activity from the northern SEC3 summit vent, repeated at regular intervals of about every 8-9 hours. Lava fragments were ejected outside the crater rim and rolled down the flanks (figure 201). Each episode was accompanied by a sharp increase in volcanic tremor amplitude. Eight additional episodes of weak and discontinuous Strombolian activity occurred between 25 and 28 May at intervals ranging from 3 to 14 hours, each lasting about an hour, and accompanied by increased tremor amplitude. A short sequence of dense ash emissions from BN-1 on the morning of 31 May was the only ash plume reported during May.

Figure 200. During the month of May 2017, more than 35 episodes of transient increases in the amplitude of tremor were recorded by the seismic instruments at Etna. Some, but not all, of these episodes were accompanied by Strombolian activity at the N vent at the SEC3 summit. Courtesy of INGV (Attivita' dell'Etna, 20 Aprile-14 Giugno 2017).

Figure 201. The summit of the new NSEC/SEC complex at Etna on 16 May 2017 as viewed from the NW. The blue arrow indicates the eruptive vent that produced discontinuous Strombolian activity during May. Photo by M. Cantarero; courtesy of INGV (Bollettino settimanale sul monitoraggio vulcanico, geochimico e sismico del vulcano Etna, 15/05/2017-21/05/2017, No. 21/2017).

Weak and discontinuous Strombolian activity resumed at NSEC on 6 June 2017, along with a sudden increase in tremor. The activity lasted until 9 June and included four episodes of roughly one hour each. Very little material fell outside the crater rim during these events. Vigorous degassing and nighttime incandescence continued at the VOR vent during June. INGV-OE personnel inspected the summit on 23 and 29 June, and 2 July 2017. High temperatures (around 600°C) were recorded at the VOR vent on 23 June. The other fumarolic areas, especially in the fracture field between NEC and VOR, were around 250°C, cooler than when last measured on 31 August 2016. Occasional weak ash emissions began on 24 June from SEC3; they lasted for a few days and quickly dissipated near the top of the cone. They ceased late in the evening of 28 June.

In a survey by drone on 4 July 2017, INGV-OE personnel noted widespread degassing along the rim and E side of the SEC3 crater. The vent that had formed during 27 February-26 April appeared to be blocked (figure 202). During the late morning of 9 July, the vent that had formed during 26-27 April emitted a small amount of red-gray ash. The next day a small amount of ash emerged from the base of BN-1. Incandescence was frequently observed at night from the VOR vent and from the NSEC. Degassing was observed regularly throughout the month at the VOR vent, the bottom of BN-1, and NEC (figure 203).

Figure 202. Detailed view of the summit of the new SEC3 cone at Etna on 4 July 2017 taken by an INGV-OE drone. 1) eruptive vent active during 27 February-26 April; 2) eruptive vents active during 26-27 April; a) closeup of the bottom of one of the 26-27 April vents, from which a small amount of reddish-gray ash emerged on 9 July. Courtesy of INGV (Bollettino settimanale sul monitoraggio vulcanico, geochimico e sismico del vulcano Etna, 3/07/2017-9/07/2017, No. 28/2017).

Figure 203. Panoramic photos of the summit craters of Etna on 27 July 2017. VOR, seen from the northwestern edge, continued with strong degassing from the 7 August 2016 vent on the E rim; the NEC, seen from the fracture that cuts the southern rim, had modest, diffuse degassing from the fracture zone within the crater; and BN, seen from the eastern edge, had moderate degassing occurring from the vent at the base of BN-1 throughout the month. Courtesy of INGV-OE (Bollettino settimanale sul monitoraggio vulcanico, geochimico e sismico del vulcano Etna, 24/07/2017-30/07/2017, No. 31/2017).

Occasional weak, diffuse ash emissions continued during August 2017 from the bottom of BN-1. INGV-OE scientists attributed this to collapse at the base of the crater. Limited degassing was noted at NEC, but persistent degassing continued from the 7 August 2016 vent at VOR, and from a vent on the E side of NSEC in addition to a vent at the SEC3 summit (figures 204 and 205).

Figure 204. Areas of persistent degassing and fumarolic activity at Etna during August 2017. The black hatch lines outline the crater rims: BN = Bocca Nuova, which contains the NW vent (BN-1) and the SE vent (BN-2); VOR = Voragine; NEC = North East Crater; SEC = South East Crater; NSEC = New South East Crater. Yellow circles indicate the locations of the degassing mouths of VOR, BN, and both the "Cono della sella" (saddle cone, or SEC3) and the E vent at NSEC. The base map is from a 2014 DEM of the summit from INGV Aerogeophysics Laboratory - Section 2. Courtesy of INGV (Bollettino settimanale sul monitoraggio vulcanico, geochimico e sismico del vulcano Etna, 31/07/2017-06/08/2017, No. 32/2017).

Figure 205. Aerial photographs of the summit crater area of Etna taken on 16 August 2017. a) view from ENE; b) view from the SE. Weak fumarolic activity is visible from the E vent of the New South East Crater (NSEC). More intense and continuous degassing emerges from the Central Crater (VOR and BN). See figure 204 for additional label explanations. Photos by Piero Berti; courtesy of Butterfly Helicopter Services and INGV-OE (Bollettino settimanale sul monitoraggio vulcanico, geochimico e sismico del vulcano Etna, 14/08/2017-20/08/2017, No. 34/2017).

Information Contacts: Sezione di Catania - Osservatorio Etneo, Istituto Nazionale di Geofisica e Vulcanologia (INGV-OE), Sezione di Catania, Piazza Roma 2, 95123 Catania, Italy (URL: http://www.ct.ingv.it/it/); NASA Earth Observatory, EOS Project Science Office, NASA Goddard Space Flight Center, Goddard, Maryland, USA (URL: http://earthobservatory.nasa.gov/); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); Global Times, http://www.globaltimes.cn/galleries/774.html.

April 2018 (BGVN 43:04) Cite this Report

Persistent degassing from multiple vents; minor ash emissions and pyroclastic ejecta, September 2017-March 2018

Figure 206. A modified digital elevation model (DEM) of the summit area at Etna showing the major craters. The hatched black lines highlight the rims of the summit craters: BN = Bocca Nuova, which contains the NW depression (BN-1) and the SE depression (BN-2); VOR = Voragine with an active vent on its E rim that opened in August 2016; NEC = Northeast Crater; SEC = South-East Crater; NSEC = New Southeast Crater; and "Cono della Sella" or CdS, which emerged in early 2017, shown in red. The yellow dots indicate the locations of significant degassing vents at VOR, BN, and NSEC. Courtesy of INGV (Report 51/2017, Bollettino settimanale sul monitoraggio vulcanico, geochimico e sismico del vulcano Etna, 11/12/2017-17/12/2017, issue date-19/12/2017).

The most recent eruptive episode began with ash emissions from a new vent in the saddle between NSEC and SEC on 20 January 2017, followed by Strombolian activity a few days later (BGVN 42:10). Activity intensified at the end of February when the first of several lava flows emerged from this and other adjacent vents. By mid-March 2017, Strombolian activity, ash emissions, and lava flows had created a cone higher than the adjacent NSEC and SEC cones, referred to as the "Cono della Sella" (CdS) or saddle cone. An effusive episode at the end of April 2017 sent flows down both the N and S flanks of the new cone from multiple vents. Intermittent Strombolian activity and persistent fumarolic activity continued from multiple crater areas, and minor ash emissions were observed a few times through August 2017. The Osservatorio Etneo (OE), which provides weekly reports and special updates on activity, is run by the Catania Branch of Italy's Istituo Nazionale di Geofisica e Vulcanologica (INGV). This report uses information from INGV to summarize events between September 2017 and March 2018.

Although still exhibiting intermittent volcanism, activity at Etna was at low levels during September 2017-March 2018. A comparison of the thermal activity of that period with the previous interval of November 2016-August 2017 (figure 186, BGVN 42:10) demonstrates the order of magnitude decrease from the earlier period (figure 207). Persistent degassing occurred throughout this interval, often with incandescent gas and periodic ash emissions resulting from continued subsidence around crater vents and from small explosive events. Ashfall was reported once in the cities S of Etna in mid-January 2018, and a minor episode of Strombolian activity and ash emissions took place at the eastern vent of NSEC in mid-February 2018.

Figure 207. Thermal activity at Etna was substantially decreased compared to earlier in 2017 (figure 186, BGVN 42:10) as seen in this MIROVA graph that plots data for the year ending on 12 July 2018. Courtesy of MIROVA.

Activity during September-December 2017. Active degassing at the beginning of September 2017 occurred from the vent at the E rim of the Voragine crater (VOR), and from the NW vent of Bocca Nuova (BN-1) (figure 208). At the Northeast Crater (NEC) and the SE Crater (SEC)-New South East Crater (NSEC) complex, which included the new "Cono del Sella" (CdS), there was widespread degassing from the fumarolic fields located in the bottoms and walls of the craters. Minor explosive activity was reported on 19 September 2017 from BN and NSEC, and nighttime incandescence was reported from the other craters. On 20 September small sporadic ash emissions were noted from NSEC and VOR. Incandescence at night was observed at the SEC-NSEC complex for the remainder of the month, and strong degassing continued at the VOR vent.

Figure 208. Active degassing was evident at the summit craters of Etna on 24 August 2017. a) degassing from Bocca Nuova (BN). b) the active vent on the E rim of Voragine (VOR) was mostly steam. Courtesy of INGV (Report 35/2017, Bollettino settimanale sul monitoraggio vulcanico, geochimico e sismico del vulcano Etna, 21/08/2017-27/08/2017, issue date 29/08/2017).

Occasional ash emissions were observed during the second week of October 2017 from the Cono della Sella (CdS) (figure 209). A minor ash emission was also reported on 16 October from the SEC-NSEC complex. Minor emissions of brown ash were reported from BN-1 during the last week of October. In the late afternoon of 26 October, a single explosion occurred at one of the three mouths of the Cono della Sella crater. The explosion generated a short jet of incandescent material and a small ash plume that quickly dispersed.

Figure 209. An ash emission occurred on 13 October 2017 from the Cono della Sella (CdS) at Etna. These images were taken from the M. Cagliato (left) and La Montagnola (right) webcams. Intense degassing from VOR was also visible in the La Montagnola image. Courtesy of INGV (Report 42/2017, Bollettino settimanale sul monitoraggio vulcanico, geochimico e sismico del vulcano Etna, 09/10/2017-15/10/2017, issue date 17/10/2017).

Cloudy weather during November resulted in limited visibility for much of the month. A small, isolated explosion containing minor ash occurred at SEC on 14 November 2017. During the third week of November, a new pit crater appeared at the bottom of NEC that measured 70 x 50 m (figure 210), and intense degassing was observed from BN-1. Frequent small ash emissions were reported from CdS during 24-26 November. In the last week of the month, pulsating degassing from the craters could be detected during periods of limited visibility, as well as a series of explosions with ash emissions from SEC.

Figure 210. A new pit crater opened at the bottom of NEC at Etna during the third week of November 2017. A) Map of the summit crater area (DEM 2014) showing the pit crater location at the bottom of the NEC and one of the main fumaroles at the bottom (orange arrow). B) View of the bottom of NEC from the S on 23 November 2017, the orange arrow is the fumarole and the white hatched line indicates the rim of the new pit crater. C) The S flank of the NEC, showing the locations of the thermal cameras that created the images of the new pit in images D and E. Courtesy of INGV, (Report 48/2017, Bollettino settimanale sul monitoraggio vulcanico, geochimico e sismico del vulcano Etna, 20/11/2017-26/11/2017, issue date 28/11/2017).

Degassing from the summit craters persisted throughout December 2017 with intermittent incandescence observed from fumaroles at NSEC. A few ash emissions were recorded from CdS, including overnight on 14-15 December (figure 211).

Figure 211. Minor degassing, fumaroles, and incandescence were recorded at the summit craters of Etna in early December 2017. a) Degassing from BN and VOR on the morning of 13 December 2017, seen from the S. b) Image taken from the high-resolution webcam at Monte Cagliato (EMCH, E side of Etna) showing incandescence at the E vent of NSEC in the early hours of 12 December 2017. c) Puff of ash emitted by CdS on the morning of 15 December 2017, recorded by the Montagnola (EMOV) webcam. Courtesy of INGV (Report 51/2017, Bollettino settimanale sul monitoraggio vulcanico, geochimico e sismico del vulcano Etna, 11/12/2017-17/12/2017, issue date 19/12/2017).

Activity during January-March 2018. Similar activity continued throughout January 2018; a small ash emission was observed from CdS on 5 January, and a puff of brown ash emerged from NSEC the next day. Incandescence degassing also continued from the NSEC vents. During the second week of the month, 20 small explosive events were observed from the eastern vent at NSEC, although cloud cover obscured the summit for much of the time. Minor ash emissions continued from NSEC for the rest of the month, along with nighttime incandescence, especially strong from BN-1. On 22 January a modest ashfall affected the communities S of Etna including the city of Catania (27 km S); the lack of visibility prevented identification of which crater produced the ash. By the end of the month, the pit crater at the base of NEC had expanded, causing erosion of the inner E wall (figure 212). In spite of the low level of activity during this period, SO₂ emissions were occasionally recorded with satellite instruments. The most significant SO₂ plumes were measured during the last few days of January (figure 213).

Figure 212. Activity during January 2018 at Etna included strong incandescence from BN-1, numerous small explosive events from NSEC, and expansion of the pit crater at the base of NEC. The hatched black lines highlight the edge of the summit craters: BN = Bocca Nuova, including the NW depression (BN-1) and the SE depression (BN-2); VOR = Voragine; NEC = Northeast Crater; SEC = South-East Crater; NSEC = New Southeast Crater. The yellow dots indicate the positions of the degassing vents of VOR, NEC and NSEC (E vent and "Cono della Sella"). The yellow dots with a red border indicate the vents characterized by strong incandescence (BN-1) and occasional ash emissions (NSEC, E vent). Courtesy of INGV, Report 06/2018, Bollettino settimanale sul monitoraggio vulcanico, geochimico e sismico del vulcano Etna, 29/01/2018-04/02/2018, issue date, 06/02/2018).

Figure 213. Significant SO₂ plumes were measured from Etna on 29 (left) and 31 (right) January 2018 by the OMI instrument on NASA's Aura satellite. Courtesy of NASA Goddard Space Flight Center.

Two weak ash emissions occurred at NSEC during the first week of February 2018. The frequency of explosions increased during 15-16 February to 1-2 events per hour, producing moderate amounts of brown-gray ash and incandescent pyroclastic material (figure 214); heightened activity lasted for several days. The explosions were heard 20 km E and S from the summit. Faint, non-explosive emissions of gray ash were observed on the morning of 17 February 2018 from NEC (figure 215).

Figure 214. Ash and incandescent material were ejected from the E vent of NSEC at Etna during 17 February 2018. a) Ash emission from the E vent at NSEC viewed by the Tremestieri Etneo webcam from the S flank on the morning of 17 February 2018. b) Incandescent material ejected during one of the explosions from the same vent, on the evening of 17 February 2018. Photo by Michele Mammino, used by INGV with permission of the author. Courtesy of INGV (Report 08/2018, Bollettino settimanale sul monitoraggio vulcanico, geochimico e sismico del vulcano Etna, 12/02/2018-18/02/2018 (issue date 20/02/2018).

Figure 215. A weak ash emission rose from Etna's NEC at 1005 local time on 17 February 2018, as seen by the Zafferana Etnea webcam. Courtesy of INGV, Report 08/2018, Bollettino settimanale sul monitoraggio vulcanico, geochimico e sismico del vulcano Etna, 12/02/2018-18/02/2018, issue date 20/02/2018).

Degassing continued at the summit craters for the remainder of February and throughout March 2018. During an inspection by INGV on 10 March, the expansion of the pit crater at the bottom of NEC was noted, as was continuing collapses of the internal walls which produced minor ash emissions. Activity at the E vent of NSEC included a minor ash emission on 2 March 2018; occasional ejection of incandescent pyroclastic material and modest ash emissions continued throughout the month (figure 216). The ash emissions occurred at irregular intervals, varying from a few tens of minutes to a few hours, more frequently in the last days of the month.

Figure 216. Explosive activity from the vent on the E side of NSEC at Etna, taken from the Tremestieri Etneo webcam on the S flank on 8 March 2018. Ash emissions were accompanied by incandescent tephra that landed on the flanks. Photographic sequence by B. Behncke. Courtesy of INGV, Report 11/2018, Bollettino Settimanale, 05/03/2018-11/03/2018, issue date 13/03/2018).

August 2018 (BGVN 43:08) Cite this Report

Degassing continues, accompanied by intermittent ash emissions and small Strombolian explosions in June and July 2018

Etna is the tallest active volcano in continental Europe with persistent activity at multiple summit craters and vents. The active craters are Bocca Nuova and Voragine within the Central Crater, the Northeast Crater, Southeast Crater, and the New Southeast Crater (figure 217). This report summarizes activity from April to July 2018 and is based on reports by the Istituto Nazionale di Geofisica e Vulcanologia (INGV).

Figure 217. The active summit craters of Etna volcano: the Bocca Nuova and Voragine craters that occupy the older Central Crater, the Northeast Crater (Cratere di Nord-Est), Southeast Crater (Cratere di Sud-Est), and the New Southeast Crater (Nuovo Cratere di Sud-Est). The years given in parentheses indicate when the craters formed. Photo by Marco Neri, courtesy of INGV (19 July 2018 blog).

Activity through April was characterized by degassing at the summit craters (figure 218), with modest ash emissions from the New Southeast Crater and Northeast Crater in the first week, and occasional small ash emissions at the end of the month. Reduced activity dominated by degassing continued into May with modest ash emission from the Southeast and Northeast craters during the second week, and isolated ash emissions from the Northeast Crater in the second half of the month continuing into June.

Figure 218. Degassing at the Bocca Nuova crater at the summit of Etna in late April. The top image is a photograph of the crater with the location of the bottom image, which is a thermal image showing the degassing and temperature at the vent reaching over 400°C. Courtesy of INGV (Weekly report No. 18/2018 for 24 to 30 April 2018, issued on 2 May 2018).

Throughout June the activity consisted of degassing at the summit craters with isolated diffuse ash emission from Northeast Crater (figure 219). This continued through to July until low-energy Strombolian activity commenced in the Bocca Nuova (from two vents) and Northeast craters (figures 220 and 221). The Strombolian explosions were small, lasting up to several tens of seconds, and were sometimes accompanied by red-brown ash emission. The ejected material was confined to within the craters. More energetic bursts were visible from the INGV surveillance camera located in Milo.

Figure 219. Photos of isolated dilute red-brown ash emissions from the Etna Northeast Crater on the 6 and 8 June. Courtesy of INGV (Report No. 24/2018 for the period 4 to 10 June 2018, issued on 12 June 2018).

Figure 220. A sequence of thermal infrared images of a Strombolian explosion at the Etna Bocca Nuova crater on 17 July 2018. Two vents are active (A and B), with vent B ejecting lava up to a few tens of meters above the vent. The color scale on the right of the images indicates the temperature in Celsius. Images taken by Giuseppe Salerno, courtesy of INGV (24 July 2018 INGV blog).

Figure 221. Photos of Strombolian explosions at the base of the Etna Northeast Crater on 20 and 21 July 2018. The explosions occur when gas pockets burst and eject incandescent fluid lava above the vent. Photo by Michele Mammino, courtesy of INGV (24 July 2018 blog).

Information Contacts: Sezione di Catania - Osservatorio Etneo, Istituto Nazionale di Geofisica e Vulcanologia (INGV), Sezione di Catania, Piazza Roma 2, 95123 Catania, Italy (URL: http://www.ct.ingv.it/it/); Blog INGVvulcani, Istituto Nazionale di Geofisica e Vulcanologia (INGV) (URL: http://ingvvulcani.wordpress.com).

December 2018 (BGVN 43:12) Cite this Report

Lava flows emerge from NSEC in late August and late November 2018; Strombolian activity continues from multiple vents

Italy's Mount Etna on the island of Sicily has had historically recorded eruptions for the past 3,500 years and has been erupting continuously since September 2013 through at least November 2018. Lava flows, explosive eruptions with ash plumes, and Strombolian lava fountains commonly occur from its summit areas that include the Northeast Crater (NEC), the Voragine-Bocca Nuova (or Central) complex (VOR-BN), the Southeast Crater (SEC) (formed in 1978), and the New Southeast Crater (NSEC) (formed in 2011). A new crater, referred to as the "cono della sella" (saddle cone), emerged during early 2017 in the area between SEC and NSEC and has become the highest part of the SEC-NSEC complex. Activity during late 2017 and early 2018 consisted mostly of sporadic Strombolian activity with infrequent minor ash emissions from multiple vents at various summit craters. Lava flow activity resumed in late August 2018 and again in late November and is covered in this report with information provided primarily by the Osservatorio Etneo (OE), part of the Catania Branch of Italy's Istituo Nazionale di Geofisica e Vulcanologica (INGV).

After several months of low-level activity in early 2018, increases in Strombolian activity at several vents began in mid-July (BGVN 43:08). This was followed by new lava flows emerging from the saddle cone and the E vent of the NSEC complex in late August. Discontinuous low-intensity Strombolian activity and intermittent ash emissions were reported from multiple vents at various summit craters during September through November. In late November, renewed Strombolian activity and a new, small flow emerged from a small scoria cone inside the E vent of the NSEC crater and persisted through the end of the month. The MIROVA thermal anomaly correspond to ground observations of increased thermal activity at Etna beginning in mid-July, peaking in late August, and increasing again at the end of November 2018 (figure 222).

Figure 222. MIROVA thermal anomaly graph for Etna from April through early December 2018 shows the increases in thermal activity from lava flows and increased Strombolian activity in late August and late November. Courtesy of MIROVA.

Low-energy Strombolian activity resumed at both of the Bocca Nuova BN-1 vents as well as the vents in the Northeast Crater (NEC) during the second week of July 2018 and continued throughout the month. The activity from BN-1 was nearly continuous, but not always visible; occasionally, lava fragments rose 100 m and could be seen outside of the crater rim. Intermittent ash emissions accompanied the Strombolian activity. Activity at NEC was characterized by strong and prolonged explosions (up to several tens of seconds), sometimes with reddish-brown ash emissions (figure 223). Three vents on the floor of NEC continued to widen due to collapse of the inner walls. A seismic swarm on 18-19 July was located between 4 and 9 km depth.

Figure 223. Ash emissions from the Northeast Crater of Etna on a) 27 July and b) 28 July 2018 rose a few tens of meters and quickly dispersed. Left image by INGV personnel, right image by volcanology guide Francesco Ciancitto. Courtesy of INGV (Rep. 31/2018, ETNA, Bollettino Settimanale, 23/07/2018 - 29/07/2018, data emissione 31/07/2018).

During a field inspection on 30 July INGV personnel noted activity at the three vents at the bottom of Northeast Crater; the farthest west produced ash emissions, the center produced steam, and the vent under the NE crater wall produced Strombolian activity that sent ejecta as high as the crater rim. Frequent ash emissions from NEC were observed on 3, 4, and 5 August. During the first week of August 2018 Strombolian activity also continued at BN-1 (figure 224). The webcam at Montagnola (EMOH) recorded incandescence at night from Bocca Nuova.

Figure 224. Activity during the first half of August 2018 at Etna was concentrated at BN-1, the Northeast Crater (NEC), and the E vent of the New Southeast Crater (NSEC), shown in red. Courtesy of INGV (Rep. 33/2018, ETNA, Weekly Bulletin, 08/06/2018 - 12/08/2018, issue date 08/14/2018).

After several months of calm, explosive activity also resumed at the E vent of the of the New Southeast Crater, high on the E flank, in early August. An explosion in the early morning of 1 August 2018 generated a gray-brown ash plume that rose several hundred meters above the summit (figure 225). Smaller emissions occurred throughout the day, and the EMOH camera recorded sporadic Strombolian explosions at night, which continued through the first week of August.

Figure 225. After several months of calm, a resurgence of explosive activity was observed at the E vent (formed 25 November 2015) on the high E flank of the New Southeast Crater. The activity started with an explosion at 0408 UTC (= local time -2 hours), and generated a gray-brown ash plume that rose several hundred meters above the top of the volcano (a, b). In the following hours other smaller ash emissions occurred, and in the evening, the EMOH camera recorded sporadic Strombolian explosions (c). This activity continued, with fluctuations in the frequency and magnitude of the explosions, for the rest of the month (d, e, f). Courtesy of INGV (Rep. 32/2018, ETNA, Bollettino Settimanale, 30/07/2018 - 05/08/2018, data emissione 07/08/2018).

Similar activity at BN-1, NEC, and the reactivated vent at NSEC continued through the second and third weeks of August. On 16 August 2018 a new vent opened in the BN-2 area on the E side of the Voragine (inactive since December 2015) and exhibited both degassing and Strombolian activity (figure 226). During that week Strombolian activity also continued at the NEC, but activity became more sporadic at the E vent of NSEC. During the last week of August, Strombolian activity and intense degassing continued in the western sector of Bocca Nuova (BN-1). Occasionally, lapilli fragments a few centimeters in diameter were ejected onto the S rim of the crater. Strombolian activity also continued from multiple vents at the bottom of NEC. The frequency and intensity of explosions was variable and increased significantly during 22 August, ejecting coarse pyroclastic material outside the crater rim.

Figure 226. The crater floor of Bocca Nuova at Etna on 16 and 17 August 2018 with thermal (a) and visible (b) images. The incandescent areas are highlighted with colors ranging from yellow to red and white in the thermal image. BN-1 (reactivated in November 2016) is in the foreground, and vent BN-2, which re-opened on 16 August in the south-eastern sector of the Bocca Nuova, is in the back (upper right). Thermal image by Francesco Ciancitto, photograph by Marco Neri. Courtesy of INGV (L'Etna non va in vacanza: aumenta di intensità l'attività eruttiva sommitale, 23 Agosto 2018, INGV Blog).

Beginning on 23 August 2018 about 1800 UTC, activity resumed at the saddle cone located between the old cone of the Southeast Crater (SEC) and the new cone (NSEC). Strombolian activity, initially modest, quickly became more intense, producing almost continuous explosions with the launch of coarse ejecta up to a height of 100-150 m. At 1830 UTC, while Strombolian explosions of modest intensity were also taking place at the E vent of NSEC, a small lava flow emerged from the E vent and traveled a few hundred meters E towards the Valle del Bove. Shortly after 1830 UTC another lava overflow was also observed moving N from the saddle cone (figures 227 and 228).

Figure 227. Strombolian ejecta rose 100 m from the cono della sella (saddle cone) at the New Southeast Crater of Etna and lava flowed from both the E vent (left) and N from the saddle cone (right), shortly before midnight on 23 August 2018. Photo by Boris Behncke, courtesy of INGV blog 25 August 2018 (L'Etna fa gli straordinari: attività eruttiva al Nuovo Cratere di Sud-Est).

Figure 228. Map of the summit crater area (DEM 2014, Aerogeophysics Laboratory - Rome Section 2, modified). BN = Bocca Nuova; VOR = Voragine; NEC = Northeast Crater; SEC = Southeast Crater; NSEC = New Southeast Crater. The yellow dots indicate the position of the degassing vents and those in red are the vents with Strombolian activity. The map also shows the flows produced by the saddle cone and the E vent of NSEC through 27 August 2018. Courtesy of INGV (Rep. N° 35/2018, ETNA, Bollettino Settimanale, 20/08/2018 - 26/08/2018, data emissione 28/08/2018).

Strombolian explosions of moderate intensity continued throughout the night from the saddle cone. The following morning (24 August) a small lava overflow emerged from the vent and stopped after traveling a few tens of meters towards the S flank of the NSEC cone (figure 228, small orange flow within saddle, and figure 229b). The Strombolian activity was accompanied by an abundant and continuous emission of ash, whichformed a small plume that rose a few hundred meters from the vent (figure 229c). The Strombolian activity at the saddle cone decreased gradually on 25 August.

Figure 229. Eruptive activity at Etna during 23-24 August 2018. a) 23 August shortly before midnight; Strombolian activity from the saddle cone and lava flows from the E vent of the NSEC (white arrow) and from the cone of the saddle northwards (red arrow). Photo by B. Behncke taken from Fornazzo. b) 24 August, Strombolian activity and small lava overflow southward taken by the thermal camera of La Montagnola. c) 24 August, ash emitted during the Strombolian activity from the cone of the saddle, taken by the visible camera of La Montagnola. Courtesy of INGV (Rep. 35/2018, ETNA, Bollettino Settimanale, 20/08/2018 - 26/08/2018, data emissione 28/08/2018).

Strombolian activity was continuing on 27 August 2018 at NSEC, and the flow to the N into the Valle del Leone began cooling after lava stopped feeding it that evening. The same day, a new lava overflow emerged from the E vent of NSEC (figure 230) and flowed E towards the Valle del Bove for about 24 hours (figure 231).

Figure 230. Map of the summit crater area of Etna (DEM 2014, Aerogeophysics Laboratory - Rome Section 2, modified). BN = Bocca Nuova; VOR = Voragine; NEC = Northeast Crater; SEC = Southeast Crater; NSEC = New Southeast Crater. The yellow dots are degassing vents and those in red have Strombolian activity. The map also shows the flows produced by NSEC during the last two weeks of August 2018. The yellow flow was cooling by 27 August when the new red flow emerged from the E vent of NSEC and lasted for about 24 hours. Courtesy of INGV (Rep. 36/2018, ETNA, Bollettino Settimanale, 27/08/2018 - 02/09/2018, data emissione 04/09/2018).

Figure 231. A thermal image taken by Pizzi Deneri on 27 August 2018 at Etna shows the two flows on the flanks of NSEC. View is from the N. The flow labelled in red flows E from the E vent, and the other flow travels N from the Cono della sella (saddle cone) into the Valle del Leone and then moves east. Courtesy of INGV (Rep. 36/2018, ETNA, Bollettino Settimanale, 27/08/2018 - 02/09/2018, data emissione 04/09/2018).

Discontinuous Strombolian activity continued from NSEC after the effusive activity ended in late August. Several loud explosions from NSEC were reported by people living near the E flank of Etna during the first week of September. Strombolian activity, modest ash emissions, and significant gas emissions were also produced by BN-1; BN-2 exhibited only continuous degassing activity. Explosive activity declined during the second week of September. Discontinuous low-intensity Strombolian activity and intermittent ash emissions from Bocca Nuova, New Southeast Crater, and Northeast Crater characterized activity for the remainder of September. During the last week of the month, NEC produced frequent gray-brown ash emissions from a vent located in the western part of the crater floor, and included jets of ash, blocks, and volcanic bombs (figure 232).

Figure 232. Ash emissions from Etna's Northeast Crater in late September 2018. The four top images are explosions from a vent at the bottom of NEC on 24 September 2018; the bottom image is one of the many ash emissions observed on 30 September. Courtesy of INGV (Rep. N° 40/2018, ETNA, Bollettino Settimanale, 24/09/2018 - 30/09/2018, data emissione 02/10/2018).

Discontinuous low-intensity Strombolian activity and intermittent ash emissions from the Bocca Nuova, the New Southeast Crater, and Northeast Crater characterized activity during all of October 2018. Two vents remained active at the bottom of Bocca Nuova (BN-1). During a visit on 16 October, INGV-OE geologists noted that the northernmost vent produced nearly continuous Strombolian activity with frequent explosions; occasionally fragments exceeded the crater rim in height but still fell within the crater. The southernmost vent, on the crater floor about 130 m from the edge, was characterized by explosive activity that produced mainly spattering which covered both the crater floor and walls (figure 233). On 25 October the webcam at Bronte recorded an ash emission from Bocca Nuova that resulted from three closely-spaced explosions. The ash was red and dispersed rapidly to the S causing ashfall near Torre del Filosofo and Rifugio Sapienza.

Figure 233. Inside the Bocca Nuova BN-1 crater at Etna on 16 October 2018, two vents were active. The northernmost vent (yellow arrow) had Strombolian activity; the southernmost vent, visible on the right, produced mostly "spattering". Photo by M. Coltelli, courtesy of INGV (Rep. N° 43/2018, ETNA, Bollettino Settimanale, 15/10/2018 - 21/10/2018, data emissione 23/10/2018).

Strombolian activity at NSEC gradually intensified during the first week of November 2018 and was sometimes accompanied by ash emissions that rapidly dispersed, falling mainly near the vent and in the Valle del Bove to the E. Audible explosions from the activity were heard in Zafferana Etnea on the E flank. Several clear views of the summit and details of the active vents were well exposed during an overflight on a clear 9 November day (figure 234).

Figure 234. An aerial view of the Etna summit craters taken on a clear 9 November 2018 day with the assistance of the 2nd Coast Guard Core of Catania. View is to the NW. BN = Bocca Nuova; VOR = Voragine; NEC = Northeast Crater; SEC = Southeast Crater; NSEC = New Southeast Crater. Courtesy of INGV (Rep. N° 46/2018, ETNA, Bollettino Settimanale, 05/11/2018 - 11/11/2018, data emissione 13/11/2018).

Three vents were visible at BN-1 during the 9 November 2018 overflight (figure 235); continuous Strombolian activity occurred at vent 1, whose fallout of pyroclastic debris remained within the crater; discontinuous Strombolian activity was observed at vent 2 associated with weak, pulsing ash emissions; only degassing activities were observed at vent 3. At BN-2, intense degassing accompanied discontinuous Strombolian activity that was associated with weak pulsating ash emissions, and several high temperature gas emission points. Scientists also observed a collapse on a portion of the northern inner wall of BN-1 from the explosion on 25 October.

Figure 235. Aerial view of Bocca Nuova (BN) and Voragine (VOR) at Etna on 9 November 2018 taken with helicopter support of the 2nd Coast Guard Core of Catania. The yellow hatched line indicates the wall of the area that collapsed on 25 October 2018. Inset a) thermal image of Bocca Nuova showing the structure of the three eruptive vents within BN-1 and the eruptive vent within the BN-2. Courtesy of INGV (Rep. N° 46/2018, ETNA, Bollettino Settimanale, 05/11/2018 - 11/11/2018, data emissione 13/11/2018).

Modest outgassing continued at Voragine (VOR) from the 7 August 2016 vent near the rim during November. At NEC, continuous and intense Strombolian activity from the crater floor caused pyroclastic ejecta to land outside the crater rim (figure 236). At the NSEC complex, high-temperature anomalies were visible at the NW crater edge, and the E vent of NSEC had a small scoria cone that produced discontinuous Strombolian explosions and minor ash emissions (figure 237).

Figure 236. Aerial view of Voragine (VOR) and the Northeast Crater (NEC) at Etna taken on 9 November 2018 with helicopter support of the 2nd Coast Guard Core of Catania. The 7 August 2016 vent at VOR had a vigorous steam emission (yellow arrow). Inset a) thermal image showed the Strombolian activity in the bottom of NEC. Courtesy of INGV (Rep. N° 46/2018, ETNA, Bollettino Settimanale, 05/11/2018 - 11/11/2018, data emissione 13/11/2018).

Figure 237. Thermal activity was evident in several places at the SEC-NSEC complex at Etna during the 9 November 2018 overflight with the helicopter of the 2nd Coast Guard Core of Catania (inset a, upper image). The small scoria cone (conetto di scorie) was visible inside the E vent (Bocca orientale) of the New Southeast Crater, seen from the East on 9 November (lower image). Upper image from INGV weekly (Rep. N° 46/2018, ETNA, Bollettino Settimanale, 05/11/2018 - 11/11/2018, data emissione 13/11/2018), lower image by Stefano Branca (INGV-Osservatorio Etneo) from INGV blog (Piccoli coni crescono: aggiornamento sullo stato di attività dell'Etna al 7 dicembre 2018).

A seismic swarm with over 40 events affected the W flank of Etna on 20 November 2018; the hypocenters were located between 15 and 27 km depth. A small lava flow also emerged on 20 November from the scoria cone inside the E vent at NSEC. The flow lasted for a few hours and remained inside the E vent. A new flow from the same scoria cone at the NSEC east vent appeared on 26 November accompanied by continued Strombolian activity. The flow remained high on the E flank at an elevation of about 3,200 m. Flow activity continued into the first days of December with frequent incandescent blocks moving down the NSEC E flank (figure 238). Elsewhere at Etna, Strombolian activity continued accompanied by sporadic and modest ash emissions from Bocca Nuova, the New Southeast Crater and the Northeast Crater through the end of November (figure 239).

Figure 238. Strombolian activity and emission of a small lava flow from the E vent of the New Southeast Crater was seen from the E at dawn on 29 November 2018. The lava flow was very short, but the detachment and rolling of numerous incandescent blocks from the front and sides of the flow created the impression that the flow reached the base of the New Southeast Crater cone. The scoria cone inside the E vent grew considerably compared to its size observed on 9 November (figure 237). Photo by Giò Giusa. Courtesy of INGV, INGV Blog (Piccoli coni crescono: aggiornamento sullo stato di attività dell'Etna al 7 dicembre 2018).

Figure 239. Incandescence from Strombolian activity was visible inside the NSEC (right) and BN (left) craters at Etna on 22 November 2018 as viewed from Tremestieri Etneo. Photo by B. Behncke, courtesy of INGV (Rep. N° 48/2018, ETNA, Bollettino Settimanale, 19/11/2018 - 25/11/2018, data emissione 27/11/2018).

April 2019 (BGVN 44:04) Cite this Report

Lava flows from NSEC scoria cone and SE flank fissure in December 2018; ash emissions through March 2019

Italy's Mount Etna on the island of Sicily has had historically recorded eruptions for the past 3,500 years and has been erupting continuously since September 2013 through at least March 2019. Lava flows, explosive eruptions with ash plumes, and Strombolian lava fountains commonly occur from its summit areas that include the Northeast Crater (NEC), the Voragine-Bocca Nuova (or Central) complex (VOR-BN), the Southeast Crater (SEC, formed in 1978), and the New Southeast Crater (NSEC, formed in 2011). A new crater, referred to as the "cono della sella" (saddle cone), emerged during early 2017 in the area between SEC and NSEC and has become the highest part of the SEC-NSEC complex. After several months of low-level activity in early 2018, increases in Strombolian activity at several vents began in mid-July (BGVN 43:08). This was followed by new lava flows emerging from the saddle cone and the E vent of the NSEC complex in late August and discontinuous Strombolian activity and intermittent ash emissions through November 2018 (BGVN 43:12). An eruption from a new fissure produced a lava flow into the Valle del Bove in late December 2018 and is covered in this report along with activity through March 2019 that included frequent ash emissions. Information is provided primarily by the Osservatorio Etneo (OE), part of the Catania Branch of Italy's Istituo Nazionale di Geofisica e Vulcanologica (INGV).

For the first three weeks of December 2018, Strombolian activity and ash emissions continued from the summit vents. A series of small flows from multiple vents near the scoria cone inside NSEC formed a small flow field on the E flank mid-month. A lateral eruption from a fissure on the SE flank of NSEC opened on 24 December and produced a series of flows that traveled E into the Valle del Bove for three days. Sporadic ash emissions, some with dense plumes and significant SO₂ emissions, were typical throughout January and February 2019. Activity declined significantly during March 2019 to minor ash emissions and ongoing outgassing from the summit vents. The MIROVA plot of thermal energy recorded the increased heat from the lava flows during December 2018, along with minor pulses from the ash emissions and Strombolian activity in January and February (figure 240).

Figure 240. The Etna MIROVA thermal anomaly data for 5 July 2018 through March 2019 showed a spike in thermal activity from lava flows and increased Strombolian activity in late August and during December 2018. Courtesy of MIROVA.

Activity during December 2018. Strombolian activity, with modest ash emissions, continued from the Bocca Nuova, NSEC, and NEC during the first three weeks of December. Lava flowed from the scoria cone located within the E vent of NSEC and was associated with incandescent blocks rolling down the E flank of NSEC. Variable Strombolian activity at the scoria cone beginning on 4 December produced continuous overlapping small flows from several vents near the scoria cone for two weeks (figure 241). Intermittent explosions lasted 5-10 minutes with similar length pauses; activity increased on 16 December with near-continuous lava effusion. Several small flows traveled NE, E, and SE down the E flank of NSEC during the second and third weeks of the month (figure 242). A few flows reached the base of the cone at 2,900 m elevation and were almost a kilometer in length. Small collapses of portions of the lava field also produced minor plumes of ash.

Figure 241. Map of the summit crater area at Etna (DEM 2014). Black hatch lines outline the edge of the summit craters: BN = Bocca Nuova, with the north-western depression (BN-1) and the south-eastern depression (BN-2); VOR = Voragine; NEC = Northeast Crater; SEC = Southeast Crater; NSEC = New Southeast Crater. Yellow circles are degassing vents, and red circles are vents with Strombolian activity and/or ash emissions. The cooling lava field from the E vent scoria cone at NSEC is shown in yellow; the red flows were active on 17 December 2018. Courtesy of INGV (Report 51/2018, ETNA, Bollettino Settimanale, 10/12/2018 - 16/12/2018, data emissione 18/12/2018).

Figure 242. The scoria cone inside the E vent of NSEC at Etna produced multiple small lava flows and Strombolian explosions for most of the first half of December 2018. (a) Strombolian activity at the scoria cone inside the E vent of the New Southeast Crater, seen from Milo (on Etna's eastern slope) on 11 December 2018. (b) Summit area of Etna seen from the south on 11 December 2018. (c) Eastern flank of the New South-East Crater seen from Fornazzo (eastern slope of Etna), with Strombolian activity and lava flows on 16 December 2018. (d) Active lava flows seen from Zafferana (eastern slope of Etna) on 16 December 2018. Courtesy of INGV (Report 51/2018, ETNA, Bollettino Settimanale, 10/12/2018 - 16/12/2018, data emissione 18/12/2018).

A lateral eruption and intense seismic swarm began on 24 December 2018 from a nearly 2-km-long fissure trending NNW-SSE on the SE flank of NSEC; it produced a flow into the Valle del Bove and covered about 1 km² (figures 243). The other summit craters produced intense Strombolian activity and abundant ash emissions during 24-27 December. Beginning around 0800 local time on 24 December, degassing intensity from the summit craters increased significantly. In the following hours, intermittent reddish-gray ash emissions rose from Bocca Nuova and NEC becoming continuous by late morning. Shortly after noon, an eruptive fissure opened up at the southeastern base of NSEC, releasing intense Strombolian activity which rapidly formed a dense plume of dark ash. A second smaller fissure located between NSEC and NEC also opened at the same time and produced weaker Strombolian activity that lasted a few tens of minutes. Over the following two hours, the main fissure spread SE, crossing over the western edge of the Valle del Bove and reaching down to 2,400 m elevation. Continuous Strombolian activity of variable intensity occurred at NEC and Bocca Nuova. The ash cloud created by the multiple eruptive vents generated a dense plume that drifted SE, producing ashfall mainly in the area around Zafferana Etnea and Santa Venerina (figure 244).

Figure 243. Preliminary map of the lava flows and scoria cones at Etna active during the eruption of 24-27 December 2018. The topographic base used was provided by TECNOLAB of the INGV Catania Section Observatory Etneo, Laboratory for Technological Advances in Volcano Geophysics. The abbreviations at the top left identify the various summit craters (NEC = North-East Crater, VOR = Voragine, BN = Bocca Nuova, SEC = South-East Crater, NSEC = New South-East Crater). Courtesy of INGV (Report 01/2019, ETNA, Bollettino Settimanale, 24/12/2018 - 30/12/2018, data emissione 01/01/2019).

Figure 244. Eruptive activity from the fissure at Etna that opened on 24 December 2018 included multiple flows, Strombolian explosions, and a significant ash plume that caused ashfall in nearby communities. Top left: The eruptive fissure opened near the edge of the western wall of the Valle del Bove. Top right: An ash and steam plume produced by the opening of the fissure, taken from the south. Bottom left: Ash fall on a sidewalk in Zafferana Etnea. Bottom right: Multiple lava flows were fed by an eruptive fissure that opened along the western wall of the Valle del Bove. Images taken on 24 December by B. Behncke. Courtesy of INGV (25 dicembre 2018, Redazione INGV Vulcani, L'eruzione laterale etnea iniziata il 24 dicembre 2018).

As the fissure opened it fed several flows that descended the W face of the Valle del Bove (figure 245), past Serra Giannicola Grande, merged into a single flow at the base of the wall, and continued E across the valley floor. Ash emissions decreased significantly from Bocca Nuova and NEC after 1430 on 24 December. By 1800 the fissure was active mainly at the lower end where it continued to feed the flow in the Valle del Bove with strong Strombolian activity and abundant ash emissions. Around 1830 intense Strombolian activity resumed at Bocca Nuova along with abundant ash emissions which gradually decreased overnight. Effusive activity from the fissure continued through 26 December when it decreased significantly; new lava feeding the flow ended on 27 December, but the flow front continued to move slowly (figure 246). Degassing continued at Bocca Nuova, forming a dilute ash plume that drifted hundreds of km S before dissipating. A persistent SO₂ plume was measured with satellite instruments drifting SSE during 25-30 December while the eruptive fissure was active (figure 247).

Figure 245. Visual and thermal images of the 24-27 December 2018 fissure vent at Etna taken on 26 December 2018. (a) The eruptive fissure (yellow arrows) opened on 24 December 2018 along the W wall of the Valle del Bove and sent fresh lava down the wall (black areas), the yellow dashed rectangles indicate the areas shown with thermal images in c and d. (b) The crew that carried out the overflight on 26 December, using the helicopter of the 2nd Coast Guard Air Force in Catania. (c) and (d) are thermal camera images of the eruptive fissure that highlight the flows moving down the W wall of Valle del Bove. Visible image photo by Marco Neri. Thermal images by Stefano Branca. Courtesy of INGV (Report 01/2019, ETNA, Bollettino Settimanale, 24/12/2018 - 30/12/2018, data emissione 01/01/2019).

Figure 246. The flow from the fissure eruption at Etna traveled past Serra Giannicola Grande and E into the Valle del Bove during 24-27 December 2018. By the time of this image at 1600 on 27 December, the lava flows were no longer being fed with new material and were almost stationary within the Valle del Bove. Photo by Marco Neri, courtesy of INGV (Report 01/2019, ETNA, Bollettino Settimanale, 24/12/2018 - 30/12/2018, data emissione 01/01/2019).

Figure 247. The OMPS instrument on the Suomi NPP satellite measured significant SO₂ plumes from Etna during the December eruptive episode, shown here by data on (clockwise from top left) 25, 27, 29, and 30 December 2018. The SO₂ plumes on these days all drifted SSE from Etna. Courtesy of NASA Goddard Space Flight Center.

A significant increase in the release of seismic strain and frequency of earthquakes began around 0830 on 24 December 2018. Around 300 events occurred during the first three hours of increased seismicity which continued throughout the week, with over 2,000 events recorded in different areas around Etna. The initial swarm was located in the summit area near the fissure with events located 0-3 km below sea level; subsequent seismicity was located in the Valle del Bove and included multiple earthquakes with magnitudes greater than M 4.0. The E and SW slopes of the volcano were also affected by seismic events. The largest earthquake (M 4.8) was recorded on 26 December at 0319 local time, located about 1 km below sea level between the towns of Fleri and Pennisi on the Faglia Fiandaca fault. It was widely felt in many urban centers and caused damage in some areas. INGV noted that it was likely not generated by movement of magmatic material in the epicentral area.

Activity during January 2019. No lava flow activity was reported in January, but sporadic ash emissions and weak Strombolian activity persisted at NEC and Bocca Nuova (figure 248); occasional nighttime incandescent bursts were seen from Voragine. During one of these ash-emission episodes, on the evening of 18 January, fine ashfall was reported on the SE flank in the towns of Zafferana Etnea and Santa Venerina. Slight increases in volcanic tremor amplitude accompanied incandescent flashes from Voragine crater on the evenings of 16 and 18 January and in the early morning of 21 January (figure 249). On 19 January gas emissions and explosions were reported from a new vent near the NE edge of VOR, about 40 m NW from the 7 August 2016 vent (figure 250).

Figure 248. Strong degassing from the summit craters at Etna was accompanied by ash emissions from NEC on 16 (a) and 19 January 2019 (b). The images were taken with the high-resolution webcam at Monte Cagliato (located E of Etna). Courtesy of INGV (Report 04/2019, ETNA, Bollettino Settimanale, 14/01/2019 - 20/01/2019, data emissione 22/01/2019).

Figure 249. Episodes of strong incandescence appeared at Etna's Voragine crater at 1710 UTC on 16 January (a), at 1143 UTC on 18 January (b), and at 0307 on 21 January (c). Photo (a) was taken from Tremestieri Etneo (south side of Etna), (b) and (c) were recorded by the high resolution camera in Monte Cagliato (eastern slope of Etna). Courtesy of INGV (Report 04/2019, ETNA, Bollettino Settimanale, 14/01/2019 - 20/01/2019, data emissione 22/01/2019).

Figure 250. A newly opened vent under the NE rim of the Voragine crater at Etna was observed on 19 January 2019. Behind it on the right, about 40 m SE, is the 7 August 2016 vent. Video taken by Prof. Carmelo Ferlito, Department of Biological, Geological and Environmental Sciences of the University of Catania. Courtesy of INGV (Report 04/2019, ETNA, Bollettino Settimanale, 14/01/2019 - 20/01/2019, data emissione 22/01/2019).

Newly available higher resolution SO₂ data from the TROPOMI Tropospheric Monitoring Instrument on board the Copernicus Sentinel-5 Precursor (S5P) satellite showed persistent SO₂ plumes from Etna that drifted significant distances in multiple directions before dissipating for much of the month. The strongest plumes were recorded during 16-22 January 2019 (figure 251).

Figure 251. Sulfur dioxide plumes were recorded from Etna during most days in January 2019 from the TROPOMI Tropospheric Monitoring Instrument on the Copernicus S5P satellite. The densest plumes were recorded during 16-22 January; plumes from 18, 19, 20 and 21 January 2019 are shown here. Courtesy of NASA Goddard Space Flight Center.

Ash emissions intensified during the last week of January. During the morning of 23 January 2019 a dense ash plume drifted ENE from NEC, producing ashfall on the E flank of the volcano as far as the coast, including in Giarre (figure 252). Discontinuous ash emissions were reported from Bocca Nuova on 25 January; the following morning ash emissions intensified again from NEC and drifted S, producing ashfall in the S flank as far as Catania (figure 253). Emissions persisted until sometime during the night of 26-27 January. The ashfall from 22-23 and 26 January were analyzed by INGV personnel; the components were 95-97% lithic fragments and crystals with only 3-5% juvenile material. An ash plume from Bocca Nuova on 28 January drifted E and produced ashfall in the Valle del Bove. Ash emission decreased from Bocca Nuova on 29-30 January; only dilute ash was observed from NEC during the last few days of the month.

Figure 252. Dense ash emissions during the morning of 23 January 2019 at Etna were observed (a) from the Catania camera CUAD (ECV), (b) from the Catania CUAD high resolution camera (ECVH), (c) from the area stop at Linera on the A18 Messina-Catania motorway (photo B. Behncke), and (d) from the hamlet of Pisano, near Zafferana Etnea, on the SE slope of the volcano (photo B. Behncke). Courtesy of INGV (Report 05/2019; ETNA, Bollettino Settimanale, 21/01/2019 - 27/01/2019, data emissione 29/01/2019).

Figure 253. Ash emissions covered the snow on the S flank of Etna on 26 January 2019. Photo was taken from the SS 121 at the Adrano junction, on the SW flank of the volcano. Photo by R. Corsaro, courtesy of INGV (Report 05/2019; ETNA, Bollettino Settimanale, 21/01/2019 - 27/01/2019 ,data emissione 29/01/2019).

Activity during February 2019. Typical degassing and discontinuous explosive activity from the summit characterized Etna during February. An explosion was observed at NEC at 0230 UTC on 2 February which initially produced a dense ash plume that drifted NE, producing ashfall in the summit area and the Piano Provenzana. Ash emission decreased throughout the day. Repeated ash emissions were visible beginning in the afternoon of 6 February from NEC after several days of cloudy weather. Continuous ash emissions were observed overnight on 7-8 February, producing a dilute plume that drifted S then SE. A similar dilute ash emission was observed on 9 February; the plume drifted SW. Analysis of the ash by INGV indicated a similar composition to the samples measured two weeks prior. Webcams captured numerous pulsating ash emissions from NEC in mid-February, many of which produced substantial SO₂ plumes (figure 254). Emissions increased in intensity and frequency and were nearly continuous during most of the third week, with plumes drifting W, S, and SE resulting in ashfall in those directions, and also led to temporary air space closures in Catania and Comiso (figures 255 and 256). Also during the third week, Strombolian activity took place at BN-1, while pulsating degassing was observed at BN-2. Incandescent degassing continued at the vent located on the N edge of Voragine. Irregular ash emissions that rapidly dispersed near the summit were produced by BN on 26 and 27 February.

Figure 254. Substantial SO₂ plumes accompanied ash emissions from Etna during many days in February 2019. The largest plumes were captured with the TROPOMI instrument on the Sentinel-5P satellite on 19, 20, 21, and 22 February. Courtesy of NASA Goddard Space Flight Center.

Figure 255. Ash emission from Etna's North-East Crater (NEC) on the morning of 18 February 2019 was captured by the INGV-OE webcam in Milo. The different colored lines roughly indicate the topographic profiles observable from that position of the various summit craters of Etna: NSEC = New South-East Crater; BN = Bocca Nuova; VOR = Voragine. Courtesy of INGV (Report 09/2019, ETNA, Bollettino Settimanale, 18/02/2019 - 24/02/2019, data emissione 26/02/2019).

Figure 256. An ash emission drifted W from Etna's NEC on 19 February 2019 as viewed from Tremestieri Etneo, located 20 km S of the volcano. Photo by Boris Behncke, courtesy of INGV-OE (Report 09/2019, ETNA, Bollettino Settimanale, 18/02/2019 - 24/02/2019, data emissione 26/02/2019).

Activity during March 2019. Discontinuous and moderate outgassing characterized activity at all the summit vents of Etna throughout March 2018 after an ash plume from Bocca Nuova on 2 March reached 4 km above the crater. The ash plume was accompanied by seismic activity that INGV concluded was likely related to an intra-crater collapse. The discontinuous degassing was interrupted on 16 March by a single small emission of brown ash from Bocca Nuova which rapidly dissipated (figure 257). During a site visit on 30 March, INGV personnel noted pulsating degassing with apparent temperatures above 250°C from the new vent formed in mid-January at the E rim of Voragine (figure 258). At NEC, low-temperature pulsating degassing was occurring at the vent at the bottom of the crater and from fumaroles along the inner walls (figure 259).

Figure 257. A small ash emission from the BN crater on 16 March 2019 was recorded by the high-resolution webcams in Monte Cagliato, on the eastern slope of Etna (a) and in Bronte, on the west side (b). Courtesy of INGV (Report 12/2019, ETNA, Bollettino Settimanale, 11/03/2019 - 17/03/2019, data emissione 19/03/2019).

Figure 258. Degassing continued at the vents along the E edge of Voragine crater at Etna on 30 March 2019, producing temperatures in excess of 250°C. In the background is the NE Crater (NEC) whose southern edge was affected by modest collapses in March 2019. Courtesy of INGV (Report 14/2019, ETNA, Bollettino Settimanale, 25/03/2019 - 31/03/2019, data emissione 02/04/2019).

Figure 259. Degassing continued from the vents located on the bottom of the NE Crater at Etna on 30 March 2019 as seen from the eastern edge with visual and thermal images. Courtesy of INGV (Report 14/2019, ETNA, Bollettino Settimanale, 25/03/2019 - 31/03/2019, (data emissione 02/04/2019).

Information Contacts: Sezione di Catania - Osservatorio Etneo, Istituto Nazionale di Geofisica e Vulcanologia (INGV), Sezione di Catania, Piazza Roma 2, 95123 Catania, Italy (URL: http://www.ct.ingv.it/it/ ); Blog INGVvulcani, Istituto Nazionale di Geofisica e Vulcanologia (INGV); (URL: http://ingvvulcani.wordpress.com); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); Global Sulfur Dioxide Monitoring Page, Atmospheric Chemistry and Dynamics Laboratory, NASA Goddard Space Flight Center (NASA/GSFC), 8800 Greenbelt Road, Goddard, Maryland, USA (URL: https://so2.gsfc.nasa.gov/).

October 2019 (BGVN 44:10) Cite this Report

Five lava flows and numerous ash plumes and Strombolian explosions, April-September 2019

Italy's Mount Etna on the island of Sicily has had historically recorded eruptions for the past 3,500 years and has been erupting continuously since September 2013 through at least September 2019. Lava flows, explosive eruptions with ash plumes, and Strombolian lava fountains commonly occur from its summit areas that include the Northeast Crater (NEC), the Voragine-Bocca Nuova (or Central) complex (VOR-BN), the Southeast Crater (SEC, formed in 1978), and the New Southeast Crater (NSEC, formed in 2011). The newest crater, referred to as the "cono della sella" (saddle cone), emerged during early 2017 in the area between SEC and NSEC. Varying activity that included several lava flows, Strombolian activity, and numerous ash plumes from most of the active summit vents and several flank fissures occurred during April-September 2019, the period covered in this report, with information provided primarily by the Osservatorio Etneo (OE), part of the Catania Branch of Italy's Istituo Nazionale di Geofisica e Vulcanologica (INGV).

Degassing of variable intensity was typical activity from all the vents at Etna during much of April 2019. Intermittent ash emission and Strombolian activity occurred at Bocca Nuova, especially during the last week. Minor ash emissions were reported from NEC and NSEC the last week as well. Most of the activity at the summit during May 2019 was focused around the New South East Crater (NSEC); repeated Strombolian activity was witnessed from the E vent near the summit throughout the month. Beginning on 30 May, two fissures opened on the N and SE flanks of NSEC and produced lava flows that traveled E and SE across the W wall of the Valle del Bove. The flows ceased during the first week of June; activity for the rest of that month consisted of intermittent explosions with small ash plumes from Voragine and Bocca Nuova. Discontinuous Strombolian explosions and isolated ash emissions from NEC, NSEC, and Bocca Nuova characterized activity during the first half of July 2019; the explosions intensified at NSEC later in the month. A lava flow emerged from the lower NE flank of NSEC on 18 July that lasted for several days. Explosions produced substantial ash plumes from the NSEC summit crater, causing ashfall nearby, and a new flow emerged from a fissure on the S flank of NSEC on 27 July.

Explosions with intermittent ash emissions during August 2019 were focused primarily on the North East Crater (NEC), with occasional ash emissions from Bocca Nuova. These continued into early September. Activity increased to include Strombolian explosions with the ash emissions at NEC, Bocca Nuova, and Voragine where a scoria cone formed deep within the crater from continued Strombolian activity. A lava flow emerged from the base of the scoria cone on 18 September and was active for about four days, sending branches of lava into multiple areas of the adjacent Bocca Nuova crater. Ash emissions at NEC continued during the end of the month. The multiple episodes of varying activity during the period were reflected in the MIROVA thermal energy data; spikes of thermal activity that corresponded to periods of lava effusion were apparent late May-early June, multiple times in July, and during the second half of September (figure 260).

Figure 260. The multiple episodes of varying activity at Etna from 11 December 2018 through September 2019 were reflected in the MIROVA thermal energy data; spikes of thermal activity were apparent in late April, late May-early June, multiple times in July, and during the second half of September. The largest energy spikes correlated with lava flows. Courtesy of MIROVA.

Activity during April-May 2019. During a site visit to the summit on 1 April scientists from INGV noted weak degassing from both pit craters, BN-1 and BN-2, within Bocca Nuova (BN); the Voragine (VOR) and North East Crater (NEC) were emitting abundant steam and gas emissions. The New Southeast Crater (NSEC) also had significant fumarolic activity concentrated primarily on the crater rim along with gas plumes visible from both the E vent and the 24 December 2018 flank fissure (figure 261). A brief episode of ash emission was observed from BN on the morning of 8 April. Persistent pulsating flashes of incandescence were noted at the E vent of NSEC during the second week. A new vent was observed in the inner wall of the Voragine crater during an inspection on 19 April, located immediately below the vent which formed on 12 January 2019 (figure 262). During the last week of April there were ten episodes of ash emission from BN, two from NEC, and one produced by the E vent at NSEC. Strombolian activity was observed on the morning of 28 April at BN-1, and persistent incandescence was visible from the E vent of NSEC. Early on 30 April both BN-1 and BN-2 were producing explosions every few seconds. Coarse ejecta (lapilli and bombs) rose higher than the crater rim; most fell back within the crater, but some material was observed on the rim the following day.

Figure 261. During a site visit to the summit of Etna on 1 April 2019 scientists from INGV noted weak degassing from both pit craters, BN-1 and BN-2, within Bocca Nuova (BN); Voragine (VOR) and North East Crater (NEC) were emitting abundant steam and gas emissions, and the New Southeast Crater (NSEC) also had significant fumarolic activity concentrated primarily on the crater rim along with gas plumes visible from both the E vent (bocca orientale) and the 24 December 2018 flank fissure. Courtesy of INGV, photos by Laboratorio di Cartografia FlyeEye Team (Report 15/2019, ETNA, Bollettino Settimanale, 01/04/2019 - 07/04/2019, data emissione 09/04/2019).

Figure 262. A new vent was observed at the W rim of Etna's Voragine crater on 19 April 2019. INGV scientists concluded that it likely formed during 17-18 April. It was located immediately below a pit crater that opened on 12 January 2019. Inset shows thermal image of the vents. Courtesy of INGV (Report 17/2019, ETNA, Bollettino Settimanale, 15/04/2019 - 21/04/2019, data emissione 24/04/2019).

Activity at the summit during May 2019 was focused around the New South East Crater (NSEC). Discontinuous Strombolian activity was observed at the E vent of NSEC early on 2 May accompanied by ash emissions from the summit vent that rose about 1,000 m (figure 263). Explosion frequency increased beginning on 5 May with weak and discontinuous ash emissions reported from the NSEC summit for the next several days; ash emissions were also observed from the Saddle vent and the NSEC E vent during 6-8 May. In addition to ash emissions and Strombolian activity continuing from both the summit and E vents at NSEC during the third and fourth weeks, overnight on 17-18 May several larger Strombolian explosions sent pyroclastic ejecta tens of meters above the crater rim (figure 264). The explosion intervals ranged from a few minutes to a few hours. The new vent that had formed at Voragine in mid-April coalesced with the 12 January vent during the second week of May; dilute ash was observed from the BN-1 vent on 23 May.

Figure 263. Strombolian activity at the E vent of NSEC at Etna was accompanied by ash emission on 2 May 2019. Left image is from the thermal camera at La Montagnola and the right image is from Tremestieri Etneo, taken by B. Behncke. Coutesy of INGV (Report 19/2019, ETNA, Bollettino Settimanale, 29/04/2019 - 05/05/2019, data emissione 07/05/2019).

Figure 264. Strombolian activity sent ejecta from a vent at Etna's NSEC crater on 14 May 2019 (a) and was captured by the Monte Cagliato thermal camera. Ash emission from the same vent was also visible that day (b) and on 17 May (c). Strombolian explosions from the E Vent of NSEC on 17 May (d) were captured by the EMOH (Montagnola) webcam. Courtesy of INGV (Report 21/2019, ETNA, Bollettino Settimanale, 13/05/2019 - 19/05/2019, data emissione 21/05/2019).

A fissure opened at the base of the N flank of NSEC shortly after midnight on 30 May 2019 at an elevation of about 3,150 m (figure 265). It produced mild explosive activity and a lava flow that spread towards the W wall of the Valle del Bove. By 0800 UTC the flow had reached an elevation of 2,050 m. A second fissure opened at 0335 the same morning at the base of the SE flank of NSEC at an elevation of 3,050 m. The lava flowed along the W wall of the Valle del Bove towards Serra Giannicola Grande and had reached an elevation of 2,260 m by 0815. Strong winds dispersed ash emissions from the fissures to the NE for much of the day; ashfall occurred in Linguaglossa (figure 266). The Toulouse VAAC reported an ash plume drifting ENE at 3.9 km altitude on 30 May. Samples of the ash that were collected and analyzed were shown to be about 70% lithic clasts, 25% crystals, and about 5% juvenile material. It became clear the next day that two vents along the SE-flank fissure initially produced separate flows that coalesced into a single flow which expanded along the W wall of Valle del Bove. By 0830 on 31 May that flow had reached an elevation of 1,700 m at the base of Serra Giannicola Grande. The fissure at the base of the N flank continued to propagate along the W wall of Valle del Bove also, and had reached an elevation of 2,050 near Monte Simone by 1030 on 31 May (figure 267). When the new eruptive activity began on 29 May, inclinometers measured slight but prolonged deflation of the volcano.

Figure 265. Two fissures opened at Etna during the early morning of 30 May 2019. One started from the base of the N flank of the NSEC/SEC complex and flowed E towards the Valle del Bove, and a second fissure with two vents opened on the SE flank of NSEC and flowed SE towards Serra Giannicola Grande. Mapping of the lava flows were done with drones, using the Sentinel 2 satellite images of 30 May and thermal images from 2 June taken at the Schiena dell'Asino. Courtesy of INGV (Report 23/2019, ETNA, Bollettino Settimanale, 27/05/2019 - 02/06/2019, data emissione 04/06/2019).

Figure 266. Lava flows broke out at Etna on both the N and SE flanks of NSEC on 30 May 2019. Ash emissions were also produced from the fissures. The northern flank fissure is seen from the (a) Monte Cagliato thermal camera (EMCT) and (b) the Montagnola high definition camera (EMOH). The fissure on the SE flank was seen from the Montagnola thermal (c) and high definition (d) (EMOH) webcams. Ash emissions and lava flows were visible on the flank (e) and ashfall was recorded in Linguaglossa (f). Courtesy of INGV (Report 23/2019, ETNA, Bollettino Settimanale, 27/05/2019 - 02/06/2019, data emissione 04/06/2019).

Figure 267. Images of the active lava flows at Etna on 31 May 2019 indicated the extent of the flow activity. Lava was flowing from two vents along a fissure on the SE flank (a and b, drone images courtesy of the FlyEye Team OE). The thermal image of the flow (c) is from Schiena dell'Asi, the visible photo (d) is also taken from Schiena dell'Asi by L. Lodato. The thermal (e) and visual (f) images of the active lava fields were taken from the Monte Cagliato (EMCT) thermal webcam and the Monte Cagliato (EMCH) high definition webcam. Courtesy of INGV (Report 23/2019, ETNA, Bollettino Settimanale, 27/05/2019 - 02/06/2019, data emissione 04/06/2019).

Activity during June-July 2019. The flow from the N flank of NSEC ceased advancing on 1 June 2019, but the active spattering continued from the fissure on the SE flank for a few more days. The SE-flank flow had reached 1,700 m elevation in the Valle del Bove by the afternoon of 2 June (figure 268). The intensity and frequency of the explosions decreased over the next few days, with the active flow front receding back towards the vent until it stopped moving on 6 June. The NE rim of the summit cone at NSEC appeared lowered by several meters after the eruption ceased. The lava flows and explosions of 30 May-2 June produced persistent SO₂ emissions that drifted E and N for over 800 km (figure 269).

Figure 268. During the morning of 1 June 2019 Strombolian and effusive activity at Etna continued from the fissure on the SE flank of NSEC (a and b, photos by M. Neri). By the evening of 1 June there was only one remaining arm of the flow that was active (c) as seen in the Monte Cagliato (EMCT) thermal webcam. The following evening, 2 June, another thermal image(d, photo by S. Scollo) showed the remaining active arm. Courtesy of INGV (Report 23/2019, ETNA, Bollettino Settimanale, 27/05/2019 - 02/06/2019).

Figure 269. Active lava flows and Strombolian activity at Etna during 30 May-2 June 2019 contributed to significant SO₂ plumes that drifted E and NE from the volcano during this time, extending as far as 800 km from the source. Captured by the TROPOMI instrument on the Sentinel 5P satellite, courtesy of NASA Goddard Space Flight Center.

Activity for the rest of June 2019 moved to the other craters, mainly Voragine, after the flows ceased at NSEC. On the morning of 6 June there were sporadic ash emissions from NEC that quickly dissipated. A small ash plume appeared from Bocca Nuova (BN) on 11 June. An explosive sequence that began on 13 June from the crater floor of Voragine continued intermittently through the third week of the month (figure 270) and produced several small ash plumes. A new vent opened on the crater floor and produced a small ash plume; ejecta also landed on the crater rim several times. On 22 June small, discontinuous ash emissions were produced from BN-1; they dispersed rapidly, but intermittent explosions continued during the following week. By the end of the month, only BN was exhibiting activity other than degassing; incandescence from the crater was seen during the night of 24 June and three isolated ash emissions were seen in the webcams on 26 June.

Figure 270. An ash plume at Etna rose from the Voragine crater on 15 June 2019 during a series of intermittent explosions. Image taken from the Torre del Filosofo by M. Coltelli. Courtesy of INGV (Report 25/2019, ETNA, Bollettino Settimanale, 10/06/2019 - 16/06/2019, data emissione 18/06/2019).

Discontinuous Strombolian explosions and isolated ash emissions characterized activity during the first half of July 2019. Pulsating degassing from NEC produced ash emissions on 2 and 3 July (figure 271), and incandescence on 4 and 5 July. Intense degassing was observed at NSEC during 1-5 July, this turned into isolated ash emissions and Strombolian activity on 5 and 6 July from the E vent with explosions occurring every 1-5 minutes; the ejecta landed on the upper E flank. Dilute ash emissions were observed from Bocca Nuova on 6 July. NEC produced two major ash emissions on the evening of 8 July and the late morning of 13 July. The ash plumes quickly dispersed in the summit area. Strombolian activity at the E vent of NSEC was witnessed on 14 July. Explosive activity at Bocca Nuova remained deep within the crater during mid-July. Steam produced by the 13 June 2019 vent on the floor of Voragine occasionally contained dilute ash. During 15-17 July sporadic explosions were observed at NSEC accompanied by small puffs of ash that rapidly dispersed.

Figure 271. Surveillance cameras at Etna captured images of explosions with ash emissions from NEC on 2 (top) and 3 (bottom) July 2019. The left images are from Montagnola and the right images are from Monte Cagliato. Courtesy of INGV (Report 28/2019, ETNA, Bollettino Settimanale, 01/07/2019 - 07/07/2019, data emissione 09/07/2019).

Beginning early on 18 July, Strombolian activity increased at NSEC from an explosion every 1-2 minutes to multiple explosions per minute in the following hours. Continuous activity during the evening decreased sharply around 2200. About an hour later visual and thermal surveillance cameras on Monte Cagliato recorded the opening of a vent on the lower NE flank of NSEC; lava slowly advanced from the vent towards Valle del Leone (figures 272 and 273). Explosive activity resumed at the NSEC summit a few hours later, accompanied by occasional ash emissions from NEC and Bocca Nuova. Explosions tapered off briefly by noon on 19 July, but a sudden increase in explosive activity during the afternoon of 19 July produced Strombolian activity and sporadic ash emissions from three vents inside the NSEC crater. Ashfall was reported that evening in communities on the S flank of Etna. The Toulouse VAAC reported significant ash above the summit at 3.7 km altitude. Activity declined again later that evening at NSEC, but abundant ash emission began at NEC that lasted until the morning of 20 July. A new phase of explosive activity began at NSEC around 0700 on 20 July with an ash plume and an increase in lava emission from the vent on the NE flank (figure 274). By the evening of 20 July only a small amount of material was feeding the lava flow; the farthest advanced fronts were at an elevation around 2,150 m, above Monte Simone. A few small ash emissions were observed at Bocca Nuova on 21 July.

Figure 272. Map of the summit craters of Etna showing the active vents and the lava flow of 19-21 July 2019. The base is modified from a 2014 DEM created by Laboratorio di Aerogeofisica-Sezione Roma 2. Black hatch marks indicate the crater rims: BN = Bocca Nuova, with NW BN-1 and SE BN-2; VOR = Voragine; NEC = North East Crater; SEC = South East Crater; NSEC = New South East Crater. Red circles indicate areas with ash emissions and/or Strombolian activity, yellow circles indicate steam and/or gas emissions only. Courtesy of INGV (Report 30/2019, ETNA, Bollettino Settimanale, 15/07/2019 - 21/07/2019, data emissione 23/07/2019).

Figure 273. Activity at Etna on 18 and 19 July 2019 included a new lava flow from a vent on the NE flank of NSEC and Strombolian activity at the NSEC summit vent. (a) Start of the flow from a vent on the NE flank of NSEC seen from the high-resolution camera at Monte Cagliato (EMCH) at 2307 UTC on 18 July. (b) Strombolian activity at the NSEC and glow of the new lava flow on the right seen from Tremestieri Etneo, 2347 that evening. (c) A new advancing lava flow and brown ash emission from NEC seen from the EMCH camera, 0338 on 19 July; (d) lava flow seen from the thermal camera at Monte Cagliato, 0700 on 19 July. Courtesy of INGV (Report 30/2019, ETNA, Bollettino Settimanale, 15/07/2019 - 21/07/2019, data emissione 23/07/2019).

Figure 274. Activity at Etna on 20 July 2019 included (a) ash emission from both NSEC and NEC craters at 0402 seen from Tremestieri Etneo, (b) ash from NSEC and the active flow on the SE flank at 0608 seen from the Monte Cagliato high-resolution camera, (c) ash emission from NSEC at 0700 seen by Tremesteieri Etneo, and (d) explosive activity at NSEC and the lava flow on the W wall of the Valle del Bove at 0700 seen from the Monte Cagliato thermal camera. Courtesy of INGV (Report 30/2019, ETNA, Bollettino Settimanale, 15/07/2019 - 21/07/2019, data emissione 23/07/2019).

Visible and thermal images taken on 24 July 2019 indicated only degassing at BN-1 and BN-2, and limited degassing from low-temperature fumaroles from the multiple vents at VOR (figure 275). After a few days of quiet, NSEC resumed discontinuous ash emissions on 25 July. A sudden increase in the amplitude of volcanic tremor was noted early on 27 July, which was followed a few hours later by the opening of a new eruptive fissure on the S flank of NSEC (figure 276). Explosive activity intensified and produced a dense ash-rich plume that dispersed to the E at an estimated altitude of 4.5-5 km. A thin layer of ash was reported in Giarre, Riposto, and Torre Archirafi. A lava flow emerged from the S portion of the fissure and expanded SW and S. By 1135 the most advanced front had reached and passed the N side of the base of the Barbagallo Mountians at an elevation of about 2,850 m. It continued to spread down into the area between Monte Frumento Supino and the pyroclastic cones of 2002-2003 (figure 277). A series of particularly strong explosions occurred from NSEC around midday, producing an ash plume that rose to 7.5 km altitude. By this time the most advanced lava fronts were located at an elevation of about 2,600 m, but they were rapidly advancing SSW towards Monte Nero, surrounding Monte Frumento Supino from the W. Explosive activity decreased significantly early in the morning on 28 July; flow activity also slowed around the same time. Occasional puffs of reddish-brown ash were noted from NEC during the morning as well. The explosions and the lava effusion ceased on the evening of 28 July. An isolated ash emission from Bocca Nuova in the early hours of 31 July was the last activity reported in July. A substantial SO₂ plume (6.59 DU) from the explosions on 27 July had drifted to the E coast of the Adriatic Sea by midday on 28 July and was detected in satellite instruments.

Figure 275. Degassing was the only activity occurring at the multiple vents at Etna's Voragine crater on 24 July 2019. The joined pit crater from the 12 January and 18 April 2019 vents is at the upper left; the newest vent formed 16 June 2019 is at lower left and appears cool in the thermal image inset a. Photo and annotations by S. Branca. Courtesy of INGV (Rep. N° 31/2019, ETNA, Bollettino Settimanale, 22/07/2019 - 28/07/2019, data emissione 30/07/2019).

Figure 276. A new eruptive fissure at Etna opened on the S flank of NSEC on 27 July 2019 (line of red circles). The base map is modified from a 2014 DEM created by Laboratorio di Aerogeofisica-Sezione Roma 2. Black hatch marks indicate the crater rims: BN=Bocca Nuova, with NW BN-1 and SE BN-2; VOR = Voragine; NEC = North East Crater; SEC = South East Crater; NSEC = New South East Crater. Red circles indicate areas with ash emissions and/or Strombolian activity, yellow circles indicate steam and/or gas emissions only. Courtesy of INGV (Report 31/2019, ETNA, Bollettino Settimanale, 22/07/2019 - 28/07/2019, data emissione 30/07/2019).

Figure 277. Lava flows and substantial ash emissions were reported at Etna on 27 July 2019. The lava flow at 1216 was located at about 2,600 m elevation (a). A thermal image of the S flank of NSEC showed the extent of the flow activity (b). A large ash plume formed after several explosions at NSEC at 1221 (c). Thermal images of the emissions were captured by the Montagnola (EMOT) webcam and by an INGV operator (d, e). Photos by S. Branca (a), B. Behncke (c), and E. Pecora (b, e). Courtesy of INGV (Report 31/2019, ETNA, Bollettino Settimanale, 22/07/2019 - 28/07/2019, data emissione 30/07/2019).

Activity during August-September 2019. Activity during August 2019 was focused primarily on the North East Crater (NEC), with occasional ash emissions from Bocca Nuova. The plumes were occasionally dense and dark brown from NEC. Weak emissions of dilute ash from NEC quickly dispersed on the morning of 4 August, followed by more intermittent ash emissions during 6-10 August; a few had significant concentrations of ash that drifted SE. Part of the N rim of NEC collapsed during the explosions of early August (figure 278). During a site inspection to the summit by INGV personnel on 16 August, continuous degassing at Bocca Nuova was interrupted every 10-15 minutes by explosions, but no ejecta was noted. Discontinuous emissions from NEC formed small ash plumes that rose a few hundred meters and remained in the summit area (figure 279). Thermal surveys that day indicated high temperatures of about 800°C along a 10-m-fracture zone on the northern rim of VOR. Ash emissions from NEC were persistent through 20 August when they decreased significantly; a few explosions had dilute ash emissions from Bocca Nuova that day and the next (figure 280). Sulfur dioxide emissions were notable during 19-22 August, drifting S and W hundreds of kilometers before dissipating. Isolated and dilute ash from NEC early on 28 August was interpreted by INGV as resulting from collapses along the inner crater walls. During site inspections on 27, 28, and 30 August, deep explosions from Bocca Nuova were heard, and degassing was observed at all of the summit vents.

Figure 278. Part of the N rim of the NEC crater at Etna collapsed during explosions in early August 2019. In this image from 10 August 2019 the collapsed N wall is shown by white arrows, the old crater rim is the dashed yellow line, and the new rim is the solid yellow line. Photo by Michele Mammino, courtesy of INGV (Report 33/2019, ETNA, Bollettino Settimanale, 05/08/2019 - 11/08/2019, data emissione 13/08/2019).

Figure 279. Discontinuous emissions at Etna on 16 August 2019 from the NEC crater formed small ash plumes that rose a few hundred meters and remained in the summit area (a). Smaller ash plumes remained within the crater (b and c). Courtesy of INGV (Report 34/2019, ETNA, Bollettino Settimanale, 12/08/2019 - 18/08/2019, data emissione 20/08/2019).

Figure 280. In the foreground weak degassing occurs on 21 August 2019 at Etna's BN-2 vent inside Bocca Nuova while a small ash plume in the background rises from NEC. Photo by F. Ciancitto, courtesy of INGV (Report 35/2019, ETNA, Bollettino Settimanale, 19/08/2019 - 25/08/2019, data emissione 27/08/2019).

Activity during September 2019 began with discontinuous and dilute ash emissions from NEC and Bocca Nuova, as well as episodes of Strombolian activity at both vents. This was followed by increased Strombolian activity, ash emissions, and a lava flow at Voragine. Isolated ash emissions occurred at NEC and VOR on 4 and 5 September. Sporadic deep explosions were heard from BN-1 during a site inspection on 7 September. Overnight during 7-8 September the visual webcams recorded incandescence at NEC and pyroclastic ejecta observed outside the crater rim that coincided with increased tremor activity. A more intense episode of Strombolian activity began the following evening at NEC. Activity was continuous from 1800 on 9 September to 0500 on 10 September, and produced dilute ash emissions that quickly dispersed (figure 281). Slight ashfall was reported in Piedimonte Etneo, Giarre-Riposto, and Rifugio Citelli. Continuous puffs of dilute ash were observed beginning at dawn on 11 September with sporadic ejecta again landing outside the crater rim. Significant SO₂ plumes were measured by satellite instruments on 10 and 11 September (figure 282).

Figure 281. Activity at Etna overnight during 9-10 September 2019 included Strombolian activity and dilute ash emissions from NEC that were observed from webcams on the S, W, and E flanks. Courtesy of INGV (Report 38/2019, ETNA, Bollettino Settimanale, 09/09/2019 - 15/09/2019, data emissione 17/09/2019).

Figure 282. Significant SO₂ plumes from Etna were detected on 10 and 11 September 2019. Increased Strombolian activity was reported by INGV from the NEC crater during 9-11 September. Courtesy of NASA Goddard Space Center.

In addition to the Strombolian activity at NEC on 12 September, ash emissions began that morning at VOR. They increased in frequency and then transitioned to near-continuous Strombolian activity that produced ejecta which landed in the base of the adjacent Bocca Nuova crater. The explosions from the Strombolian activity were felt in Zafferana Etnea, Aci S. Antonio, Pedara, and neighboring areas. On 13 September the webcams observed multiple periods of continuous ash emissions from NEC and short, intense pulses of ash from VOR that accompanied Strombolian activity; coarse ejecta rose 20 m above and landed outside of the crater rim, producing impact craters on the W side of the summit between VOR and BN. The vent that sourced the Strombolian activity was located in the deepest part of the Voragine crater. By 15 September, continued ejecta had formed a scoria cone around the vent inside VOR (figure 283).

Figure 283. On 13 September 2019 Strombolian activity at Etna's NEC and VOR craters increased (a). INGV personnel observed an ash emission from NEC (b), a Strombolian explosion with ejecta from VOR (c), and impact craters from the ejecta around the rim (d). The continued activity at VOR produced a scoria cone inside the crater that grew noticeably between 13 (e) and 15 (f) September. Photos (a) and (e) courtesy of L. D'Agata, photo (f) by B. Behncke. Courtesy of INGV (Report 38/2019, ETNA, Bollettino Settimanale, 09/09/2019 - 15/09/2019, data emissione 17/09/2019).

Explosive activity inside VOR increased on the afternoon of 18 September 2019. Pyroclastic ejecta and ash erupted from several vents and reached heights of several tens of meters. A lava flow emerged from the W base of the scoria cone and headed S, advancing several hundred meters (figure 284). It then flowed over the saddle that divides VOR and BN, split into two branches, and entered Bocca Nuova. One stream poured into BN-1, and another stopped near the edge of the BN-2 pit crater. By 22 September the flow was cooling, but strong Strombolian activity continued inside Voragine. NEC was characterized by large-scale ash emissions during the end of September, including one in the morning of 27 September that sent a plume over the S flank of Etna before dissipating (figure 285). Strombolian activity continued within Bocca Nuova during the last week of the month.

Figure 284. Significant Strombolian and lava flow activity at Etna affected the Voragine crater on 18 and 19 September 2019. Visible and thermal images of the scoria cone (cono scorie) and lava flow (colata) inside Etna's large Voragine crater on 19 September 2019 (top) were taken from the southern edge of BN. Photo by F. Ciancitto. The bottom images were taken from the SW rim of BN on 18 September (left) by M. Tomasello and (right) 19 September by INGV personnel. Courtesy of INGV (Report 39/2019, ETNA, Bollettino Settimanale, 16/09/2019 - 22/09/2019, data emissione 24/09/2019).

Figure 285. An ash emission from Etna's NEC crater early on 27 September 2019 sent a plume drifting S before dissipating. It was captured by both the high-definition webcam of Bronte (EBVH, left) and the Milo (EMV) webcam. Courtesy of INGV (Report 40/2019, ETNA, Bollettino Settimanale, 23/09/2019 - 29/09/2019, data emissione 01/10/2019).

April 2020 (BGVN 45:04) Cite this Report

Strombolian explosions and ash emissions continue, October 2019-March 2020

Mount Etna is a stratovolcano located on the island of Sicily, Italy, with historical eruptions that date back 3,500 years. The most recent eruptive period began in September 2013 and has continued through March 2020. Activity is characterized by Strombolian explosions, lava flows, and ash plumes that commonly occur from the summit area, including the Northeast Crater (NEC), the Voragine-Bocca Nuova (or Central) complex (VOR-BN), the Southeast Crater (SEC, formed in 1978), and the New Southeast Crater (NSEC, formed in 2011). The newest crater, referred to as the "cono della sella" (saddle cone), emerged during early 2017 in the area between SEC and NSEC. This reporting period covers information from October 2019 through March 2020 and includes frequent explosions and ash plumes. The primary source of information comes from the Osservatorio Etneo (OE), part of the Catania Branch of Italy's Istituo Nazionale di Geofisica e Vulcanologica (INGV).

Summary of activity during October 2019-March 2020. Strombolian activity and gas-and-steam and ash emissions were frequently observed at Etna throughout the entire reporting period, according to INGV and Toulouse VAAC notices. Activity was largely located within the main cone (Voragine-Bocca Nuova complex), the Northeast Crater (NEC), and the New Southeast Crater (NSEC). On 1, 17, and 19 October, ash plumes rose to a maximum altitude of 5 km. Due to constant Strombolian explosions, ground observations showed that a scoria cone located on the floor of the VOR Crater had begun to grow in late November and again in late January 2020. A lava flow was first detected on 6 December at the base of the scoria cone in the VOR Crater, which traveled toward the adjacent BN Crater. Additional lava flows were observed intermittently throughout the reporting period in the same crater. On 13 March, another small scoria cone had formed in the main VOR-BN complex due to Strombolian explosions.

MIROVA (Middle InfraRed Observation of Volcanic Activity) analysis of MODIS satellite data shows multiple episodes of thermal activity varying in power from 22 June 2019 to March 2020 (figure 286). The power and frequency of these thermal anomalies significantly decreased between August to mid-September. The pulse of activity in mid-September reflected a lava flow from the VOR Crater (BGVN 44:10). By late October through November, thermal anomalies were relatively weaker and less frequent. The next pulse in thermal activity reflected in the MIROVA graph occurred in early December, followed by another shortly after in early January, both of which were due to new lava flows from the VOR Crater. After 9 January the thermal anomalies remained frequent and strong; active lava flows continued through March accompanied by Strombolian explosions, gas-and-steam, SO₂, and ash emissions. The most recent distinct pulse in thermal activity was seen in mid-March; on 13 March, another lava flow formed, accompanied by an increase in seismicity. This lava flow, like the previous ones, also originated in the VOR Crater and traveled W toward the BN Crater.

Figure 286. Multiple episodes of varying activity at Etna from 22 June 2019 through March 2020 were reflected in the MIROVA thermal energy data (Log Radiative Power). Courtesy of MIROVA.

Activity during October-December 2019. During October 2019, VONA (Volcano Observatory Notice for Aviation) notices issued by INGV reported ash plumes rose to a maximum altitude of 5 km on 1, 17, and 19 October. Strombolian explosions occurred frequently. Explosions were detected primarily in the VOR-BN Craters, ejecting coarse pyroclastic material that fell back into the crater area and occasionally rising above the crater rim. Ash emissions rose from the VOR-BN and NEC while intense gas-and-steam emissions were observed in the NSEC (figure 287). Between 10-12 and 14-20 October fine ashfall was observed in Pedara, Mascalucia, Nicolosi, San Giovanni La Punta, and Catania. In addition to these ash emissions, the explosive Strombolian activity contributed to significant SO₂ plumes that drifted in different directions (figure 288).

Figure 287. Webcam images of ash emissions from the NE Crater at Etna from the a) CUAD (Catania) webcam on 10 October 2019; b) Milo webcam on 11 October 2019; c) Milo webcam on 12 October 2019; d) M.te Cagliato webcam on 13 October 2019. Courtesy of INGV (Report 42/2019, ETNA, Bollettino Settimanale, 07/10/2019 - 13/10/2019, data emissione 15/10/2019).

Figure 288. Strombolian activity at Etna contributed to significant SO₂ plumes that drifted in multiple directions during the intermittent explosions in October 2019. Top left: 1 October 2019. Top right: 2 October 2019. Middle left: 15 October 2019. Middle right: 18 October 2019. Bottom left: 13 November 2019. Bottom right: 1 December 2019. Captured by the TROPOMI instrument on the Sentinel 5P satellite, courtesy of NASA Global Sulfur Dioxide Monitoring Page.

The INGV weekly bulletin covering activity between 25 October and 1 November 2019 reported that Strombolian explosions occurred at intervals of 5-10 minutes from within the VOR-BN and NEC, ejecting incandescent material above the crater rim, accompanied by modest ash emissions. In addition, gas-and-steam emissions were observed from all the summit craters. Field observations showed the cone in the crater floor of VOR that began to grow in mid-September 2019 had continued to grow throughout the month. During the week of 4-10 November, Strombolian activity within the Bocca Nuova Crater was accompanied by gas-and-steam emissions. The explosions in the VOR Crater occasionally ejected incandescent ejecta above the crater rim (figures 289 and 290). For the remainder of the month Strombolian explosions continued in the VOR-BN and NEC, producing sporadic ash emissions. Isolated and discontinuous explosions in the New Southeast Crater (NSEC) also produced fine ash, though gas-and-steam emissions still dominated the activity at this crater. Additionally, the explosions from these summit craters were frequently accompanied by strong SO₂ emissions that drifted in different directions as discrete plumes.

Figure 289. Photo of Strombolian activity and crater incandescence in the Voragine Crater at Etna on 15 November 2019. Photo by B. Behncke, taken by Tremestieri Etneo. Courtesy of INGV (Report 47/2019, ETNA, Bollettino Settimanale, 11/11/2019 - 17/11/2019, data emissione 19/11/2019).

Figure 290. Webcam images of summit crater activity during 26-29 November and 1 December 2019 at Etna. a) image recorded by the high-resolution camera on Montagnola (EMOV); b) and c) webcam images taken from Tremestieri Etneo on the southern slope of Etna showing summit incandescence; d) image recorded by the thermal camera on Montagnola (EMOT) showing summit incandescence at the NSEC. Courtesy of INGV (Report 49/2019, ETNA, Bollettino Settimanale, 25/11/2019 - 01/12/2019, data emissione 03/12/2019).

Frequent Strombolian explosions continued through December 2019 within the VOR-BN, NEC, and NSEC Craters with sporadic ash emissions observed in the VOR-BN and NEC. On 6 December, Strombolian explosions increased in the NSEC; webcam images showed incandescent pyroclastic material ejected above the crater rim. On the morning of 6 December a lava flow was observed from the base of the scoria cone in the VOR Crater that traveled toward the adjacent Bocca Nuova Crater. INGV reported that a new vent opened on the side of the saddle cone (NSEC) on 11 December and produced explosions until 14 December.

Activity during January-March 2020. On 9 January 2020 an aerial flight organized by RAI Linea Bianca and the state police showed the VOR Crater continuing to produce lava that was flowing over the crater rim into the BN Crater with some explosive activity in the scoria cone. Explosive Strombolian activity produced strong and distinct SO₂ plumes (figure 291) and ash emissions through March, according to the weekly INGV reports, VONA notices, and satellite imagery. Several ash emissions during 21-22 January rose from the vent that opened on 11 December. According to INGV’s weekly bulletin for 21-26 January, the scoria cone in the VOR crater produced Strombolian explosions that increased in frequency and contributed to rapid cone growth, particularly the N part of the cone. Lava traveled down the S flank of the cone and into the adjacent Bocca Nuova Crater, filling the E crater (BN-2) (figure 292). The NEC had discontinuous Strombolian activity and periodic, diffuse ash emissions.

Figure 291. Distinct SO₂ plumes drifting in multiple directions from Etna were visible in satellite imagery as Strombolian activity continued through March 2020. Top left: 21 January 2020. Top right: 2 February 2020. Bottom left: 10 March 2020. Bottom right: 19 March 2020. Captured by the TROPOMI instrument on the Sentinel 5P satellite, courtesy of NASA Global Sulfur Dioxide Monitoring Page.

Figure 292. a) A map of the lava field at Etna showing cooled flows (yellow) and active flows (red). The base of the scoria cone is outlined in black while the crater rim is outlined in red. b) Thermal image of the Bocca Nuova and Voragine Craters. The bright orange is the warmest temperature measure in the flow. Courtesy of INGV, photos by Laboratorio di Cartografia FlyeEye Team (Report 10/2020, ETNA, Bollettino Settimanale, 24/02/2020 - 01/03/2020, data emissione 03/03/2020).

Strombolian explosions continued into February 2020, accompanied by ash emissions and lava flows from the previous months (figure 293). During 17-23 February, INGV reported that some subsidence was observed in the central portion of the Bocca Nuova Crater. During 24 February to 1 March, the Strombolian explosions ejected lava from the VOR Crater up to 150-200 m above the vent as bombs fell on the W edge of the VOR crater rim (figure 294). Lava flows continued to move into the W part of the Bocca Nuova Crater.

Figure 293. Webcam images of A) Strombolian activity and B) effusive activity fed by the scoria cone grown inside the VOR Crater at Etna taken on 1 February 2020. C) Thermal image of the lava field produced by the VOR Crater taken by L. Lodato on 3 February (bottom left). Image of BN-1 taken by F. Ciancitto on 3 February in the summit area (bottom right). Courtesy of INGV; Report 06/2020, ETNA, Bollettino Settimanale, 27/01/2020 - 02/02/2020, data emissione 04/02/2020 (top) and Report 07/2020, ETNA, Bollettino Settimanale, 03/02/2020 - 09/02/2020, data emissione 11/02/2020 (bottom).

Figure 294. Photos of the VOR intra-crater scoria cone at Etna: a) Strombolian activity resumed on 25 February 2020 from the SW edge of BN taken by B. Behncke; b) weak Strombolian activity from the vent at the base N of the cone on 29 February 2020 from the W edge of VOR taken by V. Greco; c) old vent present at the base N of the cone, taken on 17 February 2020 from the E edge of VOR taken by B. Behncke; d) view of the flank of the cone, taken on 24 February 2020 from the W edge of VOR taken by F. Ciancitto. Courtesy of INGV (Report 10/2020, ETNA, Bollettino Settimanale, 24/02/2020 - 01/03/2020, data emissione 03/03/2020).

During 9-15 March 2020 Strombolian activity was detected in the VOR Crater while discontinuous ash emissions rose from the NEC and NSEC. Bombs were found in the N saddle between the VOR and NSEC craters. On 9 March, a small scoria cone that had formed in the Bocca Nuova Crater and was ejecting bombs and lava tens of meters above the S crater rim. The lava flow from the VOR Crater was no longer advancing. A third scoria cone had formed on 13 March NE in the main VOR-BN complex due to the Strombolian explosions on 29 February. Another lava flow formed on 13 March, accompanied by an increase in seismicity. The weekly report for 16-22 March reported Strombolian activity detected in the VOR Crater and gas-and-steam and rare ash emissions observed in the NEC and NSEC (figure 295). Explosions in the Bocca Nuova Crater ejected spatter and bombs 100 m high.

Figure 295. Map of the summit crater area of Etna showing the active vents and lava flows during 16-22 March 2020. Black hatch marks indicate the crater rims: BN = Bocca Nuova, with NW BN-1 and SE BN-2; VOR = Voragine; NEC = North East Crater; SEC = South East Crater; NSEC = New South East Crater. Red circles indicate areas with ash emissions and/or Strombolian activity, yellow circles indicate steam and/or gas emissions only. The base is modified from a 2014 DEM created by Laboratorio di Aerogeofisica-Sezione Roma 2. Courtesy of INGV (Report 13/2020, ETNA, Bollettino Settimanale, 16/03/2020 - 22/03/2020, data emissione 24/03/2020).

Information Contacts: Sezione di Catania - Osservatorio Etneo, Istituto Nazionale di Geofisica e Vulcanologia (INGV), Sezione di Catania, Piazza Roma 2, 95123 Catania, Italy (URL: http://www.ct.ingv.it/it/); Toulouse Volcanic Ash Advisory Center (VAAC), Météo-France, 42 Avenue Gaspard Coriolis, F-31057 Toulouse cedex, France (URL: http://www.meteo.fr/aeroweb/info/vaac/); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); Global Sulfur Dioxide Monitoring Page, Atmospheric Chemistry and Dynamics Laboratory, NASA Goddard Space Flight Center (NASA/GSFC), 8800 Greenbelt Road, Goddard, Maryland, USA (URL: https://so2.gsfc.nasa.gov/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground); Boris Behncke, Sonia Calvari, and Marco Neri, Istituto Nazionale di Geofisica e Vulcanologia (INGV), Sezione di Catania, Piazza Roma 2, 95123 Catania, Italy (URL: https://twitter.com/etnaboris, Image at https://twitter.com/etnaboris/status/1183640328760414209/photo/1).

September 2020 (BGVN 45:09) Cite this Report

Effusive activity in early April; frequent Strombolian explosions and ash emissions during April-July 2020

Etna, located on the island of Sicily, Italy, is a stratovolcano that has had historical eruptions dating back 3,500 years. Its most recent eruptive period began in September 2013 and has continued through July 2020, characterized by Strombolian explosions, lava flows, and ash plumes. Activity has commonly originated from the summit areas, including the Northeast Crater (NEC), the Voragine-Bocca Nuova (or Central) complex (VOR-BN), the Southeast Crater (SEC, formed in 1978), and the New Southeast Crater (NSEC, formed in 2011). The newest crater, referred to as the "cono della sella" (saddle cone), emerged during early 2017 in the area between SEC and NSEC. Volcanism during this reporting period from April through July 2020 includes frequent Strombolian explosions primarily in the Voragine and NSEC craters, ash emissions, some lava effusions, and gas-and-steam emissions. Information primarily comes from weekly reports by the Osservatorio Etneo (OE), part of the Catania Branch of Italy's Istituo Nazionale di Geofisica e Vulcanologica (INGV).

Summary of activity during April-July 2020. Degassing of variable intensity is typical activity from all summit vents at Etna during the reporting period. Intra-crater Strombolian explosions and ash emissions that rose to a maximum altitude of 5 km on 19 April primarily originated from the Voragine (VOR) and New Southeast Crater (NSEC) craters. At night, summit crater incandescence was occasionally visible in conjunction with explosions and degassing. During 18-19 April small lava flows were observed in the VOR and NSEC craters that descended toward the BN from the VOR Crater and the upper E and S flanks of the NSEC. On 19 April a significant eruptive event began with Strombolian explosions that gradually evolved into lava fountaining activity, ejecting hot material and spatter from the NSEC. Ash plumes that were produced during this event resulted in ashfall to the E of Etna. The flows had stopped by the end of April; activity during May consisted of Strombolian explosions in both the VOR and NSEC craters and intermittent ash plumes rising 4.5 km altitude. On 22 May Strombolian explosions in the NSEC produced multiple ash plumes, which resulted in ashfall to the S. INGV reported that the pit crater at the bottom of BN had widened and was accompanied by degassing. Explosions with intermittent ash emissions continued during June and July and were primarily focused in the VOR and NSEC craters; mild Strombolian activity in the SEC was reported in mid-July.

MIROVA (Middle InfraRed Observation of Volcanic Activity) analysis of MODIS satellite data shows multiple episodes of thermal activity throughout the reporting period (figure 296). In early April, the frequency and power of the thermal anomalies began to decrease through mid-June; in July, they had increased in power again but remained less frequent compared to activity in January through March. According to the MODVOLC thermal algorithm, a total of seven alerts were detected in the summit craters during 10 April (1), 17 April (1), 24 April (2), 10 July (1), 13 July (1), and 29 July (1) 2020. These thermal hotspots were typically registered during or after a Strombolian event. Frequent Strombolian activity contributed to distinct SO₂ plumes that drifted in different directions (figure 297).

Figure 296. Multiple episodes of varying thermal activity at Etna from 14 October 2019 through July 2020 were reflected in the MIROVA data (Log Radiative Power). In early April, the frequency and power of the thermal anomalies decreased through mid-June. In July, the thermal anomalies increased in power, but did not increase in frequency. Courtesy of MIROVA.

Figure 297. Distinct SO₂ plumes from Etna were detected on multiple days during April to July 2020 due to frequent Strombolian explosions, including, 24 April (top left), 9 May (top right), 25 June (bottom left), and 21 July (bottom right) 2020. Captured by the TROPOMI instrument on the Sentinel 5P satellite, courtesy of NASA Global Sulfur Dioxide Monitoring Page.

Activity during April-May 2020. During April, INGV reported Strombolian explosions that produced some ash emissions and intra-crater effusive activity within the Voragine Crater (VOR) and abundant degassing from the New Southeast Crater (NSEC), Northeast Crater (NEC), and from two vents on the cono della sella (saddle cone) that were sometimes accompanied by a modest amount of ash (figure 298). At night, summit crater incandescence was observed in the cono della salla. The Strombolian activity in the VOR built intra-crater scoria cones while lava flows traveled down the S flank of the largest, main cone. On 18 April effusive activity from the main cone in the VOR Crater traveled 30 m toward the Bocca Nuova (BN) Crater; the pit crater at the bottom of the BN crater had widened compared to previous observations. A brief episode of Strombolian explosions that started around 0830 on 19 April in the NSEC gradually evolved into modest lava fountaining activity by 0915, rising to 3 km altitude and ejecting bombs up to 100 m (figure 299). A large spatter deposit was found 50 m from the vent and 3-4 small lava flows were descending the NSEC crater rim; two of these summit lava flows were observed at 1006, confined to the upper E and S flanks of the cone. Around 1030, one or two vents in the cono della sella produced a gas-and-steam and ash plume that rose 5 km altitude and drifted E, resulting in ashfall on the E flank of Etna in the Valle del Bove, as well as between the towns of Zafferana Etnea (10 km SE) and Linguaglossa (17 km NE). At night, flashes of incandescence were visible at the summit. By 1155, the lava fountaining had gradually slowed, stopping completely around 1300. The NEC continued to produce gas-and-steam emissions with some intra-crater explosive activity. During the week of 20-26 April, Strombolian activity in the VOR intra-crater scoria cone ejected pyroclastic material several hundred meters above the crater rim while the lava flows had significantly decreased, though continued to travel on the E flank of the main cone. Weak, intra-crater Strombolian activity with occasional ash emissions and nightly summit incandescence were observed in the NSEC (figure 300). By 30 April there were no longer any active lava flows; the entire flow field had begun cooling. The mass of the SO₂ emissions varied in April from 5,000-15,000 tons per day.

Figure 298. Photos of Strombolian explosions at Etna in the Voragine Crater (top left), strong degassing at the Northeast Crater (NEC) (top right), and incandescent flashes and Strombolian activity in the New Southeast Crater (NSEC) seen from Tremestieri Etneo (bottom row) on 10 April 2020. Photos by Francesco Ciancitto (top row) and Boris Behncke (bottom row), courtesy of INGV.

Figure 299. Strombolian activity at Etna’s “cono della sella” of the NSEC crater on 19 April 2020 included (a-b) lava fountaining that rose 3 km altitude, ejecting bomb-sized material and a spatter deposit captured by the Montagnola (EMOV) thermal camera. (c-d) An eruptive column and increased white gas-and-steam and ash emissions were captured by the Montagnola (EMOV) visible camera and (e-f) were also seen from Tremestieri Etneo captured by Boris Behncke. Courtesy of INGV (Report 17/2020, ETNA, Bollettino Settimanale, 13/04/2020 – 19/04/2020, data emissione 21/04/2020).

Figure 300. Webcam images showing intra-crater explosive activity at Etna in the Voragine (VOR) and New Southeast Crater (NSEC) on 24 April 2020 captured by the (a-b) Montagnola and (c) Monte Cagliato cameras. At night, summit incandescence was visible and accompanied by strong degassing. Courtesy of INGV (Report 18/2020, ETNA, Bollettino Settimanale, 20/04/2020 – 26/04/2020, data emissione 28/04/2020).

Strombolian explosions produced periodic ash emissions and ejected mild, discontinuous incandescent material in the VOR Crater; the coarse material was deposited onto the S flank of BN (figure 301). Pulsating degassing continued from the summit craters, some of which were accompanied by incandescent flashes at night. The Strombolian activity in the cono della sella occasionally produced reddish ash during 3-4 May. During 5 and 8 May, there was an increase in ash emissions at the NSEC that drifted SSE. A strong explosive event in the VOR Crater located E of the main cone produced a significant amount of ash and ejected coarse material, which included blocks and bombs measuring 15-20 cm, that fell on the W edge of the crater, as well as on the S terrace of the BN Crater (figure 302).

Figure 301. Photos of Strombolian explosions and summit incandescence at Etna on 4 May (left) and during the night of 11-12 May. Photos by Gianni Pennisi (left) and Boris Behncke (right, seen from Tremestieri Etneo). Courtesy of INGV.

Figure 302. A photo on 5 May (left) and thermal image on 8 May (right) of Strombolian explosions at Etna in the Voragine Crater accompanied by a dense, gray ash plume. Photo by Daniele Andronico. Courtesy of INGV (Report 20/2020, ETNA, Bollettino Settimanale, 04/05/2020 – 10/05/2020, data emissione 12/05/2020).

On 10 May degassing continued in the NSEC while Strombolian activity fluctuated in both the VOR and NSEC Craters, ejecting ballistics beyond the crater rim; in the latter, some of the blocks fell back in, accumulated on the edge, and rolled down the slopes (figure 303). During the week of 11-17 May, eruptive activity at the VOR Crater was the lowest observed since early March; there were 4-5 weak, low intensity pulses not accompanied by bombs or ashfall in the VOR Crater. Degassing continued in the BN Crater. The crater of the cono della sella had widened further N following collapses due to the Strombolian activity, which exposed the internal wall.

Figure 303. Map of the summit craters of Etna showing the active vents, the area of cooled lava flows (light green), and the location of the widening pit crater in the Bocca Nuova (BN) Crater (light blue circle) updated on 9 May 2020. The base is modified from a 2014 DEM created by Laboratorio di Aerogeofisica-Sezione Roma 2. Black hatch marks indicate the crater rims: BN = Bocca Nuova, with NW BN-1 and SE BN-2; VOR = Voragine; NEC = North East Crater; SEC = South East Crater; NSEC = New South East Crater. Red circles indicate areas with ash emissions and/or Strombolian activity, yellow circles indicate steam and/or gas emissions only. Courtesy of INGV (Report 29/2020, ETNA, Bollettino Settimanale, 06/07/2020 – 12/07/2020, data emissione 14/07/2020).

On 18 May an ash plume from the NSEC rose 4.5 km altitude and drifted NE. Strombolian explosions on 22 May at the NSEC produced multiple ash plumes that rose 4.5 km altitude and drifted S and SW (figure 304), depositing a thin layer of ash on the S slope, and resulting in ashfall in Catania (27 km S). Explosions from the VOR Crater had ejected a deposit of large clasts (greater than 30 cm) on the NE flank, between the VOR Crater and NEC on 23 May. INGV reported that the pit crater in the BN continued to widen and degassing was observed in the NSEC, VOR Crater, and NEC. During the week of 25-31 May persistent visible flashes of incandescence at night were observed, which suggested there was intra-crater Strombolian activity in the SEC and NSEC. The mass of the SO₂ plumes varied between 5,000-9,000 tons per day.

Figure 304. Photo of repeated Strombolian activity and ash emissions rising from Etna above the New Southeast Crater (NSEC) on 22 May 2020 seen from Zafferana Etnea on the SE flank at 0955 local time. Photo by Boris Behncke, INGV.

Activity during June-July 2020. During June, moderate intra-crater Strombolian activity with intermittent ash emissions continued in the NSEC and occurred more sporadically in the VOR Crater; at night, incandescence of variable intensity was observed at the summit. During the week of 8-14 June, Strombolian explosions in the cono della sella generated some incandescence and rare jets of incandescent material above the crater rim, though no ash emissions were reported. On the morning of 14 June a sequence of ten small explosions in the VOR Crater ejected incandescent material just above the crater rim and produced small ash emissions. On 25 June an overflight showed the developing pit crater in the center of the BN, accompanied by degassing along the S edge of the wall; degassing continued from the NEC, VOR Crater, SEC, and NSEC (figure 305). The mass of the SO₂ plumes measured 5,000-7,000 tons per day, according to INGV.

Figure 305. Aerial photo of Etna from the NE during an overflight on 25 June 2020 by the Catania Coast Guard (2 Nucleo Aereo della Guardia Costiera di Catania) showing degassing of the summit craters. Photo captured from the Aw139 helicopter by Stefano Branca. Courtesy of INGV (Report 27/2020, ETNA, Bollettino Settimanale, 22/06/2020 – 28/06/2020, data emissione 30/06/2020).

Similar modest, intra-crater Strombolian explosions in the NSEC, sporadic explosions in the VOR Crater, and degassing in the BN, VOR Crater, and NEC persisted into July. On 2 July degassing in the NEC was accompanied by weak intra-crater Strombolian activity. Intermittent weak ash emissions and ejecta from the NSEC and VOR Crater were observed during the month. During the week of 6-12 July INGV reported gas-and-steam emissions continued to rise from the vent in the pit crater at the bottom of BN (figure 306). On 11 July mild Strombolian activity, nighttime incandescence, and degassing was visible in the SEC (figure 307). By 15 July there was a modest increase in activity in the NSEC and VOR Craters, generating ash emissions and ejecting material over the crater rims while the other summit craters were dominantly characterized by degassing. On 31 July an explosion in the NSEC produced an ash plume that rose 4.5 km altitude.

Figure 306. Photos of the bottom of the Bocca Nuova (BN) crater at Etna on 8 July 2020 showing the developing pit crater (left) and degassing. Minor ash emissions were visible in the background at the Voragine Crater (right). Both photos by Daniele Andronico. Courtesy of INGV (Report 29/2020, ETNA, Bollettino Settimanale, 06/07/2020 – 12/07/2020, data emissione 14/07/2020).

Figure 307. Mild Strombolian activity and summit incandescence in the “cono della sella” (saddle vent) at the Southeast crater (SEC) of Etna on 11 July 2020, seen from Piano del Vescovo (left) and Piano Vetore (right). Photo by Boris Behncke, INGV.

Information Contacts: Sezione di Catania - Osservatorio Etneo, Istituto Nazionale di Geofisica e Vulcanologia (INGV), Sezione di Catania, Piazza Roma 2, 95123 Catania, Italy (URL: http://www.ct.ingv.it/it/); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); Hawai'i Institute of Geophysics and Planetology (HIGP) - MODVOLC Thermal Alerts System, School of Ocean and Earth Science and Technology (SOEST), Univ. of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://modis.higp.hawaii.edu/); Global Sulfur Dioxide Monitoring Page, Atmospheric Chemistry and Dynamics Laboratory, NASA Goddard Space Flight Center (NASA/GSFC), 8800 Greenbelt Road, Goddard, Maryland, USA (URL: https://so2.gsfc.nasa.gov/); Boris Behncke, Istituto Nazionale di Geofisica e Vulcanologia (INGV), Sezione di Catania, Piazza Roma 2, 95123 Catania, Italy.

December 2020 (BGVN 45:12) Cite this Report

Strombolian explosions and ash plumes persist from multiple craters during August-November 2020

Etna, on the island of Sicily, Italy, and has had documented eruptions dating back 3,500 years. Its most recent eruptive period began in September 2013 and has continued through November 2020, characterized by frequent Strombolian explosions, effusive activity, and ash plumes. Activity has commonly originated from the summit areas, including the Northeast Crater (NEC), the Voragine-Bocca Nuova (or Central) complex (VOR-BN), the Southeast Crater (SEC, formed in 1978), and the New Southeast Crater (NSEC, formed in 2011). The newest crater, referred to as the "cono della sella" (saddle cone), emerged during early 2017 in the area between SEC and NSEC. This report from August through November 2020 updates activity consisting of frequent Strombolian explosions, ash plumes, summit crater incandescence, degassing, and some ashfall based on information primarily from weekly reports by the Osservatorio Etneo (OE), part of the Catania Branch of Italy's Istituo Nazionale di Geofisica e Vulcanologica (INGV).

Summary of activity during August-November 2020. Intra-crater Strombolian explosions that varied in frequency and intensity throughout the reporting period, and the accompanying ash emissions that rose to a maximum altitude of 4.5 km, primarily originated from the Northeast Crater (NEC), the New Southeast Crater (NSEC), and intermittently from the Voragine Crater (VOR). Degassing of variable intensity typically occurred at the VOR and the Bocca Nuova (BN) Crater. At night, occasional summit crater incandescence was visible in webcam images, accompanied by explosions and gas-and-ash emissions. On 14 August strong Strombolian explosions produced an ash plume that rose to 4.5 km altitude and drifted SE, resulting in ashfall between Pedara, Trecastagni, and Viagrande. INGV reported that the central pit crater at the bottom of BN continued to widen, and on 9 September scientists observed that a new pit crater had formed NW of the central depression and was widening due to crater wall collapses. During late October to 1 November, INGV reported that small lava flows originated from scoria cones in the NEC and were visible from the edge of the crater but did not spill over.

MIROVA (Middle InfraRed Observation of Volcanic Activity) analysis of MODIS satellite data shows frequent thermal activity of varying strength throughout the reporting period (figure 308). In late October, the frequency of the thermal anomalies increased, and continued through November. According to the MODVOLC thermal algorithm, a total of 31 alerts were detected in the summit craters during August through November; thermal anomalies were reported for five days in August, four days in September, four days in October, and eight days in November. Frequent Strombolian activity contributed to distinct SO₂ plumes that drifted in multiple directions (figure 309).

Figure 308. Strong and frequent thermal activity at Etna was detected during August through November 2020, as reflected in the MIROVA data (Log Radiative Power). Beginning in late October, the frequency of the thermal anomalies increased compared to the previous months. Courtesy of MIROVA.

Figure 309. Distinct SO₂ plumes from Etna were detected on multiple days during August to November 2020 due to frequent Strombolian explosions, including 29 August (top left), 8 September (top right), 1 October (bottom left), and 11 November (bottom right) 2020. SO₂ plumes were observed drifting in multiple directions. Captured by the TROPOMI instrument on the Sentinel 5P satellite, courtesy of NASA Global Sulfur Dioxide Monitoring Page.

Activity during August-September 2020. During August, INGV reported intra-crater Strombolian explosions in the NEC, VOR, and NSEC (including the cono della sella) craters, which produced discontinuous ash emissions rising above each crater (figure 310). Gas-and-steam emissions were the dominant activity in the BN crater. INGV noted that the central pit crater on the floor of BN had been gradually widening since April. On 2 August a slight increase in explosivity resulted in minor ashfall in Trecastagni and Acicastello. Explosive activity occasionally ejected material above the crater rim up to several tens of meters. On the morning of 7 August incandescent Strombolian activity was visible in the NSEC (figure 311). During the evening of 10-11 August surveillance cameras showed the explosions ejecting incandescent material on the surrounding flanks. On 14 August intense Strombolian activity in the saddle cone of the NSEC produced an ash plume that rose to 4-4.5 km altitude and drifted SE, resulting in ashfall between Pedara, Trecastagni, and Viagrande. By the evening activity had sharply declined, according to a VONA (Volcano Observatory Notice for Aviation) report, though sporadic ash emissions continued. A new series of ash emissions associated with explosions of varying intensity began on 15 August in the NSEC. A resulting ash plume rose to 4-4.5 km altitude and drifted ESE. On 17 August gas-and-steam emissions were seen rising above the VOR crater, accompanied by persistent Strombolian explosions. Between the afternoon and early morning of 20-21 August surveillance cameras showed an increased intensity and frequency of ash emissions above the NSEC and NEC that rose to 4-4.5 km altitude and drifted SSE. INGV-OE scientists reported minor ashfall in Trecastagni, Viagrande, and Catania. During 24-30 August ground observers reported that the intra-crater explosions in the NEC originated from two explosive vents; the BN crater exhibited gas-and-steam emissions from the central pit crater, which continued to widen. During 25-26 August explosive activity increased at the NSEC with ash emissions rising to 4.5 km and drifting SSE, which resulted in modest ashfall in Catania, Viagrande, and Trecastagni; by morning, the volume of ash emissions had decreased, though explosions persisted. During 28-29 August discontinuous and modest ash emissions originating from the NSEC rose 4.5 km altitude drifting E and ENE but did not result in ashfall. Emissions had stopped by 1747 on 29 August, though intense gas-and-steam emissions continued, occasionally accompanied by mild explosive activity (figure 312).

Figure 310. An ash plume accompanied Strombolian explosions at Etna on 3 August (top left) and 4 August (top right) and as seen from the Montagnola (EMOV) thermal camera in the NSEC. Continuous Strombolian activity and summit crater incandescence was observed on 7 August (bottom left); an ash plume was visible in the Monte Cagliato surveillance camera during the day on 9 August (bottom right). Courtesy of INGV (Report 33/2020, ETNA, Bollettino Settimanale, 03/08/2020 – 09/08/2020, data emissione 11/08/2020).

Figure 311. Strombolian explosions and summit crater incandescence was observed at Etna’s New Southeast Crater (NSEC “cono della sella”) during the early morning of 7 August 2020 seen from Tremestieri Etneo. Photo by Boris Behncke, INGV.

Figure 312. Photo of the S edge of the Bocca Nuova Crater at Etna on 29 August 2020 showing degassing in the pit crater. The main scoria cone within the Voragine Crater is visible in the background. Courtesy of INGV (Report 36/2020, ETNA, Bollettino Settimanale, 24/08/2020 – 30/08/2020, data emissione 01/09/2020).

Strombolian activity of varying intensity continued in the NSEC and NEC during September, producing sporadic ash emissions (figure 313). The BN and VOR craters were characterized by gas-and-steam emissions. Explosions in the NSEC ejected coarse pyroclastic material above the crater rim several tens of meters, some of which were deposited on the S flank, and accompanied by sporadic ash emissions; these explosions continued to widen the depression in the saddle cone of the NSEC. Intermittent nighttime crater incandescence was observed in the NSEC. Sporadic and weak ash emissions were observed in the VOR. On 9 September INGV scientists reported intense degassing from the center pit crater in the BN. To the NW of this center depression, a new pit crater had formed and began to widen due to the collapse of the crater walls (figure 314). On 26 September explosions in the NSEC produced an ash plume that rose to 4 km altitude and drifted E, though no ashfall was reported.

Figure 313. Webcam image showing explosions in the New Southeast Crater and resulting ash emissions on 1 September 2020. Courtesy of INGV (Report 37/2020, ETNA, Bollettino Settimanale, 31/08/2020 – 06/09/2020, data emissione 08/09/2020).

Figure 314. Photos of the bottom of the W edge of the Bocca Nuova Crater at Etna on 9 September 2020. Gas-and-steam emissions are visible rising above the pit crater in the background. In the foreground a new pit crater had formed to the NW of the central pit crater (yellow dotted line). Photo was taken from the S edge of the BN crater. Courtesy of INGV (Report 38/2020, ETNA, Bollettino Settimanale, 07/09/2020 – 13/09/2020, data emissione 15/09/2020).

Activity during October-November 2020. Similar variable Strombolian activity continued into October in the NSEC (cono della sella) and NEC; isolated and weak ash emissions were visible in the VOR crater and gas-and-steam emissions continued in both the VOR and BN craters. On 1 October an increase in explosive activity in the NSEC occurred around 0800, which produced an ash plume rising to 4.5 km altitude, drifting E. Ash emissions on 3 October were mostly confined to the summit crater, but some drifted toward the Valle del Bove. On 7 October Strombolian explosions in the NSEC generated an ash plume that rose to 4.5 km altitude drifting E and ESE. INGV personnel reported ashfall as a result in the Citelli Refuge. On 9 October drone observations showed at least three active scoria cones on the floor of the NEC with diameters of 30-40 m and heights of 10 m; a fourth vent was later reported in November (figure 315). INGV reported that activity characterized by Strombolian explosions and spatter was fed by these vents, accompanied by intense intra-crater fumarolic activity.

Figure 315. Map of the summit craters of Etna showing the active vents and the area of cooled lava flows (light green) updated on 9 October 2020. The base is modified from a 2014 DEM created by Laboratorio di Aerogeofisica-Sezione Roma 2. The hatch marks indicate the crater rims: BN = Bocca Nuova; VOR = Voragine; NEC = North East Crater; SEC = South East Crater; NSEC = New South East Crater. Red circles indicate areas with ash emissions and/or Strombolian activity, yellow circles indicate steam and/or gas emissions only. Courtesy of INGV (Report 44/2020, ETNA, Bollettino Settimanale, 19/10/2020 – 25/10/2020, data emissione 27/10/2020).

During 12-18 October surveillance cameras captured incandescence in the NEC and pyroclastic material seen during more intense explosions. During the week of 19-25 October several thermal anomalies were detected on the NEC and BN crater floor. Particularly at night, thermal and surveillance cameras observed incandescent ejecta rising above the NSEC (figure 316). On 23 October a helicopter overflight along the W side of Etna showed continued explosions at the NSEC, which produced both ash emissions and incandescent shreds of lava. An associated ash plume rose to 4.5 km altitude and drifted SSE. Sporadic ash emissions were also observed in the BN crater (figure 316). During 26 October to 1 November occasional Strombolian activity resumed in the VOR which ejected material over the crater rim. The BN crater activity was characterized by small intra-crater collapses and consequent ash emissions. In the NEC, similar explosive activity persisted with the addition of small lava flows from the scoria cones, which were visible from the crater edge, though activity remained confined to the crater.

Figure 316. Photos showing Strombolian activity at the New Southeast Crater at Etna on 25 October 2020 (top left); ash emissions were observed during 22 October 2020 (top right). Ash emissions rose above the Bocca Nuova Crater on 22 October (bottom left) and weak ash emissions were seen above the Voragine Crater on 22 October (bottom right). Courtesy of INGV (Report 44/2020, ETNA, Bollettino Settimanale, 19/10/2020 – 25/10/2020, data emissione 27/10/2020).

Activity in November continued with variable Strombolian explosions accompanied by discontinuous ash emissions from the NSEC, NEC, and BN. During more intense explosions, ejecta reached several tens of meters above the crater, sometimes falling just outside the crater rim. Intensive degassing in the BN crater revealed occasional reddish ash in the new W pit crater that formed in September. The central pit crater was primarily characterized by intense gas-and-steam emissions and intra-crater wall collapses. Four vents were observed on the bottom of the NEC during 2-8 November, though only three of them produced Strombolian explosions, the fourth was quiet. On 5 November Strombolian explosions in BN originated from the W pit crater; coarser material was ejected above the pit crater rim. By 12 November Strombolian activity had decreased, explosions in the BN had deposited material on the S flank. Out of the three active NEC scoria cones, only one was continuously exploding, the second had discontinuous explosions, and the third was primarily emitting gas-and-steam. On 15 November faint ash emissions from the E side of the NSEC were observed (figure 317). On 20 November sporadic explosive activity continued from the NSEC and BN, the former of which occasionally ejected material above the crater rim (figure 318).

Figure 317. Webcam images of the New Southeast Crater at Etna on 14 (left) and 15 (right) November 2020 showing Strombolian activity in the cono della sella (left) and the E vent shown by the black arrow (right). Images were taken by the Montagnola webcam. Courtesy of INGV (Report 47/2020, ETNA, Bollettino Settimanale, 09/11/2020 – 15/11/2020, data emissione 17/11/2020).

Figure 318. Drone image of the New Southeast Crater at Etna on 21 November 2020 showing an ash plume rising above the inner crater rim (black line). Fallout is visible within the crater rim (small red circles). Courtesy of INGV (Report 48/2020, ETNA, Bollettino Settimanale, 16/11/2020 – 21/11/2020, data emissione 24/11/2020).

Information Contacts: Sezione di Catania - Osservatorio Etneo, Istituto Nazionale di Geofisica e Vulcanologia (INGV), Sezione di Catania, Piazza Roma 2, 95123 Catania, Italy (URL: http://www.ct.ingv.it/it/); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); Hawai'i Institute of Geophysics and Planetology (HIGP) - MODVOLC Thermal Alerts System, School of Ocean and Earth Science and Technology (SOEST), Univ. of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://modis.higp.hawaii.edu/); Global Sulfur Dioxide Monitoring Page, Atmospheric Chemistry and Dynamics Laboratory, NASA Goddard Space Flight Center (NASA/GSFC), 8800 Greenbelt Road, Goddard, Maryland, USA (URL: https://so2.gsfc.nasa.gov/); Boris Behncke, Istituto Nazionale di Geofisica e Vulcanologia (INGV), Sezione di Catania, Piazza Roma 2, 95123 Catania, Italy (URL: https://twitter.com/etnaboris).

April 2021 (BGVN 46:04) Cite this Report

Frequent explosions, ash plumes, fountaining, and lava flows during December 2020-March 2021

Etna is located on the island of Sicily, Italy, and has had eruptions that date back 3,500 years. Its most recent eruptive period began in September 2013 and more recently has been characterized by frequent Strombolian explosions, effusive activity, and ash emissions. Activity has commonly originated from the summit areas, including the Northeast Crater (NEC), the Voragine-Bocca Nuova (or Central) complex (VOR-BN), the Southeast Crater (SEC, formed in 1978), and the New Southeast Crater (NSEC, formed in 2011). Another crater, referred to as the "cono della sella" (saddle cone), developed during early 2017 in the area between SEC and NSEC. This report covers activity from December 2020 through March 2021, consisting of frequent Strombolian explosions of variable intensity, effusive activity, ash emissions, and ashfall. Information for this report comes from weekly and special reports by the Osservatorio Etneo (OE), part of the Catania Branch of Italy's Istituo Nazionale di Geofisica e Vulcanologica (INGV).

Summary of activity during December 2020-March 2021. Intra-crater Strombolian explosions that varied in frequency and intensity throughout the reporting period, and the accompanying ash plumes that rose to a maximum altitude of 11 km, primarily originated from the Southeast Crater (SEC), Voragine Crater (VOR), and occasionally the Northeast Crater (NEC) and Bocca Nuova Crater (BN). Beginning in mid-February a series of short lava fountaining events occurred in the SEC that continued through March. These episodes were also characterized by accompanying ash plumes, incandescent ejecta, and lava flows.

MIROVA (Middle InfraRed Observation of Volcanic Activity) analysis of MODIS satellite data shows strong and frequent thermal anomalies throughout the reporting period (figure 319). Some of these anomalies were markedly high in mid-December, mid-January, and mid-March. According to the MODVOLC thermal algorithm, a total of 190 alerts were detected in the summit craters during December through March; thermal anomalies were reported for nine days in December, eleven days in January, fifteen days in February, and sixteen days in March. Frequent Strombolian activity contributed to distinct SO₂ plumes that drifted in multiple directions (figure 320).

Figure 319. Strong and frequent thermal anomalies at Etna were detected during December 2020 through March 2021, as reflected in the MIROVA data (Log Radiative Power). Some thermal anomalies were significantly high in mid-December, mid-January, and mid-March. Courtesy of MIROVA.

Figure 320. Distinct SO₂ plumes from Etna were detected by the TROPOMI instrument on the Sentinel-5P satellite on multiple days during December 2020 to March 2021 due to frequent Strombolian explosions, including 22 December (top left) 2020, 20 January (top right), 21 February (bottom left), and 7 March (bottom right) 2021. Courtesy of NASA Global Sulfur Dioxide Monitoring Page.

Activity during December 2020. During December, INGV reported intra-crater Strombolian explosions in the SEC, NEC, and BN. During the more intense SEC explosions material was ejected onto the flanks. Gas-and-steam emissions were reported in the VOR. A field survey on 13-14 December showed that the SEC was an irregular ellipse 150 x 230 m open to the SW. On 13 December Strombolian activity intensified at 2020 and around 2300 evolved to lava fountains which lasted through 2350, though explosions continued. Collapses of the SW part of the SEC at 2315 resulted in pyroclastic flows that traveled up to 2 km, covering the Monte Frumento Supino cone (SSW flank). Around that time two fissures opened on the SW flank of the SEC and produced lava flows until about 2350 (figure 321). A third minor pyroclastic flow went down the SSW flank at 2330. Two lava fountains were seen during 0050-0110 on 14 December.

Figure 321. Photos of Strombolian activity at the Southeast Crater at Etna on the evening of 14 December 2020 (left) seen from Tremestieri Etneo (20 km S) and a thermal image showing the Bocca Nuova, Voragine, and three active vents in the SEC seen from the Montagnola (EMOV) thermal camera at 0949 (UTC) on 15 December (right). Courtesy of INGV (Report 52/2020, ETNA, Bollettino Settimanale, 14/12/2020 – 20/12/2020, data emissione 22/12/2020).

During a field inspection on 14 December scientists noted that the two lava flows on the S and SW flanks were cooling; the S flow had widened near the base of the SEC and formed four main lobes, one of which had stopped just NW of the cones that formed in 2002-2003 (figure 322). The SW flow traveled SSW, branched, curved around the W part of Monte Frumento Supino, and then stopped. An explosion in the easternmost SEC vent generated an ash plume at 1352 that rose to 4 km altitude and drifted S. Additionally, on 14 December sporadic ash explosions resumed in the VOR; incandescent ejecta was visible at night. On 15 December a new lava flow formed on the SW flank of the SEC at 0924 that advanced a few hundred meters. Eruptive activity briefly stopped in the E vent of the SEC during the afternoon of the 15th and during 16-18 December exhibited strong degassing and nighttime incandescence.

Figure 322. Map of the Southeastern Crater (SEC) at Etna showing active lava flows and the cono della sella (red dot). The light green hatch mark represents the location of the eruptive fissure that opened on the SEC flank. The lava flow extended about 2 km SW, and by 14 December had formed four main lobes. The black arrow represents the direction of the pyroclastic flow after the collapse of the SW portion of the SEC cone. This map uses ground observations and thermal image analysis on a PlanetScope satellite image. Courtesy of INGV (Report 51/2020, ETNA, Bollettino Settimanale, 07/12/2020 – 13/12/2020, data emissione 15/12/2020).

Seismic tremor amplitude gradually increased on 20 December, though weather conditions prevented observations. On 21 December at 1008 Strombolian activity increased in the SEC from the central and easternmost vents. Activity evolved to lava fountaining that lasted an hour, as well as an ash plume that rose to 10 km altitude and drifted NE. An active lava flow was still visible on the SW part of the cone which had collapsed on 13 December. A second flow was observed at 1521 on the S slope of the SEC that descended toward the Valle del Bove. Activity continued through the night (figure 323), and on 22 December at 0350 Strombolian activity increased in the central and easternmost vents; around 0415 a lava flow from the SW flank traveled W, overlapping cooling lava from 21 December. Lava fountaining began again at 0519 and fed three lava flows: one from the S flank traveled SW for 2.8 km and was 600 m wide, branching off to the W and E of Monte Frumento Supino, a second that traveled 2.8 km E toward the Valle del Bove, and a third that originated at the E vent of the SEC that traveled 1.3 km ENE toward the Valle del Leone (figure 324). At 0520 a few small phreatic explosions in the Valle del Bove were due to the lava flow interacting with snow. By 0600 the lava fountains gradually subsided and stopped, though Strombolian explosions persisted at varying intensities. On 24 December at 0830 explosive activity in the E vent of the SEC gradually increased, ejecting material above the crater rim and emitting ash that drifted E.

Figure 323. Photo of Etna’s Southeast Crater showing a new episode of lava fountaining during the early morning on 22 December 2020 viewed from Tremestieri Etneo, south of the volcano. Photo by Boris Behncke, INGV.

Figure 324. Thermal webcam images showing (top left) Strombolian explosions and (top right) lava fountaining in the Southeast Crater seen from the Nicolosi (ENT) and Montagnola (EMOT) cameras on 22 December 2020. Lava flows were visible traveling toward the Valle del Bove and Valle del Leone seen from the Monte Cagliato (EMCT) (bottom left) and Schiena della’asino (ESR) (bottom right). Courtesy of INGV (Report 53/2020, ETNA, Bollettino Settimanale, 21/12/2020 – 27/12/2020, data emissione 29/12/2020).

On 29 December at 0750 there was a gradual increase in explosive activity in the E vent of the SEC, producing ash emissions that drifted ENE. Around 0900 Strombolian activity further intensified, ejecting coarse material onto the E flank of SEC (figure 325), but by 1000 the explosions had decreased. Intra-crater Strombolian activity in the NEC, VOR, and BN continued with sporadic ash emissions through the rest of the month; explosions in the VOR intensified, ejecting material above the crater rim.

Figure 325. Photos of the Strombolian activity at the Voragine (left background) and Southeast Crater (right foreground) at Etna on the evening of 28 December (left) and ash emissions rising from the SEC on the morning of 29 December (right) 2020. Photos by Boris Behncke, INGV.

Activity during January 2021. Activity in January continued with intra-crater Strombolian explosions of variable intensity in the SEC, NEC, VOR, and BN with sporadic ash emissions. On 4 and 6 January at least two episodes of intense Strombolian explosions produced continuous ash plumes that drifted E and ejected coarse pyroclastic material. A lava flow on 17 January breached the SEC at 0740 and traveled to the base of the cone toward the Valle del Bove (figure 326); the lava effusion rate increased at 0819, and the flow reached an elevation of 3 km by 1000. Volcanic tremor amplitude and Strombolian activity intensified at 2000 on 18 January, evolving into lava fountains through 2130. A lava flow emerged in the E vent of the SEC at 2015 and moved 2 km ESE toward the Valle del Bove. Lava fountaining produced a plume that drifted SE, resulting in ashfall in Fleri and Acicastello (figure 327). During 2130-2147 a second lava flow on the N side of the SEC reached a length of 1.3 km. By 19 January the explosions decreased in intensity and the lava flows had begun to cool. On 20 January a new lava flow on the N side of the SEC traveled ENE at 0140, overlapping the previous flow on the 18th; by 1830 it was no longer active. The VOR was characterized by almost continuous Strombolian explosions that ejected material above the crater rim. Satellite imagery from 27 January showed that a small lava flow from a vent in the N section of the VOR was pouring into the BN. The BN also produced Strombolian explosions that often ejected material above the crater rim. At night, summit crater incandescence was observed in the NEC.

Figure 326. Map of the summit craters of Etna showing the active vents and lava flow field on 18 January 2021. The base is modified from a 2014 DEM created by Laboratorio di Aerogeofisica-Sezione Roma 2. The hatch marks indicate the crater rims: BN = Bocca Nuova; VOR = Voragine; NEC = North East Crater; SEC = South East Crater. Red circles indicate areas with ash emissions and/or Strombolian activity. Yellow circles indicate steam and/or gas emissions only. The red shape highlights the active lava flow on 18 January and the yellow and orange shape highlights the cooling lava flow from 17 January. Courtesy of INGV (Report 04/2021, ETNA, Bollettino Settimanale, 18/01/2021 – 26/01/2021, data emissione 26/01/2021).

Figure 327. Photos of lava fountains and an ash plume in the SEC at Etna that resulted in ashfall on the SE flank (top) as well as in Fleri (bottom left) and Acicastello (bottom right). Photo a was taken from Tremestieri on the S side of the volcano. Courtesy of INGV (Report 04/2021, ETNA, Bollettino Settimanale, 18/01/2021 – 26/01/2021, data emissione 26/01/2021).

Activity during February 2021. Variable Strombolian activity continued into February at all four summit craters; the last time this occurred was during 1998-1999. The most intense, almost continuous, Strombolian explosions at the SEC originated from two vents in the eastern top of the cone; less intense activity occurred at the S vent. Intra-crater Strombolian activity at the NEC sometimes produced nighttime incandescence. Explosions at the BN sometimes ejected coarse material above the crater rim. A field inspection on 5 February showed that three scoria cones had been built around vents at the bottom of the crater. Another nearby cone occasionally produced dense emissions. Intra-crater lava flows continued to spill into the BN from the VOR, overlapping those formed in late January. On 6 February around 0530 Strombolian activity intensified in the E vent of the SEC and produced an ash plume that drifted E.

During the morning of 15 February explosive activity at the SEC intensified, with activity continuing at the E vents. Sporadic and sometimes violent explosions were also observed at the saddle cone; intra-crater explosive activity continued in the BN, VOR, and NEC. On 16 February at 1700 lava began advancing down the E flank of the SEC for a few kilometers. A partial cone collapse at 1705 produced a pyroclastic flow that traveled 1.5 km along the W wall of the Valle del Bove. The activity changed to lava fountains around 1710, rising 500-600 m high and generating an ash plume that rose to 6-10 km altitude and drifted S (figure 328). Centimeter-sized lapilli and ash was observed in Nicolosi (16 km S), Mascalucia (19 km S), and as far as Catania (29 km SSE) while fine ashfall was reported in Syracuse (60-80 km SSE). Lava flows continued to advance into the Valle del Bove, reaching an elevation of 2 km by 1759. Another lava flow from the SEC traveled N toward the Valle del Leone; smaller lava flows traveled N and S, reaching 2.9 km elevation. Explosive activity decreased and lava fountaining stopped between 1800 and 1838, though ashfall continued; by 2025 the lava flows had stopped. Strombolian activity persisted at the SEC overnight during 16-17 February and stopped by 0715 on 17 February, though sporadic explosions were reported in the VOR at 0420, 0435, 0444.

Figure 328. Photos during 15-16 February of Strombolian activity at the summit craters at Etna on 15 February 2021 (top left); a pyroclastic flow that occurred at the beginning of the eruptive event on 16 February at 1805 (top right); an eruption plume that was a result from the eruptive event on 16 February, seen from the S (bottom left); map of the lava flows on 16 February showing the active vents (red dots), degassing vents (yellow dots), summit craters (black hatch marks), and direction of the lava flows (light green and dark green), as well as the maximum length (4 km) and volume (2.6 million cubic meters) (bottom right). Courtesy of INGV (Report 08/2021, ETNA, Bollettino Settimanale, 15/02/2021 – 21/02/2021, data emissione 23/02/2021).

An eruptive event began at 2330 on 17 February, about 30 hours after the previous one, with a lava flow from the E vents in the SEC, followed by lava fountaining at 0100 on the 18th that rose 600-700 m (figure 329). The lava flow advanced toward the Valle del Bove, the NE, SE, and SW through the saddle vent (“bocca della sella”), covering an area of about 1 km. A second flow on the N flank of the SEC moving toward the Valle del Leone was about 1 km long. Another flow was reported on the S side of the SEC. The resulting ash plume drifted SE, causing ashfall in Zafferana, Etna, and Acireale. The lava fountains ended between 0140-0155 on 18 February, though the lava flows continued to advance.

Figure 329. Activity at Etna during 17-18 February 2021 included lava flows and fountaining. The initial lava flow is seen in a thermal camera image just before midnight from Monte Cagliato on the E side of the volcano (top left). Lava fountains that rose 600-700 m high and lava flows are seen from Milos shortly after midnight (top right). An eruption plume seen from Milos at 0020 on 18 February was accompanied by nighttime incandescence, lava fountains, and lava flows (bottom left). A map of the lava flows on 17-18 February shows the active vents (red dots), degassing vents (yellow dots), summit craters (black hatch marks), and direction of the lava flows (yellow and green), as well as the maximum length (4.1 km) and volume (4 million cubic meters) of the flows (bottom right). Courtesy of INGV (Report 08/2021, ETNA, Bollettino Settimanale, 15/02/2021 – 21/02/2021, data emissione 23/02/2021).

During the morning of 19 February a lava flow effused from the E vents in the SEC at 0855, followed by a rapid increase in explosions and renewed lava fountaining (figure 330). A line of 4-5 vents produced “fan-shaped” lava fountains at 0953. An ash plume rose to 10 km altitude and drifted SE, causing ashfall in some towns. The lava flow that descended toward the Valle del Bove interacted with snow, causing strong explosions, and were accompanied by rockfalls on the flanks of the SEC. By 1110 the explosive activity had stopped.

Figure 330. Thermal images of the lava flow at Etna around 0900 (local) on 19 February 2021 taken with the thermal camera in Monte Cagliato (top left). Later lava fountains reached 600-700 m high, based on the thermal image from Monte Cagliato (top right). A strong ash plume was observed from Pisano (SE) (bottom left). A map of the lava flows on 19 February showing the active vents (red dots), degassing vents (yellow dots), summit craters (black hatch marks), and direction of the lava flows (orange and green), as well as the maximum length (3.8 km) and volume (4 million cubic meters) (bottom right). Courtesy of INGV (Report 08/2021, ETNA, Bollettino Settimanale, 15/02/2021 – 21/02/2021, data emissione 23/02/2021).

Weak Strombolian activity was visible in the late afternoon of 20 February (figure 331). At 2230 a small lava flow from the E vent in the SEC descended 150-200 m into the Valle del Bove. By 2300 the activity had changed to pulsating lava fountains. Beginning at 0100 on 21 February more western vents became active and the E vents ejected lava 600-800 m high. At 0128 lava fountains were ejecting lava up to 1 km high and were sustained for about 10 minutes (figure 331). At the same time, a lava flow from the saddle vent moved a few hundred meters SW. An ash plume rose to 10 km altitude, resulting in ashfall on the SW flank. At 0200 the lava fountains decreased in intensity and by 0220 explosive activity stopped. Periodic ash emissions rose from both the S and E vents later in the evening. A lava flow in the SEC advanced 1 km toward the Valle del Bove. Lava fountains and Strombolian explosions continued at multiple vents. Activity intensified again during 0218-0220 on the 22nd, with lava fountains over 1 km high sending incandescent material onto the flanks. Lava flows in the Valle del Bove reached 3.5-4 km from the crater. During 0430-0515 about 20 strong explosions from SEC vents ejected incandescent bombs that landed at the base of the cone. The NEC was characterized by strong degassing and crater incandescence, often accompanied by Strombolian activity.

Figure 331. Images of weak Strombolian activity in the eastern vents of the SEC at Etna at sunset on 20 February 2021 (top left). Thermal image from the Bronte thermal camera showing strong Strombolian activity at 0131 (local) on 21 February (top right). A strong ash plume at 0205 on 21 February was observed from Tremestieri Etneo (bottom left). A map of the lava flows during 20-21 February showing the active vents (red dots), degassing vents (yellow dots), summit craters (black hatch marks), and direction of the lava flows (red and green), as well as the maximum length (3.2 km) and volume (2.9 million cubic meters) (bottom right). Courtesy of INGV (Report 08/2021, ETNA, Bollettino Settimanale, 15/02/2021 – 21/02/2021, data emissione 23/02/2021).

During the evening on 22 February weak Strombolian explosions were visible in the SEC. The frequency and intensity of the explosions increased and by 2210 material was ejected onto the flanks. Jets of lava were ejected 300 m high at 2305, and by 2327 lava fountains were reported from a second SEC vent. Lava overflowed the crater at 2328 toward the Valle del Bove. Within the first hour of 23 February lava fountains rose more than 1.5 km and an ash plume reached 10 km altitude, causing ashfall to the NW. Lava overflowed the S vent and descended SW. At 0115 the lava fountains decreased. Strombolian activity intensified again at 0450, accompanied by ash emissions. Two lava flows traveled SW and SE, the latter of which reached 1.7-1.8 km elevation. By 1000 the lava flows were no longer active; the flow on the SW flank had traveled a few hundred meters, overlapping the previous flows.

The lava fountaining episodes continued; Strombolian activity at the two vents in the SEC increased during the late afternoon on 24 February that evolved into lava fountains reaching 400 m above the crater. Ash emissions also persisted in the SEC. Lava overflows from the crater headed ESE toward the Valle del Bove as far as 2-4 km and in the S area of the SEC. During 1900-2122 the lava fountains reached 500 m high and a resulting ash plume rose as high as 11 km altitude. A second lava flow traveled SW and at 2100 a pyroclastic flow descended 1 km into the Valle del Bove. The lava fountains in the SEC stopped by 2335, though the lava flow remained active in the SW and E sections.

Weak Strombolian activity on 28 February was visible at 0810 that evolved to lava fountains at 0839, feeding lava flows that traveled E toward the Valle del Bove. The fountains abruptly intensified at 0902 with jets of lava rising 700 m above the crater rim. An ash plume rose as high as 11 km altitude and drifted ESE, resulting in ashfall to the E (figure 332). A small lava flow at the S part of the SEC began at 0909, followed by a pyroclastic flow at 0920. The lava fountains ended abruptly at 0933, though the lava descending E remained active. By 1526 the lava flow in the Valle del Bove was no longer active.

Figure 332. Photo of a strong ash plume rising above Etna’s Southeast Crater on the morning of 28 February 2021 that drifted ESE, with ashfall visible. Taken from Tremestieri Etneo. Photo by Boris Behncke, INGV.

Activity during March 2021. Weak Strombolian activity resumed on 2 March at 1145 in the SEC, which increased in intensity at 1234 with ash emissions. From 1324 to 1550 lava fountains generated an ash plume 9 km above the crater, depositing ash and lapilli in Nicolosi, Aci San Antonio (18 km SE), Pedara (15 km SSE), and Catania (29 km SSE). On 4 March Strombolian explosions increased at 0200 and produced ash emissions that dispersed NE (figure 333). At the same time, Strombolian activity from VOR ejected material above the crater. Degassing persisted in the NEC. Around 0320 the Strombolian explosions in the SEC evolved to lava fountains and at 0515 a lava flow from the E section of the base of the cone was traveling toward the Valle del Bove. Strombolian activity in VOR changed to lava fountains at 0859 that were 300 m high. An ash plume rose 11 km above the crater, depositing ash and lapilli in Fiumefreddo (19 km ENE), Linguaglossa (17 km ESE), and the area of Reggio Calabria. Lava fountains continued.

Figure 333. Photos of the beginning an eruptive episode characterized by an early lava flow originating from Etna’s Southeast Crater (right foreground) and an explosion at the Voragine Crater (left background) on 4 March 2021 (left). Dense gray ash plumes and white degassing plumes were visible from several summit vents on 4 March (right). Taken from Tremestieri Etneo. Photos by Boris Behncke, INGV.

Another eruptive episode on 7 March starting between 0100 and 0200 included Strombolian explosions and minor lava effusions at the E base of the SEC that descended into the Valle del Bove. At 0430 an increase in Strombolian activity generated an ash plume that rose to 5 km altitude and drifted E. The lava reached an elevation of 2.8 km altitude by 0450. Strombolian activity intensified again at 0520 and the lava flow advanced to 2.7 km elevation. Lava fountains at 0720 generated another ash plume that rose to 10 km altitude and drifted E. INGV-OE personnel reported ash and lapilli deposits in Milo (11 km ESE), Fornazzo (10 km ESE), Trepunti (17 km ESE), Giarre (17 km ESE), Macchia di Giarre (16 km ESE), Mascali (18 km E), Riposto (19 km ESE), and Torre Archirafi (20 km ESE). Strombolian activity resumed at 1050 and was over by 1500.

Similar Strombolian activity in the SEC on 10 March changed to lava fountaining and a large eruption plume that rose to at least 9 km altitude and drifted ENE (figure 334). Ash and lapilli were reported in Mascali, Giarre, and Fiumefreddo. A lava flow from the S vent reached an elevation of 1.8 km. By 0430 on 10 March the lava fountaining had stopped, though sporadic ash emissions continued until 0700. On 12 March Strombolian activity in the SEC and accompanying ash emissions began again. As the activity intensified, lava overflowed the E part of the SEC, descending toward the Valle del Bove. Lava fountaining was observed up to 500 m and generating an ash plume that rose to 6 km altitude and drifted E. Within an hour, lava had advanced from an elevation of 2.8 km to 2 km. By 0939 the ash plume had risen to 9-10 km altitude and resulted in ashfall in Fleri, Milo, Fornazzo , Giarre, Santa Venerina (15 km SE), and Torre Archirafi (20 km ESE) (figure 335). Lava fountaining had stopped at 1050, though weak Strombolian activity and ash emissions persisted until 1115. The lava flow advanced as far as 1.7 km elevation while a second lava flow expanded on the W slope of the Valle del Bove for an average length of 3 km and a volume of roughly 1 million cubic meters. Strombolian activity continued in the NEC, BN, and VOR, producing minor ash emissions.

Figure 334. Photo of the nighttime lava fountaining activity at Etna during 9-10 March 2021. Courtesy of INGV Youtube channel.

Figure 335. Photo of an ash plume rising above Etna’s Southeast Crater on the morning of 12 March 2021. Taken from Tremestieri Etneo. Photo by Boris Behncke, INGV.

On 14 March Strombolian activity began at 2110 that evolved into lava fountaining at 0048 on the 15th (figure 336). Lava traveled toward the Valle del Bove as an ash plume drifted E (figure 337). By 0343 lava fountaining had stopped, though weak Strombolian activity and lava flows continued. On 17 March at 0155 weak Strombolian activity was observed, changing into lava fountaining at 0319. An ash plume drifted SE and a lava flow was moving toward the Valle del Bove, the latter of which overlapped the one from 15 March. Due to cloud cover, observations were limited and discontinuous. Fountaining activity stopped at 0717 and was followed by explosive activity. Weather conditions cleared the summit on 18 March at 2142, showing explosions in the SEC and a lava flow in the Valle del Bove. On 19 March at 0734 explosive activity was visible in the SEC, which intensified at 0915, accompanied by ash emissions. Lava fountaining started at 0935 with an accompanying ash plume that drifted ENE. By 1136 lava fountaining had stopped and changed to Strombolian activity, which gradually decreased. Only sporadic explosions were visible with minor ash emissions by 1350; lava flows along the Valle del Bove were reported in the late morning.

Figure 336. Photo of a lava fountain episode at Etna’s Southeast Crater during the night of 14-15 March 2021. Taken from Tremestieri Etneo. Photo by Boris Behncke, INGV.

Figure 337. A map of the lava flows on 15 March 2021 showing the active vents (red dots), degassing vents (yellow dots), summit craters (black hatch marks), and direction of the lava flows (blue), as well as the maximum length (2.7 km) and volume (1.1 million cubic meters) (bottom right). Courtesy of INGV (Report 12/2021, ETNA, Bollettino Settimanale, 15/03/2021 – 21/03/2021, data emissione 23/03/2021).

Though weather conditions often prevented a clear view of the summit, weak Strombolian activity was reported in the SEC at 2005 on 23 March, which had evolved into lava fountaining at 0330 on 24 March (figure 338). At 0335 a lava flow from the SEC was seen branching toward the Valle del Bove and the SE. A pyroclastic flow followed the lava at 0336, descending into the Valle del Bove. The lava fountains generated an ash plume that rose to 6-7 km altitude and drifted SSE, resulting in ashfall on the S slope and in Catania. Lava fountaining gradually decreased at 0700 and by 0945, it had stopped; the lava flows continued to advance. Intra-crater Strombolian activity continued in the NEC, BN, and VOR, accompanied by sporadic weak ash emissions. After the fountains stopped, another ash plume was seen rising to 4.5 km altitude and drifting SE. At night, ashfall was reported in Milia and Trecastagni (16 km SE). The explosions had stopped by 1347. By 25 March the two active lava flows had stopped.

Figure 338. Photos of the lava fountain episode and incandescent Strombolian activity at Etna’s Southeast Crater during 23 (left) and 24 (right) March 2021. Taken from Tremestieri Etneo. Photos by Boris Behncke, INGV.

On 30 March weak Strombolian activity in the SEC resumed around 0607 with a single ash explosion that quickly dispersed near the summit (figure 339). Over the course of the day activity at the SEC gradually changed from degassing to continuous weak Strombolian activity at about 1830 from at least two active vents. This activity increased during the night, throwing lava above the crater rim accompanied by sporadic ash emissions. Several lava flows effused from the S base vent. The main part of the flow traveled toward the Valle del Bove with other smaller flows descending to the S and SW. Two other vents at the S base had opened by the evening, one of which ejected spatter a few tens of meters high. Throughout the night, periods of lava fountaining were detected while the main lava flow descended the W wall of the Valle del Bove. Strombolian activity intensified at 1850 and produced an ash plume that rose to 4 km altitude and drifted SSW. At 0000 there was a gradual transition from Strombolian activity to lava fountaining.

Figure 339. Photo of an ash plume rising from Etna’s Southeast Crater on the morning of 30 March 2021. Photo by Boris Behncke, INGV.

Information Contacts: Sezione di Catania - Osservatorio Etneo, Istituto Nazionale di Geofisica e Vulcanologia (INGV), Sezione di Catania, Piazza Roma 2, 95123 Catania, Italy (URL: http://www.ct.ingv.it/it/ ); Boris Behncke, Istituto Nazionale di Geofisica e Vulcanologia (INGV), Sezione di Catania, Piazza Roma 2, 95123 Catania, Italy; MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); Hawai'i Institute of Geophysics and Planetology (HIGP) - MODVOLC Thermal Alerts System, School of Ocean and Earth Science and Technology (SOEST), Univ. of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://modis.higp.hawaii.edu/); NASA Global Sulfur Dioxide Monitoring Page, Atmospheric Chemistry and Dynamics Laboratory, NASA Goddard Space Flight Center (NASA/GSFC), 8800 Greenbelt Road, Goddard, Maryland, USA (URL: https://so2.gsfc.nasa.gov/).

August 2021 (BGVN 46:08) Cite this Report

Strombolian explosions, ash plumes, lava fountaining, and flows during April-July 2021

Etna, located on the island of Sicily, Italy, has documented records of historical eruptions dating back to 1500 BCE. Activity has frequently originated from its summit areas, which include the Northeast Crater (NEC), the Voragine-Bocca Nuova (or Central) complex (VOR-BN), the Southeast Crater (SEC, formed in 1978), and the New Southeast Crater (NSEC, formed in 2011). Another crater, referred to as the "cono della sella" (saddle cone), developed during early 2017 between SEC and NSEC. Its most recent eruptive period began in September 2013 and more recently has been characterized by Strombolian explosions, ash plumes, lava fountaining, and flows (BGVN 46:04). This report updates activity from April through July 2021, covering similar eruptive events, based on weekly and special reports by the Osservatorio Etneo (OE), part of the Catania Branch of Italy's Istituo Nazionale di Geofisica e Vulcanologica (INGV) and satellite data.

Summary of activity during April-July 2021. Volcanism was relatively low at Etna during April and mid-May, primarily characterized by Strombolian explosions and white gas-and-steam emissions. Beginning on 19 May 2021, activity intensified and remained high through July. Intra-crater Strombolian explosions varied in intensity and frequency dominantly in the Southeast Crater (SEC), accompanied by ash plumes that rose to a maximum altitude of 10 km, resulting in ashfall in nearby communities, lava flows primarily on the SW flank, and lava fountains that rose up to 1 km above the summit. Occasional isolated ash emissions were observed above the Northeast Crater (NEC) while degassing primarily characterized the Bocca Nuova Crater (BN) and the Voragine Crater (VOR).

MIROVA (Middle InfraRed Observation of Volcanic Activity) analysis of MODIS satellite data shows strong and frequent thermal anomalies during a majority of the reporting period; during April through mid-May there was a notable decline in the intensity of the anomalies, which was followed by a significant strong pulse, representing the lava flows in June and July (figure 340). This stronger thermal activity was also reflected in data from the MODVOLC thermal algorithm, a total of 183 alerts were detected in the summit crater during April through July; thermal anomalies were reported for four days in April, nine days in May, sixteen days in June, and twelve days in July. Additionally, the lava flows were clearly visible in Sentinel-2 infrared satellite imagery during June and July descending the SW and SE flanks from SEC (figure 341). Frequent Strombolian activity contributed to distinct sulfur dioxide plumes that exceeded two Dobson Units (DUs) that drifted generally S and E (figure 342).

Figure 340. Strong and frequent thermal anomalies at Etna were detected during April through July 2021, as reflected in the MIROVA data (Log Radiative Power). Briefly during April and mid-May, the intensity of the thermal anomalies markedly decreased before renewed lava flows resulted in significantly high anomalies. Courtesy of MIROVA.

Figure 341. Sentinel-2 infrared satellite imagery showing the strong lava flows mainly descending the SW and SE flanks of Etna during June-July 2021, frequently accompanied by white gas-and-steam emissions and thermal anomalies in the northern summit craters. The lava flows shown are all originating from the Southeast Crater (SEC). Lava descended the SW flank on 13 June (top left), 18 June (top right), 23 June (middle left), 26 June (middle right), 3 July (bottom left), and 8 July (bottom right) 2021, getting progressively cooler through July. Flows were visible on the SE flank on 23 June and 26 June. Images using “Atmospheric penetration” (bands 12, 11, 8A) rendering. Courtesy of Sentinel Hub Playground.

Figure 342. Sulfur dioxide plumes exceeding 2 Dobson Units (DUs) from Etna were detected by the TROPOMI instrument on the Sentinel-5P satellite on 1 April drifting S (top left), 26 May drifting E (top right), 27 June drifting E (bottom left), and 20 July drifting NE and SE (bottom right) 2021. Courtesy of NASA Global Sulfur Dioxide Monitoring Page.

Activity during April 2021. During April, INGV reported intra-crater Strombolian explosions in NEC, BN, and SEC. On 1 April around 0100 the SEC explosions transitioned into lava fountaining, generating an ash plume at 0940 that rose to 9 km altitude and drifted SSW. At 0200 a lava flow was reported in the eastern edge of SEC, moving toward the upper part of the VOR-BN complex (Valle del Bove) over the older flows that appeared during March 2021. By 1000 the fountaining had stopped, though explosions continued, producing ash plumes that rose to 5.5-9 km altitude and drifted S and SSW. As a result, ashfall was reported in Milia, Nicolosi, and Catania, and lapilli up to 1 cm was reported in Rifugio Sapienza. A second lava flow appeared at 1040, originating from the same eastern vent and migrating toward VOR-BN. Explosivity gradually declined around 1320 in SEC; by 2300 the lava flows had begun to cool and explosions were no longer observed in the summit crater. During the rest of the month volcanism was relatively low, though intra-crater Strombolian explosions continued in NEC and BN; degassing was prominent in SEC, VOR-BN, and NEC craters. Explosions would eject material tens of meters above the crater rim in NEC, accompanied by some ash emissions. At VOR-BN, an overflight on 13 April noted that activity was focused in the western vents, ejecting reddish ash emissions. An explosion in the eastern vent in SEC at 0030 on 25 April ejected incandescent material 350 m above the crater rim; an ash plume was visible drifting S.

Activity during May 2021. Activity during the first half of May remained similar to the previous month, with degassing at the summit craters and weak, intermittent Strombolian explosions occurring at the eastern vents in SEC, accompanied by ash emissions (figure 343). During the second week of May, INGV reported isolated ash emissions from NEC. On 19 May at 0221 the Strombolian activity in SEC intensified, accompanied by ash emissions, which evolved into lava fountaining by 0234 (figure 344). At the same time, a lava flow was observed traveling down the SW flank, reaching an elevation of 2.8 km. This event lasted three and a half hours, after which the fountains and explosions stopped abruptly. The lava flow was 1.8 km long, 1.5 m thick, and had a volume of 450,000 m³. On 22 May at 0134 Strombolian explosions continued in SEC, generating ash plumes that drifted SE. By 0302 the explosions evolved into lava fountains that ejected material to the NE. A second lava flow developed on the SW flank, overlapping the one from the 19th, advancing to 3 km elevation. It was 1 km long, 1.5 m thick, and had a volume of 150,000 m³. A third lava flow was observed on the E flank was 0.5 km long, 1.5 m thick, and a volume of 70,000 m³. At 0454 the lava fountain and explosive activity had stopped abruptly.

Figure 343. Map of the summit craters at Etna showing the active vents during early May 2021. The base is modified from a 2014 DEM created by Laboratorio di Aerogeofisica-Sezione Roma 2. The hatch marks indicate the crater rims: BN = Bocca Nuova; VOR = Voragine; NEC = North East Crater; SEC = South East Crater. Red circles indicate areas with ash emissions and/or Strombolian activity. Yellow circles indicate steam and/or gas emissions only; degassing was the dominant activity at the summit craters during April through mid-May. A single vent in the eastern part of SEC was explosive. Courtesy of INGV (Report 19/2021, ETNA, Bollettino Settimanale, 03/05/2021 – 09/05/2021, data emissione 11/05/2021).

Figure 344. Thermal images of the intense lava fountaining activity at Etna on 19 May (left) and 22 May (right) 2021 taken with the EMOT thermal camera. Courtesy of INGV (Report 21/2021, ETNA, Bollettino Settimanale, 17/05/2021 – 23/05/2021, data emissione 25/05/2021).

On 24 May explosions were accompanied by a lava flow on the SW flank that descended to 900 m elevation, was 1.5 m thick, and had an erupted volume of 150,000 m³. The most intense phase of the explosions occurred during 2235 and 2345; activity ended around 0010. On 25 May an ash plume rose to 4 km altitude and drifted ENE at 1020; by 1820 explosive activity resumed. Two eruptive episodes on 26 May with peaks at 0350 and 1300 resulted in fine ashfall in Milo (10 km E). The next day, explosions intensified in SEC at 1450 while tephra fell in Giarre (17 km ESE), Milo, and Fornazzo (10 km ESE), though inclement weather prevents visual observations. On 28 May three explosive events were detected beginning at 0830, reaching a maximum intensity at 0900, and ending at 0930. As a result, ashfall was reported in Giarre. A second explosive episode occurred during 1740 and 1815 and a third, more intense explosive episode occurred during 2115-2350. On 30 May explosions beginning at 0545 lasted for two hours and resulted in fine ashfall in Petrulli (12 km SE).

Activity during June 2021. Variable Strombolian activity persisted during June, mainly in SEC; minor and diffuse ash emissions occurred at BN and ash emissions were reported on 4 June in NEC. Degassing was reported in BN and VOR. Weak Strombolian activity in SEC began at 0850 on 2 June, producing minor and diffuse ash plumes, which intensified around 1000 and transitioned to lava fountains that lasted more than two hours (figure 345). The lava fountains generated ash plumes that rose to 5-6 km altitude and drifted E, resulting in ashfall N of Zafferana, near Petrulli and Santa Venerina (figure 345). A lava flow was observed on the S flank of SEC that traveled SW. Fountains stopped at 1245. During the night and early morning of 3-4 June weak intra-crater explosions continued. On 4 June activity increased at 1530 and was characterized by discontinuous ash emissions and a lava flow descending the S flank of SEC. Lava fountains began at 1820 and generated an ash plume that rose to 6.5 km altitude and drifted SE. Ejecta was deposited in Aci Castello, Aciterzza, San Giovanni, La Punta, Tremestieri, Catania, Viagrande, and between Pedara, Fleri, and Siracusa. By 1930 the fountaining had stopped; webcam images showed that by 2300 the lava flow remained active at an elevation of 2.8 km and was a thickness of 2 m.

Figure 345. Webcam and thermal images of the dense ash plumes rising from SEC summit crater at Etna on 1 June (top left), 2 June (top right and bottom left), and 4 June (bottom right) 2021 taken with the EMOV webcam and EMOT thermal camera. Courtesy of INGV (Report 23/2021, ETNA, Bollettino Settimanale, 31/05/2021 – 06/06/2021, data emissione 08/06/2021).

On 9 June at 0110 intra-crater Strombolian activity was reported in the saddle cone, accompanied by discontinuous ash emissions, which continued through 11 June. Coarse material was ejected tens of meters from the edge of SEC, falling back into the crater. The lava flow descending the SW flank on 12 June reached an elevation of 2.7 km and was 1.7 km long, 1.5 m thick, and had a volume of 700,000 m³. At 2130 explosions transitioned into lava fountains that rose 400-500 m above the crater and produced an ash plume that rose to 5.5 km altitude and drifted SSE. Ashfall was reported in Sapienza, Refuge, Nicolosi, Tremestieri, Belpasso, and Catania. The fountains ended at 2350, alongside a cooling flow on the SW flank, though Strombolian explosions continued in SEC.

Several lava fountaining episodes were reported during 1332-1450 on 16 June, 2220 on 18 June to 0210 on 19 June, 2040-2215 on 19 June, 1131 on 20 June to 0214 on 21 June, overnight during 21-22 June, and during the early hours of 22 and 23 June. Each episode began with Strombolian explosions, followed by fountaining and crater overflows descending the SW and SE flanks toward the Valle del Bove (S) on 16 June while those on 21 June traveled 1 km SW toward Monte Frumento Supino, stopping at 2.9 km elevation (figure 341). Ash plumes rose as high as 8 km altitude, causing ashfall the S and SSE. INGV reported nine lava fountain episodes at SEC occurred during 21-27 June; explosive activity was concentrated in the W part of SEC at three of the four saddle vents, though some weak, isolated explosions were detected in the E vents (figure 346). The episodes generated ash plumes rising 5-10 km altitude while lava flows descended the SW and SE flanks (figure 346). An effusive vent was detected on the SE flank of SEC on 23 June. The lava fountaining events have caused SEC cone to grow significantly.

Figure 346. Webcam images of the incandescent lava fountains and gray ash plumes rising from Etna during 21-27 June 2021. Lava flows could be seen on the flanks of the volcano on 21 June (top left), 23 June (top right and middle left), and 25 June (middle right and bottom left) 2021. All photos were taken by Tremestieri on the S flank 20 km from SEC. Courtesy of INGV (Report 26/2021, ETNA, Bollettino Settimanale, 21/06/2021 – 27/06/2021, data emissione 29/06/2021).

Activity during July 2021. Strombolian activity, lava fountains, and ash plumes from SEC continued in July, in addition to occasional gas-and-ash emissions in NEC and BN. Three episodes of lava fountains generated ash plumes that rose 5-10 km altitude, resulting in ashfall to the E and SE. The first episode occurred at SEC at 0040 on 2 July, beginning with Strombolian explosions. Resulting ash plumes drifted ESE and within an hour, lava fountains were visible, accompanied by lava flows moving SW; fountaining had stopped at 0250. The second episode began at 1656 on 4 July, producing fountains at 1725 and ash plumes, ending by 1900 (figure 347). Lava flows traveled SW and ENE while the ash plumes drifted ESE. The last episode occurred at 2330 on 6 July; ash plumes rose to 5 km altitude and drifted SE; ash deposits were observed on the S flank. Explosions intensified at 0000 on 7 July with fountaining occurring thirty minutes later, rising as high as 1 km. A small lava flow originated from the S side of the cone and traveled SW, reaching an elevation of 2.8 km.

Figure 347. Webcam image of an ash plume from Etna on 4 July 2021 taken from the EMOV (Montagnola) camera. Courtesy of INGV (Report 30/2021, ETNA, Bollettino Settimanale, 19/07/2021 – 25/07/2021, data emissione 27/07/2021).

During fieldwork on 7 July scientists observed bombs up to 1 m in diameter on the N side of Mount Barbagallo, while smaller bombs were observed farther away. Lapilli was reported in the S part of Tremestieri, and ash was deposited in Nicolosi, as well as other communities downwind. This episode lasted about two hours. A second episode that began at 2100 on 8 July consisted of Strombolian activity and lava fountains. Ash plumes rose to 3.4 km altitude and drifted SE, resulting in ashfall and the front of the lava flow reached 2.4 km elevation. On 14 July explosions generated an ash plume that rose to 9 km altitude and drifted NE, which resulted in 1-cm-thick lapilli and ash deposits in the Rocca Campana district, as well as in the Rifugio, Citelli, and Presa, with ashfall in Taormina and the S part of Calabria. Another lava flow on the S flank of SEC was moving SW and had begun to cool by 15 July.

On 20 July at 0150 explosions in SEC generated ash emissions that drifted SSE; at 0650 the intensity of these explosions increased and eventually evolved into lava fountains at 0920. At the same time, a lava flow along the side of the SW flank of SEC was reported, as well as deposits of material on the S and E flanks of the volcano. Two lava flows moving SW were detected on the N flank of SEC, stopping at an elevation of 2.9 km. An ash plume drifted E and resulted in ashfall on the E flank and in Zafferana, Milo, and Fornazzo. On 26 July INGV reported continuous ash emissions at NEC that rose to 6 km altitude and drifted N. Strombolian activity intensified again at 0925 on 28 July in SEC, generating discontinuous ash emissions (figure 348); this episode stopped by 2318. Explosions in SEC began again at 1915 on 31 July, producing ash plumes that rose to 5 km altitude and drifted SE, resulting in ashfall in Fornazzo and Milo. At 2115 a lava flow down the SW flank reached 2.8 km elevation.

Figure 348. Webcam images of the Strombolian explosions in the SEC on 28 July 2021 (top left) and the lava fountain activity on 31 July (top right) taken from surveillance cameras in Monte Cagliato and Bronte. Ashfall was observed in Fornazzo (bottom left) and Milo (bottom right). Courtesy of INGV (Report 31/2021, ETNA, Bollettino Settimanale, 26/07/2021 – 01/08/2021, data emissione 03/08/2021).

Information Contacts: Sezione di Catania - Osservatorio Etneo, Istituto Nazionale di Geofisica e Vulcanologia (INGV), Sezione di Catania, Piazza Roma 2, 95123 Catania, Italy (URL: http://www.ct.ingv.it/it/ ); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); Hawai'i Institute of Geophysics and Planetology (HIGP) - MODVOLC Thermal Alerts System, School of Ocean and Earth Science and Technology (SOEST), Univ. of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://modis.higp.hawaii.edu/); NASA Global Sulfur Dioxide Monitoring Page, Atmospheric Chemistry and Dynamics Laboratory, NASA Goddard Space Flight Center (NASA/GSFC), 8800 Greenbelt Road, Goddard, Maryland, USA (URL: https://so2.gsfc.nasa.gov/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground).

March 2022 (BGVN 47:03) Cite this Report

Strombolian activity, ash emissions to 10 km altitude, and lava flows at SEC through January 2022

Etna, located on the Italian island of Sicily, has documented records of eruptions dating back to 1500 BCE. Activity has frequently originated from its multi-cone summit where several craters have formed and evolved over decades. The current configuration consists of the Northeast Crater (NEC), the Voragine (VOR) and Bocca Nuova (BN) craters that were formerly the ‘Central’ crater, and the Southeast crater (SEC). The original Southeast crater formed in 1978, and a second eruptive site formed on its SE flank in 2011 was named the New Southeast Crater (NSEC). Another eruptive site between these two was referred to as the "cono della sella" (saddle cone) and developed during early 2017. Continued activity at both NSEC and the saddle cone created a larger new multi-vent crater area adjacent to the original SEC summit crater, and the whole area is again referred to as SEC (BGVN 46:08, figure 343). The numerous eruptive episodes at SEC during 2021 have gradually but significantly changed the shape of the cone; a new digital terrain model was created on 25 July 2021 that indicates that the highest point on the volcano is now the northern rim of the Southeast crater at 3,357 ± 3 m, replacing the former summit which was the rim of NEC (figure 349).

Figure 349. A digital model of the surface (DSM) of Etna, based on Pléiades satellite images (spatial resolution 50 cm) acquired on 13 and 25 July 2021 indicated that the highest point of the volcano is now the northern rim of the Southeast crater (SEC) and is no longer the rim of Northeast crater (NEC). Courtesy of INGV (Report 32/2021, ETNA, Bollettino Settimanale, 02/08/2021 - 08/08/2021).

Etna’s current eruptive period began in September 2013 and has recently been characterized by Strombolian explosions, ash plumes, lava fountaining, pyroclastic flows, and lava flows associated primarily with the Southeast crater (SEC). This report covers ongoing activity from August 2021 through January 2022, based on weekly and special reports by the Osservatorio Etneo (OE), part of the Catania Branch of Italy's Istituo Nazionale di Geofisica e Vulcanologica (INGV) and satellite data.

Summary of activity during August 2021-January 2022. Most of the activity during August 2021-January 2022 occurred in the vicinity of the Southeast Crater (SEC) cone. Persistent degassing from fumaroles and vents at Bocca Nuova (BN), Voragine (VOR), and Northeast Crater (NEC) were accompanied by occasional diffuse ash emissions (table 11). Explosions, Strombolian activity, lava fountains, and pyroclastic flows continued to reshape the SEC summit into a large interconnected multi-crater area. Multiple lava flows, recurring Strombolian activity, and a lava jet were observed at SEC during 31 July-1 August, 7-10 August, and 27-30 August. Lava fountaining, dense ash plumes, and lava flows on the SW flank were observed at SEC on 21 September. During 20-23 October activity at SEC included an 800-m-high lava fountain, Strombolian activity, 10-km-high ash emissions, and a lava flow. Strombolian activity and ash emissions were reported again from SEC during 4-8 and 14-15 December, and two lava flows emerged from a vent several kilometers E in the Valle de Bove during 13-15 December.

Table 11. Summary of activity at the four primary crater areas at the summit of Etna during August 2021-January 2022. Information is from INGV weekly reports.

Month	Bocca Nuova (BN)	Voragine (VOR)	Northeast Crater (NEC)	Southeast Crater (SEC)	Other Activity
Aug 2021	Pulsating, discontinuous degassing from both vents, BN-1 and BN-2	Degassing from fumaroles around the crater rim	Degassing, Isolated reddish brown ash emissions, plumes reach 6 km on 4-5 and 10 Aug	Intense degassing; Two lava flows 31 Jul-1 Aug; Repeated episodes of Strombolian activity 7-10 Aug, three lava flows to E 9-10 Aug; Strombolian activity 27-30 Aug; 400 m high lava jet on 29 Aug; two lava flows to E, SW 27-29 Aug	Ashfall between Lavinaio and Zafferana, and Acireale and Pozzillo, and in Milo, Fornazzo, San Alfio,and Giarre
Sep 2021	Pulsating, discontinuous degassing from both vents, BN-1 and BN-2	Degassing from fumaroles around the crater rim	Fumarolic degassing	Lava fountaining 21 Sep, ash plume to 8 km, lava flow on S flank flows SW	Ashfall in Zafferana, Milo, Fornazzo, Riposto, Giarre and Mascali from 21 Sep event
Oct 2021	Both pulsating and continuous degassing and sporadic ash emission	Fumarolic degassing	Fumarolic degassing, rare dilute ash emissions	Continuous fumarolic degassing on E rim; Strombolian explosions and lava fountain 800 m high, ash emissions to 10 km altitude and lava flow 20-23 Oct	Ash and lapilli in the communities around Vena, Presa, Piedimonte Etneo, Taormina and as far as the province of Reggio Calabria.
Nov 2021	Degassing mostly from vent BN-1	Degassing from fumaroles around the crater rim	Degassing; explosions with dilute ash emissions on 20 Nov	Degassing around the crater rim; sporadic and dilute ash emissions	--
Dec 2021	Degassing and discontinuous, dilute reddish ash emissions	Weak degassing from fumaroles around the crater rim	Degassing; dilute and discontinuous red ash emissions during first and last weeks	Degassing from fumaroles around the crater rim; Strombolian activity and ash emissions 4-8, 14-15 Dec	Two vents opened with lava flows, W wall of Valle de Bove, 13-15 Dec; Ashfall affected the S flank of the volcano and was reported as far as Capo Passero
Jan 2022	Degassing; sporadic and dilute pulsating reddish ash emissions	Weak degassing from fumaroles	Degassing; dilute ash emission 16 Jan	Weak degassing from fumaroles; discontinuous Strombolian activity and dilute ash emissions	--

Increases in satellite thermal anomaly power correlated closely with observations of lava flows and/or Strombolian activity. MODVOLC thermal alerts were issued during 1-3, 10, and 30-31 August, 2 and 21 September, 23 October, and 4-5 and 14 December 2021. MIROVA log radiative power data from 20 May 2021 through January 2022 showed pulses of high or very high energy during those same intervals (figure 350). Sentinel-2 satellite imagery captured large thermal anomalies that corresponded to lava flows during August and September (figure 351). Major explosive and lava flow events from SEC in August, September, and October were followed by large SO₂ plumes recorded by the TROPOMI Instrument on the Sentinel-5P satellite (figure 352).

Figure 350. The MIROVA log radiative power graph of thermal energy at Etna from 20 May 2021 through January 2022 showed generally decreasing thermal energy during the period with spikes that correspond to observations of lava flows. Courtesy of MIROVA.

Figure 351. Several Sentinel-2 images captured thermal anomalies from lava flows at Etna’s SEC cone. The flows that started on 31 July 2021 were still cooling on 2 August (top left); on 10 August three areas of fresh lava were still very warm (top right); two flows that were active during 27-29 August were still very warm on 30 August (bottom left), and one covered a large area of the SW flank of SEC. An intense anomaly on 21 September corresponded to the flow from the SEC crater that was active that day on the S flank (bottom right). Images use Atmospheric penetration rendering (bands 12, 11, 8a). Courtesy of Sentinel Hub Playground.

Figure 352. Large SO₂ plumes were released from Etna following strong explosive and effusive events at the SEC crater on 1 and 9 August, 21 September, and 23 October 2021. Courtesy of NASA Global Sulfur Dioxide Monitoring Page.

Activity during August 2021. Explosions at SEC on 28 and 31 July 2021 produced Strombolian activity and ash emissions that drifted SE and produced ashfall in Fornazzo and Milo (BGVN 46:08, figure 348). The Toulouse VAAC reported a large SO₂ plume drifting NE between Italy and Greece at 6-9 km altitude on 1 August. Late on 31 July two lava flows emerged from SEC and were active for about two hours on the flanks of the SEC cone; one flowed N to 2,900 m elevation and the other flowed SE to about 2,840 m elevation (figure 353). The Toulouse VAAC reported an ash plume drifting NE on 4 August at 6.1 km altitude. On 7 and 8 August 2021 Strombolian activity resumed at SEC with periodic explosions sending incandescent ejecta beyond the crater rim, and ash emissions that drifted SE at 4.3 km altitude (figure 354).

Figure 353. Two lava flows emerged from the summit of Etna’s SEC late on 31 July 2021; one flowed N and the other SW, they were active for about two hours. Red circles are active vents, yellow circles are degassing vents. BN: Bocca Nuova; VOR: Voragine; NEC: Northeast Crater; SEC: Southeast Crater. The topographical reference base on which the updates have been superimposed is the 2014 DEM developed by the Laboratory of Aerogeophysics - Section Rome 2. Courtesy of INGV (Report 31/2021, ETNA, Bollettino Settimanale, 26/07/2021 - 01/08/2021).

Figure 354. Strombolian activity at Etna’s Southeast Crater on the evenings of 7 August (a, b) and 8 August 2021 (c, d) were recorded by the Monte Cagliato EMCH (a, c) and Montagnola EMOV (b, d) webcams. Courtesy of INGV (Report 32/2021, ETNA, Bollettino Settimanale, 02/08/2021 - 08/08/2021).

In the early hours of 9 August Strombolian activity at SEC grew into a lava flow from the eastern vent that moved E along the western wall of Valle de Bove (figure 355). A second lava flow that headed SW started about one hour later. A third lava flow then emerged from a vent at the SE base of the SEC cone. Ash emissions from the activity drifted SE at 9 km altitude and affected the towns between Lavinaio and Zafferana as far up the coast to Acireale and Pozzillo. It was visible up to 150 km ESE before it dissipated. The lava flows reached 2,900 m elevation and had ceased by the next day (figure 356). On 10 August a dense reddish ash plume from NEC rose to 6 km altitude and drifted E, causing ashfall in Zafferana.

Figure 355. Images taken early on 9 August 2021 from Etna showed Strombolian activity at SEC that produced a lava flow from the eastern vent which moved E along the western wall of Valle de Bove (a, b thermal and La Montagnola visible webcams). Thermal and visible webcams of M. Cagliato (c, d) showed the lava flow along the western wall of the Valle del Bove. The visible webcam of M. Veneretta located on M. Peloritani (e) showed the eruptive column dispersed towards SE at 0355 UTC. Thermal webcam image from Schiena dell'Asino (f) showed the third lava flow at 0555 UTC. Courtesy of INGV (Report 33/2021, ETNA, Bollettino Settimanale, 09/08/2021 - 15/08/2021).

Figure 356. Three lava flows emerged from Etna’s SEC craters on 9 August 2021 and flowed into Valle del Bove. BN: Bocca Nuova; VOR: Voragine; NEC: Northeast Crater; SEC: Southeast Crater. The topographical reference base is the 2014 DEM developed by the Laboratory of Aerogeophysics - Section Rome 2. Courtesy of INGV (Report 33/2021, ETNA, Bollettino Settimanale, 09/08/2021 - 15/08/2021).

A series of explosions began at SEC on 27 August 2021 and produced intermittent ash plumes that drifted E (figure 357). Strombolian activity resumed on the afternoon of 29 August; jets of lava rose 400 m and produced an ash plume that rose to 10 km altitude. Two lava flows emerged; one traveled ESE into the Valle de Bove from a vent at the base of the SEC cone and the other headed SW in the direction of Monte Frumento Supino (figure 358). Ash and lapilli fell in the towns of Fornazzo, Milo, San Alfio, and Giarre to the E. Weak Strombolian activity recurred on 30 August at SEC, and the SO₂ plume from the previous days explosions was clearly visible in satellite data over Greece, drifting E.

Figure 357. Multiple gas, steam, and ash emissions were recorded from Etna during August 2021. Steam plumes rose from Bocca Nuova crater on 25 August 2021 (a). Explosions at the Southeast crater on 27 and 28 August 2021 produced dense, dark gray ash emissions (b and c). Courtesy of INGV (Report 35/2021, ETNA, Bollettino Settimanale, 23/08/2021 - 29/08/2021).

Figure 358. Two lava flows emerged from Etna’s SEC cone on 29 August 2021. One emerged from a vent at the base of the SEC cone, and the other headed SW in the direction of Monte Frumento Supino from the SEC. BN: Bocca Nuova; VOR: Voragine; NEC: Northeast Crater; SEC: Southeast Crater. The reference base is the 2014 DEM developed by the Laboratory of Aerogeophysics - Section Rome 2. Courtesy of INGV (Report 35/2021, ETNA, Bollettino Settimanale, 23/08/2021 - 29/08/2021).

Activity during September 2021. Degassing from fumaroles and vents was observed at all of the summit craters. During a site visit on 16 September 2021, drone imagery of the SEC cone revealed fractures trending NNW-SSE and NS on the rim of the crater (figure 359). After several weeks of quiet, a lava fountain appeared at SEC on 21 September. The early morning activity started as Strombolian activity and increased to a lava fountain that lasted for about 90 minutes. The lava flow spread across the southern flank of the cone in a SW direction, flowing in a channel between Mount Barbagallo and Mount Frumento Supino (figure 360), reaching an elevation of about 2,720 m. The ash cloud rose to 8 km altitude and drifted E with lapilli and ash affecting Zafferana, Milo, Fornazzo, Riposto, Giarre, and Mascali.

Figure 359. Fractures (red lines) trending NNW-SSE and NS at Etna on the rim of the SEC crater were recorded by drone imagery on 16 September 2021 and are shown with the updated shape of the SEC summit crater. BN: Bocca Nuova; VOR: Voragine; NEC: Northeast Crater; SEC: Southeast Crater. The yellow dots represent degassing vents, and the hatched lines are the crater rims. The reference base is the 2014 DEM developed by the Laboratory of Aerogeophysics-Section Rome 2 with superimposed updates. Courtesy of INGV (Report 38/2021, ETNA, Bollettino Settimanale, 13/09/2021 - 19/09/2021).

Figure 360. The lava flow at Etna that emerged on 21 September 2021 flowed SW from the SEC in a channel between Mount Barbagallo and Mount Frumento Supino. BN: Bocca Nuova; VOR: Voragine; NEC: Northeast Crater; SEC: Southeast Crater. The yellow dots are degassing vents, the red dots are actively erupting vents. The reference base on which the 16 September 2021 update of the SEC summit has been superimposed is the 2014 DEM developed by the Laboratory of Aerogeofisica-Section Rome 2. Courtesy of INGV (Report 40/2021, ETNA, Bollettino Settimanale, 27/09/2021 - 03/10/2021).

Activity during October-November 2021. During a field inspection on 4 October by INGV personnel, drone images showed a deepening of the SW and E edges of the SEC. Rare, small ash emissions were observed from NEC during the second week of the month. Weak Strombolian activity resumed at SEC in the morning of 20 October. Sporadic explosions were accompanied by small ash and gas plumes that drifted SW. Activity increased in the afternoon on 21 October, with explosions sending ejecta beyond the crater rim, and discontinuous ash emissions drifting E. During the evening of 22 October activity intensified further with increasing ash emissions into the morning of 23 October when several very strong explosions were followed by a lava fountain which reach as high as 800 m and produced an ash plume that rose to 10 km altitude and drifted ENE (figure 361). Pyroclastic material fell in that direction on the communities around Vena, Presa, Piedimonte Etneo, Taormina, and as far as the province of Reggio Calabria. Shortly after the explosions a pyroclastic flow occurred on the E flank of the SEC cone where it traveled 1.5 km down the western wall of Valle de Bove (figure 362). About one hour later there was a second pyroclastic flow of similar size; this was followed by several smaller flows including one that split into two branches with one moving S and one SE, traveling a few hundred meters.

Figure 361. The steam and ash plume from a large eruption at Etna on 23 October 2021 rose as high as 10 km altitude and drifted ENE. It was recorded from Adrano webcam on the SW flank at 0913 UTC. Courtesy of INGV (Report 43/2021, ETNA, Bollettino Settimanale, 18/10/2021 - 24/10/2021).

Figure 362. Pyroclastic flows generated during the large eruptive event at Etna on 23 October 2021 descended the E flank for 1.5 km at 0900 (a) and 0958 (b) UTC. Courtesy of INGV (Report 43/2021, ETNA, Bollettino Settimanale, 18/10/2021 - 24/10/2021).

The pyroclastic flows emerged from a new collapse area that extended E from the existing crater at SEC. A lava flow emerged from the eastern edge of this opening and traveled E down the western slope of Valle de Bove to an elevation of 2,150 m (figure 363). Lava fountaining ended mid-morning on 23 October; the lava flow ceased being fed that evening (figure 364). Cloudy weather prevented observations during most of the last week of the month, but during 27-28 October small ash emissions were observed from SEC from two separate emission points. During the first week of November, sporadic dilute ash emissions were observed from SEC. Explosions with dilute ash emissions were observed from NEC on 20 November 2021 (figure 365). Degassing from fumaroles and vents continued from the other crater areas.

Figure 363. A new collapse area formed at the summit of Etna’s SEC during the eruptive activity of 23 October 2021, shown by the white hatched oval. Pyroclastic flows emerged from this area as well as a new flow that descended the SE flank of SEC into the Valle de Bove. Updates to the shape of the SEC summit crater were measured on 20 October. The map was developed using an algorithm by task 11 Annex B2, which allows orthorectification of the images taken by the thermal camera of Monte Cagliato and Schiena dell’Asino. Courtesy of INGV (Report 43/2021, ETNA, Bollettino Settimanale, 18/10/2021 - 24/10/2021).

Figure 364. The large eruptive event at Etna’s SEC on 23 October 2021 produced a dense steam and ash plume, and a lava flow that descended the SE flank into the Valle del Bove. It was recorded by INGV personnel in the field (a) and by the thermal cameras of Monte Cagliato (b) and Schiena dell'Asino (c). Courtesy of INGV (Report 43/2021, ETNA, Bollettino Settimanale, 18/10/2021 - 24/10/2021).

Figure 365. Explosions with diffuse ash emissions were observed at Etna’s NEC (right) on 20 November 2021 from the Monte Gagliato webcam. Courtesy of INGV (Report 47/2021, ETNA, Bollettino Settimanale, 15/11/2021 - 21/11/2021).

Activity during December 2021-January 2022. Diffuse and discontinuous ash emissions were observed at NEC on 1 December, and ash dispersed rapidly near the summit. On the morning of 4 December sporadic ash emissions were observed at SEC by both INGV field personnel and webcams. During that afternoon, Strombolian activity was visible at SEC in the webcams, and continued through 8 December along with sporadic ash emissions that drifted ENE. On the afternoon of 13 December, a lava flow emerged from a vent low in the western wall of the Valle de Bove at an elevation of about 2,100 m, immediately north of the Serra Giannicola Grande (figure 366). A secondary vent opened a few tens of meters below the first one. The two vents fed a small flow which was active until early on 15 December. The flow traveled 600 m SE and reached the base of the Valle de Bove at about 1,820 m elevation (figure 367).

Figure 366. All of the 2021 lava flows from the Southeast Crater (SEC) at Etna are shown in gray. The 13 December 2021 flow that emerged from the W wall of the Valle de Bove is shown in red. In the yellow box is the detail of the SEC rim from the Skysat satellite image acquired on 15 December 2021 at 0926 UTC, spatial resolution 50 cm; the red line at the crater delimits the deposit of unconsolidated material detected in satellite images, the black hatched lines represent the crater rims. The red circle: active vent; yellow circle: degassing vent. Courtesy of INVG (Report 51/2021 ETNA, ETNA, BOLLETTINO SETTIMANALE, SETTIMANA DI RIFERIMENTO 13/12/2021 - 19/12/2021).

Figure 367. The 13 December 2021 lava flow at Etna that originated from the W wall of Valle de Bove traveled 600 m SE into the valley. Images show a) thermal image at 2158 (local) on 13 December acquired during the inspection near Mt. Fontane (E side); b) viewed from San Leonardello (Giarre, E side) at 2230 (local) on 13 December (photo B. Behncke); c) the visible camera of Mt.Cagliato (E side) at 0620 (local time) on 14 December; d) view from Schiena dell’Asino (S side) at 1130 (local) on 14 December (photo F. Ciancitto). Courtesy of INVG (Report 51/2021 ETNA, ETNA, BOLLETTINO SETTIMANALE, SETTIMANA DI RIFERIMENTO 13/12/2021 - 19/12/2021).

On the morning of 14 December 2021 Strombolian activity started at SEC accompanied by dense, fine-grained reddish ash that rose to 7 km altitude and drifted S. Ash emission continued in pulses through early on 15 December. Ashfall affected the southern flank of the volcano and was reported as far as Capo Passero. A small deposit of unconsolidated debris, about 250 m long, was visible in satellite imagery in the depression formed near the SEC summit from the 23 October 2021 activity (figure 366). This material was partially remobilized during the Strombolian activity of 14 December. Diffuse and discontinuous emissions of reddish ash were observed from BN and NEC during the second half of December (figure 368), and from NEC on 16 January 2022. Weak Strombolian activity resumed at SEC on 30-31 January with diffuse ash emissions quickly dispersing near the summit area.

Figure 368. Diffuse and discontinuous emissions of reddish ash were observed from Etna’s (a) Bocca Nuova (BN) and (b) Northeast Crater (NEC) during observations by INGV personnel on the morning of 24 December 2021. Courtesy of INGV (Report 52/2021 ETNA, ETNA, BOLLETTINO SETTIMANALE, SETTIMANA DI RIFERIMENTO 20/12/2021 - 26/12/2021).

Information Contacts: Sezione di Catania - Osservatorio Etneo, Istituto Nazionale di Geofisica e Vulcanologia (INGV), Sezione di Catania, Piazza Roma 2, 95123 Catania, Italy (URL: http://www.ct.ingv.it/it/ ); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); Hawai'i Institute of Geophysics and Planetology (HIGP) - MODVOLC Thermal Alerts System, School of Ocean and Earth Science and Technology (SOEST), Univ. of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://modis.higp.hawaii.edu/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground); NASA Global Sulfur Dioxide Monitoring Page, Atmospheric Chemistry and Dynamics Laboratory, NASA Goddard Space Flight Center (NASA/GSFC), 8800 Greenbelt Road, Goddard MD 20771, USA (URL: https://so2.gsfc.nasa.gov/).

July 2022 (BGVN 47:07) Cite this Report

Lava flows, pyroclastic flows, Strombolian explosions, and ash plumes during February-June 2022

Etna is located on the island of Sicily, Italy, and has had documented records of eruptions dating back to 1500 BCE. Activity frequently originates from multiple cones at the summit, where several craters have formed and evolved. The currently active craters consist of Northeast Crater (NEC), Voragine (VOR), and Bocca Nuova (BN) that were formerly the “Central” crater, and the Southeast Crater (SEC). The original Southeast crater formed in 1978, and a second eruptive site that opened on its SE flank in 2011 was named the New Southeast Crater (NSEC). Another eruptive site between the SEC and NSEC was referred to as the "cono della sella" (saddle cone) and developed during early 2017. The current eruption period began in September 2013 and has consisted of Strombolian explosions, ash plumes, lava fountaining, pyroclastic flows, and lava flows associated primarily with the Southeast crater (SEC). This report covers continuing activity during February through June 2022, based on weekly and special reports by the Osservatorio Etneo (OE), part of the Catania Branch of Italy's Istituo Nazionale di Geofisica e Vulcanologica (INGV) and satellite data.

Summary of activity during February-June 2022. Most of the strong eruptive activity during February-June 2022 occurred in the Southeast Crater (SEC), which included Strombolian explosions, ash plumes, lava fountains, and lava flows. Persistent fumarolic activity at Bocca Nuova (BN), Voragine (VOR), and Northeast Crater (NEC) were accompanied by occasional diffuse ash emissions (table 12). Lava flows were reported by INGV during 10-11 and 21 February, 12, 20, and 29 May, and 6 and 11 June, moving SW, N, and NE. Lava fountaining occurred on 10 and 21 February. Pyroclastic flows were detected on 10 February, 12 May, and 20-21 May. Intermittent ash plumes rose to 3.5-12 km altitude throughout the reporting period, accompanied by Strombolian explosions. INGV reported that the eruption ended during the night of 15-16 June following effusive activity in the Valle del Bove.

A total of 201 MODVOLC thermal alerts were detected during the reporting period: 32 during February, 114 during May, and 71 during June. During these months specifically, INGV reported strong Strombolian explosions, lava fountains, and lava flows, which contributed to the stronger thermal activity detected in satellite data. These notable numbers also correlate to spikes detected in thermal activity in the MIROVA graph (figure 369). The lava flows that originated from SEC were also visible in Sentinel-2 infrared satellite imagery during February, May, and June, moving down the SW and NE flanks (figure 370). Accompanying this strong thermal activity were occasional sulfur dioxide plumes, as shown on 11 February and 24 May and recorded by the TROPOMI instrument on the Sentinel-5P satellite, where the emissions reached more than 2 Dobson Units (DU) and drifted generally N and NE (figure 371).

Table 12. Summary of activity at the four primary crater areas at the summit of Etna during February-June 2022. Information is from INGV weekly reports.

Month	Bocca Nuova (BN)	Voragine (VOR)	Northeast Crater (NEC)	Southeast Crater (SEC)	Other activity
Feb 2022	Variable degassing and sporadic and modest to dilute ash emissions.	Variable degassing.	Variable degassing and sporadic and modest ash emissions.	Mild and discontinuous degassing and ash emissions; modest Strombolian explosions. Lava effusions and fountains.	Ashfall in Viagrande, Trecastagni, Zafferana, Milo, Acicastello, Petrulli
Mar 2022	Pulsating, discontinuous degassing.	Degassing from fumaroles around the crater rim.	Variable degassing and sporadic ash emissions.	Weak degassing from fumaroles; discontinuous Strombolian activity and dilute ash emissions.	--
Apr 2022	Variable and sometimes pulsating degassing.	No activity was detected.	Weak degassing.	Variable degassing.	--
May 2022	Pulsating, discontinuous degassing.	No activity was detected.	Variable degassing.	Degassing; Strombolian activity and dilute ash emissions, lava effusions.	Weak ashfall on the SE slope up to Catania
Jun 2022	Variable degassing.	No activity was detected.	Variable degassing.	Degassing, Strombolian explosions, ash plumes, and lava effusions.	--

Figure 369. Thermal activity at Etna varied in intensity during January through June 2022, according to this MIROVA (Log Radiative Power) graph. Two brief increases in power occurred during February. Beginning in mid-May, both the frequency and power of the detected thermal anomalies markedly increased, which corresponded to observations of lava flows. The power of these anomalies gradually declined by mid-June. Courtesy of MIROVA.

Figure 370. Multiple Sentinel-2 infrared satellite images showed lava effusion originating from Etna’s SEC on 11 February 2022 (top left), 21 February 2022 (top middle), 14 May 2022 (top right), 17 May 2022 (bottom left), 6 June 2022 (bottom middle), and 13 June 2022 (bottom right). The lava flow on 11 February descended the SW flank. On 21 February Strombolian explosions and lava fountaining activity occurred, represented by the strong thermal anomaly (bright yellow-orange) at SEC. The lava flow on 14 May traveled to the N and NE into the Valle del Leone and was still visible on 17 May, joined by additional new flows near the summit crater. A continuous flow on 6 June was visible moving E from a new effusive vent and began to cool by 13 June. Images use Atmospheric penetration rendering (bands 12, 11, 8a). Courtesy of Sentinel Hub Playground.

Figure 371. Sulfur dioxide plumes were emitted from Etna following strong explosive and effusive events at SEC on 11 February 2022 (left) and 24 May 2022 (right). The plumes drifted N and NE, respectively. Courtesy of NASA Global Sulfur Dioxide Monitoring Page.

Activity during February 2022. Discontinuous Strombolian activity and mild ash emissions occurred at SEC during February, while degassing was reported at BN, NEC, and VOR. During the early morning of 2 February, the Strombolian explosions had stopped. On 10 February modest explosive activity resumed in SEC, as detected by video surveillance cameras. The activity was initially confined to the crater and generated discontinuous and mild ash emissions that drifted SW. As a result, there was a collapse detected on the S flank of SEC, which often showed a thermal anomaly in infrared cameras. That same day, at 1520, a new lava flow was visible from SEC that traveled WSW. The front of the flow reached an elevation of 2.9 km by 1956. At 2140 INGV reported a lava fountain at SEC, accompanied by an ash plume 8-10 km high that drifted W. Around 2140, 2219, and 2226, three pyroclastic flows breached the S flank of SEC, two of which traveled a few hundred meters toward the Valle Bove while the last one went S. As a result, some small collapses of material produced small ash emissions. This activity continued to be observed through the next day. By 11 February, the fountaining activity has stopped, but the lava flow from SEC continued, the front of which had advanced to 2.7 km elevation. On 11 February at 1107 the lava flow from SEC had stopped, though weak and discontinuous explosions persisted, emitted weak ash emissions that drifted to the NW. These explosions also resuspended and redeposited pyroclastic material in areas to the NW, particularly in Maletto and up to the Tyrrhenian coast of Sicily, in S Agata di Militello and Capo d'Orlando. A thermal anomaly was detected at the SE base of SEC the same day. On 15 and 18 February modest ash emissions occurred at NEC, which was deposited in the summit area.

Two small ash emissions from SEC were detected on 20 February (figure 372). INGV reported that on 21 February weak Strombolian activity persisted at SEC, accompanied by lava fountaining; an ash plume rose to 10 km altitude and drifted SE (figure 373). A lava overflow was detected around 1210 from SEC that descended toward the SW (figure 374). An ash plume was also visible, rising to 11 km altitude. By 1340 the lava fountaining stopped at SEC, but explosions continued, producing an ash plume that rose to 12 km altitude that drifted SSE. Some ashfall was reported in Viagrande, Trecastagni, and Zafferana. The lava flow continued to be fed weakly, the front of which is located at an elevation of 2.9 km and expanded to the E. Explosive activity in SEC stopped by 1350 on 21 February. INGV personnel in the field reported ashfall from the lava fountain activity in Viagrande, Milo, and Acicastello, and was mainly dispersed between Petrulli and Zafferana. After the fountaining a small pit crater formed and began showing signs of weak degassing. Additionally, surveillance cameras and INGV personnel reported another lava flow moving along the eastern slope of SEC, the front of which was at an estimated elevation of 2.9 km.

Figure 372. Ash emissions were visible in satellite images rising above Etna’s Southeast Crater on 20 February 2022 taken at 1006 UTC (left) and 1650 UTC (right). Images taken with a high-resolution camera from Etna’s eastern slope (left) and the south slope (right). Courtesy of INGV (Report 08/2022, ETNA, Bollettino Settimanale, 14/02/2022 - 20/02/2022).

Figure 373. Strombolian activity at Etna’s SEC was observed by the La Montagnola (south) thermal camera on 21 February 2022 (top left), which generated strong ash plumes, as seen from the webcam image later in the day on 21 February 2022 (top right). Lava fountaining activity and a lava flow was recorded by the La Montagnola and Nicolosi (south) thermal cameras (bottom left). Two lava flows on the S and E slopes of SEC were seen in the Nicolosi thermal camera images (bottom right). The inset image on the bottom right was taken by the Mt. Cagliato (east) thermal camera showing the lava flow on the E slope. Courtesy of INGV (Report 08/2022, ETNA, Bollettino Settimanale, 14/02/2022 - 20/02/2022).

Figure 374. Map of the summit area of Etna showing the location and direction of the lava flow (light orange color) that began on 21 February 2022. The locations of each of the active craters are labeled as NEC (Northeast Crater), VOR (Voragine), BN (Bocca Nuova), and SEC (Southeast Crater). The red dots represent active craters, the yellow dots represent craters with degassing activity, and the green dots represent the location of GPS points taken by INGV personnel. The map was created using Sentinel-2 and PlanetScope data on 23 and 24 February, respectively, and the GPS track was acquired by INGV personnel on 24 February 2022. Courtesy of INGV (Report 08/2022, ETNA, Bollettino Settimanale, 14/02/2022 - 20/02/2022).

Weak Strombolian explosions were detected in SEC again during 22-25 February; during the morning of 23 February the lava flow moving along the lower E slope had started to cool. Several collapses were observed on the S flank of SEC and on the upper E slope following the lava fountaining, which caused fewer and more dilute ash puffs. On 24 February at 1338 surveillance cameras showed ash emissions rising above NEC that drifted SSE, followed by other less intense ash pulses.

Activity during March-April 2022. Activity during March and April was relatively low and consisted of gas-and-steam emissions from the summit craters, sporadic ash emissions from NEC, and modest collapses of material from the inner walls of SEC. Thermal activity in the summit area was low after the lava fountaining on 21 February. On 3 March a thermal anomaly was observed on the S inner wall of SEC associated with an ash cloud that rapidly dispersed into the atmosphere. According to INGV, the anomaly was likely caused by hot material that had accumulated during activity on 21 February. During the morning of 18 March a small ash emission was visible from the base of the S slope of SEC (figure 375).

Figure 375. Webcam images observed by the La Montagnola (south) camera showing the small ash emission emitted from the base of Etna’s SEC as indicated by the yellow arrow. BN is also visible in the background. Courtesy of INGV (Report 12/2022, ETNA, Bollettino Settimanale, 14/03/2022 - 22/03/2022).

An overflight on 8 April described intense gas-and-steam pulses from two vents in the center of BN. No activity was detected in VOR. Some small fumarolic activity and weak gas-and-steam emissions were observed in SEC and NEC. During the early morning hours of 27 April, very faint reddish ash emissions were observed in webcam images. Some degassing was also visible at SEC, mainly from fumaroles along the N crater rim and near the collapsed area from 10 February. On 21 April at 1006 a small landslide occurred on the S flank of the cone, accompanied by a thermal anomaly that was visible from the Montagnola camera. Another landslide event occurred at the same place on 22 April at 2214.

Activity during May 2022. Strombolian activity continued in SEC during May, occasionally accompanied by ash emissions. Some effusive activity was also reported in the Valle del Bove. On 9 May a mild ash emission was observed at SEC; similar and more frequent events occurred on the 11th. Thermal cameras showed an active vent on the upper N side of the cone. On 12 May at 1900 ash emissions intensified and rose to 3.5 km altitude from SEC to the SW from one or more vents along the N side of the crater. Small pyroclastic flows were reported on the N flank of SEC and reached the N base of the crater on 12 May. Additionally, a small lava flow effused from an eruptive vent and traveled N and NE into the snowy Valle del Leone, where lava blocks that rolled onto the snow caused gas-and-steam plumes. The SEC was also affected by discontinuous and variable Strombolian explosions, where the most intense phases ejected ash into the atmosphere, some of which dispersed to the SW during 14-15 May.

By 17 May the lava flow developed toward the ENE in the Valle del Leone, the front of which reached an elevation of 2.3-2.4 km. On 18 May the lava flow had begun to cool while new flows developed from the vent and followed the older flow (figure 376). On 20 May at 1730 a second effusive vent open on the N side of SEC at an elevation of 3.2 km. A small lava flow effused from this new vent that traveled NE (figure 377). During 20-21 May a pyroclastic flow originated from SEC and traveled NNE for 700 m. There was a gradual increase in explosive activity at SEC on 22 May at 1940, which produced ash emissions that rose to 5 km altitude and extended to the S. Weak ashfall was reported on the SE flank as far as Catania. At the same time, the lava emissions continued with varying intensity at the effusive vents formed on 12 and 20 May. On 29 May a third effusive vent opened in the upper part of the Valle del Bove and Strombolian activity at SEC stopped. Field observations showed that in the upper part of the W wall of the Valle del Bove there were two points of lava effusion along an eruptive fissure-oriented ENE. In the following days, low-rate effusion was reported, with flows reaching an elevation of 2.1 km. A series of fractures on the E side of SEC were noted at 3-3.2 km elevation; slope instability generated avalanches of material.

Figure 376. Thermal images taken of Etna’s SEC on 18 May 2022 showing the active and cooling lava flows. Strombolian explosions continued at the summit crater. The brighter active flow is in the foreground (towards bottom right in each image), while the flow in the background has started to cool. Courtesy of INGV (Report 21/2022, ETNA, Bollettino Settimanale, 16/05/2022 - 22/05/2022).

Figure 377. Map of the summit area of Etna showing the location and direction of the lava flows (red and light green) that began on 20 May 2022 (light green) and 22 May 2022 (red). Both lava flows traveled to the N and NE. The locations of each of the active craters are labeled as NEC (Northeast Crater), VOR (Voragine), BN (Bocca Nuova), and SEC (Southeast Crater). The red dots represent active craters and the yellow dots represent craters with degassing activity. The topographic base was taken from Pleiades images from 22 August 2020, while the topography of craters was obtained from photogrammetric processing of photos taken on a helicopter flyover on 8 April 2022. Courtesy of INGV (Report 21/2022, ETNA, Bollettino Settimanale, 16/05/2022 - 22/05/2022).

Activity during June 2022. Strombolian at SEC occasionally accompanied by ash emissions continued during June. Variable and pulsating effusive activity also persisted in the upper part of the Valle del Bove. Over time, the variability in effusion rate was reflected in the development of a branched lava field with overlapping flows. The flow fronts reached a maximum height of about 1.9 km altitude on 5 June and retreated to 2.4 km altitude on 6 June (figure 378).

Figure 378. An updated map of Etna’s SEC showing the lava flow field on 6 June 2022. The red color represents an active lava flow on 6 June, orange color represents an active lava flow on 5 June, and yellow represents a cooling lava flow. Each of the flows traveled to the ENE. The locations of each of the active craters are labeled as NEC (Northeast Crater), VOR (Voragine), BN (Bocca Nuova), and SEC (Southeast Crater). The blue hatched line represents places of collapse. The topographic base was taken from Pleiades images from 22 August 2020, while the topography of craters was obtained from photogrammetric processing of photos from a helicopter flyover on 8 April 2022. Courtesy of INGV (Report 23/2022, ETNA, Bollettino Settimanale, 30/05/2022 - 05/06/2022).

Ongoing ash emissions reported on 1 June drifted SSE. Variable Strombolian activity continued and was accompanied by a lava flow on 2 June (figure 379). Particularly intense explosions during 1-3 June produced continuous ash emissions that dispersed SSE (figure 380). An ash plume on 3 June rose to 4-5 km altitude and drifted SSW. During the late afternoon on 7 June a new fracture opened at the base of the N wall of the Valle del Bove. Field observations reported a slightly active lava flow on 8 June that was mostly cooling and reached a maximum length of 170 m. On 11 June another new effusive vent at an elevation of 1.9 km fed another slightly active lava flow that expanded for a few tens of meters. A field inspection on 12 June showed a total of three active effusive vents; the most advanced lava flow front reached 1.8 km elevation (figure 381). During 13-14 June a single vent located at 1.9 km elevation produced a well-fed lava flow that had advanced to 1.8 km elevation on 14 June; by the night of 15 June the flow had stopped. Drone imagery from 14 June showed that small lava tunnels had developed, and two small vents located at 1.87 km and 1.95 km elevation had formed.

Figure 379. Photo of the effusive vent at Etna’s SEC and the resulting lava flow traveling over a pre-existing lava field on 2 June 2022. Courtesy of INGV (Report 23/2022, ETNA, Bollettino Settimanale, 30/05/2022 - 05/06/2022).

Figure 380. Photos of explosive Strombolian activity at Etna’s SEC on 3 June 2022 taken during a field inspection (a) and through webcam images (b and c). Ash plumes rose as high as 5 km altitude and drifted generally S. Courtesy of INGV (Report 23/2022, ETNA, Bollettino Settimanale, 30/05/2022 - 05/06/2022).

Figure 381. A series of a thermal image and photos showing the effusive activity at Etna during 7-11 June 2022. A thermal image (top left) showing the effusive vent that opened on 7 June 2022. An annotated drone image from 8 June 2022 (top right) showing locations of cooled lava flows (outlined in yellow) and the active lava flow (red arrow). The effusive vent occurred at an elevation of 2 km (middle left) and the lava flow front stood at an elevation of 1.9 km (middle right). Various fractures were observed during a field inspection on 9 June 2022 (bottom left), and a new eruptive vent that opened on 11 June produced another lava flow (bottom right). Courtesy of INGV (Report 24/2022, ETNA, Bollettino Settimanale, 06/06/2022 - 12/06/2022).

According to INGV, effusive activity in the Valle del Bove had stopped during the night of 15-16 June and no further eruptive activity was observed. Degassing at the summit craters continued except at VOR. Gas-and-steam emissions and some small fumaroles were observed rising from the inner walls of NEC.

Information Contacts: Sezione di Catania - Osservatorio Etneo, Istituto Nazionale di Geofisica e Vulcanologia (INGV), Sezione di Catania, Piazza Roma 2, 95123 Catania, Italy (URL: http://www.ct.ingv.it/it/ ); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); Hawai'i Institute of Geophysics and Planetology (HIGP) - MODVOLC Thermal Alerts System, School of Ocean and Earth Science and Technology (SOEST), Univ. of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://modis.higp.hawaii.edu/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground); NASA Global Sulfur Dioxide Monitoring Page, Atmospheric Chemistry and Dynamics Laboratory, NASA Goddard Space Flight Center (NASA/GSFC), 8800 Greenbelt Road, Goddard MD 20771, USA (URL: https://so2.gsfc.nasa.gov/).

March 2023 (BGVN 48:03) Cite this Report

New vents and lava flows during November 2022-February 2023

Etna is located on the island of Sicily, Italy, and has had documented records of eruptions dating back to 1500 BCE. Activity frequently originates from multiple cones at the summit, where several craters have formed and evolved. The currently active craters consist of Northeast Crater (NEC), Voragine (VOR), and Bocca Nuova (BN), and the Southeast Crater (SEC); VOR and BN were previously referred to as the “Central Crater”. The original Southeast crater formed in 1978, and a second eruptive site that opened on its SE flank in 2011 was named the New Southeast Crater (NSEC). Another eruptive site between the SEC and NSEC was referred to as the "cono della sella" (saddle cone) and developed during early 2017. The previous eruption period ended in June 2022, which was characterized by Strombolian explosions, ash plumes, lava fountains, and lava flows mainly in the SEC (BGVN 47:07). No activity was reported between July and October 2022. This report covers November 2022 through February 2023 and describes new effusive activity at SEC and gas-and-steam emissions, based on weekly and special reports by the Osservatorio Etneo (OE), part of the Catania Branch of Italy's Istituo Nazionale di Geofisica e Vulcanologica (INGV) and satellite data.

Summary of activity during November 2022-February 2023. A new vent opened on the NE base of Southeast Crater (SEC) at 2.8 km elevation on 27 November 2022 that began to generate a new lava flow that traveled E toward the Valle del Leone. A second vent opened on 30 November, which also began to effuse new lava. As the flows remained active, smaller lava breakouts were detected, branching off from the primary flow. During December the lava flows expanded into both the Valle del Leone and the Valle del Bove, creating a lava flow field. Variable fumarolic degassing was reported at all summit craters (Bocca Nuova (BN), Voragine (VOR), Northeast Crater (NEC), and SEC) throughout the entire reporting period. Modest and sporadic ash emissions were detected at SEC during January through February 2023, though they were rapidly dispersed by the wind. On 6 February 2023, the lava flows stopped, and the flow field began to cool.

A total of 143 MODVOLC thermal alerts were detected during the reporting period: one during November, 16 during December, 106 during January, and 20 during February. Those higher numbers also correlate to spikes that were detected in thermal activity, based on the MIROVA graph, which showed when high thermal activity began, and when it started to decrease (figure 382). The young lava flow that originated from SEC was also visible in Sentinel-2 infrared satellite imagery during late November though early February, moving E and NE (figure 383). Accompanying this strong thermal activity were occasional sulfur dioxide plumes that exceeded 2 Dobson Units (DUs) recorded by the TROPOMI instrument on the Sentinel-5P satellite (figure 384). These plumes generally drifted S, SW, SE, and E.

Table 13. Summary of activity at the four primary crater areas at the summit of Etna during [corrected: November 2022-February 2023]. Information is from INGV weekly reports.

Month	Bocca Nuova (BN)	Voragine (VOR)	Northeast Crater (NEC)	Southeast Crater (SEC)
Nov 2022	Variable degassing.	Weak fumarolic degassing.	Weak fumarolic degassing.	Variable fumarolic degassing at the crater rim and fractures along the cone. Lava effusions.
Dec 2022	Variable degassing.	Weak fumarolic degassing.	Weak fumarolic degassing.	Weak fumarolic degassing. Lava effusions.
Jan 2023	Variable degassing.	Mild to modest fumarolic degassing.	Mild to modest fumarolic degassing.	Variable fumarolic degassing at the crater rim and fractures along the cone. Lava effusions. Modest and sporadic ash emissions.
Feb 2023	Intense degassing.	Weak degassing.	Weak degassing.	Variable degassing at the crater rim and fractures along the cone. Modest and sporadic ash emissions.

Figure 382. A strong pulse in thermal activity at Etna was detected in late November 2022 that continued at high frequency and power through January 2023, based on this MIROVA graph (Log Radiative Power). The sudden spike in activity was represented by a new lava flow that was detected at the NE base of SEC in late November. In early February the lava flows began to stop, which is shown by the visible decrease in thermal activity on this graph. Courtesy of MIROVA.

Figure 383. Sentinel-2 infrared satellite images showing the beginning of a new lava flow (bright yellow-orange) at Etna’s SEC on 28 November 2022 (top left) that traveled E toward the Valle del Leone. On 8 December 2022 (top right) and 4 January 2023 (bottom left) the lava flow had branched into multiple flows, traveling E and NE. By 1 February 2023 (bottom right) the lava flows continued E, overlapping pre-existing flows, which began to cool (black color). Some hot gas-and-steam emissions were also visible at the other summit craters, as seen on 8 December. Images use “Atmospheric penetration” rendering (bands 12, 11, 8a). Courtesy of Sentinel Hub Playground.

Figure 384. Sulfur dioxide plumes that exceeded 2 Dobson Units (DUs) rose above Etna on 28 November 2022 (top left), 8 December 2022 (top right), 4 January 2023 (bottom left), and 12 February 2023 (bottom right). The plumes drifted S, NE, SW, and SE, respectively. Courtesy of NASA Global Sulfur Dioxide Monitoring Page.

Activity during November 2022. INGV reported that around 1800 on 27 November a vent opened on the NE base of SEC at 2.8 km elevation and produced a lava flow. The flow slowly advanced 300 m E toward the Valle del Leone; additional small lava flows emplaced the first one as it remained active (figure 385). Weather conditions obscured clear views of the activity from 1000 on 28 November through 29 November, though some incandescence was visible through the clouds, which suggested ongoing effusion. On 30 November once weather conditions improved, a second vent was observed upslope from the first vent at about 2.9 km elevation. A lava flow from this second vent traveled parallel to and N of the first flow, reaching about 2.7 km elevation (figure 385).

Figure 385. Map of the new lava flows at the NE base of SEC (CSE) of Etna updated on 30 November 2022 obtained from the analysis of the Skysat satellite image from 28 November 2022 and images acquired by the Piedimonte Etneo camera. The background image is a shaded model of the terrain of the summit area obtained by processing drone images acquired during several overflights made on 15 and 21 September 2022 and 6, 21, and 23 October 2022, superimposed on the shaded model from a Pleiades image taken on 22 August 2022. The yellow color shows the development of the lava flow on 28 November and the orange color shows a second lava flow on 30 November 2022. Courtesy of INGV (Report M11/2022, ETNA, BOLLETTINO MENSILE, MESE DI RIFERIMENTO NOVEMBRE 2022).

Activity during December 2022. The vents at the NE base of SEC in the Valle del Leone continued to feed lava flows during December. The active flow field consisted of overlapping lava flows that expanded into the Valle del Leone and the Valle del Bove (figures 386 and 387). A small hornito formed at the vent area and ejected lava during 7-18 December. By 25 December the most active flow had descended to 2,150 m elevation (figure 388). Gas-and-steam emissions rose from the summit craters. The total volume of erupted lava was estimated at one million cubic meters on 30 December.

Figure 386. Map of the active and cooling lava flows at the base of SEC (CSE) of Etna updated on 18 December 2022, based on Sentinel satellite images. The background image is a shaded model of the terrain of the summit area obtained by processing drone images acquired during several overflights made on 15 and 21 September 2022 and 6, 21, and 23 October 2022, superimposed on the shaded model from a Pleiades image taken on 22 August 2022. The red color shows the active lava flow, and the yellow color shows the cooling lava flow. Courtesy of INGV (Report 51/2022, ETNA, Bollettino Settimanale, 12/12/2022 - 18/12/2022).

Figure 387. Photos of the active lava flow field at Etna taken on 16 December 2022 from the Ripe della Naca area on the ENE side of the volcano. Courtesy of Boris Behncke, INGV (Report 51/2022, ETNA, Bollettino Settimanale, 12/12/2022 - 18/12/2022).

Figure 388. Thermal images of the active and advancing lava flow on Etna taken by the Monte Cagliato camera (E side of the volcano) during 19 and 25 December 2022. The images show the progression of the lava flow (bright yellow-green) over time, with the most active lava flow traveling to an elevation of 2,150 m on 25 December. Courtesy of INGV (Report 52/2022, ETNA, Bollettino Settimanale, 19/12/2022 - 25/12/2022).

Activity during January 2023. The active lava flow field that originated from the NE base of SEC persisted during January, with overlapping flows expanding into the Valle del Leone and the Valle del Bove; the rate of these flows varied (figure 389). On 7 January the most active flow had reached an elevation of 2,170 m and the area of the flow field was an estimated 0.63 km². Gas-and-steam emissions rose from the summit craters, though primarily at BN. Lava effusion progressively decreased during the night of 16-17 January and according to INGV, had stopped by the late afternoon of 17 January (figure 390). Effusion renewed during the early morning of 18 January, which consisted of two lava flows: one of the flows traveled NE along the W edge of the lava flow field, and the other traveled E onto the steep W wall of the Valle del Bove, which reached the base of the wall on 20 January. On 21 January the rate of effusion was variable. A new lava flow descended the Valle del Bove, almost reaching the base of the W wall at around 2.2 km elevation during the evening of 22 January (figure 390). Intense gas-and-steam emissions rose from BN, and minor to moderate emissions were detected at NEC and VOR (figure 391). Fumarolic activity was localized along the crater rim and from the May-June 2022 eruptive vent at SEC, which also occasionally included flashes of incandescence at night. Modest and diluted ash emissions were also detected at SEC, which dispersed in the wind (figure 391). The area covered by lava flows from 27 November 2022 to 29 January 2023 was estimated to 0.88 km² and the total volume of material erupted ranged between 4.4-5.6 million cubic meters.

Figure 389. Photos of the active lava flow field at Etna taken by a-b) Giorgio Costa on 4 January 2023; c-d) Francesco Ciancitto on 8 January 2023; and INGV-OE EMCT thermal camera on e) 2 January 2023 and f) 8 January 2023. Courtesy of INGV (Report 02/2023, ETNA, Bollettino Settimanale, 02/01/2023 - 08/01/2023).

Figure 390. Thermal images taken by the Monte Cagliato camera on the E side of Etna during 16-23 January 2023. These images show a) reduced effusive activity (bright yellow-green) during the morning of 16 January; b) the lava flow appeared to have stopped by the afternoon of 17 January; c) effusive activity resumed on the morning of 18 January; d-e) slow advancement of the new lava flow on the W wall of the Valle del Bove during 19-20 January; and f) the new lava flow on 23 January. Courtesy of INGV (Report 04/2023, ETNA, Bollettino Settimanale, 16/01/2023 - 22/01/2023).

Figure 391. Webcam images taken by the La Montagnola camera showing a-b) degassing at Etna’s BN crater and weak ash emissions from SEC on 26 January 2023; and c-d) weak ash emissions from SEC and incandescence associated with SEC on 30 January 2023, as indicated by the yellow arrow. BN = Bocca Nuova; CSE = Southeast Crater; CNE = Northeast Crater. Courtesy of INGV (Report 05/2023, ETNA, Bollettino Settimanale, 23/01/2023 - 29/01/2023).

Activity during February 2023. During the early morning of 1 February, the effusion rate increased before decreasing during the night of 1-2 February. Then, on the morning of 2 February, the flow stopped. The flow restarted during the early afternoon of 2 February, which produced new overlapping flows onto the pre-existing lava flow field (figure 392). During the afternoon of 4 February through the next day, there was a gradual decrease in effusion rate and the lava flow field started to cool. Intense degassing was reported at BN, weak degassing occurred at VOR and NEC, and variable degassing was reported at SEC along the crater rim and near the May-June 2022 eruptive vent, the latter of which occasionally showed some incandescence at night. Diluted ash emissions were also visible, though winds rapidly dispersed them.

Figure 392. Map of the active and cooling lava flows at the base of SEC (CSE) of Etna updated on 3 February 2023 based on Sentinel satellite images. The background image is a shaded model of the terrain of the summit area obtained by processing drone images acquired during several overflights made on 15 and 21 September 2022 and 6, 21, and 23 October 2022, superimposed on the shaded model from a Pleiades image taken on 22 August 2022. The red color shows the active lava flow, and the yellow color shows the cooling lava flow. Courtesy of INGV (Report 06/2023, ETNA, Bollettino Settimanale, 01/30/2023 - 02/05/2023).

INGV reported that on 6 February the lava effusion from the vent at the NE base of SEC had ended; the total area covered by the flows was an estimated 0.96 km² and the estimated volume was 4.8-6.1 million cubic meters. A Volcano Observatory Notice for Aviation (VONA) posted on 7 February stated that the Aviation Color Code (ACC) was lowered to Yellow (the second lowest level on a four-color scale), and on 14 February the ACC was lowered to Green, indicating that activity was at background levels. INGV also noted that though the effusion had stopped, unrest was still ongoing.

Information Contacts: Sezione di Catania - Osservatorio Etneo, Istituto Nazionale di Geofisica e Vulcanologia (INGV), Sezione di Catania, Piazza Roma 2, 95123 Catania, Italy (URL: http://www.ct.ingv.it/it/ ); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); Hawai'i Institute of Geophysics and Planetology (HIGP) - MODVOLC Thermal Alerts System, School of Ocean and Earth Science and Technology (SOEST), Univ. of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://modis.higp.hawaii.edu/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground); NASA Global Sulfur Dioxide Monitoring Page, Atmospheric Chemistry and Dynamics Laboratory, NASA Goddard Space Flight Center (NASA/GSFC), 8800 Greenbelt Road, Goddard MD 20771, USA (URL: https://so2.gsfc.nasa.gov/).

August 2023 (BGVN 48:08) Cite this Report

Intermittent Strombolian activity, lava flows, and ash plumes during March-June 2023

Table 14. Summary of activity at the four primary crater areas at the summit of Etna during March-June 2023. Information is from INGV weekly reports.

Month	Bocca Nuova (BN)	Voragine (VOR)	Northeast Crater (NEC)	Southeast Crater (SEC)
Mar 2023	Continuous degassing.	Weak fumarolic degassing.	Weak fumarolic degassing.	Variable fumarolic degassing at the crater rim and fractures along the cone.
Apr 2023	Continuous degassing.	Weak fumarolic degassing.	Weak fumarolic degassing.	Intense fumarolic degassing at the crater rim and fractures along the cone.
May 2023	Continuous degassing. Strombolian activity.	Fumarolic degassing.	Fumarolic degassing.	Continuous degassing. Strombolian activity. Lava flows.
Jun 2023	Continuous degassing.	Weak degassing.	Weak degassing.	Continuous degassing.

Figure 396. Photo of ashfall near Etna from explosive activity at the Southeast crater on 21 May 2023. Courtesy of Boris Behncke, INGV.

Figure 398. Photo of weak intra-crater explosive activity at Etna’s Southeast Crater on the evening of 23 May 2023. Photo has been color corrected. Courtesy of Boris Behncke, INGV.

This compilation of synonyms and subsidiary features may not be comprehensive. Features are organized into four major categories: Cones, Craters, Domes, and Thermal Features. Synonyms of features appear indented below the primary name. In some cases additional feature type, elevation, or location details are provided.

Synonyms

Aetna | Mongibello | Etnea | Mons Gibel Utlamat | Catania, Monte di

Cones

Feature Name

Feature Type

Elevation

Latitude

Longitude

Albano, Monte

Pyroclastic cone

Arso, Monte

Pyroclastic cone

Barbagallo, Monte

Pyroclastic cone

Barca, Monte

Pyroclastic cone

Bonaccorsi-Montarello

Pyroclastic cone

Calcarazzi, Monte

Pyroclastic cone

Camercia

Pyroclastic cone

Cantone

Pyroclastic cone

Caterattte, Monte

Pyroclastic cone

Centenari, Monte

Pyroclastic cone

Cuvigghiuni

Pyroclastic cone

Difeso, Monte

Pyroclastic cone

Fleri

Pyroclastic cone

Fossa Pagani

Pyroclastic cone

Frumento della Concazze, Monte

Pyroclastic cone

Frumento Supino, Monte

Pyroclastic cone

Frumento, Monte

Pyroclastic cone

Gemellaro, Monte

Pyroclastic cone

Gervasi, Monte

Pyroclastic cone

Goma, Monte

Pyroclastic cone

Gorna, Monte

Pyroclastic cone

Josemaria Escriviá, Monte
Laghetto

Pyroclastic cone

Laghetto

Pyroclastic cone

Lepre, Monte

Pyroclastic cone

Maletto, Monte

Pyroclastic cone

Minardo, Monte

Pyroclastic cone

Mongibello

Shield volcano

Monpeloso

Pyroclastic cone

Monpilieri, Monte

Pyroclastic cone

Montagnola, La

Pyroclastic cone

Nero delle Concazze, Monte

Pyroclastic cone

Nero, Monte

Pyroclastic cone

Nocilla, Monte

Pyroclastic cone

Nunziata, Monte

Pyroclastic cone

Nuovo, Monte

Pyroclastic cone

Pian d'Erasmo

Pyroclastic cone

Piniteddu, Monte

Pyroclastic cone

Pizzillo, Monte

Pyroclastic cone

Pomiciari, Monte

Pyroclastic cone

Renatura

Pyroclastic cone

Riccò, Monti

Pyroclastic cone

Rinatu, Monte

Pyroclastic cone

Rittmann, Monte

Pyroclastic cone

Rocca Capra

Pyroclastic cone

Rosso, Monte

Pyroclastic cone

Salto del Corvo, Monte

Pyroclastic cone

San Nicola, Monte

Pyroclastic cone

Sella, Monti

Pyroclastic cone

Serra Giannicola Grande

Pyroclastic cone

Serra Pizzuta Calvarina, Monte

Pyroclastic cone

Serra Pizzuta, Monte

Pyroclastic cone

Silvestri, Monte

Pyroclastic cone

Simone, Monte

Pyroclastic cone

Sona, Monte

Pyroclastic cone

Timpa Rossa, Monte

Pyroclastic cone

Tre Monti

Pyroclastic cone

Trifoglietto

Shield volcano

Troina, Monte

Pyroclastic cone

Turchio, Monte

Pyroclastic cone

Vetore, Monte

Pyroclastic cone

Craters

Feature Name

Feature Type

Elevation

Latitude

Longitude

Bocca Nuova

Crater

Bove, Valle del

Caldera

Cisternazza

Crater

Ellittico

Pleistocene caldera

Leone, Valle del

Caldera

New Southeast Crater

Crater

Northeast Crater

Crater

Piano del Lago

Caldera

Piano, Caldera del

Caldera

Southeast Crater

Crater

Vavalaci

Pleistocene caldera

Voragine, La
Chasm, The

Crater

Basic Data

Volcano Number

Last Known Eruption

Elevation

Latitude
Longitude

211060

2024 CE

3,357 m / 11,014 ft

37.748°N
14.999°E

Morphology

Volcano Landform
Composite

Volcano Types
Stratovolcano(es)
Caldera(s)
Pyroclastic cone(s)

Rock Types

Major
Trachybasalt / Tephrite Basanite
Trachyandesite / Basaltic Trachyandesite
Basalt / Picro-Basalt

Minor
Trachyte / Trachydacite
Phono-tephrite / Tephri-phonolite

Tectonic Setting

Subduction zone
Continental crust (> 25 km)

Population

Within 5 km
Within 10 km
Within 30 km
Within 100 km

78
3,291
1,016,540
3,052,770

Geological Summary

Mount Etna, towering above Catania on the island of Sicily, has one of the world's longest documented records of volcanism, dating back to 1500 BCE. Historical lava flows of basaltic composition cover much of the surface of this massive volcano, whose edifice is the highest and most voluminous in Italy. The Mongibello stratovolcano, truncated by several small calderas, was constructed during the late Pleistocene and Holocene over an older shield volcano. The most prominent morphological feature of Etna is the Valle del Bove, a 5 x 10 km caldera open to the east. Two styles of eruptive activity typically occur, sometimes simultaneously. Persistent explosive eruptions, sometimes with minor lava emissions, take place from one or more summit craters. Flank vents, typically with higher effusion rates, are less frequently active and originate from fissures that open progressively downward from near the summit (usually accompanied by Strombolian eruptions at the upper end). Cinder cones are commonly constructed over the vents of lower-flank lava flows. Lava flows extend to the foot of the volcano on all sides and have reached the sea over a broad area on the SE flank.

This volcano is located within the Mount Etna, a UNESCO World Heritage property.

References

The following references have all been used during the compilation of data for this volcano, it is not a comprehensive bibliography.

Alparone S, Andronico D, Giammanco S, Lodato L, 2004. A multidisciplinary approach to detect active pathways for magma migration and eruption at Mt. Etna (Sicily, Italy) before the 2001 and 2002-2003 eruptions. J. Volcanol. Geotherm. Res., 136: 121-140.

Andronico D, Branca S, Calvari S, Burton M, Caltabiano T, Corsaro R A, Del Carlo P, Garfi G, Lodato L, Miraglia L, Mure F, Neri M, Pecora E, Pompilio M, Salerno G, Spampinato L, 2005. A multi-disciplinary study of the 2002-03 Etna eruption: insights into a complex plumbing system. Bull Volcanol, 67: 314-330.

Andronico D, Cristaldi A, Scollo S, 2008. The 4-5 September 2007 lava fountain at South-East Crater of Mt Etna, Italy. J. Volcanol. Geotherm. Res., 173: 325-328.

Applegarth L J, Pinkerton H, James M R, Calvari S, 2010. Morphological complexities and hazards during the emplacement of the channel-fed 'a'a lava flow fields: a study of the 2001 lower flow field on Etna. Bull Volcanol, 72: 641-656. https://doi.org/10.1007/s00445-010-0351-1

Barberi F, Brondi F, Carapezza M L, Cavarra L, Murgia C, 2003. Earthen barriers to control lava flows in the 2001 eruption of Mt. Etna. J. Volcanol. Geotherm. Res., 123: 231-243.

Barbieri M, Cristofolini R, Delitala M C, Fornaseri M, Romano R, Taddeucci A, Tolomeo L, 1993. Geochemical and Sr-isotope data on historic lavas of Mount Etna. J. Volcanol. Geotherm. Res., 56: 57-69.

Behncke B, 2002. Italy's volcanoes - the cradle of volcanology. http://boris.vulcanoetna.it/ (accessed February 11, 2002).

Behncke B, Calvari S, Giammanco S, Neri M, Pinkerton H, 2008. Pyroclastic density currents resulting from the interaction of basaltic magma with hydrothermally altered rock: an example from the 2006 summit eruption of Mount Etna, Italy. Bull Volcanol, 70: 1249-1268.

Behncke B, Neri M, 2003. The July-August 2001 eruption of Mt. Etna (Sicily). Bull Volcanol, 65: 461-476.

Behncke B, Neri M, Carniel R, 2003. An exceptional case of endogenous lava dome growth spawning pyroclastic avalanches: the 1999 Bocca Nuova eruption of Mt. Etna (Italy). J. Volcanol. Geotherm. Res., 124: 115-128.

Behncke B, Neri M, Nagay A, 2005. Lava flow hazard at Mount Etna (Italy): new data from a GIS-based study. In: Manga M, Ventura G (eds) Kinematics and dynamics of lava flows, Geol Soc Amer Spec Pap, 396: 189-208.

Behncke B, Neri M, Pecora E, Zanon V, 2006. The exceptional activity and growth of the Southeast Crater, Mount Etna (Italy), between 1996 and 2001. Bull Volcanol, 69: 149-173.

Behncke B, Pshenichny C A, 2009. Modeling unusual behavior of Mt. Etna, Italy, by means of event bush. J. Volcanol. Geotherm. Res., 185: 157-171.

Billi A, Acocella V, Funiciello R, Giordano G, Lanzafame G, Neri M, 2003. Mechanisms for ground-surface fracturing and incipient slope failure associated with the 2001 eruption of Mt. Etna, Italy: analysis of ephemeral field data. J. Volcanol. Geotherm. Res., 122: 281-294.

Branca S, Del Carlo P, 2005. Types of eruptions of Etna volcano AD 1670-2003: implications of short-term eruptive activity. Bull Volcanol, 67: 732-742.

Branca S, Del Carlo P, Lo Castro M D, De Beni E, Wijbrans J, 2009. The occurrence of Mt Barca flank eruption in the evolution of the NW periphery of Etna volcano (Italy). Bull Volcanol, 71: 79-94. https://doi.org/10.1007/s00445-008-0210-5

Budetta G, Carbone D, 1998. Temporal variations in gravity at Mt. Etna (Italy) associated with the 1989 and 1991 eruptions. Bull Volcanol, 59: 311-326.

Burton M R, Neri M, Andronico D, Branca S, Caltabiano T, Calvari S, Cosaro R A, Del Carlo P, Lanzafame G, Lodato L, Miraglia L, Salerno G, Spampinato L, 2005. Etna 2004-2005: an archetype for geodynamically-controlled effusive eruptions. Geophysical Research Letters, 32: L09303. https://doi.org/10.1029/2005GL022527.2005

Calanchi N, Dinelli E, Gasparotto G, Lucchini F, 1996. Etnean tephra layer in Albano Lake and Adriatic Sea cores: new findings of Y1-layer in the central Mediterranean area. Acta Vulc, 8: 7-13.

Calvari S, Coltelli M, Muller W, Pompilio M, Scribano V, 1994. Eruptive history of South-Eastern Crater of Mount Etna, from 1971 to 1994. Acta Vulc, 5: 11-14.

Calvari S, Coltelli M, Neri M, Pompilio M, Scribano V, 1994. The 1991-1993 Etna eruption: chronology and lava flow-field evolution. Acta Vulc, 4: 1-14.

Calvari S, Groppelli G, 1996. Relevance of the Chiancone volcaniclastic deposit in the recent history of Etna volcano (Italy). J. Volcanol. Geotherm. Res., 72: 239-258.

Calvari S, Groppelli G, Pasquare G, 1994. Preliminary geological data on the south-western wall of the Valle del Bove, Mt. Etna, Sicily. Acta Vulc, 5: 15-30.

Calvari S, Muller W, Scribano V, 1998. Eruptive activity and morphology evolution of Bocca Nuova, one of the four of Etna's summit craters, from 1988 to 1995. Acta Vulcanologica, 10: 27-31.

Calvari S, Pinkerton H, 2004. Birth, growth and morphologic evolution of the 'Laghetto' cinder cone during the 2001 Etna eruption. J. Volcanol. Geotherm. Res., 132: 225-239.

Calvari S, Tanner L H, Groppelli G, 1998. Debris-avalanche deposits of the Milo Lahar sequence and the opening of the Valle del Bove on Etna volcano (Italy). J. Volcanol. Geotherm. Res., 87: 193-209. https://doi.org/10.1016/S0377-0273(98)00089-4

Clover F M, 1983. Olympiodorus of Thebes and the Historia Augusta. Antiquitas Beitrage Hist-Augusta-Forschung, 15: 127-156.

Clover F M, 1981. (pers. comm.).

Coltelli M, Del Carlo P, Vezzoli L, 2000. Stratigraphic constraints for explosive activity in the past 100 ka at Etna volcano, Italy. Internatl J Earth Sci, 89: 665-677.

Coltelli M, Garduno V H, Neri M, Pasquare G, Pompilio M, 1994. Geology of the northern wall of Valle del Bove, Mt. Etna (Sicily). Acta Vulc, 5: 55-68.

Corazzato C, Tibaldi A, 2006. Fracture control on type, morphology and distribution of parasitic volcanic cones: an example from Mt. Etna, Italy. J. Volcanol. Geotherm. Res., 158: 177-194.

Corsaro R A, Cristofolini R, 1996. Origin and differentiation of recent basaltic magmas from Mount Etna. Mineral Petr, 57: 1-21.

Corsaro R A, Cristofolini R, Patane L, 1996. The 1669 eruption at Mount Etna: chronology, petrology and geochemistry, with inferences on the magma sources and ascent mechanisms. Bull Volcanol, 58: 348-358.

Corsaro R A, Pompilio M, 2004. Magma dynamics in the shallow plumbing system of Mt. Etna as recorded by compositional variations in the volcanics of recent summit activity (1995-1999). J. Volcanol. Geotherm. Res., 137: 55-71.

Crisci G M, Di Gregorio S, Rongo R, Scarpelli M, Spataro W, Calvari S, 2003. Revisiting the 1669 Etnean eruptive crisis using a cellular automata model and implications for volcanic hazards in the Catania area. J. Volcanol. Geotherm. Res., 123: 211-230.

Del Carlo P, Branca S, 1998. Tephrostratigraphic dating of the pre-1300 AD SE flank eruptions of Mt Etna. Acta Vulc, 10: 33-37.

Ferlito C, Coltorti M, Cristofolini R, Giacomoni P P, 2009. The contemporaneous emission of low-K and high-K trachybasalts and the role of the NE Rift during the 2002 eruptive event, Mt. Etna, Italy. Bull Volcanol, 71: 575-587. https://doi.org/10.1007/s00445-008-0243-9

Ferlito C, Viccaro M, Nicotra E, Cristofolini R, 2010. Relationship between the flank sliding of the South East Crater (Mt. Etna, Italy) and the paroxysmal event of November 16, 2006. Bull Volcanol, 72: 1179-1190. https://doi.org/10.1007/s00445-010-0384-5

Fornaciai A, Behncke B, Favalli M, Neri M, Tarquini S, Boschi E, 2010. Detecting short-term evolution of Etnean scoria cones: a LIDAR-based approach. Bull Volcanol, 72: 1209-1222. https://doi.org/10.1007/s00445-010-0394-3

Garduno V H, Neri M, Pasquare G, Borgia A, Tibaldi A, 1997. Geology of the NE-Rift of Mount Etna (Sicily, Italy). Acta Vulc, 9: 91-100.

Gillot P-Y, Kieffer G, Romano R, 1994. The evolution of Mount Etna in the light of potassium-argon dating. Acta Vulc, 5: 81-87.

Green J, Short N M, 1971. Volcanic Landforms and Surface Features: a Photographic Atlas and Glossary. New York: Springer-Verlag, 519 p.

Gresta S, Ripepe M, Marchetti E, D'Amico S, Coltelli M, Harris A J L, Privitera E, 2004. Seismoacoutstic measurements during the July-August 2001 eruption of Mt. Etna volcano, Italy. J. Volcanol. Geotherm. Res., 137: 219-230.

Guest J E, 1982. Styles of eruptions and flow morphology on Mt. Etna. Mem Soc Geol Italiana, 23: 49-67.

Guidoboni E, Ciuccarelli C, 2008. First historical evidence of a significant Mt. Etna eruption in 1224. J. Volcanol. Geotherm. Res., 178: 693-700.

Houghton B F, Wilson C J N, Del Carlo P, Coltelli M, Sable J E, Carey R, 2004. The influence of conduit processes on changes in style of basaltic Plinian eruptions: Tarawera 1886 and Etna 122 BC. J. Volcanol. Geotherm. Res., 137: 1-14.

Imbo G, 1965. Italy. Catalog of Active Volcanoes of the World and Solfatara Fields, Rome: IAVCEI, 18: 1-72.

Lautze N C, Harris A J L, Bailey J E, Ripepe M, Calvari S, Dehn J, Rowland S K, Evans-Jones K, 2004. Pulsed lava effusion at Mount Etna during 2001. J. Volcanol. Geotherm. Res., 137: 231-246.

Murray J B, Stevens N F, 2000. New formulae for estimating lava flow volumes at Mt. Etna volcano, Sicily. Bull Volcanol, 61: 515-526.

Neri M, Acocella V, 2006. The 2004-2005 Etna eruption: implications for flank deformation and structural behavior of the volcano. J. Volcanol. Geotherm. Res., 158: 195-206.

Neri M, Acocella V, Behncke B, 2004. The role of the Pernicana Fault System in the spreading of Mt. Etna (Italy) during the 2002-2003 eruption. Bull Volcanol, 66: 417-430.

Rodwell G F, 1878. Etna: A History of the Mountain and of its Eruptions. London: C Kegan Paul & Co, 146 p.

Romano R (ed), 1982. Mount Etna volcano. Mem Soc Geol Italiana, 23: 1-205.

Romano R, Sturiale C, Lentini F, 1979. Geological Map of Mount Etna. CNR Istit Internatl Vulc, Catania, 1:50,000 geol map.

Rymer H, Cassidy J, Locke C A, Murray J B, 1995. Magma movements in Etna volcano associated with the major 1991-93 lava eruption: evidence from gravity and deformation. Bull Volcanol, 57: 451-461.

Spampinato L, Calvari S, Oppenheimer C, Lodato L, 2008. Shallow magma transport for the 2002-3 Mt. Etna eruption inferred from thermal infrared surveys. J. Volcanol. Geotherm. Res., 177: 301-312.

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Tanguy J C, 1981. Les eruptions historiques de l'Etna: chronologie et localisation. Bull Volcanol, 44: 585-640.

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Eruptive History

There is data available for 147 confirmed Holocene eruptive periods.

2022 Nov 27 - 2024 Oct 17 (continuing) Confirmed Eruption VEI: 2

Episode 1 | Eruption

Southeast Crater

2022 Nov 27 - 2023 Feb 6

Evidence from Observations: Reported

List of 3 Events for Episode 1 at Southeast Crater

Start Date	End Date	Event Type	Event Remarks
2022 Nov 27	- - - -	Lava flow
2023 Jan 23	- - - -	Ash	Diffuse ash emissions first noted.
2023 Jan 23	- - - -	VEI (Explosivity Index)	VEI 1

Episode 2 | Eruption

Southeast Crater

2023 May 6 - 2023 Dec 23

Evidence from Observations: Reported

List of 2 Events for Episode 2 at Southeast Crater

	Start Date	End Date	Event Type	Event Remarks
	2023 May 6	- - - -	Explosion	Explosion at SE Crater occurred at 2325 on 6 May and produced a diffuse ash emission that rapidly dispersed around the crater area.
	2023 May 6	- - - -	VEI (Explosivity Index)	VEI 1

Episode 3 | Eruption

Bocca Nuova

2024 Apr 7 - 2024 Oct 17 (continuing)

Evidence from Observations: Seismicity

List of 2 Events for Episode 3 at Bocca Nuova

	Start Date	End Date	Event Type	Event Remarks
	2024 Apr 7	- - - -	Ash Plume	Dense ash emission from Bocca Nuova Crater rose about 1.6 km above the summit.
	2024 Apr 7	- - - -	VEI (Explosivity Index)	VEI 2

2013 Sep 3 - 2022 Jun 17 Confirmed Eruption VEI: 3

Episode 1 | Eruption

New Southeast Crater (NSEC)

2013 Sep 3 - 2015 Feb 1

Evidence from Observations: Reported

List of 130 Events for Episode 1 at New Southeast Crater (NSEC)

Start Date	End Date	Event Type	Event Remarks
2013 Sep 3	2013 Sep 6	Ash Plume	Sezione di Catania - Osservatorio Etneo reported that a series of small and sporadic ash emissions from Etna's New Southeast Crater (NSEC) began during the morning of 3 September 2013. At daybreak on 6 September small ash puffs were emitted once or twice per hour.
2013 Sep 6	- - - -	Incandescent ejecta	Weak Strombolian activity from NSEC was observed during the early morning of 6 September.
2013 Oct 25	2013 Oct 28	Thermal Anomaly	Twelve MODVOLC thermal alerts were issued.
2013 Oct 26	- - - -	Ash Plume	Sezione di Catania - Osservatorio Etneo reported that a gas plume laden with pyroclastic material rose several kilometers above the summit and drifted SW, affecting population centers as far as the Caltanissetta area.
2013 Oct 26	- - - -	Ash Plume	Based on INGV, PIREP, Satellite and webcam information, the Toulouse VAAC reported an eruption started at 0200 UTC. Ash was observed in satellite imagery at 0600 UTC at 6.1 km altitude. At 1100 UTC they noted ash at 7.6 km altitude, and that the eruption stopped around 1100 UTC.
2013 Oct 26	- - - -	Ashfall	Sezione di Catania - Osservatorio Etneo reported that a gas plume laden with pyroclastic material rose several kilometers above the summit and drifted SW, affecting population centers as far as the Caltanissetta area.
2013 Oct 26	- - - -	Lava fountains	Sezione di Catania - Osservatorio Etneo reported that Etna's New Southeast Crater (NSEC) produced a new episode of lava fountaining. Lava fountaining from NSEC continued through the late morning and was then followed by a long series of powerful explosions audible to many tens of kilometers away.
2013 Oct 26	- - - -	Explosion	Sezione di Catania - Osservatorio Etneo reported that lava fountaining from NSEC continued through the late morning and was then followed by a long series of powerful explosions audible to many tens of kilometers away.
2013 Oct 26	- - - -	Audible Sounds	Sezione di Catania - Osservatorio Etneo reported that lava fountaining from NSEC continued through the late morning and was then followed by a long series of powerful explosions audible to many tens of kilometers away.
2013 Oct 26	- - - -	Incandescent ejecta	Sezione di Catania - Osservatorio Etneo reported that strombolian explosions occurred in the late evening.
2013 Oct 26	2013 Oct 27	Lava flow	Lava emitted from the saddle between the two cones of the Southeast Crater (SEC, NSEC) advanced S, destroying two wooden shacks at Torre del Filosofo. Another smaller lava flow descended the SE flank of the NSEC cone, partially filling the deep collapse scar formed during the 27 April 2013 paroxysm. Lava flows continued to advance the next day.
2013 Oct 26	- - - -	Property Damage	Lava emitted from the saddle between the two cones of the Southeast Crater advanced S, destroying two wooden shacks at Torre del Filosofo.
2013 Oct 27	- - - -	Degassing	Based on SIGONELLA volcanic report, INGV webcam, and satellite imagery, the Toulouse VAAC reported a plume of water vapor at 0800 UTC between 2.1 and 4.3 km altitude. No ash or gas was identified on satellite imagery.
2013 Oct 29	- - - -	Ash Plume	Based on an Airep, the Toulouse VAAC reported at 1030 UTC a feeble to moderate ash plume observed at 0930 UTC moving W between 3.4 and 3.9 km altitude.
2013 Nov 5	2013 Nov 8	Ash Plume	INGV reported a brief glow seen on surveillance cameras was followed by ash emissions at NSEC. Ash emissions occurred at 1251 and 1254 on 6 November and were quickly dispersed by the wind. During 6-7 November several phases of frequent explosions produced ash puffs visible during the daytime. On 8 November the explosions occurred at intervals of several hours, producing small ash plumes that rose a few hundred meters above the summit and drifted ENE.
2013 Nov 6	2013 Nov 8	Explosion	During 6-7 November several phases of frequent explosions produced ash puffs visible during the daytime. Strombolian activity was visible at night. On 8 November the explosions occurred at intervals of several hours, producing small ash plumes that rose a few hundred meters above the summit and drifted ENE.
2013 Nov 6	2013 Nov 7	Incandescent ejecta	During 6-7 November several phases of frequent explosions produced ash puffs visible during the daytime. Strombolian activity was visible at night.
2013 Nov 10	2013 Nov 11	Incandescent ejecta	A culminating phase of lava fountains, ash emissions, and lava flows began at 0500 on 11 November, after about 10 hours of gradually intensifying Strombolian activity. Vigorous Strombolian activity continued, with explosions at intervals of 1-2 minutes, which launched incandescent material as high as 150 m above the crater rim. At night during 11-12 November Strombolian activity ceased.
2013 Nov 10	2013 Nov 12	Thermal Anomaly	Four MODVOLC thermal alerts were issued.
2013 Nov 11	- - - -	Seismicity (tremor)	A culminating phase of lava fountains, ash emissions, and lava flows began at 0500 on 11 November, after about 10 hours of gradually intensifying Strombolian activity. Weather conditions prevented visual observations, but a strong increase in the volcanic tremor amplitude was detected.
2013 Nov 11	- - - -	Explosion	A culminating phase of lava fountains, ash emissions, and lava flows began at 0500 on 11 November. The phase of maximum intensity lasted about 7.5 hours, ending around 1130; the cessation of lava fountaining was followed by a long series of powerful explosions that generated loud bangs heard mostly in the N sector of the volcano. Vigorous Strombolian activity continued, with explosions at intervals of 1-2 minutes, which launched incandescent material as high as 150 m above the crater rim.
2013 Nov 11	- - - -	Ash Plume	A culminating phase of lava fountains, ash emissions, and lava flows began at 0500 on 11 November. Ash and lapilli fell in areas E and NE.
2013 Nov 11	- - - -	Ash Plume	Based on Webcam information, the Toulouse VAAC reported that the cloud identifiable on the webcam may have contained ash.
2013 Nov 11	- - - -	Lava fountains	A culminating phase of lava fountains, ash emissions, and lava flows began at 0500 on 11 November, after about 10 hours of gradually intensifying Strombolian activity. The phase of maximum intensity lasted about 7.5 hours, ending around 1130; the cessation of lava fountaining was followed by a long series of powerful explosions that generated loud bangs heard mostly in the N sector of the volcano.
2013 Nov 11	2013 Nov 12	Lava flow	A culminating phase of lava fountains, ash emissions, and lava flows began at 0500 on 11 November. The phase of maximum intensity lasted about 7.5 hours, ending around 1130. A voluminous lava flow expanded S from the NSEC, and two smaller lava flows traveled ESE and NE. At night during 11-12 November Strombolian activity ceased and the lava flows were no longer active.
2013 Nov 11	- - - -	Audible Sounds	The phase of maximum intensity lasted about 7.5 hours, ending around 1130; the cessation of lava fountaining was followed by a long series of powerful explosions that generated loud bangs heard mostly in the N sector of the volcano.
2013 Nov 13	2013 Nov 14	Incandescent ejecta	INGV reported that weak Strombolian explosions from Etna’s New Southeast Crater (NSEC) were visible on 13 November 2013. INGV-Osservatorio Etneo staff visited the area the next day and noted that explosions were heard one to three times per minute. Sporadic ejections of incandescent pyroclastics were observed after nightfall.
2013 Nov 16	- - - -	Incandescent ejecta	Strombolian activity gradually intensified.
2013 Nov 17	- - - -	Ash Plume	A new paroxysmal eruptive episode was characterized by violent Strombolian activity and pulsating lava fountains, emission of lava flows that traveled S, ESE, and NE, and the formation of an eruption column charged with pyroclastic material that drifted NE.
2013 Nov 17	- - - -	Incandescent ejecta	A new paroxysmal eruptive episode was characterized by violent Strombolian activity and pulsating lava fountains, emission of lava flows that traveled S, ESE, and NE, and the formation of an eruption column charged with pyroclastic material that drifted NE. Strombolian activity continued until the late evening.
2013 Nov 17	- - - -	Lava fountains	A new paroxysmal eruptive episode was characterized by violent Strombolian activity and pulsating lava fountains, emission of lava flows that traveled S, ESE, and NE, and the formation of an eruption column charged with pyroclastic material that drifted NE.
2013 Nov 17	- - - -	Lava flow	A new paroxysmal eruptive episode was characterized by violent Strombolian activity and pulsating lava fountains, emission of lava flows that traveled S, ESE, and NE, and the formation of an eruption column charged with pyroclastic material that drifted NE. After nightfall, a small lava flow issued from an effusive vent located on the lower E flank of the NSEC cone.
2013 Nov 17	- - - -	Degassing	Based on INGV, Webcam, Airep and SAIT information, the Toulouse VAAC reported a low intensity eruption in progress at 2303 UTC on 16 November. At 0200 UTC on 17 November the plume was moving E at 11.0 km altitude. The plume seemed to be mainly composed of steam. At 0600 UTC they reported that the eruption stopped at about 0500 UTC and that the plume was moving E at 10.7 km altitude. The plume seemed to be mainly composed of steam and SO₂.
2013 Nov 17	- - - -	Explosion	The episode ended with a long series of powerful explosions and loud bangs heard tens of kilometers away.
2013 Nov 17	2013 Nov 19	Thermal Anomaly	Nineteen MOVOLC thermal alerts were issued.
2013 Nov 17	- - - -	Audible Sounds	The episode ended with a long series of powerful explosions and loud bangs heard tens of kilometers away.
2013 Nov 21	2013 Nov 24	Thermal Anomaly	Eight MODVOLC thermal alerts were issued.
2013 Nov 23	- - - -	Ash Plume	INGV reported an eruptive episode at NSEC characterized by a rapid evolution from Strombolian activity to lava fountains, an ash plume that rose several kilometers and drifted NE, and lava flows that were significantly less extensive than those emitted during the 16-17 November event.
2013 Nov 23	- - - -	Ash Plume	Based on a notice to airmen, INGV information, satellite data, and webcam images, the Toulouse VAAC reported an ash cloud "of severe intensity" that started at 0930 UTC, and initially rose to 4.3 km altitude. The eruption ended one hour later. The plume was observed at 3.9 km altitude at 1200 UTC. At 1300 UTC the ash plume was reported at 9.1-11.6 km altitude before dissipating. It had dissipated by 2042 UTC, only S02 was observed in satellite imagery.
2013 Nov 23	- - - -	Incandescent ejecta	INGV reported an eruptive episode at NSEC characterized by a rapid evolution from Strombolian activity to lava fountains, an ash plume that rose several kilometers and drifted NE, and lava flows that were significantly less extensive than those emitted during the 16-17 November event.
2013 Nov 23	- - - -	Lava fountains	INGV reported an eruptive episode at NSEC characterized by a rapid evolution from Strombolian activity to lava fountains, an ash plume that rose several kilometers and drifted NE, and lava flows that were significantly less extensive than those emitted during the 16-17 November event.
2013 Nov 23	- - - -	Lava flow	INGV reported an eruptive episode at NSEC characterized by a rapid evolution from Strombolian activity to lava fountains, an ash plume that rose several kilometers and drifted NE, and lava flows that were significantly less extensive than those emitted during the 16-17 November event.
2013 Nov 23	- - - -	VEI (Explosivity Index)	VEI 2
2013 Nov 28	- - - -	Observation	Based on INGV, webcam and seismic information, the Toulouse VAAC reported that an eruption started at 1730 UTC. They reported that the eruption had restarted at 1930 UTC and ash was not identifiable in satellite imagery. They reported that the eruption stopped at 2330 UTC.
2013 Nov 28	2013 Nov 29	Lava flow	INGV reported on the 18th paroxysm occurred from Etna’s New Southeast Crater (NSEC) late in the afternoon on 28 November. Weather clouds prevented observations of the event. See BGNV 38:09, figure 147 for map of the flow.
2013 Nov 28	2013 Nov 29	Thermal Anomaly	Twenty-two MODVOLC thermal alerts were issued.
2013 Dec 2	- - - -	Observation	Based on INGV, Webcam and Seismic monitoring, the Toulouse VAAC reported that an eruption started at 1820 UTC. Ash was not identifiable from satellite data due to weather. They reported that the eruption ended at 2300 UTC.
2013 Dec 2	2013 Dec 3	Explosion	Vigorous Strombolian activity on 2 December produced a plume comprised mostly of gas drifting N. The activity intensified during the evening and evolved into a paroxysmal event that finished by 2330. The event was characterized by tall lava fountains, lava flows, and a plume laden with pyroclastic material that drifted NNW and deposited ash and lapilli in that area. The next day sporadic explosions continued, inclement weather however prevented visual observations.
2013 Dec 2	- - - -	Ash Plume	Vigorous Strombolian activity on 2 December produced a plume comprised mostly of gas drifting N. The activity intensified during the evening and evolved into a paroxysmal event that finished by 2330. The event was characterized by tall lava fountains, lava flows, and a plume laden with pyroclastic material that drifted NNW and deposited ash and lapilli in that area.
2013 Dec 2	- - - -	Ashfall	Eruptive activity intensified during the evening and evolved into a paroxysmal event that finished by 2330. The event was characterized by tall lava fountains, lava flows, and a plume laden with pyroclastic material that drifted NNW and deposited ash and lapilli in that area.
2013 Dec 2	2013 Dec 3	Incandescent ejecta	Vigorous Strombolian activity on 2 December produced a plume comprised mostly of gas drifting N. The activity intensified during the evening and evolved into a paroxysmal event that finished by 2330. The next day sporadic explosions continued, inclement weather however prevented visual observations.
2013 Dec 2	- - - -	Lava fountains	Eruptive activity intensified during the evening and evolved into a paroxysmal event that finished by 2330. The event was characterized by tall lava fountains, lava flows, and a plume laden with pyroclastic material that drifted NNW and deposited ash and lapilli in that area.
2013 Dec 2	- - - -	Lava flow	Eruptive activity intensified during the evening and evolved into a paroxysmal event that finished by 2330. The event was characterized by tall lava fountains, lava flows, and a plume laden with pyroclastic material that drifted NNW and deposited ash and lapilli in that area. The lava flows traveled SSE, SE, NE, and S.
2013 Dec 4	2013 Dec 6	Thermal Anomaly	Six MODVOLC thermal alerts were issued.
2013 Dec 14	- - - -	Ash Plume	Based on INGV, webcam and NOTAM information, the Toulouse VAAC reported that an eruption started at 0827 UTC. Intermittent ash emission below 4.6 km altitude was reported. At 1445 UTC they reported that ash emission was not significant, and intermittent ash emission below 3.7 km altitude was reported.
2013 Dec 14	- - - -	Explosion	A strong explosion at 0925 from a vent near the NE rim generated an ash plume that rose 2 km.
2013 Dec 14	2013 Dec 15	Ash Plume	A strong explosion at 0925 from a vent near the NE rim generated an ash plume that rose 2 km. Over the next few hours activity continued to intensify and a diffuse ash plume drifted ESE. Explosive activity continued to produce copious amounts of ash until about 0830 the next day. According to a news article, the ash emissions caused the cancellation of more than 20 flights in and out of the Catania airport.
2013 Dec 14	2013 Dec 15	Incandescent ejecta	Intermittent ash emission gradually turned into Strombolian activity. After 1413 the activity intensified; small ash puffs were produced and Strombolian explosions ejected incandescent pyroclastics onto the flanks of the cone. During the night explosive activity continued to intensify, and by 0330 on 15 December Strombolian activity was intense and virtually continuous. After 0500 explosive activity started to diminish, and at 0550 the volcanic tremor amplitude and the intensity and frequency of Strombolian explosions showed a sharp drop.
2013 Dec 14	2013 Dec 18	Lava flow	At 2323 lava overflowed the SE crater rim and flowed towards the Valle del Bove. At 0610 and 0633 the next day two vents opened within the deep trench cutting the SE flank of the NSEC cone (where lava was still flowing from the crater since the previous evening), the first just a few tens of meters below the crater rim, the second about 100 m further downslope. Both vents initially produced lava fountains for a few minutes, with jets a few tens of meters high, and then produced lava flows that descended through the trench. At night during 15-16 December lava flows continued to flow towards the Valle del Bove. Lava effusion gradually diminished, but at about 1430 on 16 December, a short fissure opened on the lower NE flank of the NSEC cone, producing a small lava flow which advanced a few hundred meters. Very slow lava effusion continued, at a gradually decreasing rate, from the fissure on the NE flank of the NSEC cone, through the night of 17-18 December.
2013 Dec 14	2013 Dec 19	Thermal Anomaly	Forty-seven MODVOLC thermal alerts were issued.
2013 Dec 15	2013 Dec 16	Ash Plume	Based on Webcam, NOTAM, and MTOSAT satellite information, the Toulouse VAAC reported at 0600 UTC a stationary plume at 3.4 km altitude that was not identifiable in satellite imagery. The plume seemed to contain mainly steam and SO₂. At 1200 UTC sporadic ash emission was ongoing with the plume at 3.9 km altitude but eruption intensity had decreased. Some ash was temporarily observed on satellite imagery extending 90 km ESE. Sporadic ash emission was observed at 1800 UTC stationary at 4.3 km altitude. The plume was mostly steam and SO₂ with minor ash extending 130 km ESE. Sporadic ash emission was observed at 0000 on 16 December at 4.3 km altitude. Intermittent ash emission was observed at 0600 UTC at 4.3 km altitude. The eruption was still going on and ash emission was decreasing at 1145 UTC, 1703 UTC, and 2230 UTC and not identifiable from satellite data. The eruption had stopped by 0545 UTC on 17 December.
2013 Dec 15	2013 Dec 17	Ash Plume	Between 0945 on 15 December and the morning of 16 December ash emission varied in frequency and intensity, related to variations in the intensity of the Strombolian activity at NSEC. Strombolian activity at NSEC continued through 16 December at a slowly decreasing rate and with numerous minor intensifications that generated diluted ash plumes. Explosive activity finally ceased around midnight on 17 December.
2013 Dec 15	2013 Dec 16	Ashfall	The more intense explosive periods produced greater amounts of ash leading to ashfall in populated areas on the E and SE flank, from the Milo-Zafferana area toward the Ionian coast. At night during 15-16 December a shift in wind direction caused ashfall in areas SE, S, and SW.
2013 Dec 15	2013 Dec 17	Incandescent ejecta	Between 0945 on 15 December and the morning of 16 December ash emission varied in frequency and intensity, related to variations in the intensity of the Strombolian activity. During the afternoon and evening of 15 December explosive activity lasted a few to a few tens of minutes and Strombolian activity became significantly more intense or passed into pulsating, low lava fountains. Strombolian activity at the NSEC continued through 16 December at a slowly decreasing rate and with numerous minor intensifications that generated diluted ash plumes. Explosive activity finally ceased around midnight on 17 December.
2013 Dec 15	- - - -	Lava fountains	At 0610 and 0633 two vents opened within the deep trench cutting the SE flank of the NSEC cone (where lava was still flowing from the crater since the previous evening), the first just a few tens of meters below the crater rim, the second about 100 m further downslope. Both vents initially produced lava fountains for a few minutes, with jets a few tens of meters high, and then produced lava flows that descended through the trench. During the afternoon and evening of 15 December explosive activity lasted a few to a few tens of minutes and Strombolian activity became significantly more intense or passed into pulsating, low lava fountains.
2013 Dec 25	- - - -	Ash Plume	Based on INGV, Webcam, and MTOSAT imagery, the Toulouse VAAC reported ash identifiable from HRV MTOSAT data at 0800 UTC. Ash was observed at 4.3 km altitude.
2013 Dec 29	- - - -	Explosion	At 1115 NSEC produced a single Strombolian explosion, accompanied by an ash plume that rose 1 km and drifted E. Frequent powerful explosions from two vents located within the crater were audible in a vast sector around the volcano.
2013 Dec 29	- - - -	Ash Plume	At 1115 NSEC produced a single Strombolian explosion, accompanied by an ash plume that rose 1 km and drifted E. After the explosion mild Strombolian activity continued and then progressively intensified in the evening. Diffuse ash plumes drifted NE.
2013 Dec 29	- - - -	Incandescent ejecta	During the early morning hours on 29 December a camera recorded weak and sporadic incandescence from NSEC. At 1115 NSEC produced a single Strombolian explosion, accompanied by an ash plume that rose 1 km and drifted E. After the explosion mild Strombolian activity continued and then progressively intensified in the evening.
2013 Dec 29	2014 Jan 3 (in or before)	Lava flow	INGV reported that two lava flows were active, one from a vent on the E flank of the NSEC cone, and the second, fed directly from the crater, traveled down the NE flank of the cone. During 31 December 2013-1 January 2014 lava flows from a vent located on the NE flank of the cone of Etna's New Southeast Crater (NSEC) continued to travel towards the N part of the Valle de Bove; the lava flows had been active since activity resumed on 29 December. On 3 January staff doing field work noted that the effusive activity had stopped.
2013 Dec 29	- - - -	Audible Sounds	Frequent powerful explosions from two vents located within the crater were audible in a vast sector around the volcano.
2013 Dec 30	- - - -	Ash Plume	Based on INGV webcam, pilot report and MTOSAT Imagery, the Toulouse VAAC reported increasing activity at 0200 UTC that was mainly a lava flow, some steam, SO₂, and probably ash reported between 3.7 and 4.3 km altitude. Activity continued at 0800 UTC and 1200 UTC at the same intensity. A plume likely containing minor ash was reported between 3.9 and 5.2 km altitude moving NE. The webcams showed decreasing activity at 1500 UTC. The tremor continued at 2100 UTC. No activity was observed at 2350 UTC.
2013 Dec 30	2014 Jan 2	Thermal Anomaly	Nine MODVOLC thermal alerts were issued.
2014 Jan 1	- - - -	Ash Plume	A web camera photo near midday showed a dense black plume emerging from the crater.
2014 Jan 21	2014 Jan 26	Ash Plume	Some explosions generated very small ash emissions that barely rose above the crater rim. On 23 January at 0105 a small puff of gas and/or ash from the E base of the cone heralded a new lava flow that traveled W towards the Valle del Bove. On 25 January the amount of ash produced by the Strombolian activity increased. On 26 January an ash plume drifted E. By evening the amount of ash in the emissions decreased.
2014 Jan 21	2014 Jan 28	Incandescent ejecta	Strombolian activity at New Southeast Crater (NSEC) began in the evening, following 20 days of quiet. The next day, Strombolian explosions ejected incandescent pyroclastic material onto the cone flanks. The frequency and intensity of the explosions decreased early on 23 January. Weak Strombolian activity continued during 24-28 January, although on 25 January the amount of ash produced by the Strombolian activity increased. By evening on 26 January the intensity of the Strombolian activity as well as the amount of ash in the emissions decreased. INGV reported that on 28 January there was a gradual but steady decrease of activity. Weak and sporadic Strombolian explosions were detected at night, but then the thermal cameras recorded no anomalies associated with Strombolian activity.
2014 Jan 22	2014 Jan 28	Lava flow	Late in the day a small lava flow from the vent on the high E flank of the NSEC cone traveled a few hundred meters in a few hours. The lava flow stopped advancing on 23 January. At 0105 a small puff of gas and/or ash from the E base of the cone heralded a new lava flow that traveled W towards the Valle del Bove. Weak Strombolian activity and the advancing lava flow continued during 24-28 January. On 26 January The lava flow was 4 km long. Lava flows from two vents at the base of the NSEC cone continued to effuse at a very low rate on 28 January with a new lava flow advancing on top of the earlier one.
2014 Jan 22	2014 Jan 30	Thermal Anomaly	Multiple daily MODVOLC thermal alerts were issued.
2014 Feb 2	2014 Mar 26	Thermal Anomaly	Multiple near-daily MODVOLC thermal alerts were issued.
2014 Feb 3	2014 Feb 28	Lava flow	Late on 3 February 2014 observers noted that a lava flow remained active and was several hundred meters long. By 2000 on 4 February the lava flow had reached 1 km long. INGV reported that during 4-5 February there was a constant emission of lava from one or two vents at the E base of the NSEC cone. The lava flows reached the base of the W slope of the Valle del Bove on 5 February. During 9-11 February lava flows advanced. On 12 February lava continued to flow from the cone towards the Valle del Bove, and by nightfall had reached the base of the steep W wall of the valley, then advanced on the flat land to the N of Mount Centenarians. Activity during 14-15 February produced lava flows a few hundred meters long. During the afternoon of 15 February a small lava flow emerged from a new vent at the N base of the NSEC cone. The flow traveled 100 m towards the W wall of the Valle del Bove, and remained active the next day. Lava continued to flow from a vent on the lower part of the NSEC cone to the W wall of the Valle del Bove into March.
2014 Feb 4	2014 Feb 28	Ash Plume	INGV reported that almost continuous ash emissions from NSEC began at about 1300 on 4 February and continued into the night; about 5-10 ash puffs were separated by steam emissions. Ash plumes drifted E. At 2000 the ash emissions ceased. During 4-5 February activity was characterized by intermittent ash emissions accompanied by jets of incandescent pyroclastic material, and a constant emission of lava. On 6 February ash emissions ceased. Puffs of ash were observed on 8 February. Periodic ash emissions occurred during 9-11 February. At 0707 on 11 February a large quantity of reddish brown ash emitted from an area that collapsed near the vents. The unstable part of the lower E flank of the cone continued to produce small collapses and reddish ash clouds the next day. At 1208 on 15 February an explosion generated a vapor-and-ash plume. During 16-17 February and through the end of the month Strombolian activity continued to produce small quantities of ash. The unstable part of the lower E flank of the cone that collapsed on 11 February continued to produce small collapses with reddish ash clouds through the end of February.
2014 Feb 4	2014 Feb 28	Incandescent ejecta	On 4 February after sunset, jets of hot material were observed rising 100 m above the crater rim. INGV reported that during 4-5 February activity was characterized by intermittent ash emissions accompanied by jets of incandescent pyroclastic material, and a constant emission of lava. On 6 February small Strombolian explosions ejected incandescent pyroclastic material 100 m above the crater. On 7 February Strombolian explosions ejected material onto the flanks of the cone. Strombolian activity continued throughout the rest of February.
2014 Feb 11	- - - -	Pyroclastic flow	At 0707 a large, dense, reddish-brown ash cloud discharged from a lower E-flank vent area. Rather than rising much distance, the ash-charged cloud moved rapidly downslope. The cloud consisted of a dense hot avalanche or landslide that INGV also said looked very much like a pyroclastic flow. The ash laden cloud took about a minute to reach the base of the W wall of the Valle del Bove only stopping after it encountered less steep terrain. After this event, reddish brown ash emissions continued. Shortly after reaching the level ground at the base of the W wall of the Valle del Bove, the flow stopped in an area about 3.5-4 km away from source vent. A cloud of ash rose up and drifted NE.
2014 Feb 15	- - - -	Explosion	At 1208 an explosion generated a vapor-and-ash plume, and was then followed by more explosions from the same area.
2014 Mar 1	2014 Mar 22	Ash Plume	Strombolian activity and diffuse ash emissions continued to rise from one or two vents at the base of the NSEC cone. An unstable part of the lower E flank of the cone that collapsed on 11 February continued to produce small collapses with reddish ash clouds. Activity intensified during 18-22 March, producing more ash, and then decreased. No ash was emitted on 23 March.
2014 Mar 1	2014 Mar 27	Incandescent ejecta	Strombolian activity and diffuse ash emissions continued to rise from one or two vents at the base of the NSEC cone. Activity intensified during 18-22 March, producing more ash, and then decreased and ceased during the night of 26-27 March, after 64 days of persistent activity.
2014 Mar 1	2014 Mar 29	Lava flow	Lava continued to flow from a vent on the lower part of the NSEC cone to the W wall of the Valle del Bove, and during 2-3 March 2014 the flows reached the base of the wall. The lava flow fed by the vent on the inside of the unstable lower portion of the lower E flank remained active on 5 March. A second flow was fed a few hundred meters downslope , with an active front on the upper margin of the 2008-2009 lava field. After several days of lava emissions from a vent on the lower part of the NSEC cone, during 5-6 March lava flows originated only from a higher vent and traveled 1.5 km towards the lower part of the W wall of the Valle del Bove. During 14-24 March lava also flowed NE in the direction of Monte Simone. Lava emissions from the lower side of the NSEC significantly decreased during the last week of March; on the evening of 28 March a small lava flow continued to advance but had stopped and was cooling the next day.
2014 Mar 20	- - - -	Ash Plume	Based on Webcam and INGV information, the Toulouse VAAC reported a pulse that possibly contained ash at 1700 UTC. Ash was not identified in satellite data.
2014 Mar 21	- - - -	Ash Plume	Based on Webcam, Sigmet, and msg SAT information, The Toulouse VAAC reported low level sporadic ash emission at ?0600 UTC. Ash was not identifiable from satellite data. At 0700 UTC the small plume with ash was weakening and it was only visible in the vicinity of Etna. By 1200 UTC the emission was sporadic with mainly steam.
2014 Mar 29	2014 Apr 4	Thermal Anomaly	Multiple daily MODVOLC thermal alerts were issued.
2014 Apr 1	2014 Apr 7 (in or before)	Lava flow	INGV reported that during the night emissions of minor lava flows from the NE base of Etna's New Southeast Crater (NSEC) cone decreased. By 7 April the lava flows had ceased.
2014 Apr 2	2014 Apr 8 (in or before)	Incandescent ejecta	Strombolian activity gradually intensified during the evening and then decreased the next morning. By 7 April Strombolian activity had sharply declined. No activity was observed on 8 April.
2014 Apr 22	2014 Jun 10	Incandescent ejecta	INGV reported that during the morning of 22 April sporadic and weak Strombolian activity resumed at the New Southeast Crater (NSEC) and continued for the next few days. Explosions ejected incandescent pyroclastic material out of the crater and onto the upper S and SE flanks of the cone. Small collapses occurred on the cone's unstable E flank. The frequency and intensity of Strombolian explosions slightly increased late in the evening on 30 April. Weak Strombolian activity continued to be detected through 1 May. During the night of 2-3 May incandescence was caused by weak high-temperature gas emissions and/or Strombolian explosions. The activity intensified on 4 May and some of the explosions ejected incandescent pyroclastic material onto the high S and SE parts of the NSEC cone. Weak Strombolian activity continued through 10 June. Some explosions ejected incandescent pyroclastic material a few tens of meters above the crater rim that rarely fell onto the outer flanks.
2014 Jun 14	- - - -	Ash Plume	Fine ash emissions were reported.
2014 Jun 14	2014 Jun 17	Incandescent ejecta	A new eruptive episode began within the NSEC, beginning with near-continuous Strombolian explosions and lava fountaining and lasted for four days.
2014 Jun 14	2014 Jun 17	Lava fountains	A new eruptive episode began within the NSEC, beginning with near-continuous Strombolian explosions and lava fountaining and lasted for four days.
2014 Jun 14	2014 Jun 18	Lava flow	On 14 June a new eruptive episode began within the NSEC. Fine ash emissions were concurrent with lava that began to overflow the SE edge of NSEC, forming a flow that continued downhill on the W wall of Valle del Bove. During the morning of 15 June the overflowing lava followed the fissure that had been formed on 28 November 2013. A spatter cone also formed in the E sector of the cone. During 14-15 June volcanic tremor increased sharply and remained at a medium-high level until 18 June when it returned to normal levels.
2014 Jun 15	2017 Jun 16	Ash Plume	Based on INGV, Webcam, Pirep, and volcanic tremor information, the Toulouse VAAC reported that an eruption started at 0305 UTC with a low level feeble emission observed at 1200 UTC at 2.1-3.7 km altitude. Ongoing activity was reported at 1745 UTC and 2315 UTC. Feeble activity continued at 0520 UTC on 16 June, but was no longer identifiable from satellite or webcam data by 1200 UTC.
2014 Jun 15	2014 Jun 18	Thermal Anomaly	Multiple daily MODVOLC thermal alerts were issued.
2014 Jul 6	2014 Jul 11	Ash Plume	Weak and sporadic Strombolian explosions and small ash emissions were observed during 6-7 July, but by 11 July this activity had ceased.
2014 Jul 6	2014 Jul 11	Incandescent ejecta	Weak and sporadic Strombolian explosions and small ash emissions were observed during 6-7 July, but by 11 July this activity had ceased.
2014 Jul 18	- - - -	Ash Plume	Based on Webcam, INGV, and Satellite imagery, the Toulouse VAAC reported a feeble eruption with an ash cloud between 2.1 and 3.7 km altitude.
2014 Aug 9	- - - -	Ash Plume	Based on INGV, Webcams, satellite imagery and Airep information, the Toulouse VAAC reported a feeble to moderate eruption at 0800 UTC with an ash cloud above the volcano that rose to about 4.0 km altitude. No ash was detected in satellite data. By 0900 UTC a significant ash emission was reported. The ash cloud was reported at 5.5 km altitude. At 1225 UTC the ash cloud in the vicinity was observed. At 1800 UTC an ash emission occurred in the vicinity of the summit.
2014 Aug 9	2014 Aug 15	Ash Plume	Strombolian activity increased at NSEC and was accompanied by small emissions of black ash that remained within the crater. Modest emissions of ash continued until 15 August.
2014 Aug 9	2014 Aug 15	Incandescent ejecta	Strombolian activity increased at NSEC and was accompanied by small emissions of black ash that remained within the crater. INGV reported that the eruption at NSEC ended on 15 August.
2014 Aug 9	2014 Aug 16	Lava flow	At 0645 an effusive vent opened on the high E flank of the NSEC cone, which caused a small landslide and emitted a lava flow that after an hour had reached the E base of the cone. By 12 August two new branches were overlapping the earlier flow. The longest flow changed direction to later descend about 3 km NE toward Monte Simone. INGV reported that the eruption at NSEC had ended on 15 August and that the lava flow activity had ceased by 16 August.
2014 Aug 9	2014 Aug 9	Cinder Cone	During the first 24 hours of activity, a small pyroclastic cone in the W portion of the NSEC summit appeared, increasing the height of the NSEC structure that began to grow in 2011.
2014 Aug 9	2014 Aug 21	Thermal Anomaly	Multiple near-daily MODVOLC thermal alerts were issued.
2014 Aug 11	- - - -	Ash Plume	Based on a VONA from INGV, webcams, and satellite data, the Toulouse VAAC reported a weak ash emission close to the summit at 0900 UTC. At 1700 UTC ash was close to the summit at 4.6 km altitude.
2014 Aug 13	- - - -	Ash Plume	Based on webcam and satellite data, the Toulouse VAAC reported ash close to the volcano at 0400 UTC. Ash was identifiable from the webcams.
2014 Aug 13	- - - -	Ash Plume	Based on Webcam and satellite data, the Toulouse VAAC reported ash close to the volcano at 1800 UTC with the ash plume at 4.6 km altitude. Ash was identifiable from the webcam, but not in satellite data.
2014 Oct 7	2014 Oct 16	Ash Plume	INGV reported that from the afternoon of 7 October through 16 October NSEC produced weak and intermittent explosive activity; small ash puffs were rapidly dispersed by the wind. During some nights small Strombolian explosions ejected incandescent material a few tens of meters above the crater rim.
2014 Oct 7	2014 Oct 16	Incandescent ejecta	INGV reported that from the afternoon of 7 October through 16 October NSEC produced weak and intermittent explosive activity; small ash puffs were rapidly dispersed by the wind. During some nights small Strombolian explosions ejected incandescent material a few tens of meters above the crater rim.
2014 Dec 20	- - - -	Ash Plume	Based on an airep and webcam information, the Toulouse VAAC reported a feeble emission at 1000 UTC. A pilot report ash 25 km SE of Catalina between 3.0 and 3.9 km altitude at 0947 UTC.
2014 Dec 28	2015 Dec 29	Ash Plume	Based on a VONA from INGV and a NOTAM the Toulouse VAAC reported an increase in seismic tremor at 1736 UTC. Ash was not identifiable in satellite or webcam information. Lava fountaining had started. Ashfall was reported on the villages on the E slopes. At 0000 UTC on 29 December a feeble Strombolian eruption was reported and seismic activity was decreasing. At 0600 UTC the activity continued with possible lava flows but no ash cloud. At 0700 UTC, ash of moderate intensity was reported between 2.1 and 3.0 km altitude extending 35 km from the volcano.
2014 Dec 28	- - - -	Explosion	Starting at 1850 the NSEC produced a short but intense eruption characterized by lava fountains, lava flows, an ash plume that drifted E, and caused ash and lapilli fall in the nearby towns. Tremor began to decrease at 1930, and indicated that the eruption was over at 2100.
2014 Dec 28	2014 Dec 29	Ash Plume	Starting at 1850 the NSEC produced a short but intense eruption characterized by lava fountains, lava flows, an ash plume that drifted E, and caused ash and lapilli fall in the nearby towns. A day after the short but intense eruption, cameras viewing Etna recorded small ash emissions from NSEC.
2014 Dec 28	- - - -	Ashfall	Coarse ash and lapilli as large as 4-5 cm were reported in Fornazzo (9 km E), and mostly coarse ash and fine lapilli were deposited in Giarre (15 km E). Fine ash was also reported in Linguaglossa 17 km NE.
2014 Dec 28	- - - -	Lava fountains	Starting at 1850 the NSEC produced a short but intense eruption characterized by lava fountains, lava flows, an ash plume that drifted E, and caused ash and lapilli fall in the nearby towns.
2014 Dec 28	- - - -	Lava flow	Starting at 1850 on 28 December the NSEC produced a short but intense eruption characterized by lava fountains, lava flows, an ash plume that drifted E, and ash and lapilli fall in the nearby towns. INGV indicated that this episode occurred at a series of eruptive vents along a NE-SW fissure that cut across the NSEC and the southern flank of the old SEC. From the two extremities of this fissure lava flows emerged, traveling SW toward the area of Milia-Galvarina and NE and E toward the northern part of the Valle del Bove near Monte Simone, reaching lengths of about 4.5 and 3.3 km, respectively.
2014 Dec 28	- - - -	Lapilli	Coarse ash and lapilli as large as 4-5 cm were reported in Fornazzo (9 km E), and mostly coarse ash and fine lapilli were deposited in Giarre (15 km E). Fine ash was also reported in Linguaglossa 17 km NE.
2014 Dec 28	2014 Dec 29	Thermal Anomaly	Fifteen MODVOLC thermal alerts were issued.
2014 Dec 29	- - - -	Ash Plume	INGV reported that a day after a short but intense eruption, cameras viewing Etna recorded small ash emissions from New Southeast Crater (NSEC).
2014 Dec 29	- - - -	Incandescence	A day after a short but intense eruption, cameras viewing Etna recorded persistent glow from the saddle between the SEC and NSEC cones at dusk.
2015 Jan 2	2015 Jan 3	Explosion	At 0530 on 2 January explosions at NSEC generated ash plumes that drifted SW. On the evening of 3 January explosions ejected incandescent material 150 m above the crater rim.
2015 Jan 2	- - - -	Ash Plume	At 0530 explosions at NSEC generated ash plumes that drifted SW.
2015 Jan 2	2015 Jan 3	Ash Plume	Based on a VONA from INGV, and Webcam information, 0700 UTC the Toulouse VAAC reported an ash emission below 4.6 km altitude since 0625 UTC. By 1200 UTC AIREP and Satellite HRV imagery indicated the ash plume was stationalry at 4.6 km altitude. At 1800 UTC ash was possible at a low level in the vicinity of the volcano. Ash emission was decreasing at 0000 on 3 January, and had ended by 0600 UTC.
2015 Jan 3	- - - -	Incandescent ejecta	Explosions ejected incandescent material 150 m above the crater rim.
2015 Feb 1	- - - -	Lava flow	A lava flow issued from a vent at the southern base of the SEC cone corresponding to the lowest part of the SW eruptive fissure from 28 December 2014, It divided into two branches and traveled 2 km S. A field survey on 2 February determined that the lava front had stopped at 1,950 m elevation near the Monte Scavo area on the SW flank.
2015 Feb 1	2015 Feb 2	Thermal Anomaly	Sixteen MODVOLC thermal alerts were issued.

Episode 2 | Eruption

Northeast crater (NEC)

2013 Oct 26 - 2014 Jan 13

Evidence from Observations: Reported

List of 6 Events for Episode 2 at Northeast crater (NEC)

Start Date	End Date	Event Type	Event Remarks
2013 Oct 26	- - - -	Ash Plume	At 1019 vigorous ash emissions from the Northeast Crater formed a dark brown plume that rose 1 km; ash emissions from that crater continued through late evening.
2013 Oct 26	- - - -	VEI (Explosivity Index)	VEI 1
2013 Dec 15	- - - -	Ash Plume	Small and periodic ash emissions occurred from Northeast Crater.
2013 Dec 15	2013 Dec 16	Thermal Anomaly	Small thermal anomalies were detected with a thermal camera.
2013 Dec 29	- - - -	Degassing	Strong pulsating degassing occurred at Northeast Crater.
2014 Jan 4	2014 Jan 22	Ash Plume	INGV reported that during 4-13 January nearly continuous emissions of reddish ash from Etna's Northeast Crater were visible. Strong degassing continued at least through 22 January.

Episode 3 | Eruption

Bocca Nuova (BN)

2014 Mar 8 - 2014 Mar 8

Evidence from Observations: Reported

List of 3 Events for Episode 3 at Bocca Nuova (BN)

Start Date	End Date	Event Type	Event Remarks
2014 Mar 8	- - - -	Ash Plume	Sporadic emissions of hot material with small amounts of volcanic ash originated from Bocca Nuova.
2014 Mar 8	- - - -	Incandescent ejecta	Sporadic emissions of hot material with small amounts of volcanic ash originated from Bocca Nuova.
2014 Mar 8	- - - -	VEI (Explosivity Index)	VEI 1

Episode 4 | Eruption

Northeast crater (NEC)

2014 Jul 5 - 2014 Aug 9

Evidence from Observations: Reported

List of 13 Events for Episode 4 at Northeast crater (NEC)

Start Date	End Date	Event Type	Event Remarks
2014 Apr 30	- - - -	Degassing	Degassing increased and thermal anomalies were detected by a camera.
2014 Jul 5	- - - -	Fissure	After images of a thermal anomaly in webcam images from Monte Cagliato, located on the E flank of Etna, a new, small fissure (tens of meters long) at the E base of the North East Crater (NEC) was observed by INGV Etna observatory personnel. The vent was located between 3,015 and 3,025 m elevation.
2014 Jul 5	2014 Jul 25	Incandescent ejecta	Activity from the new fissure included frequent Strombolian explosions that were audible in nearby towns.
2014 Jul 5	2014 Jul 25	Lava flow	Weak spattering from the vent fed a lava flow that initially extended about 100 m. The lava flow diverged, and the longest of the two branches extended ~1.5 km, reaching the bottom of Valle del Leone.
2014 Jul 5	2014 Aug 9	Thermal Anomaly	Multiple near-daily MODVOLC thermal alerts were issued.
2014 Jul 5	2014 Jul 25	Audible Sounds	Activity from the new fissure included frequent Strombolian explosions that were audible in nearby towns.
2014 Jul 25	2014 Jul 31	Ash Plume	About 1114 local time, a new eruptive vent opened near the 5 July eruptive fissure. This new vent ("25 July vent"), located at a distance of about 150-200 m to the N of the one from 5 July, was a source of Strombolian explosions, accompanied at times by modest quantities of ash. This activity continued through 31 July.
2014 Jul 25	2014 Jul 31	Incandescent ejecta	At about 1114 local time, a new eruptive vent opened near the 5 July eruptive fissure. This new vent ("25 July vent"), located at a distance of about 150-200 m to the N of the one from 5 July, was a source of Strombolian explosions, accompanied at times by modest quantities of ash. This activity continued through 31 July. The Strombolian explosions occurred at intervals of about 2-5 seconds and were often accompanied by visible compression waves ("flashing arcs") and audible rumblings up to a few tens of meters away, mostly in the E and NE sectors of the volcano.
2014 Jul 25	2014 Aug 9	Lava flow	The lava flows, which reached about 1.8 km in length, (halting on the saddle between the Valle del Leone and the Valle del Bove), overlapped the earlier ones, with active fronts at least 1 km from the effusive vent.
2014 Jul 25	2014 Jul 31	Bombs	Bombs and scoria occasionally rose 200 m high and fell within a few hundred meter radius around the vent.
2014 Jul 25	- - - -	VEI (Explosivity Index)	VEI 1
2014 Aug 9	- - - -	Ash Plume	From the 25 July vent, there began a gradual increase in the ash emissions that formed an ash plume, which rose to 1 km above the vent area. With the intensification of activity at the NSEC, the eruptive activity at the E flank of the NEC diminished.
2014 Aug 9	- - - -	Incandescent ejecta	Strong Strombolian activity renewed at the July 25 vent in the evening.

Episode 5 | Eruption

Voragine Crater (VOR)

2015 Jan 1 - 2015 Jan 14

Evidence from Observations: Reported

List of 11 Events for Episode 5 at Voragine Crater (VOR)

Start Date	End Date	Event Type	Event Remarks
2015 Jan 1	2015 Jan 2	Incandescent ejecta	During the night cameras recorded intermittent flashes from Voragine Crater, indicating Strombolian activity there for the first time in nearly two years.
2015 Jan 3	2015 Jan 10	Explosion
2015 Jan 3	2015 Jan 7	Incandescent ejecta	INGV reported that incandescent pyroclastic material rose up to 150 m above the crater rim and occasionally fell outside the crater onto the W and SW flanks; this was accompanied by minor ash emissions rising a few hundred meters.
2015 Jan 5	2015 Jan 10	Thermal Anomaly	Nine MODVOLC thermal alerts were issued.
2015 Jan 7	- - - -	Ash Plume	Many of the small explosions generated brown ash plumes that rose a few hundred meters above Etna's summit and quickly dissipated.
2015 Jan 8	2015 Jan 9	Incandescent ejecta	Strombolian activity increased on 8 January, possibly from two vents within the crater. Pyroclastic material continued to be ejected out of the crater. Early on 9 January Strombolian activity again decreased and gave way to ash emissions that rose several hundred meters.
2015 Jan 9	2015 Jan 10	Ash Plume	Early on 9 January Strombolian activity again decreased and gave way to ash emissions that rose several hundred meters. Ash emissions continued the next morning, decreased, and had almost completely ceased by late morning. Ash emissions resumed in the afternoon and were sometimes accompanied by Strombolian explosions.
2015 Jan 9	- - - -	VEI (Explosivity Index)	VEI 1
2015 Jan 13	- - - -	Ash Plume	Based on INGV, Webcam, and Satellite imagery, at 0736 UTC the Toulouse VAAC reported an ash emission since 0736 UTC below 3.7 km altitude. The ash plume extended 16 km S. Ash emission had stopped by 1200 UTC.
2015 Jan 13	2015 Jan 14	Ash Plume	During the morning new ash emissions began at the Voragine. For some hours, these emissions were continuous, but successively diminished in the afternoon to every 5-10 minutes. Marco Neri, of the INGV- Osservatorio Etneo, during a helicopter overflight on 14 January, captured a clear view of these emissions and of the summit crater area.
2015 Jan 14	- - - -	Incandescent ejecta	INGV reported that in the evening weak Strombolian activity was recorded at Etna's Voragine Crater and Northeast Crater.

Episode 6 | Eruption

Northeast crater (NEC)

2015 Jan 14 - 2015 Jan 31

Evidence from Observations: Reported

List of 4 Events for Episode 6 at Northeast crater (NEC)

Start Date	End Date	Event Type	Event Remarks
2015 Jan 14	2015 Jan 31	Ash Plume	According to INGV, Strombolian and ash plume activity resumed at the NEC for a few days, but clouds obscured the summit area for most of the rest of the month. Intense degassing and minor ash was seen during clear weather through 31 January. Pulsating ash emissions occasionally drifted SE.
2015 Jan 14	2015 Jan 17	Incandescent ejecta	Strombolian and ash plume activity resumed at the NEC for a few days, but clouds obscured the summit area for most of the rest of the month.
2015 Jan 14	- - - -	VEI (Explosivity Index)	VEI 1
2015 Jan 15	- - - -	Ash Plume	Based on INGV and Webcam information, at 0000 UTC the Toulouse VAAC reported an ash plume visible over the volcano since 2350 UTC on 14 January. Ash was possible in the vicinity below 4.6 km altitude.

Episode 7 | Eruption

Saddle Cone (SEC3)

2015 Jan 31 - 2015 Feb 1

Evidence from Observations: Reported

List of 9 Events for Episode 7 at Saddle Cone (SEC3)

Start Date	End Date	Event Type	Event Remarks
2015 Jan 31	2015 Feb 2	Explosion	A new eruptive episode began on 31 January and continued through the morning of 2 February. Explosions occurred every few seconds and ejected incandescent bombs 200 m high, which fell on the S flank of the SEC.
2015 Jan 31	2015 Feb 2	Bombs	Explosions occurred every few seconds and ejected incandescent bombs 200 m high, which fell on the S flank of the SEC.
2015 Jan 31	- - - -	Ash Plume	A sudden increase in volcanic tremor amplitude in the early morning indicated a new ash emission from the summit which was obscured from view by clouds.
2015 Jan 31	- - - -	Ashfall	Later in the morning, fine ash fell over the snow in Rifugio Citelle (6 km NE).
2015 Jan 31	2015 Feb 2	Incandescent ejecta	Poor meteorological conditions prevented views of the summit area during the first 36 hours of the eruption. During improved viewing conditions on the evening of 1 February, volcanologists observed lively Strombolian activity from a single vent in the saddle between the SEC and NSEC cones. At dawn on 2 February the Strombolian activity produced a dense ash cloud that drifted E. At about 0750 emissions stopped, and volcanic tremor suddenly decreased.
2015 Jan 31	- - - -	Ash Plume	Based on an INGV VONA, at 1900 UTC the Toulouse VAAC reported explosive activity at the summit. A significant ash emission occurred but the ash cloud was not observable.
2015 Jan 31	- - - -	VEI (Explosivity Index)	VEI 1
2015 Feb 2	- - - -	Ash Plume	At dawn the Strombolian activity produced a dense ash cloud that drifted E. At about 0550 emissions stopped and volcanic tremor suddenly decreased.
2015 Feb 2	- - - -	Ash Plume	Based on INGV, Webcam information, and Satellite information, at 0600 UTC the Toulouse VAAC reported that an ash emission started at 0600 UTC with an ash plume moving E at 3.9 km altitude. The emission had finished by 1145 UTC.

Episode 8 | Eruption

Bocca Nuova (BN)

2015 Apr 12 - 2015 Aug 24

Evidence from Observations: Reported

List of 7 Events for Episode 8 at Bocca Nuova (BN)

Start Date	End Date	Event Type	Event Remarks
2015 Apr 12	- - - -	Explosion	INGV reported that two explosions from the W part of Etna’s Bocca Nuova Crater were recorded within a 3-minute period beginning at 1505.
2015 Apr 12	- - - -	Ash Plume	An ash emission from Bocca Nuova produced a plume a few tens of meters high that drifted SE, leaving fallout of fine reddish ash on the snow covering the western wall of the Bove Valley above 2,000 m elevation. A second smaller emission later in the day quickly dissipated.
2015 Apr 12	- - - -	Ashfall	An ash emission from Bocca Nuova produced a plume a few tens of meters high that drifted SE, leaving fallout of fine reddish ash on the snow covering the western wall of the Bove Valley above 2,000 m elevation.
2015 Apr 12	- - - -	VEI (Explosivity Index)	VEI 1
2015 May 1	- - - -	Ash Plume	A small brownish-red ash plume rose from BN; it likely resulted from a collapse inside the NW crater wall.
2015 May 15	- - - -	Ash Plume	During the morning a series of strong ash emissions lasting 2-3 minutes each continued from BN for about two hours.
2015 Aug 24	- - - -	Ash Plume	Darker emissions of gas and small amounts of fine-grained ash were observed rising from the pit located in the center of the crater floor.

Episode 9 | Eruption

New Southeast Crater (NSEC)

2015 May 11 - 2015 May 16

Evidence from Observations: Reported

List of 18 Events for Episode 9 at New Southeast Crater (NSEC)

Start Date	End Date	Event Type	Event Remarks
2015 May 2	2015 May 3	Seismicity (tremor)	A sudden increase in tremor amplitude and intense degassing had no visible activity, and after a few days tremor returned to normal levels.
2015 May 3	- - - -	Degassing	Based on a VONA issued by INGV, at 0500 UTC the Toulouse VAAC reported that no ash emission was detected.
2015 May 11	2015 May 12	Incandescent ejecta	INGV reported weak Strombolian activity inside Etna’s New Southeast Crater (NSEC), mainly from a depression on the E part of the crater and sometimes from a second vent in the middle of the crater.
2015 May 12	- - - -	Ash Plume	Based on Webcam, Satellite and VONA information, at 1515 UTC on 13 May the Toulouse VAAC reported small Strombolian explosions since 12 May. The webcam showed bursts of ash in the vicinity of the volcano. No ash was detected in satellite data.
2015 May 12	- - - -	Incandescent ejecta	Based on Webcam, Satellite and VONA information, at 1515 UTC on 13 May the Toulouse VAAC reported small Strombolian explosions since 12 May. The webcam showed bursts of ash in the vicinity of the volcano. No ash was detected in satellite data.
2015 May 12	2015 May 16	Thermal Anomaly	Multiple daily MODVOLC thermal alerts were issued.
2015 May 13	- - - -	Fissure	At 0410 a series of small collapses accompanied the opening of three vents, along a fracture oriented E-W, below the E rim of NSEC, one of which effused a small lava flow.
2015 May 13	2015 May 16	Lava flow	At 0410 a series of small collapses accompanied the opening of three vents, one of which effused a small lava flow. A single lava flow traveled NE towards Mt. Rittman, and then E towards Mt. Simone where it formed two branches. One branch approached the base of the N wall of the Valle del Bove while the other traveled W to a distance 5 km from NSEC.
2015 May 13	- - - -	Fissure	At 0800 a fracture at the vent propagated 200 m from the rim down the cone within 10 minutes.
2015 May 13	- - - -	Ash Plume	This event was accompanied by collapses, along with reddish ash ejection onto the summit area and the high S flank.
2015 May 13	2015 May 15	Incandescent ejecta	Strombolian activity increased that night and was characterized by almost continuous Strombolian explosions, sometimes accompanied by ash emissions.
2015 May 13	- - - -	Ash Plume	Based on VONA from INGV and webcam information, at 1817 UTC the Toulouse VAAC reported activity increasing since 1800 UTC. Ash emission was observed in the vicinity of the volcano.
2015 May 13	2015 May 15	Ash Plume	Ash plumes rose a few hundred meters and dispersed with the wind.
2015 May 13	2015 May 15	Ashfall	Minor ashfall was reported in areas from the S to the NE.
2015 May 13	- - - -	VEI (Explosivity Index)	VEI 1
2015 May 14	- - - -	Ash Plume	Based on VONA from INGV and webcam information, at 0942 UTC the Toulouse VAAC reported activity increasing since 0800 UTC. Ash emission was observed in the vicinity of the volcano.
2015 May 14	2015 May 15	Ash Plume	Based on VONA from INGV and webcam information, at 1800 UTC the Toulouse VAAC reported Strombolian activity from 1740 UTC. Sporadic ash clouds were observed in the vicinity. At 0000 on 15 May ash clouds extended 35 km SSE. At 0600 UTC ash clouds and steam were close to the summit. By 0900 UTC the plume was mainly steam and SO₂. At 1200 UTC and 1800 UTC ash was close to the summit.
2015 May 14	2015 May 15	Incandescent ejecta	Based on VONA from INGV and webcam information, at 1800 UTC the Toulouse VAAC reported Strombolian activity from 1740 UTC. Sporadic ash clouds were observed in the vicinity. Continued Strombolian activity was reported at 0000, 0600, 0900, 1200, and 1800 on 15 May.

Episode 10 | Eruption

Northeast crater (NEC)

2015 May 20 - 2016 May 23

Evidence from Observations: Reported

List of 38 Events for Episode 10 at Northeast crater (NEC)

Start Date	End Date	Event Type	Event Remarks
2015 May 20	- - - -	Ash Plume	During the morning there were sporadic brown ash emissions from the NEC.
2015 May 20	- - - -	VEI (Explosivity Index)	VEI 1
2015 Jul 16 (in or before)	2015 Jul 21 (in or after)	Ash Plume	During a field visit on 16 July 2015, INGV scientists witnessed intense pulsating gas emissions and loud noises at NEC; the gas often contained small amounts of reddish fine-grained ash. Increased gas emissions on 18 and 19 July rose a few hundred meters above the summit and occasionally released appreciable amounts of reddish ash that covered the W flank of the crater. Small puffs with minor ash were intermittent for the next several days.
2015 Oct 4	- - - -	Ash Plume	Small but appreciable amounts of reddish ash which quickly dissipated were contained in a gas plume from NEC.
2015 Dec 7	2015 Dec 14	Ash Plume	Ash plumes accompanied by sporadic Strombolian activity were ejected from the NEC beginning on 7 December, and lasting intermittently through 14 December.
2015 Dec 8	- - - -	Ash Plume	Weak Strombolian activity and ash emission were observed at the Northeast Crater.
2015 Dec 8	- - - -	Incandescent ejecta	Weak Strombolian activity and ash emissions were observed at the Northeast Crater.
2015 Dec 9	- - - -	Ash Plume	INGV reported that grayish-brown ash plumes rose from Etna's Northeast Crater and drifted SE.
2015 Dec 9	- - - -	Ash Plume	Based on Webcam, Satellite and Sigmet information, at 0400 UTC and 1000 UTC the Toulouse VAAC reported an eruption still ongoing with ash emissions at 4.6 km altitude. Activity seemed to be decreasing at 1500 UTC. Weak eruptive activity was ongoing at 2100 UTC but no significant ash emission was detected.
2015 Dec 9	2015 Dec 11	Incandescent ejecta	Strombolian activity was detected at NEC, with a few ejected incandescence bombs falling onto the outer flank and abundant ash emissions. Activity gradually diminished over a few days.
2016 Jan 15 (in or after)	2016 Feb 9	Ash Plume	Emissions from NEC often contained trace amounts of ash. Modest amounts of brown ash were observed from the NEC in the morning of 9 February.
2016 Feb 23	- - - -	Explosion	At 0422 an explosion at Northeast Crater (NEC) ejected incandescent tephra several tens of meters above the crater rim, and produced a dark ash plume that drifted NE. A camera recorded lightning flashes in the plume. Weak ash emission rose from the crater during the rest of the morning.
2016 Feb 23	- - - -	Ash Plume	At 0422 an explosion at Northeast Crater (NEC) ejected incandescent tephra several tens of meters above the crater rim, and produced a dark ash plume that drifted NE. A camera recorded lightning flashes in the plume. Weak ash emission rose from the crater during the rest of the morning.
2016 Feb 23	- - - -	Ashfall	Ashfall was reported in Linguaglossa, Gaggi, and Santa Teresa Riva (40 km NE) from this event.
2016 Feb 23	- - - -	Incandescent ejecta	At 0422 an explosion at Northeast Crater (NEC) ejected incandescent tephra several tens of meters above the crater rim, and produced a dark ash plume that drifted NE. A camera recorded lightning flashes in the plume.
2016 Feb 23	- - - -	Lightning	At 0422 an explosion at Northeast Crater (NEC) ejected incandescent tephra several tens of meters above the crater rim, and produced a dark ash plume that drifted NE. A camera recorded lightning flashes in the plume.
2016 Feb 25	- - - -	Ash Plume	A new emission consisted of several pulses of medium-low intensity that produced a very dilute ash plume a few meters above the crater.
2016 Mar 1 (in or after)	2016 Mar 31 (in or before)	Ash Plume	During March 2016, sporadic ash emissions at NEC accompanied persistent degassing, but there were no reports of ashfall other than in the immediate area of the crater.
2016 Mar 31	- - - -	Ash Plume	Based on INGV webcam images, a VONA and a SIGMET, the Toulouse VAAC reported a small eruption at 0730 UTC that produced an E moving ash plume at 4.6 km altitude. The plume was visible on the INGV Webcam only.
2016 Mar 31	2016 Apr 1	Ash Plume	Continuous degassing accompanied dense ash emissions from the North East Crater (NEC) and the New South East Crater (NSEC).
2016 Apr 2	2016 Apr 30 (in or before)	Ash Plume	Ash emissions continued to be weak but persistent for the rest of April from NEC and NSEC.
2016 May 1 (in or after)	2016 May 14	Ash Plume	Although visibility was limited due to weather in early May 2016, discontinuous explosive activity with minor ash emissions was observed over several days from NEC and NSEC near the top of Valle del Bove.
2016 May 16	2016 May 17	Incandescent ejecta	Webcams showed a thermal anomaly at NEC, interpreted by INGV as probable Strombolian activity.
2016 May 17	- - - -	Ash Plume	At first light on 17 May, intense degassing was observed from NEC which lasted throughout the day and included minor ash emissions.
2016 May 17	- - - -	Explosion	Strong explosions from NEC were heard about 10 km from the crater.
2016 May 17	- - - -	Audible Sounds	Strong explosions from NEC were heard about 10 km from the crater.
2016 May 17	2015 May 18	Explosion	Based on INGV VONA, Webcam, and Satellite information, at 2100 UTC the Toulouse VAAC reported that weak eruptive activity started at 2100 UTC. The weak eruption was ongoing at 0300 UTC on 18 May. No significant ash emission was detected.
2016 May 17	2016 May 18	Incandescent ejecta	INGV reported that intense Strombolian activity began at Etna's Northeast Crater (NEC) during the evening. Incandescent bombs were ejected above the crater rim and tephra was deposited on the flanks.
2016 May 18	- - - -	Ash Plume	Based on INGV Webcam, Satellite imagery, and Tremor information, at 0500 UTC the Toulouse VAAC reported a weak eruption still ongoing, and a thin ash cloud visible from the first satellite imagery of the day and again at 0900 UTC. At 1500 UTC an ash plume and SO₂ cloud was visible on satellite imagery at 4.6 km altitude. Only SO₂ was detected at 2100 UTC.
2016 May 18	- - - -	Ash Plume	Around 1250 local time (1050 UTC) Strombolian activity at NEC diminished and dark ash emissions formed briefly.
2016 May 18	- - - -	Incandescent ejecta	At 1100 UTC, a small explosive vent opened at the base of the N side of NEC (Bocca 1) that spattered for a few minutes.
2016 May 18	2016 May 19	Lava flow	Around 1530 UTC, an improvement in weather conditions permitted observation of a new lava flow in the Valle del Bove. The flow, fed by a vent at the base of the E side of NEC (Bocca 2), headed E towards Monte Simone, and stopped at an elevation of approximately 2,400 m.
2016 May 21	- - - -	Incandescence	A thermal camera recorded activity from a vent in the S portion of Northeast Crater (NEC).
2016 May 22	2016 May 23	Explosion	In the evening Strombolian activity resumed at NEC; the rate and intensity of the activity fluctuated through the night. The strongest explosions ejected incandescent bombs up to a few hundred meters above the crater rim and onto the flanks.
2016 May 22	2016 May 23	Incandescent ejecta	In the evening Strombolian activity resumed at NEC; the rate and intensity of the activity fluctuated through the night. The strongest explosions ejected incandescent bombs up to a few hundred meters above the crater rim and onto the flanks.
2016 May 22	2016 May 23	Bombs	In the evening Strombolian activity resumed at NEC; the rate and intensity of the activity fluctuated through the night. The strongest explosions ejected incandescent bombs up to a few hundred meters above the crater rim and onto the flanks.
2016 May 22	- - - -	Thermal Anomaly	Eight MODVOLC thermal alerts were issued.
2017 May 1 (in or after)	2017 May 31 (in or before)	Degassing	At NEC, degassing continued from the large fumarole field at the bottom of the summit crater.

Episode 11 | Eruption

Voragine Crater (VOR)

2015 Aug 20 - 2015 Dec 19

Evidence from Observations: Reported

List of 49 Events for Episode 11 at Voragine Crater (VOR)

Start Date	End Date	Event Type	Event Remarks
2015 Aug 20	- - - -	Ash Plume	Minor ash emissions were noted from VOR.
2015 Aug 24	- - - -	Ash Plume	Frequent gas emissions that included minor ash were observed at VOR.
2015 Sep 18	- - - -	Ash Plume	The Montagnola webcam captured a minor ash emission from VOR.
2015 Oct 12	2015 Oct 18	Ash Plume	Activity was characterized by sporadic, minor ash emissions from VOR; they were brownish-red, and were ejected during pulsating events that lasted for a few tens of seconds, repeating for as long as a few hours.
2015 Oct 19	- - - -	Explosion	Explosive activity was witnessed by a field crew at the bottom of VOR. Lithic fragments and ash was ejected in the immediate area of the crater.
2015 Oct 27	- - - -	Explosion	During an inspection, Strombolian explosions every 5-10 minutes sent incandescent pyroclastic material around the crater and produced minor ash emissions. A few bombs fell along the NW crater rim.
2015 Oct 27	- - - -	Ash Plume	Strombolian explosions every 5-10 minutes sent incandescent pyroclastic material around the crater and produced minor ash emissions.
2015 Oct 27	- - - -	Incandescent ejecta	Strombolian explosions every 5-10 minutes sent incandescent pyroclastic material around the crater.
2015 Oct 27	- - - -	Bombs	A few bombs fell along the NW crater rim.
2015 Oct 31 (in or after)	2015 Nov 2 (in or before)	Ashfall	On the morning of 2 November, after stormy weather conditions had blocked views of the summit for several days, volcanic ash was observed on the camera lens of the Montagnola (EMOV) webcam that was later washed away by rain. During a 4 November field survey, an ash deposit was discovered within layers of snow that fell between 31 October and 2 November on the upper part of the S flank. The source of the ash remains unknown. This event is included in this episode as VOR was the most recently active vent.
2015 Nov 14	- - - -	Explosion	During a field visit, INGV scientists observed intracrater explosive activity continuing at VOR which included several explosions with abundant ash emissions, interspersed with periods of strong spattering.
2015 Nov 14	- - - -	Ash Plume	During a field visit, INGV scientists observed intracrater explosive activity continuing at VOR which included several explosions with abundant ash emissions, interspersed with periods of strong spattering.
2015 Nov 14	- - - -	Incandescent ejecta	During field visit, INGV scientists observed intracrater explosive activity continuing at VOR which included several explosions with abundant ash emissions, interspersed with periods of strong spattering.
2015 Nov 14	- - - -	Bombs	On the E rim of the crater, several fresh, large (40 cm) clasts of volcanic debris had landed as far as 12 m from the edge of the rim.
2015 Nov 15 (in or before)	2015 Nov 21	Ash Plume	By the third week in November 2015, ash emissions from VOR were more frequent and reached high enough levels to be visible from the webcams on the S slope.
2015 Nov 19	- - - -	Lapilli	Lapilli and bombs rising more than 10 m above the northern edge of VOR were observed on a site visit.
2015 Nov 19	- - - -	Bombs	Lapilli and bombs rising more than 10 m above the northern edge of VOR were observed on a site visit.
2015 Nov 20	2015 Nov 21	Seismicity (tremor)	A slow and gradual increase in the magnitude of volcanic tremor was noted, but there was no visible change at the summit.
2015 Dec 2	- - - -	Explosion	INGV reported that after a progressive intensification of activity during the evening of 2 December, an eruption at Etna's Voragine Crater peaked between 0330 and 0410 on 3 December.
2015 Dec 2	- - - -	Ash Plume	Based on VONA from INGV and webcam information, at 2300 UTC the Toulouse VAAC reported Strombolian activity. The webcam showed an ash cloud in the close vicinity.
2015 Dec 2	- - - -	Incandescent ejecta	While on a site visit to VOR, INGV observed continuing Strombolian explosions with material ejected tens of meters above the crater rim.
2015 Dec 2	- - - -	Incandescent ejecta	Based on VONA from INGV and webcam information, at 2300 UTC the Toulouse VAAC reported Strombolian activity. The webcam showed an ash cloud in the close vicinity.
2015 Dec 2 (in or before)	- - - -	Cinder Cone	The cone at the bottom of the crater continued to grow from the previous week.
2015 Dec 2	2015 Dec 3	Thermal Anomaly	Seven MODVOLC thermal alerts were issued.
2015 Dec 3	- - - -	Ash Plume	Based on INGV webcam, VONA, and SIGMET information, at 0300 UTC the Toulouse VAAC reported than an explosive eruption occurred at 0200 UTC that produced an ash plume that rose to 10.7 km altitude and drifted NE. At 0400 UTC the eruption and ash emission were decreasing. At 1000 UTC minor activity was reported in the vicinity. A plume, composed mostly of SO₂ was dissipating, moving NE at 6.1 km altitude.
2015 Dec 3	- - - -	Ashfall	An ash plume rose several kilometers high and drifted NE, ashfall was reported in Linguaglossa (17 km NE), Francavilla di Sicilia (20 km NE), Milazzo, Messina (70 km NE) and Reggio Calabria (70 km NE). Activity had almost ceased by dawn.
2015 Dec 3	- - - -	Incandescent ejecta	After about one hour, activity diminished and returned to less intense Strombolian activity.
2015 Dec 3	- - - -	Lava fountains	During the peak period sustained lava fountains rose over 1 km above the crater with some jets of hot material rising 3 km high.
2015 Dec 3	- - - -	VEI (Explosivity Index)	VEI 3
2015 Dec 4	- - - -	Explosion	The explosive activity at VOR intensified around 0900 UTC, this episode lasted until about 1025 UTC.
2015 Dec 4	- - - -	Ash Plume	Based on Satellite data and VONA information, at 0900 UTC the Toulouse VAAC reported ash emission visible on the webcam moving S at 3.7 km altitude. The ash cloud was discernible on the summit. A plume of water vapor was reported at 13.1 km altitude.
2015 Dec 4	- - - -	Lava fountains	At about 1000 renewed activity at Voragine Crater was characterized by tall lava fountains and an ash plume that rose 7-8 km high.
2015 Dec 4	- - - -	Ash Plume	According to INGV, at about 1000 renewed activity produced lava fountains and an ash plume that rose 7-8 km high. The ash plume had a mushrooming top and produced deposits of coarse-grained pyroclastic material on the upper SW flank above 2 km elevation.
2015 Dec 4	- - - -	Ash Plume	Based on INGV VONA, Webcam, and Message data, at 1000 UTC the Toulouse VAAC reported an ongoing eruption with an ash plume top reaching 9-11 km altitude, according to INGV. Ash clouds were observed moving S at 3.7 km altitude and E at 10.7 km altitude. Ash was clearly observed on the webcam. Satellite data showed mainly ice and water at the top of the volcanic cloud. At 1500 UTC an ash plume observed on the webcam near the summit was dissipating, moving S at 3.7 km altitude.
2015 Dec 4	- - - -	Tephra	The ash plume had a mushrooming top and produced deposits of coarse-grained pyroclastic material on the upper SW flank above 2 km elevation.
2015 Dec 4	- - - -	Ashfall	Ashfall was reported in Giarre-Zafferana Etnea on the E flank.
2015 Dec 4	- - - -	Explosion	Based on INGV VONA, Webcam, and Satellite data, at 2100 UTC the Toulouse VAAC reported that an eruption started at 2045 UTC.
2015 Dec 4	2015 Dec 5	Lava fountains	Two more events occurred at Voragine Crater, between 2130 and 2215 on 4 December and 1555 and 1635 on 5 December, again producing tall lava fountains and many-kilometer-high ash plumes.
2015 Dec 4	2015 Dec 5	Ash Plume	Two more events occurred at Voragine Crater, between 2130 and 2215 on 4 December and 1555 and 1635 on 5 December, again producing tall lava fountains and many-kilometer-high ash plumes. The Toulouse VAAC reported a plume near the summit drifting S at 3.7 km altitude on 4 December, and another plume drifting N on 5 December that was composed of mostly SO₂.
2015 Dec 4	- - - -	VEI (Explosivity Index)	VEI 3
2015 Dec 5	- - - -	Explosion	Based on INGV VONA, Webcam, and Satellite data, at 0300 UTC 0900 UTC the Toulouse VAAC reported Strombolian explosions.
2015 Dec 5	- - - -	Incandescent ejecta	Based on INGV VONA, Webcam, and Satellite data, at 0300 UTC 0900 UTC the Toulouse VAAC reported Strombolian explosions.
2015 Dec 5	- - - -	Ash Plume	Based on INGV VONA, Webcam, and Satellite data, at 0900 UTC the Toulouse VAAC reported feeble ash and steam.
2015 Dec 5	- - - -	Ash Plume	Based on INGV VONA, and Webcam information, at 1445 UTC the Toulouse VAAC reported a significant emission of ash. At 2100 UTC the explosive activity and significant ash emission had stopped. One plume was drifting N, composed mainly of SO₂, and dissipating.
2015 Dec 5	- - - -	Observation	During the evening activity at Voragine Crater progressively diminished.
2015 Dec 5	- - - -	Thermal Anomaly	Six MODVOLC thermal alerts were issued.
2015 Dec 12	- - - -	Observation	INGV scientists observed that the BN and VOR craters were essentially joined into a larger, single crater after the early December explosions, similar to the former Central Crater at Etna. VOR was covered with tens of meters of pyroclastic debris. The debris also covered much of the rest of the summit area, including the lava flows from the previous winter. The parking lot of the visitor area, located 0.5-1 km W and NW of VOR, was marked with numerous impact craters several meters in diameter.
2015 Dec 18	- - - -	Ash Plume	Voragine Crater (VOR) produced two brief ash emissions.
2015 Dec 18	2015 Dec 19	Thermal Anomaly	Two MODVOLC thermal alerts were issued. The location of the anomalies suggest either Voragine or Northeast Crater as the source.

Episode 12 | Eruption

New Southeast Crater (NSEC)

2015 Nov 8 - 2017 Feb 28

Evidence from Observations: Reported

List of 39 Events for Episode 12 at New Southeast Crater (NSEC)

Start Date	End Date	Event Type	Event Remarks
2015 Nov 8	- - - -	Explosion	A single small explosion occurred at the NSEC in the early morning.
2015 Nov 25	- - - -	Incandescent ejecta	Weak Strombolian activity began at NSEC and was observed in the Montagnola webcam.
2015 Nov 25	- - - -	Crater	This led to the formation of a new "pit crater" located a few tens of meters below the E edge of the NSEC, with a diameter of 15-20 m.
2015 Dec 2	- - - -	Ash Plume	An explosion at the NSEC pit crater in the afternoon generated minor ash emissions.
2015 Dec 3	- - - -	Ash Plume	Weak and sporadic ash emissions occurred from the NSEC pit crater.
2015 Dec 4	- - - -	Ash Plume	Frequent ash emissions from the new pit crater that had recently opened on the upper E flank of the New Southeast Crater (NSEC) cone occurred during the large eruption at Voragine Crater (VOR).
2015 Dec 6	- - - -	Incandescent ejecta	Between 0300 and 0400 surveillance cameras recorded the onset of vigorous Strombolian activity from the vent on the E flank of the NSEC cone. Strombolian activity continued through the evening.
2015 Dec 6	2015 Dec 8	Ash Plume	Based on INGV, Webcam and Satellite information, at 1130 UTC the Toulouse VAAC reported ash near the summit. At 1200 UTC they noted that activity was increasing and ash emission was occurring. A significant ash emission occurred at 1300 UTC. Ongoing moderate intensity activity was reported at 1800 UTC with an ash cloud at 3.7 km altitude. At 2300 UTC explosive activity was reported with ash emission in the vicinity of the volcano. Activity was still on going at 0300 UTC and 0900 UTC on 7 December with ash emission in the vicinity. At 1500 UTC an ash cloud was visible on the webcam in the vicinity. Sporadic eruptions were ongoing at 2050 UTC and at 0250 UTC on 8 December. No ash was detected at 0900 UTC.
2015 Dec 6	- - - -	Avalanche	Repeated collapses of both old and new material from the cone's flank generated hot avalanches that traveled a few hundred meters E towards the Valle del Bove.
2015 Dec 6	2015 Dec 7	Lava flow	Around 1700 UTC, INGV personnel observed two lava flows, fed from the NSEC, headed toward Valle del Bove; one headed E for 3.5 km and reached 2,100 m elevation, and the other advanced ENE a few hundred meters to 2,600-2,700 m elevation.
2015 Dec 6	2015 Dec 7	Thermal Anomaly	Tens of MODVOLC thermal alerts were issued each day.
2015 Dec 7	- - - -	Lava flow	Based on INGV VONA 06/1220Z, Webcam and satellite information, at 0300 UTC and 0900 UTC the Toulouse VAAC reported lava observed in the webcam.
2015 Dec 7	2015 Dec 8	Ashfall	Based on INGV VONA, Webcam, and Satellite data, at 2050 UTC and 0250 UTC on 8 December, the Toulouse VAAC reported sporadic eruptions with ashfall in the vicinity.
2015 Dec 7	- - - -	Ash Plume	The easternmost vent at NSEC began emitting dark ash plumes along with Strombolian activity that evening.
2015 Dec 7	- - - -	Incandescent ejecta	The easternmost vent at NSEC began emitting dark ash plumes along with Strombolian activity that evening.
2015 Dec 8	- - - -	Incandescent ejecta	Activity at NSEC lasted for about 48 hours, ending in the morning.
2015 Dec 9	- - - -	Thermal Anomaly	Six MODVOLC thermal alerts were issued.
2015 Dec 13	- - - -	Explosion	Renewed explosions at NSEC produced ash emissions, minor incandescence, and thermal anomalies.
2015 Dec 13	- - - -	Ash Plume	Renewed explosions at NSEC produced ash emissions, minor incandescence, and thermal anomalies.
2015 Dec 28	2016 Jan 8 (in or before)	Ash Plume	Ash emissions began at 1100 from a vent located high on the E flank of the NSEC cone. The emissions ceased in the afternoon; very minor and sporadic explosions continued from the same vent during the following days.
2016 Jan 25	2015 Jan 31	Ash Plume	During the last week of January ash emissions rose from a vent located high on the E flank of the New Southeast Crater (NSEC) cone.
2016 Feb 6	- - - -	Ash Plume	Ash emissions rose from a vent located high on the E flank of the New Southeast Crater (NSEC) cone.
2016 Mar 31	2016 Apr 1	Ash Plume	Continuous degassing accompanied dense ash emissions from the North East Crater (NEC) and the New South East Crater (NSEC).
2016 Apr 1	- - - -	Ash Plume	Based on webcam images and a VONA, the Toulouse VAAC reported a small ongoing eruption that started at 0500 UTC. It produced an ash plume that rose to 4.6 km altitude and drifted NE. The eruption had ended by 0600 UTC.
2016 Apr 2	2016 Apr 30 (in or before)	Ash Plume	Ash emissions continued to be weak but persistent for the rest of April from NEC and NSEC.
2016 May 1 (in or after)	2016 May 14	Ash Plume	Although visibility was limited due to weather in early May 2016, discontinuous explosive activity with minor ash emissions was observed over several days from NEC and NSEC near the top of Valle del Bove.
2016 May 15	2016 May 16	Incandescent ejecta	Explosive activity first observed during the night of 15-16 May 2016 at NSEC came from a pit on the E flank of the cone.
2016 May 17	2016 May 18	Incandescent ejecta	During the night, intermittent flashes, likely from explosive activity, originated from the pit on the E flank of NSEC.
2016 May 18	- - - -	Incandescence	Weak incandescence from the 25 November 2015 vent, on the upper E flank of the New Southeast Crater (NSEC) was visible.
2016 May 22	- - - -	Ash Plume	Sporadic ash emissions from a vent on the upper E flank of New Southeast Crater (NSEC) cone produced a series of ash emissions which rose several hundred meters above the summit and quickly dissipated.
2016 May 22	- - - -	Degassing	Based on a VONA, at 2215 UTC the Toulouse VAAC reported an eruption observed by cameras. Ash was not identifiable in satellite imagery. A small SO₂ cloud was observed to the E.
2016 May 23	- - - -	Ash Plume	Sporadic ash emissions continued from the vent on the upper E flank of the New Southeast Crater cone (NSEC).
2016 Jul 10	2016 Jul 28	Ash Plume	Minor ash emissions resumed at NSEC; they were observed during 10-14, 19-21, and 26-28 July.
2016 Aug 4	2016 Aug 5	Ash Plume	NSEC produced minor ash emissions again.
2016 Aug 27	2016 Aug 29	Ash Plume	Weak and episodic ash emissions also occurred from a vent on the upper E side of NSEC on 27 and 29 August.
2016 Oct 17	2016 Oct 18	Ash Plume	Dense ash emissions were produced from the 25 November 2015 vent on the upper E flank of the NSEC. A diffuse brown ash plume was observed the next day during a field inspection of the area.
2016 Nov 6	- - - -	Ash Plume	Intermittent diffuse brown ash emissions were again observed.
2016 Dec 31	- - - -	Ash Plume	A diffuse ash plume was noted from the vent on the upper E flank of NSEC.
2017 Feb 28	- - - -	Ash Plume	During a field survey INGV-Osservatorio Etneo staff observed sporadic emissions of vapor and brownish ash from several vents within the NSEC.

Episode 13 | Eruption

Voragine Crater (VOR)

2016 May 18 - 2017 Sep 20

Evidence from Observations: Reported

List of 57 Events for Episode 13 at Voragine Crater (VOR)

Start Date	End Date	Event Type	Event Remarks
2016 May 18	- - - -	Deformation (inflation)	An inclinometer about 1 km NW of NEC recorded rapid inflation of the summit area.
2016 May 18	- - - -	Incandescent ejecta	Around 1050 UTC (1250 local time), Strombolian activity began at VOR that rapidly evolved into a lava fountain.
2016 May 18	- - - -	Lava fountains	Around 1050 UTC (1250 local time), Strombolian activity began at VOR that rapidly evolved into a lava fountain. The lava fountain continued until about 1430 UTC.
2016 May 18	- - - -	Lava flow	Shortly after the Strombolian activity began at VOR (around 1100 UTC), lava from the VOR vent overflowed the W rim of BN and headed W towards Monte Nunziata. It traveled for about 2 km and stopped at an elevation of around 2,100 m based on observations from the Bronte thermal webcam.
2016 May 18	- - - -	Explosion	Based on INGV webcam images and satellite imagery the Toulouse VAAC reported at 2100 UTC that Explosions were still occurring at Voragine.
2016 May 18	2016 May 21	Thermal Anomaly	Nine MODVOLC thermal alerts were issued.
2016 May 19	- - - -	Seismicity (tremor)	By the morning, although adverse weather conditions prevented observations, a sudden increase in the amplitude of tremor and loud explosions heard in communities E and S of the volcano suggested another explosive episode at VOR.
2016 May 19	- - - -	Audible Sounds	By the morning, although adverse weather conditions prevented observations, volcanic tremor amplitude sharply increased, and contemporaneously loud and virtually continuous bangs were heard in populated areas to the E and S of the volcano, suggesting another explosive episode at VOR.
2016 May 19	- - - -	Explosion	By the morning, although adverse weather conditions prevented observations, a sudden increase in the amplitude of tremor and loud explosions heard in communities E and S of the volcano suggested another explosive episode at VOR.
2016 May 19	- - - -	Ash Plume	Based on INGV information, at 0600 UTC the Toulouse VAAC reported lava fountaining at the summit crater and ash emission. The thermal webcam showed low altitude activity.
2016 May 19	- - - -	Lava fountains	Based on INGV information, at 0600 UTC the Toulouse VAAC reported lava fountaining at the summit crater and ash emission.
2016 May 19	- - - -	Ash Plume	A dense eruption plume drifted E at an altitude slightly higher than 1 km above the summit of Etna.
2016 May 19	- - - -	Ashfall	Ash and lapilli fell onto the E flank of the volcano, near an area affected by the tephra fall on the previous day. Eruptive activity continued at least through 0900, though the volcanic tremor amplitude had diminished.
2016 May 19	- - - -	Lava flow	A new lava flow emerged from the W rim of BN, and headed W on top of the flow from the previous day. It divided into several arms, the longest of which flowed about 1,800 m, near Monte Nunziata, without reaching the nearby highway.
2016 May 20	- - - -	Incandescent ejecta	INGV reported that at around noon Strombolian activity was visible at Etna's Voragine (VOR) crater and produced explosion noises audible across a large area on the S and E flanks.
2016 May 20	- - - -	Audible Sounds	INGV reported that at around noon Strombolian activity was visible at Etna's Voragine (VOR) crater and produced explosion noises audible across a large area on the S and E flanks.
2016 May 21	- - - -	Ash Plume	Based on INGV information, satellite and webcam images, at 0315 UTC the Toulouse VAAC reported an eruption starting with an ash cloud present at 9.1 km altitude. At 0600 UTC the eruption was ongoing with an ash plume moving SE at 6.1 km altitude and E at 9.1 km altitude. SO₂ was present in satellite imagery. At 0900 UTC the eruption had stopped with only sporadic, small explosions occurring and no ash identifiable.
2016 May 21	- - - -	Seismicity (tremor)	Just after 0400 volcanic tremor amplitude rapidly increased and the Strombolian explosions turned into pulsating jets of lava, launching incandescent bombs 1 km S; an ash plume drifted SSE. Tremor amplitude decreased suddenly around 0600.
2016 May 21	- - - -	Incandescent ejecta	Just after 0400 volcanic tremor amplitude rapidly increased and the Strombolian explosions turned into pulsating jets of lava, launching incandescent bombs 1 km S; an ash plume drifted SSE.
2016 May 21	- - - -	Lava fountains	Just after 0400 volcanic tremor amplitude rapidly increased and the Strombolian explosions turned into pulsating jets of lava, launching incandescent bombs 1 km S; an ash plume drifted SSE.
2016 May 21	- - - -	Bombs	Just after 0400 volcanic tremor amplitude rapidly increased and the Strombolian explosions turned into pulsating jets of lava, launching incandescent bombs 1 km S; an ash plume drifted SSE.
2016 May 21	- - - -	Lava flow	Around 0400 a small lava flow was observed from the base of a fracture on the SE flank of the cone of VOR near the base of SEC. It traveled towards the Valle del Leone. Activity decreased around 0500 and was over at about 0600.
2016 May 21	- - - -	Lava flow	Lava was observed overflowing the W rim of BN around 0700, covering the flows of the previous days.
2016 May 21	2016 May 22	Incandescent ejecta	Strombolian activity was again observed from VOR during the night.
2016 May 21	- - - -	VEI (Explosivity Index)	VEI 3
2016 May 23	2016 May 26	Incandescent ejecta	A new round of weak Strombolian activity began at VOR around 1900 on 23 May 2016. Activity continued until 1750 on 24 May when explosive activity increased sharply. Vigorous Strombolian activity peaked during the night of 24-25 May. Incandescent material rose a few hundred meters into the air, and mostly fell back into the crater. It was not accompanied by a lava flow or ash plume. Activity began decreasing during the afternoon of 25 May, and ceased sometime during the following night.
2016 May 24	2016 May 25	Explosion	Based on VONA and INGV Webcam information, at 2000 UTC the Toulouse VAAC reported an eruption observed by cameras. No significant ash emission was detected. Explosive activity was increasing at 2300 UTC. Sporadic Strombolian explosions were still occurring at 0400 UTC on 25 May.
2016 May 24	2016 May 25	Ash Plume	Based on INGV VONA, Tremor, and Webcam information, at 2300 UTC the Toulouse VAAC reported explosive activity increasing and a significant ash emission ongoing. By 0400 UTC on 25 May, the ash emission was finished.
2016 May 24	2016 May 25	Thermal Anomaly	Twelve MODVOLC thermal alerts were issued.
2016 May 27 (in or before)	- - - -	Collapse	Major subsidence at VOR after the end of the Strombolian activity of 23-26 May 2016 created numerous sub-circular concentric fractures within the crater with a vent degassing at the base.
2016 May 31	- - - -	Ash Plume	A weak ash emission rose from VOR in the morning.
2016 Jun 3	- - - -	Collapse	INGV volcanologists making ground observations on 3 June noted about 10 m of subsidence of the lava surface filling BN and continued collapse at the center of VOR.
2016 Aug 7	2016 Aug 22	Explosion	Low intensity explosive activity began at VOR on 7 August, but no material was ejected beyond the crater rim. An incandescent vent was observed within the collapsed inner wall of VOR on 10 August. Explosive activity and incandescence was intermittent from this vent during 7-22 August.
2016 Aug 7	2016 Aug 22	Incandescent ejecta	Low intensity explosive activity began at VOR on 7 August, but no material was ejected beyond the crater rim. An incandescent vent was observed within the collapsed inner wall of VOR on 10 August. Explosive activity and incandescence was intermittent from this vent during 7-22 August.
2016 Aug 7	- - - -	Thermal Anomaly	A MODVOLC thermal alert was issued.
2016 Aug 10	2016 Aug 12	Thermal Anomaly	Two MODVOLC thermal alerts were issued.
2016 Aug 15	- - - -	Thermal Anomaly	A MODVOLC thermal alert was issued.
2016 Aug 22 (in or after)	2016 Sep 30 (in or before)	Incandescence	Incandescent degassing continued at the 7 August VOR vent throughout September, along with persistent fumarolic emissions from the fracture zones.
2016 Nov 1 (in or after)	2016 Nov 30 (in or before)	Fumarolic or Solfataric	Persistent fumarolic activity from the vent at VOR continued during November.
2016 Nov 28	2016 Nov 29	Incandescence	Intermittent, low-intensity incandescence at the VOR vent appeared during the night.
2016 Dec 15	- - - -	Incandescence	Incandescence in the evening from the VOR vent was recorded on the webcams.
2017 Jan 1 (in or after)	2017 Jan 31 (in or before)	Incandescence	Sporadic incandescence continued from the 7 August 2016 vent on the E side of VOR during January 2017.
2017 Jan 12	- - - -	Thermal Anomaly	A MODVOLC thermal alert was issued. Location uncertain, 7 Aug 2016 vent on E side of VOR is most likely candidate.
2017 Mar 1 (in or after)	2017 Mar 31 (in or before)	Incandescent ejecta	Intense degassing continued from VOR during March, with incandescent bursts visible on many clear nights.
2017 Mar 1 (in or after)	2017 Mar 31 (in or before)	Degassing	Intense degassing continued from VOR during March, with incandescent bursts visible on many clear nights.
2017 Apr 1 (in or after)	2017 May 31 (in or before)	Incandescence	Intense degassing with incandescence at night continued from the vent at VOR throughout April and into May 2017.
2017 Apr 1 (in or after)	2017 May 31 (in or before)	Degassing	Intense degassing with incandescence at night continued from the vent at VOR throughout April and into May 2017.
2017 May 6	- - - -	Thermal Anomaly	Two MODVOLC thermal alerts were issued. The location source is uncertain, although the 7 Aug 2016 vent on E side of VOR is a likely possibility.
2017 May 9	- - - -	Thermal Anomaly	A MODVOLC thermal alert was issued. The location source is uncertain, although the 7 Aug 2016 vent on E side of VOR is a likely possibility.
2017 May 20	- - - -	Thermal Anomaly	A MODVOLC thermal alert was issued. The location source is uncertain, although the 7 Aug 2016 vent on E side of VOR is a likely possibility.
2017 Jun 1 (in or after)	2017 Jun 30 (in or before)	Incandescence	Vigorous degassing and nighttime incandescence continued at the VOR vent during June.
2017 Jun 1 (in or after)	2017 Jun 30 (in or before)	Degassing	Vigorous degassing and nighttime incandescence continued at the VOR vent during June.
2017 Jun 23	- - - -	Thermal Anomaly	High temperatures (around 600°C) were recorded at the VOR vent.
2017 Jul 1 (in or after)	2017 Jul 31 (in or after)	Incandescence	Incandescence was frequently observed at night from the VOR vent and from the NSEC.
2017 Aug 24	- - - -	Degassing	Active degassing at the beginning occurred from the vent at the E rim of the Voragine crater (VOR), and from the NW vent of Bocca Nuova (BN-1).
2017 Sep 19	- - - -	Incandescence	Nighttime incandescence was reported.
2017 Sep 20	- - - -	Ash Plume	Small sporadic ash emissions were noted from NSEC and VOR.

Episode 14 | Eruption

Bocca Nuova (BN)

2016 Oct 8 - 2017 Oct 31 (in or after)

Evidence from Observations: Satellite (infrared)

List of 19 Events for Episode 14 at Bocca Nuova (BN)

Start Date	End Date	Event Type	Event Remarks
2016 Oct 8	2016 Oct 10	Thermal Anomaly	Two MODVOLC thermal alerts were issued.
2016 Oct 10	- - - -	Seismicity (volcanic)	A series of low-frequency seismic events were recorded at the summit, some accompanied by explosive sounds.
2016 Oct 10	- - - -	Ash Plume	The strongest seismic event produced ash and hot gas that was recorded by two thermal cameras during the early afternoon. The ash rose from the W part of BN about 100 m above the rim and drifted rapidly E.
2016 Oct 10	- - - -	Thermal Anomaly	The strongest seismic event produced ash and hot gas that was recorded by two thermal cameras during the early afternoon.
2016 Oct 10	- - - -	VEI (Explosivity Index)	VEI 1
2016 Oct 12 (in or before)	- - - -	Collapse	During an inspection on 12 October, INGV scientists noted that subsidence of about 50 m had occurred within the BN, centered near the W crater wall, and was ongoing. They observed the sudden dropping of material along concentric fractures accompanied by reddish ash and modest steam emissions.
2016 Oct 12	- - - -	Incandescence	One of the collapse events exposed an incandescent area within the fresh lava.
2016 Nov 1 (in or after)	2016 Nov 30 (in or before)	Collapse	Bottom subsidence at BN continued during November where two distinct areas of subsidence (BN-1 and BN-2) were visible.
2017 Feb 1	- - - -	Ash Plume	In the BN-1 area active degassing with minor amounts of ash was observed.
2017 Feb 1 (in or after)	2017 Feb 28 (in or before)	Collapse	Steady subsidence continued at BN, especially in the BN-1 area where active degassing with minor amounts of ash was observed on 1 February.
2017 Feb 3	- - - -	Ash Plume	Based on air reports, webcam and satellite images, at 0900 UTC the Toulouse VAAC reported a weak emission of vapor or ash close to the summit.
2017 May 31	- - - -	Ash Plume	A short sequence of dense ash emissions from BN-1 in the morning was the only ash plume at Etna reported during May.
2017 Jul 10	- - - -	Ash Plume	A small amount of ash emerged from the base of BN-1.
2017 Aug 1 (in or after)	2017 Aug 31 (in or before)	Ash Plume	Occasional weak, diffuse ash emissions continued during August 2017 from the bottom of BN-1. INGV-OE scientists attributed this to collapse at the base of the crater.
2017 Aug 24	- - - -	Degassing	Active degassing at the beginning occurred from the vent at the E rim of the Voragine crater (VOR), and from the NW vent of Bocca Nuova (BN-1).
2017 Sep 19	- - - -	Explosion	Minor explosive activity was reported on from BN and NSEC.
2017 Oct 25 (in or after)	2017 Oct 31 (in or before)	Ash Plume	Minor emissions of brown ash were reported from BN-1 during the last week of October.
2017 Nov 14	2017 Nov 21	Degassing	During the third week of November, intense degassing was observed from BN-1.
2018 Jan 15 (in or after)	2018 Jan 31 (in or before)	Incandescence	INGV reported nighttime incandescence, especially strong from BN-1.

Episode 15 | Eruption

Saddle Cone, Cono della Sella (SEC3, CdS)

2016 Dec 15 - 2018 Jan 5

Evidence from Observations: Reported

List of 80 Events for Episode 15 at Saddle Cone, Cono della Sella (SEC3, CdS)

Start Date	End Date	Event Type	Event Remarks
2016 Dec 15	- - - -	Ash Plume	Sporadic, minor brownish ash emissions occurred from the saddle area between SEC and NSEC.
2016 Dec 15 (in or after)	2017 Jan 20 (in or before)	Ash Plume	During the following five weeks weak ash emissions from the vent were observed, without being accompanied by incandescence.
2016 Dec 15	- - - -	Incandescent ejecta	That evening some of the emissions were more energetic, ejecting incandescent material out of the crater which landed on the steep S flank of the SEC cone.
2016 Dec 16	- - - -	Ashfall	A light coating of ash and a few lithic blocks appeared in the morning in the fresh snow on the flank of the SEC.
2016 Dec 16	- - - -	Blocks	A light coating of ash and a few lithic blocks appeared in the morning in the fresh snow on the flank of the SEC.
2017 Jan 20	- - - -	Ash Plume	During the early morning, the saddle vent was again active, with small black ash puffs and thermal anomalies identified by the surveillance camera.
2017 Jan 20	- - - -	Incandescent ejecta	People on the SEC observed ejected incandescent material along with ash and blocks.
2017 Jan 20	- - - -	Blocks	People on the SEC observed ejected incandescent material along with ash and blocks.
2017 Jan 20	- - - -	Thermal Anomaly	During the early morning the saddle vent was again active, with small black ash puffs and thermal anomalies identified by the surveillance camera.
2017 Jan 23	2017 Jan 25	Explosion	The frequency of explosions and ash emissions increased on 24 January but then slightly decreased the next morning.
2017 Jan 23	2017 Feb 1 (in or after)	Ash Plume	During the evening mild Strombolian activity was observed, accompanied by frequent emissions of small, black ash puffs. Small bombs were ejected onto the flank of NSEC and minor ash plumes quickly dissipated in the high winds near the summit.
2017 Jan 23	2017 Feb 1 (in or after)	Incandescent ejecta	During the evening mild Strombolian activity was observed, accompanied by frequent emissions of small, black ash puffs. The activity gradually intensified through the night, with some explosions launching incandescent material as far as the base of the SEC cone. The frequency of explosions and ash emissions increased on 24 January but then slightly decreased the next morning. Modest Strombolian activity continued into February.
2017 Jan 23	2017 Feb 1 (in or after)	Bombs	Small bombs were ejected onto the flank of NSEC and minor ash plumes quickly dissipated in the high winds near the summit.
2017 Jan 24	- - - -	Thermal Anomaly	A MODVOLC thermal alert was issued. The location of the thermal alert is off the NE flank of NEC, and not close to the Saddle Cone, so its uncertain if it belongs in this episode or goes with an unrecorded event.
2017 Jan 28	2017 Feb 1	Thermal Anomaly	Four MODVOLC thermal alerts were issued from a large area around the summit.
2017 Feb 4	- - - -	Thermal Anomaly	Four MODVOLC thermal alerts were issued.
2017 Feb 11	- - - -	Thermal Anomaly	A MODVOLC thermal alert was issued.
2017 Feb 15	2017 Feb 23	Thermal Anomaly	Ten MODVOLC thermal alerts were issued.
2017 Feb 27	2017 Feb 28	Incandescent ejecta	Based on VONA, INGV, and Webcam information, at 1900 UTC the Toulouse VAAC reported Strombolian explosions since 1745 UTC. At 2000 UTC small Strombolian explosions were ongoing. At 0000 UTC and 0600 UTC on 28 February small Strombolian explosions were ongoing. At 0600 UTC feeble seismic activity was ongoing.
2017 Feb 27	2017 Mar 1	Incandescent ejecta	INGV reported that Strombolian activity at Etna’s New Southeast Crater (NSEC) cone had gradually intensified beginning at 1700. During 27-28 February frequent Strombolian explosions ejected incandescent lava fragments up to 200 m above the vent. By late evening on 1 March, activity declined.
2017 Feb 27	2017 Mar 1	Cinder Cone	A new cone of pyroclastic material that formed around the saddle vent quickly grew to about the same elevation as the NSEC and SEC crater rims, approximately 3,290 m.
2017 Feb 27	2017 Mar 2	Lava flow	Lava overflowed the vent, quickly traveled down the S flank, and then slowed after reaching the gently sloping terrain. The flow spread SSW, towards the old cone of Monte Frumento Supino. The lava flow slowly advanced on top of the snow, and by 1 March was about 1.5 km from the vent. The lava continued to flow until 2 March 2017, when it stopped at about 2,750 m elevation with an overall length of 2,180 m, covering an area of 306 x 103 m², for a total volume of slightly less than 1 x 10⁶ m³.
2017 Feb 27	2017 Feb 28	Ash Plume	Ash from the Strombolian activity dispersed NE below 5.5 km altitude, with minor ashfall reported in Linguaglossa and Zafferana.
2017 Feb 27	2017 Feb 28	Ashfall	Ash from the Strombolian activity dispersed NE below 5.5 km altitude, with minor ashfall reported in Linguaglossa and Zafferana.
2017 Feb 27	2017 Mar 6	Thermal Anomaly	Multiple near-daily MODVOLC thermal alerts were issued.
2017 Mar 1 (in or after)	2017 Mar 15 (in or before)	Ash Plume	Sporadic ash emissions continued from the new saddle vent during early March 2017.
2017 Mar 12	2017 Mar 13	Incandescent ejecta	Weak Strombolian activity was reported during the night.
2017 Mar 13	2017 Mar 27	Thermal Anomaly	Multiple near-daily MODVOLC thermal alerts were issued.
2017 Mar 15	- - - -	Lava flow	INGV reported that during the morning of 15 March lava began to flow down the S flank of Etna's Southeast Crater (SEC) - New Southeast Crater (NSEC) cone complex. The lava flow reached the base of the cone and traveled S. By late afternoon the lava was advancing on top of lava flows from the previous eruption.
2017 Mar 15	- - - -	Incandescent ejecta	Activity rapidly intensified at 0800, and by 1000 near-constant Strombolian explosions were generating ash plumes. The intensity of the Strombolian activity reached a peak around 1840-1845, and by the evening both the eruptive activity and seismicity gradually diminished.
2017 Mar 15	2017 Mar 16	Ash Plume	Activity rapidly intensified at 0800, and by 1000 near-constant Strombolian explosions were generating ash plumes. Based on satellite, INGV, and webcam information, at 2345 UTC the Toulouse VAAC reported diffuse ash emissions drifting W near the volcano at 4.6 km altitude. At 0600 on 16 March small ash emission close to the volcano was reported. At 1200 UTC a thin ash cloud was identifiable from satellite data over the sea with ash concentration decreasing. They noted increasing ash emissions the following day drifting SW at 4.6 km altitude, that ceased and dissipated on 17 March.
2017 Mar 16	2017 Mar 17	Lava flow	Shortly before 2300 UTC on 15 March (0100 on 16 March local time), a second new flow emerged from a vent near the base of the S flank of the new NSEC/SEC cone (at about 3,200 m elevation) and traveled SE (figure 190), splitting into two lobes. INGV personnel in the summit area reported a series of phreato-magmatic explosions at 0043 (just after midnight) along the lava front at an elevation of approximately 2,700 m along the W edge of the Valle del Bove. The contact of the active flow with the underlying snow caused several explosions. An INGV volcanologist suffered minor injuries during one of the explosions. By the afternoon of 17 March 2017, the second flow had reached an elevation of about 2,600 m, near the base of the W slope of the Valle del Bove.
2017 Mar 16	- - - -	Explosion	At 1243 a phreato-magmatic explosion occurred at the front of a lava flow where it contacted an area covered with snow.
2017 Mar 16	- - - -	Phreatomagmatic	At 1243 a phreato-magmatic explosion occurred at the front of a lava flow where it contacted an area covered with snow.
2017 Mar 16	2017 Mar 17	Ash Plume	Based on Webcam, INGV and satellite information, at 1430 UTC the Toulouse VAAC reported explosive activity increasing with ash emission. At 1545 UTC and 1730 UTC the eruption was ongoing with an ash plume moving SW at 4.6 km altitude. A small ash plume was observed at 2330 UTC in satellite data at 3.9 km altitude. The eruption was weakening at 0530 UTC on 17 March with ash at 3.7 km altitude. Activity was decreasing at 0900 UTC with feeble ash SW of the summit. No ash was identifiable by 1500 UTC.
2017 Mar 16	- - - -	Ashfall	Increased emissions caused minor ashfall in Adrano and Santa Maria di Licodia (both about 17 km SW).
2017 Mar 17	2017 Mar 18	Ash Plume	Based on webcam, INGV, satellite, and air reports, at 1720 UTC the Toulouse VAAC reported increasing activity. At 2300 UTC ash emissions formed a gray cloud of ash and vapor growing above the summit at 4.9 km altitude. The eruption was ongoing at 0500 UTC on 18 March. At 1100 UTC sporadic but significant ash emission was weakening with a plume at 4.6 km altitude. At 1700 UTC the eruption was ongoing with low activity. A thin steam plume extended SE. Only feeble seismic activity was recordedat 2300 UTC.
2017 Mar 17	- - - -	VEI (Explosivity Index)	VEI 2
2017 Mar 18	2017 Mar 20	Lava flow	INGV personnel at Monte Zoccolaro (1.5 km S) spotted a third flow on 18 March, located S of the other two. The front had reached about 2,200 m elevation, and was responsible for some phreato-magmatic explosions during 18 and 19 March. Several avalanches of incandescent material reached the base of the slope at the edge of Valle del Bove as the flow fronts collapsed during 18 March. Two Landsat 8 Operational Land Imager images on 18 and 19 March captured evidence of the lava flows, an ash plume, and Strombolian activity during this episode. By 19 March, the advance had slowed as the flows began to spread out over the valley floor. The flows into the Valle del Bove ceased on 20 March.
2017 Mar 21	- - - -	Ash Plume	Based on AIREP and satellite information, at 0800 UTC the Toulouse VAAC noted an AIREP of a minor ash cloud extending 35 km WNW at 4.6 km altitude.
2017 Mar 21	2017 Apr 9	Lava flow	Once the Strombolian activity had ended, yet another lava flow emerged from the base of the cone at an elevation of about 3,010-3,030 m, and spread into several segments, one of which flowed W around Monti Barbagallo (near the former Torre del Filosofo) and then turned SW following the valley between Monti Barbagallo and Monte Frumento Supino. By 26 March the front of this flow segment had reached an elevation of 2,300 m and travelled about 2.5 km from the vent. A second segment of the flow travelled E of Monti Barbagallo, following the earlier flows that had been active along the W slope of the Valle del Bove; it slowed and broke into several additional segments, reaching 1.3 km from the vent on 26 March, and advancing through the first week of April. The active lava flow continued WSW towards the cones of the 2002-2003 eruption from the vent at the base of the NSEC/SEC cone until it stopped advancing sometime during the night between 8 and 9 April.
2017 Mar 22 (in or before)	- - - -	Cinder Cone	Strombolian activity and ash emissions ceased at the summit vent of the NSEC/SEC cone between 20 and 22 March 2017 leaving a new pyroclastic cone that rose above the adjacent NSEC and SEC cones.
2017 Mar 28	- - - -	Incandescence	Strong glow form the pit crater was observed at night.
2017 Mar 28	- - - -	Crater	Around 28 March a new pit crater had formed on the S part of the pyroclastic cone which had formed around the SEC-NSEC saddle vent.
2017 Mar 29	- - - -	Ash Plume	Based on AIREP, Satellite and INGV information, at 0800 UTC the Toulouse VAAC noted a volcanic cloud of feeble intensity reported between 3.0 and 4.3 km altitude.
2017 Mar 30	2017 Apr 1	Thermal Anomaly	Multiple near-daily MODVOLC thermal alerts were issued.
2017 Apr 4	2017 May 2	Thermal Anomaly	Multiple near-daily MODVOLC thermal alerts were issued.
2017 Apr 10	2017 Apr 12	Lava flow	Another new flow then emerged from the same vent and was active for just over 24 hours. This flow travelled SE to the W edge of the Valle del Bove and moved a few hundred meters along the edge before stopping during the day of 12 April.
2017 Apr 13	2017 Apr 14	Incandescent ejecta	During the evening, Strombolian activity at the summit crater of the NSEC/SEC cone accompanied the emergence of flows from three vents along the S flank at elevations of approximately 3,200 m, 3,150 m, and 3,010 m which headed S and SE.
2017 Apr 13	2017 Apr 16	Lava flow	During the evening, Strombolian activity at the summit crater of the NSEC/SEC cone accompanied the emergence of flows from three vents along the S flank at elevations of approximately 3,200 m, 3,150 m, and 3,010 m which headed S and SE. The upper flows were active for only a few hours, but the lower flow continued SE towards the Valle del Bove and had overlapped the 10-11 April flow by the next day. The active front of the flow was at an elevation of 2,400 m on the western slope of the Valle del Bove, just north of the Serra Giannicola Grande. A flyover on 14 April revealed the extent of the fracture system on the flank of the NSEC/SEC complex from which the numerous flows emerged. The flow rate diminished during the day of 15 April, and the flow stopped sometime during the next night.
2017 Apr 14	- - - -	Fissure	A flyover revealed the extent of the fracture system on the flank of the NSEC/SEC complex from which the numerous flows emerged.
2017 Apr 19	- - - -	Thermal Anomaly	A thermal anomaly appeared at the S edge of the NSEC/SEC summit vent, which INGV began calling SEC3, in the morning.
2017 Apr 19	2017 Apr 20	Incandescent ejecta	Weak Strombolian activity from the vent was followed by the emergence of a lava flow from the S side of the crater rim that flowed down the S flank of the cone. Explosive activity ceased at SEC3 the afternoon of 20 April.
2017 Apr 19	- - - -	Lava flow	Weak Strombolian activity from the vent was followed by the emergence of a lava flow from the S side of the crater rim that flowed down the S flank of the cone.
2017 Apr 19	- - - -	Ash Plume	Dense, brown ash emissions about an hour later accompanied the re-opening of three vents on the S flank from which new lava flows emerged.
2017 Apr 19	2017 Apr 21	Lava flow	Dense, brown ash emissions about an hour later accompanied the re-opening of three vents on the S flank from which new lava flows emerged. They formed into two branches moving down the S flank, then turned E and spread over the W slope of the Valle del Bove; by 20 April they had reached an elevation of 1,950 m. Explosive activity ceased at SEC3 that afternoon, and the flows stopped advancing sometime during the night of 20-21 April.
2017 Apr 19	- - - -	Lava fountains	Lava jets rose tens of meters above the crater rim for about an hour in the afternoon.
2017 Apr 22	- - - -	Fissure	Observations of the summit of SEC3 revealed a N-S trending graben formed in the S rim of the summit crater about 100 m long, 10 m wide, and several tens of meters deep.
2017 Apr 26	2017 Apr 28	Lava flow	A slow-moving lava flow emerged from the summit vent of SEC3. The flow made it part way down the S flank before another flow from the same vent covered it and reached the base of the flank. Strombolian activity began at the summit vent during the late evening while the flow continued to spread SE toward the Valle del Bove. The flows on both the N and S flanks had ceased by the morning of 28 April.
2017 Apr 26	2017 Apr 27	Incandescent ejecta	Strombolian activity began at the summit vent during the late evening while the flow continued to spread SE toward the Valle del Bove. Strombolian activity intensified during the early hours of 27 April and a new vent opened at the summit immediately N of the first one.
2017 Apr 27	- - - -	Fissure	At around 0220, two new eruptive fractures opened on the N flank of SEC3, from which lava flowed N toward the Valle del Leone.
2017 Apr 27	2017 Apr 28	Lava flow	At around 0220, two new eruptive fractures opened on the N flank of SEC3, from which lava flowed N toward the Valle del Leone. The flows on both the N and S flanks had ceased by the following morning.
2017 Apr 27	- - - -	Ash Plume	At daybreak, an ash plume was visible about 1.5 km above the summit drifting E. Based on VONA, webcam and INGV information, the Toulouse VAAC reported strong Strombolian activity and a dark cloud growing above the summit at 4.9 km altitude. The eruption was ongoing at 0900 UTC. Ash was not detectable due to cloud cover at 1200 UTC. The explosive eruption had stopped by 1800 UTC.
2017 Apr 27	- - - -	Phreatomagmatic	Phreato-magmatic explosions were observed in the Valle del Leone when the northern lava flow encountered snow on the ground.
2017 Apr 27	- - - -	Explosion	Phreato-magmatic explosions were observed in the Valle del Leone when the northern lava flow encountered snow on the ground.
2017 May 1 (in or after)	2017 May 31 (in or before)	Seismicity (tremor)	Several short, high-energy tremor episodes occurred in the area around SEC3. During May, more than 35 episodes of transient increases in tremor amplitude were recorded by INGV seismic instruments.
2017 May 13	- - - -	Thermal Anomaly	A MODVOLC thermal alert was issued. The summit location is uncertain but the Saddle Cone summit is a likely possibility given reports of Strombolian activity a few days later.
2017 May 15	2017 May 18	Incandescent ejecta	There were 11 episodes of Strombolian activity from the northern SEC3 summit vent, repeated at regular intervals of about every 8-9 hours. Lava fragments were ejected outside the crater rim and rolled down the flanks. Each episode was accompanied by a sharp increase in volcanic tremor amplitude.
2017 May 25 (in or after)	2017 May 28 (in or before)	Incandescent ejecta	Eight additional episodes of weak and discontinuous Strombolian activity occurred between 25 and 28 May at intervals ranging from 3 to 14 hours, each lasting about an hour, and accompanied by increased tremor amplitude.
2017 Jun 24	2017 Jun 28	Ash Plume	Occasional weak ash emissions began from SEC3; they lasted for a few days and quickly dissipated near the top of the cone. They ceased late in the evening of 28 June.
2017 Jul 9	- - - -	Ash Plume	During the late morning, the vent that had formed during 26-27 April emitted a small amount of red-gray ash.
2017 Sep 19	2017 Sep 30	Incandescence	Incandescence at night was observed.
2017 Oct 7 (in or after)	2017 Oct 14 (in or before)	Ash Plume	Occasional ash emissions were observed during the second week of October 2017 from the Cono della Sella (CdS).
2017 Oct 16	- - - -	Ash Plume	A minor ash emission was reported.
2017 Oct 26	- - - -	Explosion	In the late afternoon, a single explosion occurred at one of the three mouths of the Cono della Sella crater. The explosion generated a short jet of incandescent material and a small ash plume that quickly dispersed.
2017 Oct 26	- - - -	Ash Plume	In the late afternoon, a single explosion occurred at one of the three mouths of the Cono della Sella crater. The explosion generated a short jet of incandescent material and a small ash plume that quickly dispersed.
2017 Oct 26	- - - -	Incandescent ejecta	In the late afternoon, a single explosion occurred at one of the three mouths of the Cono della Sella crater. The explosion generated a short jet of incandescent material and a small ash plume that quickly dispersed.
2017 Nov 24	2017 Nov 26	Ash Plume	Frequent small ash emissions were reported from CdS.
2017 Dec 14	2017 Dec 15	Ash Plume	A few ash emissions were recorded from CdS, overnight.
2018 Jan 5	- - - -	Ash Plume	Based in INGV information, a small ash emission was observed from CdS.

Episode 16 | Eruption

New Southeast Crater (NSEC)

2017 Jun 6 - 2022 Jun 17

Evidence from Observations: Reported

List of 72 Events for Episode 16 at New Southeast Crater (NSEC)

Start Date	End Date	Event Type	Event Remarks
2017 Jun 6	2017 Jun 9	Seismicity (tremor)	According to INGV, weak and discontinuous Strombolian activity resumed at NSEC, along with a sudden increase in tremor. The activity lasted until 9 June and included four episodes of roughly one hour each.
2017 Jun 6	2017 Jun 9	Incandescent ejecta	According to INGV, weak and discontinuous Strombolian activity resumed at NSEC, along with a sudden increase in tremor. The activity lasted until 9 June and included four episodes of roughly one hour each. Very little material fell outside the crater rim during these events.
2017 Jul 1 (in or after)	2017 Jul 31 (in or before)	Incandescence	According to INGV, incandescence was frequently observed at night from the VOR vent and from the NSEC.
2017 Sep 19	- - - -	Explosion	Minor explosive activity was reported from BN and NSEC.
2017 Sep 20	- - - -	Ash Plume	Small sporadic ash emissions were noted from NSEC and VOR.
2017 Dec 1 (in or after)	2017 Dec 31 (in or before)	Incandescence	Intermittent incandescence was observed from fumaroles at NSEC during December.
2018 Jan 1 (in or after)	2018 Jan 7 (in or before)	Incandescence	According to INGV, incandescence degassing continued from the NSEC vents.
2018 Jan 6	- - - -	Ash Plume	According to INGV, a puff of brown ash emerged from NSEC.
2018 Jan 8 (in or after)	2018 Jan 14 (in or before)	Explosion	According to INGV, during the second week of the month, 20 small explosive events were observed from the eastern vent at NSEC, although cloud cover obscured the summit for much of the time.
2018 Jan 15 (in or after)	2018 Jan 31 (in or before)	Ash Plume	According to INGV, minor ash emissions continued from NSEC for the rest of the month.
2018 Jan 15 (in or after)	2018 Jan 31 (in or before)	Incandescence	According to INGV, nighttime incandescence, was observed from NSEC.
2018 Jan 22	- - - -	Ashfall	According to INGV, a modest ashfall affected the communities S of Etna including the city of Catania (27 km S); the lack of visibility prevented identification of which crater produced the ash; NSEC had weak and sporadic emissions during this time.
2018 Feb 1 (in or after)	2018 Feb 7 (in or before)	Ash Plume	According to INGV, two weak ash emissions occurred at NSEC during the first week of February 2018.
2018 Feb 15	2018 Feb 16	Explosion	According to INGV, the frequency of explosions increased to 1-2 events per hour, producing moderate amounts of brown-gray ash and incandescent pyroclastic material.
2018 Feb 15	2018 Feb 16	Ash Plume	According to INGV, the frequency of explosions increased to 1-2 events per hour, producing moderate amounts of brown-gray ash and incandescent pyroclastic material.
2018 Feb 15	2018 Feb 16	Incandescent ejecta	According to INGV, the frequency of explosions increased to 1-2 events per hour, producing moderate amounts of brown-gray ash and incandescent pyroclastic material.
2018 Feb 15	2018 Feb 16	Audible Sounds	According to INGV, the explosions were heard 20 km E and S from the summit.
2018 Mar 1 (in or after)	2018 Mar 31 (in or before)	Ash Plume	According to INGV, occasional ejection of incandescent pyroclastic material and modest ash emissions continued throughout the month. The ash emissions occurred at irregular intervals, varying from a few tens of minutes to a few hours, more frequently in the last days of the month.
2018 Mar 1 (in or after)	2018 Mar 31 (in or before)	Incandescent ejecta	According to INGV, occasional ejection of incandescent pyroclastic material and modest ash emissions continued throughout the month. The ash emissions occurred at irregular intervals, varying from a few tens of minutes to a few hours, more frequently in the last days of the month.
2018 Mar 2	- - - -	Ash Plume	According to INGV, activity at the E vent of NSEC included a minor ash emission.
2018 Apr 1 (in or after)	2018 Apr 7 (in or before)	Ash Plume	Activity through April was characterized by degassing at the summit craters with modest ash emissions from the New Southeast Crater in the first week.
2018 Apr 25 (in or after)	2018 Apr 30 (in or before)	Ash Plume	Activity through April was characterized by degassing at the summit craters and occasional small ash emissions at the end of the month.
2018 Aug 1	- - - -	Explosion	According to INGV, after several months of quiet conditions, explosive activity resumed at the E crater on the E flank of the New Southeast Crater (NSEC). The activity began at 0608 with a brownish-gray ash emission that rose several hundred meters above the summit. The event was followed by more ash emissions and then Strombolian activity in the evening.
2018 Aug 1	- - - -	Ash Plume	According to INGV, after several months of quiet conditions, explosive activity resumed at the E crater on the E flank of the New Southeast Crater (NSEC). The activity began at 0608 with a brownish-gray ash emission that rose several hundred meters above the summit. The event was followed by more ash emissions and then Strombolian activity in the evening.
2018 Aug 1	2018 Aug 7	Incandescent ejecta	According to INGV, after several months of quiet conditions, explosive activity resumed at the E crater on the E flank of the New Southeast Crater (NSEC). The activity began at 0608 with a brownish-gray ash emission that rose several hundred meters above the summit. The event was followed by more ash emissions and then Strombolian activity in the evening. The EMOH camera recorded sporadic Strombolian explosions at night, which continued through the first week of August.
2018 Aug 6	2018 Aug 12	Explosion	INGV reported that explosions at the E crater on the E flank of the New Southeast Crater (NSEC) generated gray-brown ash plumes that sometimes rose several hundred meters above Etna’s summit and quickly dissipated.
2018 Aug 6	2018 Aug 12	Ash Plume	INGV reported that explosions at the E crater on the E flank of the New Southeast Crater (NSEC) generated gray-brown ash plumes that sometimes rose several hundred meters above Etna’s summit and quickly dissipated.
2018 Aug 15 (in or after)	2018 Aug 21 (in or before)	Incandescent ejecta	During the third week of August Strombolian activity became more sporadic at the E vent of NSEC.
2018 Aug 23	- - - -	Incandescent ejecta	According to INGV, at 1730 Strombolian activity occurred at NSEC’s E vent.
2018 Aug 23	- - - -	Lava flow	According to INGV, at 1730 a lava flow emerged from NSEC’s E vent, and traveled a few hundred meters E towards the Valle del Bove.
2018 Aug 27	- - - -	Incandescent ejecta	Strombolian activity was continuing at NSEC.
2018 Aug 27	2018 Aug 28	Lava flow	A new lava overflow emerged from the E vent of NSEC and flowed E towards the Valle del Bove for about 24 hours.
2018 Aug 27	2018 Aug 30	Thermal Anomaly	Multiple daily MODVOLC thermal alerts were issued.
2018 Aug 28	2018 Sep 9	Incandescent ejecta	INGV reported that discontinuous Strombolian activity continued from NSEC after the effusive activity ended in late August.
2018 Sep 1 (in or after)	2018 Sep 7 (in or before)	Audible Sounds	According to INGV, several loud explosions from NSEC were reported by people living near the E flank of Etna during the first week of September.
2018 Sep 5	- - - -	Explosion	According to INGV, a few Strombolian explosions at NSEC were recorded; an explosion at 0536 generated an ash plume that produced local ashfall around the vent and in the Valle del Bove, and quickly dispersed. A similar but less intense event occurred earlier that day, at 0316.
2018 Sep 5	- - - -	Ash Plume	According to INGV, a few Strombolian explosions at NSEC were recorded; an explosion at 0536 generated an ash plume that produced local ashfall around the vent and in the Valle del Bove, and quickly dispersed. A similar but less intense event occurred earlier that day, at 0316.
2018 Sep 5	- - - -	Ashfall	According to INGV, a few Strombolian explosions at NSEC were recorded; an explosion at 0536 generated an ash plume that produced local ashfall around the vent and in the Valle del Bove, and quickly dispersed. A similar but less intense event occurred earlier that day, at 0316.
2018 Sep 8	2018 Sep 30	Incandescent ejecta	According to INGV, discontinuous low-intensity Strombolian activity and intermittent ash emissions from Bocca Nuova, New Southeast Crater, and Northeast Crater characterized activity for the remainder of September.
2018 Oct 1 (in or after)	2018 Oct 31 (in or before)	Ash Plume	According to INGV, discontinuous low-intensity Strombolian activity and intermittent ash emissions from the Bocca Nuova, the New Southeast Crater, and Northeast Crater characterized activity during all of October 2018.
2018 Oct 1 (in or after)	2018 Oct 31 (in or before)	Incandescent ejecta	According to INGV, discontinuous low-intensity Strombolian activity and intermittent ash emissions from the Bocca Nuova, the New Southeast Crater, and Northeast Crater characterized activity during all of October 2018.
2018 Oct 15 (in or after)	2018 Oct 21 (in or before)	Ash Plume	According to INGV the E vent in NSEC produced Strombolian explosions and ash emissions which rapidly dispersed.
2018 Oct 15 (in or after)	2018 Oct 21 (in or before)	Incandescent ejecta	According to INGV, the E vent in NSEC produced Strombolian explosions and ash emissions which rapidly dispersed.
2018 Nov 1 (in or after)	2018 Nov 7 (in or before)	Ash Plume	According to INGV, Strombolian activity at NSEC gradually intensified during the first week of November 2018 and was sometimes accompanied by ash emissions that rapidly dispersed, falling mainly near the vent and in the Valle del Bove to the E.
2018 Nov 1 (in or after)	2018 Nov 30 (in or before)	Ash Plume	According to INGV, at the NSEC complex, high-temperature anomalies were visible at the NW crater edge, and the E vent of NSEC had a small scoria cone that produced discontinuous Strombolian explosions and minor ash emissions.
2018 Nov 1 (in or after)	2018 Nov 7 (in or before)	Ashfall	According to INGV, Strombolian activity at NSEC gradually intensified during the first week of November 2018 and was sometimes accompanied by ash emissions that rapidly dispersed, falling mainly near the vent and in the Valle del Bove to the E.
2018 Nov 1 (in or after)	2018 Nov 7 (in or before)	Incandescent ejecta	According to INGV, Strombolian activity at NSEC gradually intensified during the first week of November 2018 and was sometimes accompanied by ash emissions that rapidly dispersed, falling mainly near the vent and in the Valle del Bove to the E.
2018 Nov 1 (in or after)	2018 Nov 30 (in or before)	Incandescent ejecta	According to INGV, at the NSEC complex, high-temperature anomalies were visible at the NW crater edge, and the E vent of NSEC had a small scoria cone that produced discontinuous Strombolian explosions and minor ash emissions.
2018 Nov 1 (in or after)	2018 Nov 30 (in or before)	Cinder Cone	According to INGV, at the NSEC complex, high-temperature anomalies were visible at the NW crater edge, and the E vent of NSEC had a small scoria cone that produced discontinuous Strombolian explosions and minor ash emissions.
2018 Nov 1 (in or after)	2018 Nov 7 (in or before)	Audible Sounds	According to INGV, audible explosions from the activity were heard in Zafferana Etnea on the E flank.
2018 Nov 20	- - - -	Seismicity (volcanic)	According to INGV, a seismic swarm with over 40 events affected the W flank of Etna; the hypocenters were located between 15 and 27 km depth. Included with NSEC as the lava flow emerged from there shortly after.
2018 Nov 20	- - - -	Lava flow	According to INGV, a small lava flow emerged from the scoria cone inside the E vent at NSEC. The flow lasted for a few hours and remained inside the E vent.
2018 Nov 26	- - - -	Incandescent ejecta	According to INGV, a new flow from the same scoria cone at the NSEC east vent appeared accompanied by continued Strombolian activity.
2018 Nov 26	2018 Dec 5 (in or before) ± 2 days	Lava flow	According to INGV, a new flow from the same scoria cone at the NSEC east vent appeared on 26 November accompanied by continued Strombolian activity. The flow remained high on the E flank at an elevation of about 3,200 m. Flow activity continued into the first days of December with frequent incandescent blocks moving down the NSEC E flank. Small overlapping flows traveled about 500 m down the E flank of the cone. Incandescent blocks generated by the lava flows rolled to the base of the cone, and occasional small collapses produced minor ash plumes.
2018 Nov 28	- - - -	Thermal Anomaly	Two MODVOLC thermal alerts were issued. Likely locations are BN and NSEC.
2018 Nov 29	- - - -	Thermal Anomaly	Eight MODVOLC thermal alerts were issued. Likely locations include BN, NEC, and NSEC.
2018 Dec 1 (in or after)	2018 Dec 21 (in or before)	Incandescent ejecta	INGV reported that Strombolian activity, with modest ash emissions, continued from the Bocca Nuova, NSEC, and NEC during the first three weeks of December.
2018 Dec 1	- - - -	Thermal Anomaly	A MODVOLC thermal alert was issued. NSEC is the likely location.
2018 Dec 4	2018 Dec 18	Explosion	INGV reported intermittent explosions lasted 5-10 minutes with similar length pauses.
2018 Dec 4	2018 Dec 18	Incandescent ejecta	INGV reported that variable Strombolian activity at the scoria cone beginning on 4 December produced continuous overlapping small flows from several vents near the scoria cone for two weeks.
2018 Dec 4	2018 Dec 18 (in or before)	Lava flow	According to INGV, variable Strombolian activity at the scoria cone beginning on 4 December produced continuous overlapping small flows from several vents near the scoria cone for two weeks. Activity increased on 16 December with near-continuous lava effusion. Several small flows traveled NE, E, and SE down the E flank of NSEC during the second and third weeks of the month. A few flows reached the base of the cone at 2,900 m elevation and were almost a kilometer in length. Small collapses of portions of the lava field also produced minor plumes of ash.
2018 Dec 4	2018 Dec 9	Avalanche	According to INGV, incandescent blocks generated by the lava flows rolled to the base of the cone, and occasional small collapses produced minor ash plumes.
2018 Dec 4	2018 Dec 26	Thermal Anomaly	Multiple near-daily MODVOLC thermal alerts were issued. Strombolian activity and lava flows were reported from NEC, BN, and NSEC during this time.
2018 Dec 24	- - - -	Seismicity (volcanic)	According to INGV, a lateral eruption and intense seismic swarm began from a nearly 2-km-long fissure trending NNW-SSE on the SE flank of NSEC. A significant increase in the release of seismic strain and frequency of earthquakes began around 0830 on 24 December 2018. Around 300 events occurred during the first three hours of increased seismicity which continued throughout the week, with over 2,000 events recorded in different areas around Etna. The initial swarm was located in the summit area near the fissure with events located 0-3 km below sea level; subsequent seismicity was located in the Valle del Bove and included multiple earthquakes with magnitudes greater than M 4.0. The E and SW slopes of the volcano were also affected by seismic events. The largest earthquake (M 4.8) was recorded on 26 December at 0319 local time, located about 1 km below sea level between the towns of Fleri and Pennisi on the Faglia Fiandaca fault. It was widely felt in many urban centers and caused damage in some areas. INGV noted that it was likely not generated by movement of magmatic material in the epicentral area.
2018 Dec 24	- - - -	Fissure	According to INGV, a lateral eruption and intense seismic swarm began from a nearly 2-km-long fissure trending NNW-SSE on the SE flank of NSEC. Shortly after noon, an eruptive fissure opened up at the southeastern base of NSEC, releasing intense Strombolian activity which rapidly formed a dense plume of dark ash. Over the following two hours, the main fissure spread SE, crossing over the western edge of the Valle del Bove and reaching down to 2,400 m elevation.
2018 Dec 24	- - - -	Ash Plume	Shortly after noon, an eruptive fissure opened up at the southeastern base of NSEC, releasing intense Strombolian activity which rapidly formed a dense plume of dark ash. The ash cloud created by the multiple eruptive vents generated a dense plume that drifted SE, producing ashfall mainly in the area around Zafferana Etnea and Santa Venerina.
2018 Dec 24	- - - -	Ash Plume	Based on information from INGV and satellites, the Toulouse VAAC reported eruptive activity with significant ash emission started at 1115 UTC. At 1200 UTC, an ash plume was moving SE at 4.6 km altitude and explosive activity had increased. By 1500 UTC ash emission still occurred, moving SE at 5.5 km altitude. Sporadic ash emission continued at 2100 UTC at 5.5 km altitude. By 0300 UTC on 25 December, the eruption had stopped but ash was still observed at 5.5 km altitude. By 0900 UTC no significant ash emission was occurring but the eruption was ongoing. By 1500 UTC ash emission had diminished but explosive activity was still occurring.
2018 Dec 24	- - - -	Ashfall	According to INGV, the ash cloud created by the multiple eruptive vents generated a dense plume that drifted SE, producing ashfall mainly in the area around Zafferana Etnea and Santa Venerina.
2018 Dec 24	- - - -	Incandescent ejecta	According to INGV, a lateral eruption and intense seismic swarm began from a nearly 2-km-long fissure trending NNW-SSE on the SE flank of NSEC. Shortly after noon, an eruptive fissure opened up at the southeastern base of NSEC, releasing intense Strombolian activity which rapidly formed a dense plume of dark ash.
2018 Dec 24	2018 Dec 27	Lava flow	According to INGV, a lateral eruption and intense seismic swarm began from a nearly 2-km-long fissure trending NNW-SSE on the SE flank of NSEC; it produced a flow into the Valle del Bove and covered about 1 km². As the fissure opened it fed several flows that descended the W face of the Valle del Bove, past Serra Giannicola Grande, merged into a single flow at the base of the wall, and continued E across the valley floor. By 1800 the fissure was active mainly at the lower end where it continued to feed the flow in the Valle del Bove with strong Strombolian activity and abundant ash emissions. Effusive activity from the fissure continued through 26 December when it decreased significantly; new lava feeding the flow ended on 27 December, but the flow front continued to move slowly.
2018 Dec 24	- - - -	Fissure	A second smaller fissure located between NSEC and NEC also opened at the same time and produced weaker Strombolian activity that lasted a few tens of minutes.
2018 Dec 24	- - - -	Incandescent ejecta	A second smaller fissure located between NSEC and NEC also opened at the same time and produced weaker Strombolian activity that lasted a few tens of minutes.

Episode 17 | Eruption

Southeast Crater (SEC)

2017 Nov 14 - 2017 Nov 30 (in or before)

Evidence from Observations: Reported

List of 5 Events for Episode 17 at Southeast Crater (SEC)

Start Date	End Date	Event Type	Event Remarks
2017 Nov 14	- - - -	Explosion	A small, isolated explosion containing minor ash occurred at SEC.
2017 Nov 14	- - - -	Ash Plume	A small, isolated explosion containing minor ash occurred at SEC.
2017 Nov 14	- - - -	VEI (Explosivity Index)	VEI 1
2017 Nov 21	2017 Nov 30	Explosion	In the last week of the month, a series of explosions with ash emissions from SEC was detected.
2017 Nov 21	2017 Nov 30	Ash Plume	In the last week of the month, pulsating degassing from the craters could be detected during periods of limited visibility, as well as a series of explosions with ash emissions from SEC.

Episode 18 | Eruption

Northeast Crater (NEC)

2018 Feb 17 - Unknown

Evidence from Observations: Reported

List of 47 Events for Episode 18 at Northeast Crater (NEC)

Start Date	End Date	Event Type	Event Remarks
2017 Nov 14	2017 Nov 21	Crater	According to INGV, during the third week of November, a new pit crater appeared at the bottom of NEC that measured 70 x 50 m.
2018 Jan 31 (in or before)	- - - -	Crater	According to INGV, by the end of the month, the pit crater at the base of NEC had expanded, causing erosion of the inner E wall.
2018 Feb 17	- - - -	Ash Plume	According to INGV, faint, non-explosive emissions of gray ash were observed in the morning from NEC.
2018 Mar 10	- - - -	Ash Plume	During an inspection by INGV the expansion of the pit crater at the bottom of NEC was noted, as was continuing collapses of the internal walls which produced minor ash emissions.
2018 Mar 10 (in or before)	- - - -	Crater	During an inspection by INGV the expansion of the pit crater at the bottom of NEC was noted, as was continuing collapses of the internal walls which produced minor ash emissions.
2018 Apr 1 (in or after)	2018 Apr 7 (in or before)	Ash Plume	According to INGV, activity through April was characterized by degassing at the summit craters with modest ash emissions from the Northeast Crater in the first week.
2018 Apr 25 (in or after)	2018 Apr 30 (in or before)	Ash Plume	According to INGV, activity through April was characterized by degassing at the summit craters and occasional small ash emissions at the end of the month.
2018 May 7 (in or after)	2018 May 31 (in or before)	Ash Plume	According to INGV, reduced activity dominated by degassing continued into May with modest ash emission from the Northeast crater during the second week, and isolated ash emissions from the Northeast Crater in the second half of the month continuing into June.
2018 Jun 1 (in or after)	2018 Jun 30 (in or before)	Ash Plume	According to INGV, Throughout June activity consisted of degassing at the summit craters with isolated diffuse ash emission from Northeast Crater.
2018 Jul 9	2018 Jul 15	Ash Plume	INGV reported that strong and prolonged roars (up to several tens of seconds) from NEC were sometimes accompanied by gray-brown and reddish ash emissions.
2018 Jul 9	2018 Jul 15	Incandescent ejecta	INGV reported that gas emissions continued to rise from Etna’s summit craters. Visibility of the fairly continuous, low-energy, Strombolian activity deep within the Northeast Crater (NEC) and Bocca Nuova was sometimes hindered by gas emissions. Ejected incandescent material fell back into the crater.
2018 Jul 9	2018 Jul 15	Audible Sounds	INGV reported that strong and prolonged roars (up to several tens of seconds) from NEC were sometimes accompanied by gray-brown and reddish ash emissions.
2018 Jul 16	2018 Jul 22	Explosion	INGV reported that activity at NEC was characterized by strong and prolonged explosions (up to several tens of seconds), sometimes with reddish-brown ash emissions. Three vents on the floor of NEC continued to widen due to collapse of the inner walls.
2018 Jul 16	2018 Jul 22	Ash Plume	INGV reported that activity at NEC was characterized by strong and prolonged explosions (up to several tens of seconds), sometimes with reddish-brown ash emissions. Three vents on the floor of NEC continued to widen due to collapse of the inner walls.
2018 Jul 16	2018 Jul 22	Incandescent ejecta	INGV reported that low-energy Strombolian activity also occurred from three vents at the bottom of Northeast Crater (NEC). The activity was mostly confined to the crater, with material falling back into the craters, though occasionally incandescent lava was ejected about 100 m above the crater rim. The activity sometimes generated ash emissions that dissipated near the summit.
2018 Jul 27	2018 Jul 28	Ash Plume	INGV observed ash emissions from the Northeast Crater of Etna that rose a few tens of meters and quickly dispersed.
2018 Jul 30	- - - -	Ash Plume	During a field inspection INGV personnel noted activity at the three vents at the bottom of Northeast Crater; the farthest west produced ash emissions, the center produced steam, and the vent under the NE crater wall produced Strombolian activity that sent ejecta as high as the crater rim.
2018 Jul 30	- - - -	Incandescent ejecta	During a field inspection INGV personnel noted activity at the three vents at the bottom of Northeast Crater; the farthest west produced ash emissions, the center produced steam, and the vent under the NE crater wall produced Strombolian activity that sent ejecta as high as the crater rim.
2018 Aug 3	2018 Aug 5	Ash Plume	According to INGV, frequent ash emissions from NEC were observed.
2018 Aug 6	2018 Aug 12	Ash Plume	INGV reported that activity at Northeast Crater (NEC) consisted of frequent ash emissions and Strombolian explosions.
2018 Aug 6	2018 Aug 12	Incandescent ejecta	INGV reported that activity at Northeast Crater (NEC) consisted of frequent ash emissions and Strombolian explosions.
2018 Aug 14 (in or after)	2018 Aug 31 (in or before)	Incandescent ejecta	During the third week of August Strombolian activity continued at NEC. Strombolian activity continued from multiple vents at the bottom of NEC during the last week of August. The frequency and intensity of explosions was variable and increased significantly during 22 August, ejecting coarse pyroclastic material outside the crater rim.
2018 Sep 3 (in or after)	2018 Sep 9 (in or before)	Incandescent ejecta	INGV reported that activity at Etna was characterized by gas emissions at the summit craters, with periodic Strombolian activity from vents in Bocca Nuova, Northeast Crater (NEC), and New Southeast Crater (NSEC).
2018 Sep 6	2018 Sep 9	Explosion	Strombolian activity occurred at NEC, and a few times explosions were accompanied by ash emissions.
2018 Sep 6	2018 Sep 9	Ash Plume	Strombolian activity occurred at NEC, and a few times explosions were accompanied by ash emissions.
2018 Sep 6	2018 Sep 9	Incandescent ejecta	Strombolian activity occurred at NEC, and a few times explosions were accompanied by ash emissions.
2018 Sep 9 (in or after)	2018 Sep 30 (in or before)	Incandescent ejecta	Discontinuous low-intensity Strombolian activity and intermittent ash emissions from Bocca Nuova, New Southeast Crater, and Northeast Crater characterized activity for the remainder of September.
2018 Sep 24	2018 Sep 30	Ash Plume	NEC produced frequent brown-gray ash emissions, and ejected blocks and bombs, from a vent located in the W part of the crater floor.
2018 Sep 24	2018 Sep 30	Incandescent ejecta	NEC produced frequent brown-gray ash emissions, and ejected blocks and bombs, from a vent located in the W part of the crater floor.
2018 Sep 24	2018 Sep 30	Bombs	NEC produced frequent brown-gray ash emissions, and ejected blocks and bombs, from a vent located in the W part of the crater floor.
2018 Oct 1 (in or after)	2018 Oct 31 (in or before)	Ash Plume	INGV reported discontinuous low-intensity Strombolian activity and intermittent ash emissions from the Bocca Nuova, the New Southeast Crater, and Northeast Crater during all of October 2018.
2018 Oct 1 (in or after)	2018 Oct 31 (in or before)	Incandescent ejecta	INGV reported discontinuous low-intensity Strombolian activity and intermittent ash emissions from the Bocca Nuova, the New Southeast Crater, and Northeast Crater during all of October 2018.
2018 Oct 1	- - - -	Thermal Anomaly	A MODVOLC thermal alert was issued. Plots directly over NEC.
2018 Oct 15 (in or after)	2018 Oct 21 (in or before)	Explosion	According to INGV, NEC activity was characterized by gas emissions and explosive activity of variable frequency and intensity.
2018 Nov 1 (in or after)	2018 Nov 30 (in or before)	Ash Plume	According to INGV, Strombolian activity continued, accompanied by sporadic and modest ash emissions from Bocca Nuova, the New Southeast Crater and the Northeast Crater through the end of November.
2018 Nov 1 (in or after)	2018 Nov 30 (in or before)	Incandescent ejecta	According to INGV, at NEC, continuous and intense Strombolian activity from the crater floor caused pyroclastic ejecta to land outside the crater rim.
2018 Nov 10	- - - -	Thermal Anomaly	A MODVOLC thermal alert was issued. Its location suggests the source closest to NEC.
2018 Nov 13	2018 Nov 15	Thermal Anomaly	Two MODVOLC thermal alerts were issued. Their locations suggest the source is closest to NEC.
2018 Nov 24	- - - -	Thermal Anomaly	A MODVOLC thermal alert was issued. The location suggests NEC crater as the source.
2018 Nov 28	- - - -	Thermal Anomaly	Eight MODVOLC thermal alerts were issued. Likely locations include BN, NEC, and NSEC.
2018 Dec 1 (in or after)	2018 Dec 21 (in or before)	Ash Plume	Strombolian activity, with modest ash emissions, continued from the Bocca Nuova, NSEC, and NEC during the first three weeks of December.
2018 Dec 1 (in or after)	2018 Dec 21 (in or before)	Incandescent ejecta	According to INGV Strombolian activity, with modest ash emissions, continued from the Bocca Nuova, NSEC, and NEC during the first three weeks of December.
2018 Dec 4	2018 Dec 26	Thermal Anomaly	Multiple near-daily MODVOLC thermal alerts were issued. Strombolian activity and lava flows were reported from NEC, BN, and NSEC during this time.
2018 Dec 24	- - - -	Ash Plume	According to INGV, beginning around 0800 local time, degassing intensity from the summit craters increased significantly. In the following hours, intermittent reddish-gray ash emissions rose from Bocca Nuova and NEC becoming continuous by late morning. Over the following two hours, the ash cloud created by the multiple eruptive vents generated a dense plume that drifted SE, producing ashfall mainly in the area around Zafferana Etnea and Santa Venerina. Ash emissions decreased significantly from Bocca Nuova and NEC after 1430.
2018 Dec 24	- - - -	Ashfall	Over the following two hours, the ash cloud created by the multiple eruptive vents generated a dense plume that drifted SE, producing ashfall mainly in the area around Zafferana Etnea and Santa Venerina.
2018 Dec 24	- - - -	Incandescent ejecta	According to INGV, over the following two hours, continuous Strombolian activity of variable intensity occurred at NEC and Bocca Nuova.
2018 Dec 29	- - - -	Thermal Anomaly	A MODVOLC thermal alert was issued.

Episode 19 | Eruption

Southeast Crater (SEC)

2018 May 8 (in or after) - 2018 May 14 (in or before)

Evidence from Observations: Reported

List of 2 Events for Episode 19 at Southeast Crater (SEC)

	Start Date	End Date	Event Type	Event Remarks
	2018 May 8 (in or after)	2018 May 14 (in or before)	Ash Plume	According to INGV, reduced activity dominated by degassing continued into May with modest ash emission from the Southeast crater during the second week.
	2018 May 8 (in or after)	- - - -	VEI (Explosivity Index)	VEI 1

Episode 20 | Eruption

Bocca Nuova (BN)

2018 Jul 9 ± 2 days - Unknown

Evidence from Observations: Reported

List of 41 Events for Episode 20 at Bocca Nuova (BN)

Start Date	End Date	Event Type	Event Remarks
2018 Jul 9 ± 2 days	2018 Jul 31 (in or before)	Ash Plume	According to INGV, low-energy Strombolian activity resumed at both of the Bocca Nuova BN-1 vents as well as the vents in the Northeast Crater (NEC) during the second week of July 2018 and continued throughout the month. The activity from BN-1 was nearly continuous, but not always visible; occasionally, lava fragments rose 100 m and could be seen outside of the crater rim. Intermittent ash emissions accompanied the Strombolian activity.
2018 Jul 9 ± 2 days	2018 Jul 31 (in or before)	Incandescent ejecta	According to INGV, low-energy Strombolian activity resumed at both of the Bocca Nuova BN-1 vents during the second week of July and continued throughout the month. The activity from BN-1 was nearly continuous, but not always visible; occasionally, lava fragments rose 100 m and could be seen outside of the crater rim. Intermittent ash emissions accompanied the Strombolian activity.
2018 Aug 1 (in or after)	2018 Aug 7 (in or before)	Incandescent ejecta	According to INGV, during the first week of August Strombolian activity continued at BN-1.
2018 Aug 6	2018 Aug 12	Incandescent ejecta	INGV reported that Strombolian explosions continued from vents in Bocca Nuova, and were particularly visible at night.
2018 Aug 7	- - - -	Thermal Anomaly	A MODVOLC thermal alert was issued. Location best matches BN.
2018 Aug 11	- - - -	Thermal Anomaly	A MODVOLC thermal alert was issued. Location best matches BN.
2018 Aug 16	- - - -	Incandescent ejecta	According to INGV, a new vent opened in the BN-2 area on the E side of the Voragine (inactive since December 2015) and exhibited both degassing and Strombolian activity.
2018 Aug 20	- - - -	Thermal Anomaly	A MODVOLC thermal alert was issued. Location best matches BN.
2018 Aug 22 (in or after)	2018 Aug 31 (in or before)	Incandescent ejecta	During the last week of August, Strombolian activity and intense degassing continued in the western sector of Bocca Nuova (BN-1). Occasionally, lapilli fragments a few centimeters in diameter were ejected onto the S rim of the crater.
2018 Aug 22 (in or after)	2018 Aug 31 (in or before)	Lapilli	During the last week of August, Strombolian activity and intense degassing continued in the western sector of Bocca Nuova (BN-1). Occasionally, lapilli fragments a few centimeters in diameter were ejected onto the S rim of the crater.
2018 Sep 1 (in or after)	2018 Sep 6 (in or before)	Ash Plume	INGV reported that Strombolian activity, modest ash emissions, and significant gas emissions were produced by BN-1; BN-2 exhibited only continuous degassing activity.
2018 Sep 1 (in or after)	2018 Sep 6 (in or before)	Incandescent ejecta	INGV reported that Strombolian activity, modest ash emissions, and significant gas emissions were produced by BN-1; BN-2 exhibited only continuous degassing activity.
2018 Sep 6	2018 Sep 9	Ash Plume	INGV reported that gas emissions were sometimes punctuated with ash emissions. Intense degassing was characteristic of the second vent (BN-2).
2018 Sep 6	2018 Sep 9	Incandescent ejecta	INGV reported that Strombolian activity at the N vent (BN-1) in Bocca Nuova occurred at 3-5-minute intervals, ejecting incandescent material that fell within the crater confines.
2018 Sep 9	2018 Sep 30	Ash Plume	INGV reported that discontinuous low-intensity Strombolian activity and intermittent ash emissions from Bocca Nuova, New Southeast Crater, and Northeast Crater characterized activity for the remainder of September.
2018 Sep 9	2018 Sep 30	Incandescent ejecta	INGV reported that discontinuous low-intensity Strombolian activity and intermittent ash emissions from Bocca Nuova, New Southeast Crater, and Northeast Crater characterized activity for the remainder of September.
2018 Sep 24	2018 Sep 30	Explosion	According to INGV, no eruptive activity was observed at BN-2, though it produced explosions deep in the crater.
2018 Sep 24	2018 Sep 30	Incandescent ejecta	According to INGV, Strombolian activity at the N vent in Bocca Nuova (BN-1) ejected incandescent material almost as high as the W crater rim.
2018 Oct 1 (in or after)	2018 Oct 31 (in or before)	Ash Plume	According to INGV, discontinuous low-intensity Strombolian activity and intermittent ash emissions from the Bocca Nuova, the New Southeast Crater, and Northeast Crater characterized activity during all of October 2018.
2018 Oct 1 (in or after)	2018 Oct 31 (in or before)	Incandescent ejecta	According to INGV, discontinuous low-intensity Strombolian activity and intermittent ash emissions from the Bocca Nuova, the New Southeast Crater, and Northeast Crater characterized activity during all of October 2018.
2018 Oct 1	- - - -	Degassing	According to INGV, a new high-temperature vent producing gas emissions was noted in the same place a fumarole had been observed the previous week.
2018 Oct 16	- - - -	Incandescent ejecta	According to INGV, two vents remained active at the bottom of Bocca Nuova (BN-1). During a visit, INGV-OE geologists noted that the northernmost vent produced nearly continuous Strombolian activity with frequent explosions; occasionally fragments exceeded the crater rim in height but still fell within the crater. The southernmost vent, on the crater floor about 130 m from the edge, was characterized by explosive activity that produced mainly spattering which covered both the crater floor and walls.
2018 Oct 25	- - - -	Explosion	According to INGV, the webcam at Bronte recorded an ash emission from Bocca Nuova that resulted from three closely-spaced explosions. The ash was red and dispersed rapidly to the S causing ashfall near Torre del Filosofo and Rifugio Sapienza.
2018 Oct 25	- - - -	Ash Plume	According to INGV, the webcam at Bronte recorded an ash emission from Bocca Nuova that resulted from three closely-spaced explosions. The ash was red and dispersed rapidly to the S causing ashfall near Torre del Filosofo and Rifugio Sapienza.
2018 Oct 25	- - - -	Ashfall	According to INGV, the webcam at Bronte recorded an ash emission from Bocca Nuova that resulted from three closely-spaced explosions. The ash was red and dispersed rapidly to the S causing ashfall near Torre del Filosofo and Rifugio Sapienza.
2018 Oct 29 (in or after)	2018 Nov 4 (in or before)	Incandescent ejecta	According to INGV, Strombolian activity and gas emissions were characteristic of the N vent in the W part of Bocca Nuova’s (BN-1) crater floor. Spattering from the southernmost vent was also visible, as well as gas emissions.
2018 Nov 1 (in or after)	2018 Nov 30 (in or before)	Ash Plume	According to INGV, Strombolian activity continued, accompanied by sporadic and modest ash emissions from Bocca Nuova, the New Southeast Crater and the Northeast Crater through the end of November.
2018 Nov 1 (in or after)	2018 Nov 30 (in or before)	Incandescent ejecta	According to INGV, Strombolian activity continued, accompanied by sporadic and modest ash emissions from Bocca Nuova, the New Southeast Crater and the Northeast Crater through the end of November.
2018 Nov 8	- - - -	Thermal Anomaly	A MODVOLC thermal alert was issued. Its location suggests that BN is the source.
2018 Nov 9	- - - -	Ash Plume	According to INGV, three vents were visible at BN-1 during an overflight; continuous Strombolian activity occurred at vent 1, whose fallout of pyroclastic debris remained within the crater; discontinuous Strombolian activity was observed at vent 2 associated with weak, pulsing ash emissions; only degassing activities were observed at vent 3. At BN-2, intense degassing accompanied discontinuous Strombolian activity that was associated with weak pulsating ash emissions, and several high temperature gas emission points. Scientists also observed a collapse on a portion of the northern inner wall of BN-1 from the explosion on 25 October.
2018 Nov 9	- - - -	Incandescent ejecta	According to INGV, three vents were visible at BN-1 during an overflight; continuous Strombolian activity occurred at vent 1, whose fallout of pyroclastic debris remained within the crater; discontinuous Strombolian activity was observed at vent 2 associated with weak, pulsing ash emissions; only degassing activities were observed at vent 3. At BN-2, intense degassing accompanied discontinuous Strombolian activity that was associated with weak pulsating ash emissions, and several high temperature gas emission points. Scientists also observed a collapse on a portion of the northern inner wall of BN-1 from the explosion on 25 October.
2018 Nov 12	- - - -	Thermal Anomaly	A MODVOLC thermal alert was issued. Its location suggests that BN is the source.
2018 Nov 22	2018 Nov 23	Thermal Anomaly	Two MODVOLC thermal alerts were issued. Their location suggests BN and NSEC as the sources.
2018 Nov 28	- - - -	Thermal Anomaly	Two MODVOLC thermal alerts were issued. Likely locations are BN and NSEC.
2018 Nov 29	- - - -	Thermal Anomaly	Eight MODVOLC thermal alerts were issued. Likely locations include BN, NEC, and NSEC.
2018 Dec 1 (in or after)	2018 Dec 21 (in or before)	Ash Plume	Strombolian activity, with modest ash emissions, continued from the Bocca Nuova, NSEC, and NEC during the first three weeks of December.
2018 Dec 1 (in or after)	2018 Dec 21 (in or before)	Incandescent ejecta	Strombolian activity, with modest ash emissions, continued from the Bocca Nuova, NSEC, and NEC during the first three weeks of December.
2018 Dec 4	2018 Dec 26	Thermal Anomaly	Multiple near-daily MODVOLC thermal alerts were issued. Strombolian activity and lava flows were reported from NEC, BN, and NSEC during this time.
2018 Dec 24	- - - -	Ash Plume	According to INGV, beginning around 0800 local time, degassing intensity from the summit craters increased significantly. In the following hours, intermittent reddish-gray ash emissions rose from Bocca Nuova and NEC becoming continuous by late morning. Over the following two hours, the ash cloud created by the multiple eruptive vents generated a dense plume that drifted SE, producing ashfall mainly in the area around Zafferana Etnea and Santa Venerina. Ash emissions decreased significantly from Bocca Nuova and NEC after 1430. Around 1830 intense Strombolian activity resumed at Bocca Nuova along with abundant ash emissions which gradually decreased overnight.
2018 Dec 24	- - - -	Ashfall	Over the following two hours, the ash cloud created by the multiple eruptive vents generated a dense plume that drifted SE, producing ashfall mainly in the area around Zafferana Etnea and Santa Venerina.
2018 Dec 24	- - - -	Incandescent ejecta	According to INGV, over the following two hours, continuous Strombolian activity of variable intensity occurred at NEC and Bocca Nuova. Around 1830 intense Strombolian activity resumed at Bocca Nuova along with abundant ash emissions which gradually decreased overnight.

Episode 21 | Eruption

Saddle Cone, Cono della Sella (SEC3, CdS)

2018 Aug 23 - 2018 Aug 27

Evidence from Observations: Reported

List of 8 Events for Episode 21 at Saddle Cone, Cono della Sella (SEC3, CdS)

Start Date	End Date	Event Type	Event Remarks
2018 Aug 23	- - - -	Explosion	Beginning about 1800 UTC, activity resumed at the saddle cone located between the old cone of the Southeast Crater (SEC) and the new cone (NSEC). Strombolian activity, initially modest, quickly became more intense, producing almost continuous explosions with the launch of coarse ejecta up to a height of 100-150 m.
2018 Aug 23	2018 Aug 25	Ash Plume	According to INGV, the Strombolian activity was accompanied by an abundant and continuous emission of ash, which formed a small plume that rose a few hundred meters from the vent
2018 Aug 23	2018 Aug 25	Incandescent ejecta	INGV reported that beginning about 1800 UTC, activity resumed at the saddle cone (CdS) located between the old cone of the Southeast Crater (SEC) and the new cone (NSEC). Strombolian activity, initially modest, quickly became more intense, producing almost continuous explosions with the launch of coarse ejecta up to a height of 100-150 m. Strombolian explosions of moderate intensity continued throughout the night from the saddle cone and then decreased gradually on 25 August.
2018 Aug 23	2018 Aug 27	Lava flow	According to INGV, shortly after 1830 UTC a lava overflow was observed moving N from the saddle cone. The flow to the N into the Valle del Leone began cooling after lava stopped feeding it in the evening on 27 August.
2018 Aug 23	2018 Aug 27	Thermal Anomaly	Multiple daily MODVOLC thermal alerts were issued. Lava flowing N from CdS.
2018 Aug 23	- - - -	VEI (Explosivity Index)	VEI 1
2018 Aug 24	- - - -	Lava flow	According to INGV, in the morning a small lava overflow emerged from the vent and stopped after traveling a few tens of meters towards the S flank of the NSEC cone.
2018 Aug 25	2018 Aug 26	Ash Plume	According to INGV, the activity at the saddle cone gradually decreased, and ash emissions were weak and occasional.

2010 Aug 25 - 2013 Apr 27 Confirmed Eruption VEI: 3

This eruption includes eight eruptive episodes from four different vent areas. The first, from Bocca Nuova (BN), began in late August 2010 and ended in December 2010. The second brief episode occurred at Northeast Crater (NEC) in mid-November 2010 and possibly in February 2011. The third episode began in late December 2010 on the flank of the Southeast Crater (SEC) cone, but grew into New Southeast Crater (NSEC) and was active until late April 2012. Bocca Nuova was again active during June-July 2011 (episode 4) and July through early October 2012 (episode 5). Episode six at NSEC went from late November 2012 through late April 2013. Renewed activity at Bocca Nuova (episode seven) began on 9 January 2013 and lasted through February 2013. The last episode occurred from Voragine Crater (VOR) and began on 27 February and ended on 17 March 2013. The overall eruption continued until the episode 6 activity at NSEC stopped on 27 April 2013.

Episode 1 | Eruption

Bocca Nuova (BN)

2010 Aug 25 - 2010 Dec 22

Evidence from Observations: Reported

Seven explosions in late August 2010 were followed by single-day events on 7 October and 22 December 2010. They produced ash plumes that resulted in ashfall up to 20 km away.

List of 12 Events for Episode 1 at Bocca Nuova (BN)

Start Date	End Date	Event Type	Event Remarks
2010 Aug 25	- - - -	Explosion	INGV-CT reported that at 1509 a powerful explosion initiated a series of ash emissions, which continued at decreasing strength for about 20 minutes.
2010 Aug 25	2010 Aug 29	Explosion	Seven explosions were recorded during this period.
2010 Aug 25	- - - -	Ash Plume	A cauliflower-shaped, dark gray ash plume rose about 1 km and drifted E.
2010 Aug 25	- - - -	Ashfall	Ashfall was reported in areas SE from Etna to Catania (27 km S).
2010 Aug 25	- - - -	Collapse	The W wall of the BN-1 crater of Bocca Nuova collapsed
2010 Aug 25	- - - -	VEI (Explosivity Index)	VEI 1
2010 Oct 7	- - - -	Explosion	The western depression at the Bocca Nuova was the source of an explosive event that occurred at 1127 and generated a small ash emission.
2010 Oct 7	- - - -	Ash Plume	The western depression at the Bocca Nuova was the source of an explosive event that occurred at 1127 and generated a small ash emission.
2010 Oct 7	- - - -	Ashfall	Ashfall was observed at the Rifugio Sapienza, on the high southern flank of the volcano at ~1,900 m.
2010 Dec 22	- - - -	Explosion	A strong explosion from the W vent of Bocca Nuova crater at 0446 produced an ash plume that rose a few hundred meters above the summit and drifted NE.
2010 Dec 22	- - - -	Ash Plume	An ash plume rose a few hundred meters above the summit and drifted NE after a strong explosion from the W vent of Bocca Nuova crater at 0446.
2010 Dec 22	- - - -	Ashfall	Minor ashfall affected areas as far as Linguaglossa (18 km NE).

Episode 2 | Eruption

Northeast Crater (NEC)

2010 Nov 11 ± 2 days - 2011 Feb 16

Evidence from Observations: Reported

Ash emissions occurring around 14-15 November 2010 came from NEC. The presumed source of emissions on 16 Feb 2011 was also NEC.

List of 5 Events for Episode 2 at Northeast Crater (NEC)

Start Date	End Date	Event Type	Event Remarks
2010 Nov 11 ± 2 days	2010 Nov 13	Ash Plume	Several days of minor ash emissions at the NEC prior to 14 November.
2010 Nov 14	2010 Nov 15	Ash Plume	On the morning of 14 November there was a significant increase in both the frequency and the volume of ash emissions.
2010 Nov 14	- - - -	VEI (Explosivity Index)	VEI 1
2010 Nov 15	- - - -	Ashfall	Ashfall deposits were 1 cm thick on the crater rim.
2011 Feb 16	- - - -	Explosion	An explosive sequence, presumably from NEC, was detected during the late evening.

Episode 3 | Eruption

New Southeast Crater (NSEC)

2010 Dec 29 - 2012 Apr 24

Evidence from Observations: Reported

When this episode started on 29 December 2010 the location was described as "the pit crater on the E flank of the SEC cone." It later grew into a new cone larger than SEC, and in August 2011 was renamed New Southeast Crater (NSEC). Strombolian activity, lava flows, and ash plumes recurred every few weeks through 24 April 2012.

List of 255 Events for Episode 3 at New Southeast Crater (NSEC)

Start Date	End Date	Event Type	Event Remarks
2010 Dec 29	- - - -	Incandescent ejecta	Extremely small amounts of incandescent material emitted from the pit crater were observed.
2011 Jan 2	2011 Jan 3	Incandescent ejecta	During the late afternoon strong incandescence at the pit crater evolved into vigorous Strombolian activity. Frequent Strombolian explosions (1-3 per minute) ejected coarse-grained incandescent material a few tens of meters above the rim of the pit.
2011 Jan 3	- - - -	Ash Plume	Based on a report from INGV and Airforce Catania Sigonella, the Toulouse VAAC reported that activity at Etna produced an ash plume that extended 50 km SE at 3.4 km altitude.
2011 Jan 3	- - - -	Thermal Anomaly	Two MODVOLC thermal alerts were issued.
2011 Jan 4	2011 Jan 6	Incandescent ejecta	Weak emissions of incandescent material were observed.
2011 Jan 11	2011 Jan 12	Incandescent ejecta	Weak Strombolian activity from the pit crater gradually became more intense the next day.
2011 Jan 12	- - - -	Explosion	Based on Meteosat imagery, the Toulouse VAAC reported that an explosion late in the day produced an ash plume that was visible as far as 185 km S at an altitude of 9.1 km.
2011 Jan 12	2011 Jan 13	Ash Plume	Based on a report from INGV and Airforce Catania Sigonella, the Toulouse VAAC reported that activity early in the day produced an ash plume that extended 25 km SE at 3.4 km altitude. Later in the day, they reported an explosion that generated an ash plume visible as far as 185 km S at an altitude of 9.1 km. The plume continued to drift at 7.6 km altitude into the next day.
2011 Jan 12	2011 Jan 13	Ashfall	Ashfall on Etna's S flank and in population centers such as Nicolosi.
2011 Jan 12	2011 Jan 13	Lava fountains	The lava fountains were sustained initially and rose 300-500 m high, then pulsated and became less vigorous, and eventually formed one single jet that rose less than 100 m. Fountaining ceased at 0055 on 13 January.
2011 Jan 12	2011 Jan 13	Lava flow	Lava breached the E crater rim and traveled to the W wall of the Valle del Bove. They descended to about 1,630 m elevation (about 4.2 km from the vent).
2011 Jan 12	2011 Jan 13	Scoria	Scoria fell in Rifugio Sapienza, at 1,910 m elevation during the night.
2011 Jan 12	2011 Jan 15	Thermal Anomaly	Multiple near-daily MODVOLC thermal alerts were issued.
2011 Jan 12	- - - -	VEI (Explosivity Index)	VEI 3
2011 Jan 13	- - - -	Explosion	Sporadic explosions within the crater generated ash emissions.
2011 Jan 13	- - - -	Collapse	Collapses in the crater occurred, producing ash emissions.
2011 Jan 14	- - - -	Ash Plume	Gray-brown ash plumes were produced due to small landslides.
2011 Feb 18	- - - -	Ashfall	Light ashfall occurred on the SW flank of the volcano.
2011 Feb 18	- - - -	Incandescent ejecta	Strombolian activity was observed by a visible-light camera.
2011 Feb 18	- - - -	Lava fountains	This eruptive episode lasted about 11 hours and produced pulsating lava fountains.
2011 Feb 18	- - - -	Lava flow	Lava flows traveled E, following the same path as that of the 12-13 January event, in the direction of the Valle del Bove.
2011 Feb 20	- - - -	Thermal Anomaly	A MODVOLC thermal alert was issued.
2011 Mar 29	2011 Apr 3	Ash Plume	A series of gas-and-ash emissions, rarely with minor incandescent material, rose from the pit crater.
2011 Apr 3	- - - -	Ash Plume	Based on NOTAM LICZ, the Toulouse VAAC reported that a feeble ash emission was observed in satellite data at 2.4-3.4 km altitude drifting NE.
2011 Apr 8	- - - -	Explosion	Explosions were associated with Strombolian activity.
2011 Apr 8	2011 Apr 10	Incandescent ejecta	Strombolian activity detected from two vents located in the W portion of the crater.
2011 Apr 9	- - - -	Explosion	Explosive activity commenced from two vents before lava flows covered the crater floor.
2011 Apr 9	- - - -	Lava flow	A lava flow advanced from the base of the SE Crater cone toward the W headwall of the Valle del Bove, as far as 1 km.
2011 Apr 9	2011 Apr 12	Thermal Anomaly	Eighteen MODVOLC thermal alerts were issued.
2011 Apr 10	- - - -	Explosion	The lava flow encountered thick snow cover, leading to violent explosive interactions that generated pyroclastic flows, and resulted in spectacular vapor-and-ash plumes.
2011 Apr 10	- - - -	Ash Plume	Based on Meteosat imagery and webcam images, the Toulouse VAAC reported that an ash plume drifted SE at 5.2 km altitude.
2011 Apr 10	- - - -	Pyroclastic flow	The lava flow encountered thick snow cover, leading to violent explosive interactions that generated pyroclastic flows, and resulted in spectacular vapor-and-ash plumes.
2011 Apr 10	- - - -	Ashfall	Ashfall affected areas downwind to the SE.
2011 Apr 10	- - - -	Lava fountains	Tremor amplitude significantly increased and culminated with vigorous lava fountaining.
2011 Apr 10	- - - -	Lava flow	The lava-flow emission rate increased dramatically. A second lava flow covered the first and traveled down into the Valle del Bove, essentially following the same path as the lava flows of 12-13 January and 18 February.
2011 May 8	2011 May 9	Explosion	Explosions were associated with Strombolian activity.
2011 May 8	2011 May 9	Incandescent ejecta	Strombolian activity observed at the pit crater on the E flank of the SE Crater.
2011 May 8	- - - -	Bombs	Incandescent bombs were ejected tens of m above the crater rim.
2011 May 8	- - - -	Audible Sounds	Loud detonations were audible many kilometers away including in Monti Sartorius (NE flank) and in Zafferana Etnea (SW flank).
2011 May 11	2011 May 12	Seismicity (tremor)	Volcanic tremor amplitude progressively increased, and at about 2030 lava started to overflow the E crater rim. An abrupt drop in the volcanic tremor amplitude at 0610 the next morning marked the end of the eruptive activity.
2011 May 11	- - - -	Ash Plume	The Toulouse VAAC issued an ash advisory based on activity observed from the Signonella Naval Air Station (LICZ) reporting an ash plume drifting 35 km SE at 3.7 km altitude. Significant ash emission was visible in webcams the next day at 3.9 km altitude.
2011 May 11	2011 May 12	Lava flow	At about 2030 lava started to overflow the E crater rim.
2011 May 11	2011 May 13	Thermal Anomaly	SIxteen MODVOLC thermal alerts were issued.
2011 May 12	- - - -	Ash Plume	Shortly before 0400 lava fountaining began which generated an ash cloud that drifted SSE.
2011 May 12	- - - -	Lava fountains	Shortly before 0400 lava fountaining began which generated an ash cloud that drifted SSE. The lava fountaining lasted around 2 hours, showing a gradual diminution around 0545.
2011 May 14	- - - -	Ash Plume	Based on NOTAM LIRR the Toulouse VAAC issued an ash advisory for an ash plume extending 45 km SE at 3.9 km altitude.
2011 May 29	- - - -	Ash Plume	Based on a volcanic activity report from LICZ, the Toulouse VAAC issued an ash advisory for a plume extending 35 km ESE at 4.6 km altitude.
2011 Jul 4	- - - -	Explosion	Explosions occurred in the pit crater located on the E flank of Etna's SE Crater cone.
2011 Jul 5	2011 Jul 7	Incandescent ejecta	Strombolian eruptions were recorded by a camera.
2011 Jul 7	- - - -	Cinder Cone	Small pyroclastic cones began to grow on the crater floor.
2011 Jul 7	2011 Jul 21	Thermal Anomaly	Multiple near-daily MODVOLC thermal alerts were issued.
2011 Jul 8	- - - -	Ash Plume	Based on a Notice to Airmen from LIRR, the Toulouse VAAC issued an ash advisory for an ash plume extending SW 45 km at 3.9 km altitude.
2011 Jul 9	- - - -	Explosion	Explosions were associated with Strombolian eruptions.
2011 Jul 9	- - - -	Ash Plume	A dense eruptive plume rose several kilometers high and drifted S and SE. Based on webcam and Meteosat imagery, the Toulouse VAAC reported an ash plume identifiable in satellite imagery at 6.1 km altitude.
2011 Jul 9	- - - -	Ashfall	Ash and lapilli fell in populated areas including Trecastagni, Viagrande, and Acireale (SE), and between Nicolosi and Catania towards the S, forcing the closure of the Fontanarossa international airport in Catania.
2011 Jul 9	- - - -	Incandescent ejecta	Strombolian activity resumed.
2011 Jul 9	- - - -	Lava fountains	Strombolian explosions turned into a continuous lava fountain.
2011 Jul 9	- - - -	Lava flow	Lava flow traveled to the upper W part of the Valle del Bove.
2011 Jul 16	- - - -	Ash Plume	A series of ash emissions from the pit crater located on the E flank of the SE Crater cone marked the resumption of explosive activity within the crater. Based on a report by LICZ, the Toulouse VAAC issued an advisory for an ash plume of moderate intensity observed drifting 35 km E at 2.1-4.3 km altitude.
2011 Jul 18	2011 Jul 19	Incandescent ejecta	Strombolian activity increased and culminated into a new eruptive episode.
2011 Jul 19	- - - -	Ash Plume	A dense plume of gas and ash drifted E.
2011 Jul 19	- - - -	Lava fountains	Lava fountains rose 200-250 m and produced heavy fallout of fluid spatter, forming several lava flows.
2011 Jul 19	- - - -	Lava flow	Lava flows traveled down the steep W slope of the Valle del Bove, following the same path as the lavas emitted during the preceding eruptive episodes, and stopped at the base near Monte Centenari. The largest lava flow descended the S flank of the cone reaching the base.
2011 Jul 24	2011 Jul 25	Incandescent ejecta	Vigorous Strombolian activity started within the crater and gradually increased through the night. Strombolian activity gradually turned into a pulsating lava fountain, accompanied by increasingly voluminous ash emissions.
2011 Jul 25	- - - -	Explosion	The final phase of the event was characterized by a series of violent explosions that produced loud detonations heard in the E and SE sectors of the volcano.
2011 Jul 25	- - - -	Ash Plume	Plumes drifted E causing ashfall between the villages of Fornazzo and Milo on the flank (10 km E), and the Ionian coast near Riposto (18 km E). Based on Webcam and satellite data, the Toulouse VAAC reported an ash plume at 3.4 km altitude.
2011 Jul 25	- - - -	Ashfall	Ash fell between the villages of Fornazzo and Milo on the flank (10 km E), and the Ionian coast near Riposto (18 km E).
2011 Jul 25	- - - -	Lava fountains	A pulsating lava fountain was accompanied by increasingly voluminous ash emissions. The fountain fluctuated between 250 and 300 m above the crater with a few jets rising 350 m.
2011 Jul 25	- - - -	Lava flow	Lava flowed through a breach on the E crater rim and divided into multiple parallel flows that reached the base of the steep W slope of the Valle del Bove near Monte Centenari.
2011 Jul 25	2011 Aug 2	Thermal Anomaly	Multiple near-daily MODVOLC thermal alerts were issued.
2011 Jul 25	- - - -	Audible Sounds	The final phase of the event was characterized by a series of violent explosions that produced loud detonations heard in the E and SE sectors of the volcano.
2011 Jul 28	- - - -	Explosion	Sporadic explosions associated with Strombolian activity occurred at the E flank of the SE Crater cone.
2011 Jul 28	- - - -	Incandescent ejecta	Strombolian explosions from the active vent on the E flank of Etna's SE Crater cone were weak and sporadic, then ceased during the night.
2011 Jul 30	- - - -	Ash Plume	Based on information from Cmr Linate, the Toulouse VAAC issued an advisory for an ash plume drifting ESE from the pit crater. Activity increased in the evening and the plume was observed at 6.1 km altitude.
2011 Jul 30	- - - -	Ashfall	Ashfall was reported in the Ionian area (18 km E).
2011 Jul 30	- - - -	Incandescent ejecta	Intermittent incandescence from the crater gradually intensified and became more frequent, then was followed by intense Strombolian activity accompanied by loud detonations.
2011 Jul 30	- - - -	Lava fountains	Strombolian activity intensified and incandescent jets became continuous. During the most intense period, fragments of fluid lava were ejected 450-500 m above the crater and fell onto the flanks of the pyroclastic cone to distances of 200-300 m. Lava fountains jetted from at least two vents located within the crater and on the upper E flank, roughly aligned WNW and ESE.
2011 Jul 30	- - - -	Lava flow	A small lava flow on the E flank descended about 100 m then rapidly chilled. Later in the day lava flowed E and the effusion rate rapidly increased; lava flowed 3 km down the W slope of the Valle del Bove.
2011 Jul 30	- - - -	Bombs	Lava bombs ejected several tens of meters fell back into the crater or around the rim.
2011 Aug 5	2011 Aug 6	Explosion	Explosions were associated with the Strombolian eruptions.
2011 Aug 5	2011 Aug 6	Ash Plume	An eruption plume laden with ash and lapilli rose a few kilometers above the crater and drifted SE. Based on satellite imagery and a notice from LIRR, The Toulouse VAAC reported an ash emission at 8.2 km altitude from an eruption that started around midnight on 6 August.
2011 Aug 5	2011 Aug 6	Ashfall	Ash-and-lapilli fall were observed in the SE sector of the volcano, between Zafferana (10 km SE) and Viagrande (16 km SSE) and between Acitrezza (23 km SE) and Pozzillo (19 km SE) along the Ionian coast.
2011 Aug 5	2011 Aug 6	Incandescent ejecta	Weak Strombolian explosions occurred in the crater during the afternoon and gradually increased over the next few hours. The activity ended early the next day.
2011 Aug 5	2011 Aug 6	Lava fountains	Strombolian activity rapidly increased and formed a lava fountain that rose 100 m above the crater rim. Activity intensified and jets of lava rose several hundred meters high. At the climax of the eruption lava fountains exceeded 500 m in height.
2011 Aug 5	2011 Aug 6	Lava flow	Lava flowed over the E rim of the crater and towards the W slope of the Valle del Bove.
2011 Aug 5	2011 Aug 8	Thermal Anomaly	Multiple near-daily MODVOLC thermal alerts were issued.
2011 Aug 11	2011 Aug 12	Explosion	Explosions were associated with the Strombolian eruptions.
2011 Aug 11	2011 Aug 12	Ash Plume	Initially sporadic ash emissions from Etna's New SE Crater produced small grayish-brown ash plumes. The next morninng Strombolian explosions produced dark ash clouds.
2011 Aug 11	2011 Aug 12	Incandescent ejecta	In the evening and throughout the night small Strombolian explosions were observed at intervals of a few tens of minutes. The next morning the Strombolian activity intensified and was accompanied by an increase in volcanic tremor amplitude.
2011 Aug 12	- - - -	Ash Plume	Based on satellite imagery and a notice from LIRR, the Toulouse VAAC reported an ash emissions at 4.3 km altitude.
2011 Aug 12	- - - -	Ashfall	Ash- and lapilli-fall affected a relatively narrow area between Zafferana (10 km SE), and the coastal area between Giarre and Acireale, on the SE flank.
2011 Aug 12	- - - -	Lava fountains	Strombolian activity rapidly intensified, and formed a pulsating lava fountain about 100 m tall.
2011 Aug 12	- - - -	Lava flow	Lava overflowed the E rim of the crater through a deep breach formed during previous eruptions. The lava descended the W slope of the Valle del Bove in numerous lobes; the most advanced lava fronts reached the base of the steep slope above Monte Centenari.
2011 Aug 12	- - - -	Cinder Cone	Large bombs and blocks fell onto the cone surrounding the New SE Crater.
2011 Aug 12	- - - -	Bombs	Ejected bombs fell onto the cone surrounding the New SE Crater.
2011 Aug 12	2011 Aug 15	Thermal Anomaly	Eleven MODVOLC thermal alerts were issued.
2011 Aug 19	- - - -	Explosion	A powerful explosion ejected incandescent bombs and produced a small ash plume.
2011 Aug 19	- - - -	Ash Plume	Throughout the day small dilute ash was emitted.
2011 Aug 19	2011 Aug 20	Incandescent ejecta	During the evening weak Strombolian activity commenced, with small explosions occurring about every 30 minutes. Strombolian activity intensified the next day causing lava flows and lava jets.
2011 Aug 19	- - - -	Bombs	Incandescent bombs were ejected due to an explosion.
2011 Aug 20	- - - -	Ash Plume	Dense plumes of gas and tephra rose 5-6 km from the crater and drifted SW, causing ash- and lapilli-fall in several areas. Based on MTOSAT imagery and a report from LICZ, the Toulouse VAAC issued a volcanic ash advisory for a plume rising to 9.1 km altitude.
2011 Aug 20	- - - -	Ashfall	Dense plumes of gas and tephra rose 5-6 km from the crater and drifted SW, causing ash- and lapilli-fall in areas such as Paternò (22 km SSW), Ragalna (13 km SSW), and Biancavilla (16 km SW). Closer to the crater, in the Torre del Filosofo area to the S, clasts up to several tens of centimeters in diameter landed on the ground.
2011 Aug 20	- - - -	Lava fountains	Lava fountaining generated heavy fallout of large pyroclastics onto the flanks of the cone. The continuous, intense ejection of pyroclastics onto the flanks of the cone generated avalanches resembling pyroclastic flows, which descended a few hundred meters beyond the base of the cone, mainly towards the S.
2011 Aug 20	- - - -	Lava flow	Lava overflowed the rim through a breach in the E crater rim traveling towards the Valle del Bove. The lower portion of the E flank of the NSEC cone began to slide and collapse under the push of lava from within the channel. A new lava flow issued from the collapsed area, taking a more southerly path than the lava emitted until then, and divided into numerous branches.
2011 Aug 20	- - - -	Cinder Cone	Lava fountaining generated heavy fallout of large pyroclastics onto the flanks of the cone. The continuous, intense ejection of pyroclastics onto the flanks of the cone generated avalanches resembling pyroclastic flows, which descended a few hundred meters beyond the base of the cone, mainly towards the S. The morphological changes affecting the pyroclastic cone surrounding the New SE Crater were significant. Besides the collapse on the lower E flank of the cone, the S and NE rims of the cone had grown in height.
2011 Aug 20	2011 Aug 22	Thermal Anomaly	Eleven MODVOLC thermal alerts were issued.
2011 Aug 20	- - - -	VEI (Explosivity Index)	VEI 3
2011 Aug 21	- - - -	Explosion	A series of ash explosions lasted for five minutes in the early morning.
2011 Aug 21	- - - -	Ash Plume	A series of ash explosions lasted for five minutes in the early morning.
2011 Aug 27	- - - -	Explosion
2011 Aug 28	- - - -	Ash Plume	A series of ash emissions from the New SE Crater took place.
2011 Aug 28	2011 Aug 29	Incandescent ejecta	Weak Strombolian activity was visible during the evening and intensified during the night.
2011 Aug 28	2011 Aug 29	Thermal Anomaly	Five MODVOLC thermal alerts were issued.
2011 Aug 29	- - - -	Ash Plume	A dense plume rose a few kilometers above the summit before drifting toward the SSE. The lava fountaining from the vents within the crater turned into ash emissions towards the end of the event. Based on a Notice to Airmen from LIRR, webcam, and satellite imagery, the Toulouse VAAC issued an ash advisory for a plume that rose as high as 7.6 km altitude.
2011 Aug 29	- - - -	Lava fountains	Two vents within the crater emitted pulsating lava fountains up to 100 m high. At 0220 the SE flank of the cone fractured and exposed a line of new eruptive vents down to the base of the cone that produced lava fountains.
2011 Aug 29	- - - -	Lava flow	Lava overflowed the rim through a breach in the E crater rim and traveled towards the Valle del Bove. A small lava flow issued from the area affected by the collapse of a portion of the cone's ESE flank during the 20 August event. A broad lava flow fed by new vents descended into the Valle del Bove, somewhat to the S of the lava flow emitted earlier during the episode.
2011 Aug 29	- - - -	Cinder Cone	At 0220 the SE flank of the cone fractured and exposed a line of new eruptive vents down to the base of the cone that produced lava fountains.
2011 Sep 6	- - - -	Ash Plume	Emissions of ash from the New SE Crater occurred.
2011 Sep 7	- - - -	Explosion	Explosions were associated with Strombolian activity.
2011 Sep 7	2011 Sep 8	Incandescent ejecta	Sporadic, very weak Strombolian explosions from the crater started during the late evening and then continued in a subdued manner through the night. A rapid increase both in the intensity and frequency of Strombolian explosions occurred the next day.
2011 Sep 8	- - - -	Explosion	Explosions were associated with Strombolian activity.
2011 Sep 8	- - - -	Ash Plume	Ash emissions were vigorous. Brief periods of repeated emissions of brown ash mixed with white water vapor occurred from two or three vents on the N flank of the New SE Crater cone. Based on webcam, satellite data and a Notice to Airmen from LICZ, the Toulouse VAAC reported a plume containing mostly SO₂ that rose to 5.8 km altitude.
2011 Sep 8	- - - -	Lava fountains	The Strombolian activity turned into a pulsating lava fountain.
2011 Sep 8	- - - -	Lava flow	Lava flowed through a deep breach in the E crater rim and along the fracture that had opened on the SE side of the cone during 29 August. The lava overflow was accompanied by repeated collapse and rockfalls from unstable portions of the cone in that area. Lava flows descended on the W slope of the Valle del Bove; expansion of the most advanced lava fronts continued for some time after feeding of the lava had ceased. Small active lava flows were observed for many hours after the cessation of activity, remaining confined to the immediate vicinity of the crater.
2011 Sep 8	- - - -	Cinder Cone	The pyroclastic cone that grew around the New SE Crater during the recent series of eruptive episodes had undergone significant morphological changes. The S and N crater rims had further increased in height, whereas degradation and mass wasting on the SE flank had become more conspicuous. A large chunk of rock on the lower SE flank was rotated and uplifted, forming a steep-sided "spine" about 20-30 m tall, with locally vertical and sub-vertical flanks.
2011 Sep 8	2011 Sep 9	Thermal Anomaly	Ten MODVOLC thermal alerts were issued.
2011 Sep 8	- - - -	Audible Sounds	Loud detonations were audible across a vast sector of Etna's densely populated SE to E flanks.
2011 Sep 8	- - - -	Collapse	Repeated collapse and rockfalls occurred from unstable portions of the cone.
2011 Sep 19	- - - -	Ash Plume	An ash plume drifted NE.
2011 Sep 19	- - - -	Ashfall	Ash and lapilli fell in an area to the N of Giarre (16 km E).
2011 Sep 19	- - - -	Incandescent ejecta	Strombolian activity occurred as spatter.
2011 Sep 19	- - - -	Lava fountains	Lava fountains rose from multiple vents within the crater. Weak spattering continued from a vent at the SE base of the SE Crater cone.
2011 Sep 19	- - - -	Lava flow	Lava flows descended the W slope of the Valle del Bove
2011 Sep 23	- - - -	Ash Plume	Based on a pilot report, the Toulouse VAAC issued an ash advisory for a plume extending 50 km ESE of the summit at 3.7 km altitude.
2011 Sep 28	- - - -	Audible Sounds	That morning, noises originated from the New SE Crater.
2011 Sep 28	- - - -	Seismicity (tremor)	At 1600 volcanic tremor amplitude started to increase, and rhythmic ash emissions that rose from a vent located within the crater were occasionally accompanied by small Strombolian explosions.
2011 Sep 28	- - - -	Ash Plume	At 1600 volcanic tremor amplitude started to increase, and rhythmic ash emissions that rose from a vent located within the crater were occasionally accompanied by small Strombolian explosions. Based on Meteosat imagery, the Toulouse VAAC reported a small ash plume in IR imagery at 11.0 km altitude.
2011 Sep 28	- - - -	Incandescent ejecta	At 1600 volcanic tremor amplitude started to increase, and rhythmic ash emissions that rose from a vent located within the crater were occasionally accompanied by small Strombolian explosions. Starting at 1930 Strombolian activity progressively increased both in the intensity and frequency of explosions, and eventually became continuous. At 2155 activity from all vents decreased, and between 2205 and 2210 all explosive activity ceased.
2011 Sep 28	- - - -	Bombs	Around 1930 bombs and scoria were ejected well beyond the crater rim. At 2133 and 2134 two powerful explosions originating from a vent on the E rim of the crater created shock waves visible in the clouds above the crater and ejected large bombs hundreds of meters away.
2011 Sep 28	- - - -	Scoria	Around 1930 bombs and scoria were ejected well beyond the crater rim.
2011 Sep 28	- - - -	Lava flow	A small amount of lava flowed through the notch in the SE flank of the volcano at 2115 and was soon followed by explosions from a vent within the same area. A vent on the N base of the New SE Crater cone emitted a small lava flow beginning at 2136. At 2155 activity from all vents decreased, lava continued to flow until 2330. The lava flow emitted from the SE flank of the cone reached the lower portion of the W slope of the Valle del Bove, somewhat SW of Monte Centenari.
2011 Sep 28	- - - -	Lava fountains	Shortly after 2115 Strombolian activity waned for a few minutes then rapidly increased, forming a sustained lava fountain that rose as high as 800 m. Lava fountains 100-150 m high commenced from a vent on the N base of the New SE Crater cone at 2136. At 2155 activity from all vents decreased.
2011 Sep 28	- - - -	Explosion	At 2133 and 2134 two powerful explosions originating from a vent on the E rim of the crater created shock waves visible in the clouds above the crater and ejected large bombs hundreds of meters away. Between 2205 and 2210 all explosive activity ceased.
2011 Sep 28	- - - -	Ashfall	Ash fell on the S flank of Etna, Nicolosi (14 km S), and Catania (27 km S).
2011 Sep 28	- - - -	VEI (Explosivity Index)	VEI 3
2011 Sep 29	2011 Sep 30	Thermal Anomaly	Eight MODVOLC thermal alerts were issued.
2011 Oct 8	- - - -	Incandescent ejecta	At about 1300 weak and discontinuous Strombolian explosions were recorded by surveillance cameras. At around 1545 vigorous Strombolian activity was observed from numerous vents along a short fissure on the SE flank of the cone, which had first been active during 29 August.
2011 Oct 8	- - - -	Explosion	Explosions were associated with the Strombolian activity.
2011 Oct 8	- - - -	Lava flow	Lava flowed from a deep notch in the SE rim of the crater. Lava flows descended on the W slope of the Valle del Bove. Eruptive vents opened on the NE flank of the cone, approximately along the fracture that first opened during 8 September, and two small lava flows were emitted. The more voluminous lava flow traveled a few hundred meters downslope.
2011 Oct 8	- - - -	Lava fountains	The change from Strombolian activity to lava fountaining and ash emissions was audible around 1630.
2011 Oct 8	- - - -	Ash Plume	A dense ash-and-vapor plume rapidly rose above the weather clouds and drifted E. Ash emissions continued until 1945. The ash cloud drifted ENE.
2011 Oct 8	- - - -	Ashfall	The ash cloud drifted ENE and produced ash- and lapilli-fall in a narrow sector from the Ripe della Naca area and the village of Puntalazzo (13 km E) to the town of Mascali (18 km E).
2011 Oct 8	- - - -	Thermal Anomaly	Seven MODVOLC thermal alerts were issued.
2011 Oct 23	- - - -	Explosion	Weak explosive activity was recorded at 1913. Explosive activity rapidly intensified at 1940 and by 2007 the crater was completely filled with lava.
2011 Oct 23	- - - -	Ash Plume	Based on INGV webcams and satellite imagery, the Toulouse VAAC reported a small plume E of the volcano at 3.9 km altitude.
2011 Oct 23	- - - -	Incandescent ejecta	Explosive activity rapidly intensified at 1940 and by 2007 that crater was completely filled with lava.
2011 Oct 23	- - - -	Lava fountains	At 2026, Strombolian activity transitioned to continuous lava fountains that rose a few tens of meters above the crater rim. At 2036, a vent opened on the SE flank of the cone, producing a second lava fountain, leading to a significant increase in the lava effusion rate. The height of the lava fountains significantly increased after 2100, reaching 300 m above the crater.
2011 Oct 23	2011 Oct 24	Lava flow	Lava overflowed through a breach in the E crater rim and traveled towards the Valle del Bove. The lava flow continued to advance towards the Valle del Bove until about 0040 on 24 October and stagnated just upslope of Monte Centenari (at 1,900 m a.s.l.)
2011 Oct 23	- - - -	Tephra	Abundant amounts of tephra fell on the E flank of the cone, forming a dense curtain, while large incandescent blocks rolled to the base of the cone on more gently sloping terrain.
2011 Oct 23	2011 Oct 25	Thermal Anomaly	Nineteen MODVOLC thermal alerts were issued.
2011 Oct 23	- - - -	Lightning	At approximately 2229 two lightning flashes near the crater were observed.
2011 Oct 24	- - - -	Tephra	Tephra affected the N portion of Zafferana (E), Milo (ESE), Fornazzo (E), downslope across Santa Venerina (SE), Dagala del Re (ESE) to Giarre (E), and Riposto (km E).
2011 Nov 15	- - - -	Thermal Anomaly	Thermal monitoring cameras at the observatory in Catania and at Montagnola, about 3.5 km S of the summit craters, recorded a small thermal anomaly at the lower end of the eruptive fissure on the SE flank of the cone at about 0700.
2011 Nov 15	- - - -	Lava flow	A small lava flow appeared at the lower end of the eruptive fissure on the SE flank of the cone at about 0700. The lava flow spread out into several branches at the SE base of the cone, advancing only a few hundred meters. Slow lava effusion continued for a few hours from a single vent in the central portion of the eruptive fissure on the SE flank of the New SEC cone. Lava flows from the eruption traveled less than 4 km toward the floor of the Valle del Bove, immediately to the N of the Serra Giannicola ridge, stopping to the SW of Monte Centenari.
2011 Nov 15	- - - -	Incandescent ejecta	Mild Strombolian activity commenced at 0900 from within the New SEC, and spattering began from several vents along the fissure on the SE flank of the cone. This activity continued for nearly three hours, increasing very slowly. At about 1155, the activity markedly and rapidly increased both within the crater and along the fissure, and just after 1200 lava fountains and ash emissions rose from the crater.
2011 Nov 15	- - - -	Lava fountains	At about 1155, the activity markedly and rapidly increased both within the crater and along the fissure, and just after 1200 lava fountains and ash emissions rose from the crater. Lava fountains then rose from vents along the SE flank fissure. Between 1245 and 1315 jets heavily laden with incandescent bombs rose as high as 800 m above the crater.
2011 Nov 15	- - - -	Bombs	Bombs and scoria fell into the cone. The most intense phase of the eruption occurred between 1245 and 1315 when jets heavily laden with incandescent bombs rose as high as 800 m above the crater. Pyroclastic material fell onto the New SEC cone, areas well beyond the base, and the nearby old SEC cone.
2011 Nov 15	- - - -	Explosion	During this phase, explosions occurred from a vent on the N flank of the New SEC cone, likely the same vent that emitted small lava flows on 28 September and 8 October.
2011 Nov 15	- - - -	Ash Plume	Just after 1200 lava fountains and ash emissions rose from the crater. At 1230 ash emissions significantly increased, especially from a vent located in the SE portion of the New SEC, and a plume of ash and gas rose several kilometers above the summit and drifted SE. Passive ash emissions lasted until just after 1400. Based on webcam and Meteosat imagery, the Toulouse VAAC reported an ash plume moving SE at 5.5 km altitude. Two hours later it had risen to 9.1 km altitude.
2011 Nov 15	- - - -	Ashfall	Ashfall affected Zafferana Etnea (SE) and Acireale (SE).
2011 Nov 15	- - - -	Cinder Cone	Pyroclastic material fell onto the New SEC cone, areas well beyond the base, and the nearby old SEC cone. The New SEC grew in height by 10 m on the S side, bringing the total height of the cone to about 180-200 m above its base.
2011 Nov 15	- - - -	Thermal Anomaly	Three MODVOLC thermal alerts were issued.
2011 Nov 15	- - - -	VEI (Explosivity Index)	VEI 3
2012 Jan 4	2012 Jan 5	Incandescent ejecta	Several hours of Strombolian activity were observed on the SE and NE slopes starting at 2230. This activity continued into the early morning of 5 January.
2012 Jan 5	- - - -	Lava flow	Around 0200 a small lava flow spread out into several branches at the SE base of the cone.
2012 Jan 5	- - - -	Incandescent ejecta	Strombolian activity increased around 0400, generating lava fountains, from several vents within the crater that rose 100-150 m above the crater.
2012 Jan 5	- - - -	Lava fountains	Strombolian activity increased around 0400, generating lava fountains, from several vents within the crater that rose 100-150 m above the crater. Around 0515 lava fountains generated a continuous eruption of ash-and-gas plumes that rose to an altitude of 2.1-2.4 km. Around 0600 active vents along the N edge of the New SEC produced intermittent lava fountains.
2012 Jan 5	- - - -	Ashfall	Significant ashfall and pyroclastic material fell onto the flanks at 0450.
2012 Jan 5	- - - -	Cinder Cone	Significant ashfall and pyroclastic material fell onto the flanks at 0450. The N slope of New SEC showed gravitational movement due to the amount of deposited pyroclastic material.
2012 Jan 5	- - - -	Ash Plume	Around 0515 lava fountains generated a continuous eruption of ash-and-gas plumes that rose to an altitude of 2.1-2.4 km. A strong explosion opened a vent on the top side of the SE cone and generated ash plumes. Passive ash emissions lasted until 0830. Based on Webcam and satellite data, the Toulouse VAAC reported an ash plume at 5.2 km altitude. A higher plume at 7.6 km altitude appeared to contain mostly SO₂.
2012 Jan 5	- - - -	Pyroclastic flow	Small pyroclastic flows went a few hundred meters down the NE, E, and S flanks of the cone.
2012 Jan 5	- - - -	Lahar or Mudflow	Lahars traveled down the NE, E, and S flanks of the cone.
2012 Jan 5	- - - -	Explosion	The most intense phase of the eruption occurred around 0620 when a strong explosion opened a vent on the top side of the SE cone, removed a portion of the SE crater rim, and generated ash plumes.
2012 Jan 5	- - - -	Thermal Anomaly	Eight MODVOLC thermal alerts were issued.
2012 Jan 27	- - - -	Explosion	Multiple explosions produced ash emissions, Strombolian activity, and a lava jet.
2012 Jan 27	2012 Jan 28	Ash Plume	An explosion generated an ash plume at that rose 400 m above the crater at 1906. An explosive ash emission at 1124 from the vent on the W portion of the crater floor was followed by others that were less intense. Sporadic ash emissions continued the next day.
2012 Jan 27	- - - -	Incandescent ejecta	At 2140 an explosion ejected incandescent material in a narrow vertical jet that rose a few tens of meters above the crater. A small Strombolian explosion occurred at 2231.
2012 Jan 28	2012 Feb 8	Incandescent ejecta	On 8 February the New SE Crater (New SEC) of Etna entered another paroxysmal eruption episode after about 12 days of Strombolian activity.
2012 Feb 6	- - - -	Ash Plume	Mild Strombolian activity and small ash emissions continued from Etna's New Southeast Crater (New SEC).
2012 Feb 8	- - - -	Explosion	During the afternoon the Strombolian activity increased in both frequency and intensity of explosions from the vent on the W portion of the crater floor, and occasionally from a vent to the E.
2012 Feb 8	2012 Feb 9	Incandescent ejecta	During the afternoon the Strombolian activity increased in both frequency and intensity of explosions from the vent on the W portion of the crater floor, and occasionally from a vent to the E. Around 2100 the Strombolian activity slowly increased, turning into a discontinuous lava fountain around 2330.
2012 Feb 8	2012 Feb 9	Lava flow	After about 1900, lava began to spill into the deep breach on the SE crater rim and then descended to the base of the cone. The lava flow expanded around 2100. The lava flow reached the W rim around 0130, descended the flank, and branched into three different flows that reached a distance of 3 km from the New SEC.
2012 Feb 8	2012 Feb 9	Lava fountains	Around 2100 and the Strombolian activity slowly increased, turning into a discontinuous lava fountain around 2330. The next day the pulsating lava fountain rose 100-500 m above the crater before becoming a continuous jet rising 300-400 m above the crater. Around 0200 and 0400, lava fountains from the two vents within the crater rose as high as 500 m above the crater. The fountain from the E vent caused abundant fallout on the crater rim and E flank. Lava fountaining started to diminish around 0530, and then around 0545 sporadic jets rose as high as 300 m above the crater.
2012 Feb 8	2012 Feb 9	Ash Plume	Based on webcam and satellite imagery, the Toulouse VAAC reported that an eruption late in the day produced an ash plume that initially reached 8.2 km altitude and was visible in satellite imagery at 9.1 km early the next morning.
2012 Feb 8	- - - -	VEI (Explosivity Index)	VEI 3
2012 Feb 9	- - - -	Tephra	A cloud with a small amount of tephra rose 6 km above the summit and then drifted W, producing some pyroclastic fallout on the upper portion of the volcano.
2012 Feb 9	- - - -	Ashfall	Pyroclastic fallout occurred on the upper part of the volcano. The fountain from the E vent caused abundant fallout on the crater rim and E flank.
2012 Feb 9	- - - -	Explosion	The vent in the SE crater breach produced strong explosions that ejected bombs many meters in diameter. These explosions generated loud bangs that were heard all over Etna.
2012 Feb 9	- - - -	Bombs	The vent in the SE crater breach produced sporadic violent explosions that ejected bombs many meters in diameter all over the E portion of the cone.
2012 Feb 9	- - - -	Audible Sounds	These explosions generated loud bangs that were heard all over Etna.
2012 Feb 9	2012 Feb 10	Thermal Anomaly	Eleven MODVOLC thermal alerts were issued.
2012 Mar 4	- - - -	Seismicity (tremor)	The beginning of the eruption was characterized by a rapid increase in volcanic tremor amplitude coincident with Strombolian explosions that increased in intensity and frequency.
2012 Mar 4	- - - -	Explosion	The beginning of the eruption was characterized by a rapid increase in volcanic tremor amplitude coincident with Strombolian explosions that increased in intensity and frequency.
2012 Mar 4	- - - -	Incandescent ejecta	The beginning of the eruption was characterized by a rapid increase in volcanic tremor amplitude coincident with Strombolian explosions that increased in intensity and frequency.
2012 Mar 4	- - - -	Lava flow	Just after 0800 lava overflowed the deep breach in the SE rim of the crater and reached the SE base of the cone within 15 minutes, then advanced towards the W rim of the Valle del Bove.
2012 Mar 4	- - - -	Lava fountains	Explosive activity changed to continuous lava fountaining at about 0830. Lava fountaining ceased at 1032, two hours after the onset of the paroxysmal phase.
2012 Mar 4	- - - -	Ash Plume	An eruption plume developed at about 0830. The eruption column rose several kilometers above the summit of Etna. Ash and lapilli were carried NE by the wind.
2012 Mar 4	- - - -	Avalanche	Large pyroclasts fell on the steep flanks of the cone, causing avalanches.
2012 Mar 4	- - - -	Pyroclastic flow	At about 0850 small pyroclastic flows generated by the partial collapse of the eruption column mainly descended the NE flank, and somewhat down the S flank.
2012 Mar 4	- - - -	Lava flow	A lava flow was emitted from a new eruptive vent on the upper SW flank of the New SEC cone and descended into the saddle between the old and new SEC cones. The lava flow emitted from the fissure on the SW flank of the cone continued advancing for a few hours after the cessation of the activity.
2012 Mar 4	- - - -	Phreatic activity	The lava interacted with snow, causing powerful explosions and small pyroclastic flows. These phreatic explosions generated jets of vapor and launched rock fragments to distances of several tens of meters.
2012 Mar 4	- - - -	Lahar or Mudflow	Phreatic explosions from the lava interacting with snow resulted in a lahar which traveled toward the "Belvedere" monitoring station, on the W rim of the Valle del Bove, and passed a few tens of meters to the N of the monitoring instruments.
2012 Mar 4	- - - -	Lava flow	A lava flow also issued from an eruptive fissure on the upper N flank of the cone and descended a few hundred meters to the NE, surrounding the N base of the cone. After descending the steep W slope of the Valle del Bove, the flow split into several branches on the more gently sloping terrain. These branches exceeded in length those of 9 February, reaching a total distance of about 3.5 km from the crater.
2012 Mar 4	- - - -	Ashfall	Ash and lapilli were carried NE by the wind, affecting the areas around Piedimonte, Etneo, and Taormina. Fine ash fell as far as the Messina area and southern Calabria.
2012 Mar 4	- - - -	Cinder Cone	The pyroclastic cone of the New SEC had grown in height, mainly on its N rim.
2012 Mar 5	2012 Mar 6	Thermal Anomaly	Seven MODVOLC thermal alerts were issued.
2012 Mar 17	- - - -	Ash Plume	Minor ash content rose from New SE Crater.
2012 Mar 18	- - - -	Seismicity (tremor)	In the early morning hours, incandescence intensified due to Strombolian activity on the crater floor, and volcanic tremor amplitude rapidly increased.
2012 Mar 18	- - - -	Incandescent ejecta	In the early morning incandescence intensified due to Strombolian activity on the crater floor.
2012 Mar 18	- - - -	Lava flow	Just before 0700 lava flowed through the deep breach in the SE crater rim. The main lava flow descended the steep W slope of the Valle del Bove. Several lava lobes, however, took a more northerly path to areas covered with thick snow. Similar to the previous episodes, the lava that flowed through the breach in the SE crater rim advanced for several hours after the cessation of the paroxysmal activity into the upper part of the Valle del Bove. The lava reached a distance of about 4 km from the source, stagnating S of Monte Centenari.
2012 Mar 18	- - - -	Phreatic activity	The main lava flow descended the steep W slope of the Valle del Bove. Several lava lobes, however, took a more northerly path to areas covered with thick snow. The interaction of the lava and snow led to rapid melting of the snow, generating small lahars, and strong explosions that produced ground-hugging vapor-and-ash clouds resembling pyroclastic flows, which repeatedly descended on the floor of the Valle del Bove. The vapor-and-ash clouds rose 1-1.5 km above the floor of the Valle del Bove. This phenomenon continued intermittently for some time after the cessation of the lava fountaining and ash emission, until about 1130.
2012 Mar 18	- - - -	Lahar or Mudflow	Several lava lobes, took a northerly path to areas covered with thick snow. The interaction of the lava and snow led to rapid melting of the snow, generating small lahars.
2012 Mar 18	- - - -	Explosion	Several lava lobes took a northerly path to areas covered with thick snow. The interaction of the lava and snow led to strong explosions that produced ground-hugging vapor-and-ash clouds resembling pyroclastic flows, which repeatedly descended on the floor of the Valle del Bove.
2012 Mar 18	- - - -	Pyroclastic flow	Several lava lobes took a northerly path to areas covered with thick snow. The interaction of the lava and snow led to strong explosions that produced ground-hugging vapor-and-ash clouds resembling pyroclastic flows, which repeatedly descended on the floor of the Valle del Bove.
2012 Mar 18	- - - -	Ash Plume	The vapor-and-ash clouds rose 1-1.5 km above the floor of the Valle del Bove.
2012 Mar 18	- - - -	Ash Plume	At about 0825 the ash content in the gas plume rising from the crater became more significant. A plume rose 4-5 km above Etna and drifted E. Strong ash emission continued without significant variations until about 1040. The last ash clouds were observed around 1110. Based on information from INGV, webcam and satellite imagery, and pilot reports, the Toulouse VAAC issued an ash advisory from a significant eruption for an ash plume at 9.1 km altitude.
2012 Mar 18	- - - -	Lava fountains	Pulsating lava fountains from a vent on the crater floor rose about 100 m high. Shortly before 0900 two vents were active within the crater and a jet of lava was emitted from another vent within the breach in the SE crater rim. During 0900-0915 lava fountaining was essentially continuous from all three vents. Lava fountaining continued without significant variations until about 1040 when it diminished.
2012 Mar 18	- - - -	Avalanche	An intense shower of coarse-grained pyroclastic material falling onto the N and NE flanks of the cone generated avalanches and clouds of rock and dust, which traveled to the base of the cone.
2012 Mar 18	- - - -	Ashfall	Ash and lapilli fell mainly in the area between the villages of Zafferana Etnea and Sant'Alfio, extending toward the Ionian Sea between Riposto and Pozzillo.
2012 Mar 18	- - - -	Lava flow	A small lava flow, emitted from a fracture on the N flank of the cone, followed the same path as a flow emitted from the same fracture during the 4 March paroxysm, and traveled a few hundred meters.
2012 Mar 18	2012 Mar 19	Thermal Anomaly	Fourteen MODVOLC thermal alerts were issued.
2012 Mar 18	- - - -	VEI (Explosivity Index)	VEI 3
2012 Apr 1	- - - -	Lava fountains	Tall lava fountains rose from vents within the crater and on the SE flank of its cone.
2012 Apr 1	- - - -	Ash Plume	A gas-and-tephra plume rose from NSEC. Based on satellite imagery, the Toulouse VAAC reported an ongoing eruption with an ash plume that rose as high as 10.4 km altitude.
2012 Apr 1	- - - -	Lava flow	Lava flows descended the flank of the cone towards the Valle del Bove.
2012 Apr 1	- - - -	Ashfall	Ash and lapilli fell over the SE sector of the volcano, affecting mainly the area between Monterosso and Zafferana Etnea, but also the area between Acireale and Giarre.
2012 Apr 1	2012 Apr 2	Thermal Anomaly	Thirteen MODVOLC thermal alerts were issued.
2012 Apr 1	- - - -	VEI (Explosivity Index)	VEI 3
2012 Apr 12	- - - -	Lava fountains	The episode included lava fountains.
2012 Apr 12	- - - -	Ash Plume	The episode included emissions of ash and lapilli.
2012 Apr 12	- - - -	Lava flow	The episode included lava flows that descended the Valle del Bove.
2012 Apr 12	- - - -	Phreatic activity	The episode included lava flows that explosively interacted with snow cover.
2012 Apr 12	- - - -	Thermal Anomaly	A MODVOLC thermal alert was issued.
2012 Apr 21	2012 Apr 22	Ash Plume	A series of small ash emissions that observed by web cameras drifted downslope to the E.
2012 Apr 23	- - - -	Lava flow	A tiny lava flow issued from an area in the upper portion of the fissure that cuts the SE flank of the cone. The lava flow slowly advanced a few hundred meters toward the Valle del Bove, but stagnated on the W rim. Another lava flow was produced later in the day.
2012 Apr 23	2012 Apr 24	Incandescent ejecta	At around 1800 the effusive vent in the upper portion of the fissure that cuts the SE flank of the cone started to vigorously spatter. A second vent became active a few tens of meters further upslope, which initially ejected spatter, but activity rapidly evolved into frequent Strombolian explosions.
2012 Apr 23	- - - -	Explosion	During the following hours, sporadic explosions were also observed from a vent located within the New SEC.
2012 Apr 24	- - - -	Lava fountains	At 0210 the Strombolian activity showed a marked increase and turned into sustained lava fountaining at 0230. The phase of most intense lava fountaining lasted approximately 25 minutes, from 0240 until 0305, after which the intensity rapidly decreased and returned to Strombolian activity, before ceasing completely around 0340.
2012 Apr 24	- - - -	Ash Plume	A plume with a heavy load of ash and lapilli rose a few kilometers and drifted NE.
2012 Apr 24	- - - -	Ashfall	A plume with a heavy load of ash and lapilli rose a few kilometers, drifted NE, and produced ashfall 15-17 km NE in Linguaglossa, Piedimonte, and Presa.
2012 Apr 24	- - - -	Lapilli	The upper part of the plume drifted E and produced pea-sized lapilli fall in the area between Fornazzo (10 km E) and Giarre (17 km E).
2012 Apr 24	2012 Apr 25	Thermal Anomaly	Seventeen MODVOLC thermal alerts were issued.
2012 May 25	- - - -	Ash Plume	Based on information from INGV Catania, the Toulouse VAAC issued a volcanic ash advisory, but ash was not detected in satellite imagery.
2012 Jun 1	- - - -	Ash Plume	Based on information from INGV Catania, the Toulouse VAAC issued a volcanic ash advisory, but ash was not detected in satellite imagery.
2012 Jun 9	- - - -	Ash Plume	Based on information from INGV Catania, the Toulouse VAAC issued a volcanic ash advisory, but ash was not detected in satellite imagery.

Episode 4 | Eruption

Bocca Nuova (BN)

2011 Jun 14 - 2011 Jul 15

Evidence from Observations: Reported

A brief episode of activity occurred at Bocca Nuova during June-July 2011 after six months of inactivity. Explosions produced ash plumes, Strombolian activity, and a small lava flow.

List of 9 Events for Episode 4 at Bocca Nuova (BN)

Start Date	End Date	Event Type	Event Remarks
2011 Jun 14	- - - -	Ash Plume	Ash rose 200-250 m above the crater rim and drifted E.
2011 Jun 14	2011 Jul 15	VEI (Explosivity Index)	VEI 1
2011 Jun 15	2011 Jun 17	Ash Plume	During limited periods of good visibility, sporadic small reddish-to-grayish-brown ash plumes were observed to occur every 5-15 minutes.
2011 Jun 16	- - - -	Ash Plume	Based on a METEOSAT image, the Toulouse VAAC issued an ash advisory for an ash plume at 3.7 km altitude.
2011 Jun 21	- - - -	Ash Plume	Based on a volcanic activity report from LICZ, the Toulouse VAAC issued an ash advisory for a plume extending 45 km S at 3.9 km altitude.
2011 Jun 22	- - - -	Ash Plume	Based on a volcanic activity report from LICZ, the Toulouse VAAC issued an ash advisory for a plume extending 45 km S at 4.3 km altitude.
2011 Jul 11	2011 Jul 15	Incandescent ejecta	Strombolian activity began from Etna's Bocca Nuova crater, representing the first magmatic eruption since 2002.
2011 Jul 12	2011 Jul 13	Bombs	The strongest explosions ejected incandescent bombs several tens of meters above the crater rim. Most bombs fell back into the crater.
2011 Jul 15	- - - -	Lava flow	Immediately to the W of the explosive vent, a lava flow was issuing from underneath a sheet of pyroclastic material deposited by the nearby Strombolian activity. The flow cascaded into a deeper depression in the W central portion of the crater floor.

Episode 5 | Eruption

Bocca Nuova (BN)

2012 Jul 2 - 2012 Oct 7

Evidence from Observations: Reported

Activity renewed at Bocca Nuova on 2 July 2012, nearly one year after a month-long period of Strombolian and effusive activity. Explosions of ash, Strombolian ejecta, and lava flows occurred during July-August and early October 2012.

List of 19 Events for Episode 5 at Bocca Nuova (BN)

Start Date	End Date	Event Type	Event Remarks
2012 Jul 2	- - - -	Incandescence	Weak incandescence began to illuminate a gas plume rising from Bocca Nuova, marking the resumption of eruptive activity in this crater nearly one year after a short period of Strombolian and effusive activity.
2012 Jul 3	2012 Jul 24	Incandescent ejecta	Strombolian activity occurred at a single vent, a few meters in diameter, at the base of the SE crater wall. Incandescent bombs and scoria ejected by the explosions fell back around the vent. On 4 July, a few bombs fell outside the E crater rim. Similar activity was also observed on 11 and 13 July. During the night of 16-17 July, continuous, bright glow from the crater was visible from populated areas around the volcano. Activity was virtually continuous for three weeks.
2012 Jul 3	2012 Jul 27	Cinder Cone	A pyroclastic cone grew around the explosive vent. The pyroclastic cone grew 30-40 m before the activity ceased. Renewed activity on 26 July increased the size of the cone.
2012 Jul 4	2012 Jul 24	Lava flow	Lava was emitted from vents on the flanks of the pyroclastic cone that had begun to grow around the explosive vent. Rarely, lava was emitted from the main explosive vent. The lava progressively covered the crater floor next to the pyroclastic cone before the activity ceased on 24 July.
2012 Jul 7	2012 Jul 10	Thermal Anomaly	Three MODVOLC thermal alerts were issued.
2012 Jul 13	2012 Jul 23	Thermal Anomaly	Multiple near-daily MODVOLC thermal alerts were issued.
2012 Jul 25	- - - -	Ash Plume	Frequent ash emissions were mostly due to explosions, and possibly from minor collapses of the summit area of the new cone.
2012 Jul 25	- - - -	VEI (Explosivity Index)	VEI 1
2012 Jul 26	2012 Aug 13	Incandescent ejecta	Episodic activity occurred every few days during the period. Frequent Strombolian explosions occurred from a vent located on the W flank of the cone on 26-27 July. Small Strombolian explosions from a vent located on the S flank of the pyroclastic cone occurred during 29 July-1 August. Strombolian activity recurred on 3-4, 6-7, 10-11, and 13 August. Some of the explosions ejected incandescent pyroclastic material well above the crater rim.
2012 Jul 26	2012 Aug 7	Lava flow	Lava flows issued from a vent located on the W flank of the cone on 26 July. The next day, the lava had almost completely filled the central subsidence pit on the floor of Bocca Nuova, and the cone had grown in height. Lava issued from a vent located on the S flank of the pyroclastic cone during 29 July-1 August. Additional lava flows occurred on 3-4 and 6-7 August.
2012 Jul 26	2012 Aug 6	Thermal Anomaly	Multiple near-daily MODVOLC thermal alerts were issued.
2012 Jul 28	2012 Aug 13	Ash Plume	There were intermittent ash emissions on 28 July, 2, 4, 6, and 11-13 August. They were particularly frequent on 13 August, and produced small, brownish-gray clouds of fine-grained tephra. Some of the ash emissions later that evening were accompanied by ejected incandescent material.
2012 Aug 10	2012 Aug 11	Thermal Anomaly	Five MODVOLC thermal alerts were issued.
2012 Oct 2	2012 Oct 8	Incandescent ejecta	During the evening of 2 October weak Strombolian activity resumed within Etna's Bocca Nuova crater, from the same vent on the SE part of the crater floor that was active in July and August 2012. Over the next few days the activity slowly intensified. The intensity of both the eruptive activity and the volcanic tremor amplitude peaked just after midnight on 7 October, and strong glow from the crater was observed from nearby populated areas. Activity decreased at 0430, and the next day dropped to the lowest levels recorded for many weeks.
2012 Oct 3	2012 Oct 8	Lava flow	A small inter-crater lava flow appeared on the S part of the floor. Lava flowed towards the W part of the crater floor and lava fountains pulsated during the peak of activity.
2012 Oct 3	2012 Oct 8	Cinder Cone	Activity slowly intensified and a small new cone developed over the old cone formed during July-August, which had subsequently nearly completely collapsed.
2012 Oct 4	2012 Oct 7	Thermal Anomaly	Five MODVOLC thermal alerts were issued.
2012 Oct 6	- - - -	Seismicity (tremor)	Volcanic tremor amplitude and eruptive activity rapidly increased in the evening.
2012 Oct 6	2012 Oct 7	Lava fountains	Lava flowed towards the W part of the crater floor and lava fountains pulsated. Some of the lava jets rose well above the crater rim before activity diminished.

Episode 6 | Eruption

New Southeast Crater (NSEC)

2012 Nov 21 - 2013 Apr 27

Evidence from Observations: Reported

Activity resumed at NSEC after about an 8-month break on 21 November 2012. Numerous eruptive episodes produced lava fountains rising hundreds of meters, significant tephra fallout, Strombolian explosions, ash emissions, pyroclastic flows, cinder cone formation, and lava flows until at least 27 April 2013; lava flows may have continued for a few days.

List of 189 Events for Episode 6 at New Southeast Crater (NSEC)

Start Date	End Date	Event Type	Event Remarks
2012 Nov 21	2012 Dec 2	Incandescence	A weak glow emanated from Etna's New Southeast Crater (NSEC) caused by the emission of high-temperature gas. The glow was most intense during 1-2 December, then rapidly diminished.
2012 Nov 22	- - - -	Seismicity (volcanic)	A seismic swarm, consisting of around seventy events, occurred below the NW flank with epicenters located in the area of Monte Maletto.
2012 Dec 24	- - - -	Incandescence	A glow reappeared.
2012 Dec 25	2012 Dec 27	Ash Plume	Sporadic and weak ash emissions from NSEC were accompanied by increased gas emissions.
2013 Jan 3	- - - -	Incandescence	A strong glow was briefly observed.
2013 Jan 20	- - - -	Seismicity (tremor)	In the early morning volcanic tremor amplitude rose, and was much more pronounced at the EBEL station about 700 m from the New Southeast Crater (NSEC) than at the ECPN station much closer to Bocca Nuova. Contemporaneously, there were reports of glow illuminating the clouds over the summit of Etna. Seismic and infrasonic data analyses suggested that the activity occurred at NSEC and consisted of mild Strombolian explosions, which ceased a few hours later.
2013 Jan 20	- - - -	Incandescent ejecta	Seismic and infrasonic data analyses suggested that the activity occurred at NSEC and consisted of mild Strombolian explosions, which lasted for a few hours.
2013 Jan 22	2013 Jan 23	Seismicity (tremor)	Tremor rapidly rose at 1840 again producing a stronger signal at the EBEL station. At about 0600 on 23 January the tremor amplitude decreased and the last explosion visible on camera footage was recorded at 0635.
2013 Jan 22	- - - -	Explosion	Glow from Strombolian activity was first recorded by a camera at 1856; the activity then became more clearly visible and the Strombolian explosions became more frequent. At about 0600 on 23 January the tremor amplitude decreased and the last explosion visible on camera footage was recorded at 0635.
2013 Jan 22	2013 Jan 23	Audible Sounds	Noises produced by the explosions were audible to residents on the E flank.
2013 Jan 22	2013 Jan 23	Incandescent ejecta	Glow from Strombolian activity was first recorded by a camera at 1856; the activity then became more clearly visible and the Strombolian explosions became more frequent. Eruptive activity continued for nearly 12 hours with minor fluctuations.
2013 Jan 22	- - - -	Bombs	Incandescent bombs were ejected as high as 100 m above the crater rim.
2013 Jan 22	- - - -	Tephra	The strongest explosions were followed by abundant fallout of coarse-grained tephra onto the flanks of the NSEC cone.
2013 Jan 22	- - - -	Thermal Anomaly	A MODVOLC thermal alert was issued.
2013 Jan 23	- - - -	Ash Plume	After the last explosion, a few small, sporadic puffs of vapor mixed with ash rose from the crater and drifted E.
2013 Jan 31	2013 Feb 1	Ash Plume	Ash emissions at New Southeast Crater (NSEC) were nearly continuous for intervals lasting from a few minutes to more than one hour. Plumes rose no higher than 100 m above the crater rims.
2013 Feb 2	- - - -	Explosion	After 0330 sporadic small explosions ejected incandescent pyroclastic material up to a few tens of meters above the crater rim. The strongest explosions (at 0345, 0400, 0409, and 0411) ejected glowing bombs onto the flanks of the NSEC cone. Small Strombolian explosions resumed in NSEC at 0512.
2013 Feb 2	- - - -	Incandescent ejecta	After 0330 sporadic small explosions ejected incandescent pyroclastic material up to a few tens of meters above the crater rim. Small Strombolian explosions resumed in NSEC at 0512. Activity at NSEC started to decrease at 0530 then ceased just before 0600. Weak intracrater activity continued for a few more hours and then by 0900 the episode was over.
2013 Feb 2	- - - -	Bombs	The strongest explosions (at 0345, 0400, 0409, and 0411) ejected glowing bombs onto the flanks of the NSEC cone.
2013 Feb 3 (?)	2013 Feb 5 (?)	Ash Plume	During the days following the 2 February eruptive episode at Etna intermittent emissions of small quantities of ash were repeatedly observed.
2013 Feb 5	- - - -	Seismicity (tremor)	Seismic data showed an instantaneous increase of tremor at 1020; volcanic tremor amplitude rose to a peak within a few minutes after the start of the activity, and began to descend after less than one hour.
2013 Feb 5	2013 Feb 6	Incandescent ejecta	A webcam recorded weak Strombolian activity at NSEC in the evening, which continued until daybreak the next day,
2013 Feb 6	2013 Feb 8	Ash Plume	Sporadic ash emissions from NSEC were observed, although poor weather conditions often prevented observations.
2013 Feb 8	- - - -	Incandescence	In the evening weak glow from NSEC was intermittently visible.
2013 Feb 13	2013 Feb 14	Incandescence	A camera recorded incandescence from Etna's New Southeast Crater (NSEC).
2013 Feb 14	- - - -	Thermal Anomaly	A MODVOLC thermal alert was issued.
2013 Feb 15	- - - -	Bombs	In the early hours of the day incandescent bombs were ejected just higher than the crater rim.
2013 Feb 15	2013 Feb 17	Incandescent ejecta	Strombolian activity gradually intensified on 17 February along with volcanic tremor amplitude. Small Strombolian explosions occurred every 1-2 seconds at daybreak, launching coarse-grained pyroclastic material a few tens of meters above the crater rim. After reaching a peak around 0700, activity started to diminish; a few hours later, the volcanic tremor amplitude returned to background levels, and by the evening there was no sign of eruptive activity.
2013 Feb 18	2013 Feb 19	Incandescent ejecta	Shortly before midnight on 18 February, the clouds dissipated from the summit area, revealing continuous weak Strombolian activity within NSEC. The eruptive activity started to intensify from one vent in the center of the crater shortly after midnight.
2013 Feb 19	- - - -	Seismicity (tremor)	During 0000-0200 the volcanic tremor amplitude rose gradually, then distinctly increased after 0200.
2013 Feb 19	- - - -	Lava flow	Not long after 0200, lava started to overflow through the deep notch in the SE crater rim, expanding slowly toward the steep W slope of the Valle del Bove. The main lava flow advanced SE, and a small lava flow that developed on the flank below the pit crater traveled along the March 2012 fracture zone between the old and new SEC cones.
2013 Feb 19	- - - -	Ash Plume	At 0457 the small pit crater that had formed on the SW rim of the NSEC on 27 August 2012 started to emit ash, and repeated rim collapses generated small landslides. During the interval from 0503 until 0507, several vents became active along a fracture from the pit crater to the notch in the SE crater rim. A dense cloud of ash rose and drifted E. Small avalanches of incandescent material generated ash clouds. During the interval between 0600 and 0615, the activity was characterized by emission of a dense ash plume with frequent jets of lava and powerful explosions, which launched large glowing bombs beyond the summit of the old Southeast Crater cone. After 0615 only ash emission persisted. Ash emissions from the NSEC diminished notably and became discontinuous; the last, weak puffs of ash were observed around 0710. Based on satellite imagery and INGV webcam images, the Toulouse VAAC reported an ash emission at 7.3 km altitude that was composed mainly of SO₂.
2013 Feb 19	- - - -	Lava fountains	Activity of the main vent within the crater rapidly increased, and at 0503 a lava fountain rose about 200 m above the summit of the cone. At 0515 lava fountains rose 300-500 m above the crater rim and produced bombs and spatter that covered the S flank of the cone. During 0516-0518 the S flank of the cone was veiled by a dense curtain of fallout from the lava fountains. Lava fountaining from the pit crater started to diminish around 0525, and at 0535 transitioned into ash emissions alternating with brief jets of incandescent lava. At 0545, one single vent, in the central portion of the NSEC, continued to produce lava fountains about 200 m high. A few minutes later, however, a new lava flow started to descend the lower SE flank of the cone, possibly after the opening of a new eruptive vent in the lower part of the notch cutting that sector of the cone. Surveillance cameras showed brief lava fountaining at that site, before all lava fountaining ceased shortly before 0600. During the interval between 0600 and 0615, the activity was characterized by emission of a dense ash plume with frequent jets of lava and powerful explosions, which launched large glowing bombs beyond the summit of the old Southeast Crater cone.
2013 Feb 19	- - - -	Tephra	The entire NSEC cone was subjected to heavy fallout of coarse-grained pyroclastic material.
2013 Feb 19	- - - -	Bombs	At 0515 lava fountains rose 300-500 m above the crater rim and produced bombs and spatter that covered the S flank of the cone. During the interval between 0600 and 0615, the activity was characterized by emission of a dense ash plume with frequent jets of lava and powerful explosions, which launched large glowing bombs beyond the summit of the old Southeast Crater cone.
2013 Feb 19	- - - -	Phreatic activity	Around 0515, dense vapor clouds rose from the upper E flank of Etna, generated by the copious fallout of incandescent pyroclastic material onto the snow.
2013 Feb 19	- - - -	Pyroclastic flow	At 0519, a more substantial avalanche of fresh material detached from the S flank of the cone, generating a small pyroclastic flow that expanded a few hundred meters first S and then E.
2013 Feb 19	- - - -	Lahar or Mudflow	At 0536 a thermal monitoring camera recorded a lahar from near the Belvedere area, which was followed by a broad lava flow that descended the steep slope and reached the base after less than 20 minutes. During its descent, the lava continued to melt snow, producing numerous small lahars. At 0550 a second lava flow N of the first also generated lahars. Finally, at about 0600, a third lava flow, which generated a lahar, descended the W slope of the Valle del Bove to the S of the first flow.
2013 Feb 19	2013 Feb 22	Lava flow	At 0536 a thermal monitoring camera recorded a lahar from near the Belvedere area, which was followed by a broad lava flow that descended the steep slope and reached the base after less than 20 minutes. During its descent, the lava continued to melt snow, producing numerous small lahars. At 0550 a second lava flow N of the first also generated lahars. Finally, at about 0600, a third lava flow, which generated a lahar, descended the W slope of the Valle del Bove to the S of the first flow. The emission of lava from below the Belvedere station decreased and completely ceased during the afternoon of 22 February.
2013 Feb 19	- - - -	Lava flow	A few minutes after 0545, a new lava flow started to descend the lower SE flank of the cone, possibly after the opening of a new eruptive vent in the lower part of the notch cutting that sector of the cone. Slow lava emissions continued for a few hours from the lowermost vent, which had opened shortly after 0547 on the SE flank of the cone.
2013 Feb 19	- - - -	Explosion	During the interval between 0600 and 0615, the activity was characterized by emission of a dense ash plume with frequent jets of lava and powerful explosions, which launched large glowing bombs beyond the summit of the old Southeast Crater cone.
2013 Feb 19	- - - -	Tephra	Tephra fell in a narrow area extending from the NSEC towards the E, including Milo and Fornazzo (10 km E), Giarre (16 km E) and Riposto (18 km E).
2013 Feb 19	- - - -	Cinder Cone	There was pronounced cone growth at NSEC during 19-20 Feb 2013.
2013 Feb 19	2013 Feb 21	Thermal Anomaly	Multiple near-daily MODVOLC thermal alerts were issued.
2013 Feb 20	- - - -	Lava fountains	Sezione di Catania - Osservatorio Etneo reported two episodes of lava fountaining from Etna's New Southeast Crater (NSEC) on 20 February. The first episode's most energetic phase occurred during 0150-0235, producing an ash plume that drifted ESE, small lahars, lava flows from the fissure cutting the SE crater rim, and lava flows from a new eruptive fissure which opened on the lower SW flank of the cone. The second episode began just after 1415 and ended at about 1450.
2013 Feb 20	- - - -	Ash Plume	The first episode's most energetic phase occurred during 0150-0235, producing an ash plume that drifted ESE. During the late morning, eruptive activity at NSEC re-intensified. The second episode began just after 1415 and ended at about 1450. An ash cloud drifted E. The Toulouse VAAC reported an ash plume at 5.5 km altitude.
2013 Feb 20	- - - -	Lahar or Mudflow	The first episode's most energetic phase occurred during 0150-0235, producing an ash plume that drifted ESE, small lahars, lava flows from the fissure cutting the SE crater rim, and lava flows from a new eruptive fissure which opened on the lower SW flank of the cone.
2013 Feb 20	2013 Feb 22	Lava flow	The first episode's most energetic phase occurred during 0150-0235, producing an ash plume that drifted ESE, small lahars, lava flows from the fissure cutting the SE crater rim, and lava flows from a new eruptive fissure which opened on the lower SW flank of the cone. After the cessation of lava fountaining, weak spattering and low-rate lava emission continued from two small fissures at the SE base of the cone. The second episode began just after 1415 and ended at about 1450. An ash cloud drifted E, and new lava flows traveled towards the Valle del Bove, following the paths of previous flows. Slow-moving lava flows from the fissures at the SE base of the NSEC continued into the next day, accompanied by sporadic, weak Strombolian explosions at the NSEC. The emission of lava from the two effusive vents at the SE base of the NSEC cone decreased and completely ceased during the afternoon of 22 February.
2013 Feb 20	- - - -	Incandescent ejecta	After the cessation of lava fountaining, weak spattering and low-rate lava emission continued from two small fissures at the SE base of the cone. During the late morning, eruptive activity at NSEC re-intensified. Slow-moving lava flows from the fissures at the SE base of the NSEC continued into the next day, accompanied by sporadic, weak Strombolian explosions at the NSEC.
2013 Feb 21	2013 Feb 22	Lava flow	At 0233 a new vent opened high on the W slope of the Valle del Bove and produced a lava flow that melted snow, creating lahars and voluminous steam plumes. Cloud cover periodically prevented observations, but at 0540 the clouds were illuminated, and at 0545 a lava flow emerged from the cloud cover. After the cessation of the explosive activity, effusive activity continued from the eruptive vents, feeding two lava flows that traveled 2.5 km down to the base of the steep W slope of the Valle del Bove. This activity continued into the morning of 22 February.
2013 Feb 21	- - - -	Lahar or Mudflow	At 0233 a new vent opened high on the W slope of the Valle del Bove and produced a lava flow that melted snow, creating lahars and voluminous steam plumes.
2013 Feb 21	- - - -	Phreatic activity	At 0233 a new vent opened high on the W slope of the Valle del Bove and produced a lava flow that melted snow, creating lahars and voluminous steam plumes.
2013 Feb 21	- - - -	Incandescent ejecta	At about 0300 Strombolian activity resumed at the NSEC; the activity became virtually continuous by 0440 and produced jets of incandescent lava that rose at most 100 m above the crater rim.
2013 Feb 21	- - - -	Lava fountains	At about 0300 Strombolian activity resumed at the NSEC; the activity became virtually continuous by 0440 and produced jets of incandescent lava that rose at most 100 m above the crater rim.
2013 Feb 21	- - - -	Ash Plume	An ash plume drifted N, causing ashfall in the area between Randazzo (15 km NNE) and Linguaglossa (7 km NE), at Patti on the Tyrrhenian (N coast of Sicily), and as far as Lipari (more than 80 km N).
2013 Feb 21	- - - -	Ashfall	An ash plume drifted N, causing ashfall in the area between Randazzo (15 km NNE) and Linguaglossa (7 km NE), at Patti on the Tyrrhenian (N coast of Sicily), and as far as Lipari (more than 80 km N).
2013 Feb 21	- - - -	Scoria	Scoria clasts up to 15 cm in diameter also fell in Linguaglossa.
2013 Feb 23	- - - -	Thermal Anomaly	At about 1625 thermal anomalies were detected from NSEC and 15 minutes later lava was visible from the vent at the SE base of the NSEC cone.
2013 Feb 23	2013 Feb 24	Lava flow	At about 1625 thermal anomalies were detected from NSEC and 15 minutes later lava was visible from the vent at the SE base of the NSEC cone. By nightfall the lava flow and Strombolian activity were visible from populated areas on the S and E flanks, although cloud cover hampered views. Activity intensified during 1900-1930; lava fountains rose at most 150 m above the crater rim and a well-fed lava flow spilled through the breach in the SE crater rim and traveled toward the W slope of the Valle del Bove. During the morning of 24 February, the lava flow emitted from NSEC continued to be fed, probably by one or more vents near Belvedere.
2013 Feb 23	- - - -	Incandescent ejecta	By nightfall the lava flow and Strombolian activity were visible from populated areas on the S and E flanks, although cloud cover hampered views. Activity intensified during 1900-1930. During that time, the emission of pyroclastic material increased dramatically, forming a dense plume that drifted NE; the entire NE flank, from the NSEC to Pizzi Deneri and beyond, was covered with a sheet of incandescent material. At 2014 the height of the lava fountains rapidly decreased, and two minutes later, the activity had changed to Strombolian explosions that ejected incandescent tephra up to 100 m above the crater rim. At 2030 all explosive activity was essentially over.
2013 Feb 23	- - - -	Ash Plume	During 1900-1930 the emission of pyroclastic material increased dramatically, forming a dense plume that drifted NE. Based on satellite data and INGV webcam images, the Toulouse VAAC reported an ash emission at 7.3 km altitude that was rapidly dissipating.
2013 Feb 23	- - - -	Lava fountains	Activity intensified during 1900-1930; lava fountains rose at most 150 m above the crater rim. Within the next 10 minutes jets of lava rose 500-800 m above the rim. High lava fountaining continued for about 35 minutes. At 2014 the height of the lava fountains rapidly decreased, and two minutes later, the activity had changed to Strombolian explosions that ejected incandescent tephra up to 100 m above the crater rim.
2013 Feb 23	- - - -	Bombs	Eyewitnesses reported the fall of large clasts, some incandescent, in the area of Monte Baracca, ~5 km NE of the NSEC.
2013 Feb 24	2013 Feb 25	Thermal Anomaly	Eight MODVOLC thermal alerts were issued.
2013 Feb 27	- - - -	Ash Plume	Based on MSG satellite information, a pilot report, and INGV observation, the Toulouse VAAC reported an ash emission composed of mostly SO₂ at 3.7 km altitude.
2013 Feb 28	- - - -	Explosion	Weak explosive activity and sporadic weak ash emissions at New SE Crater (NSEC) were observed during the early morning hours. Weak Strombolian activity in the W part of the NSEC appeared at 0917. Thirteen minutes later Strombolian activity was occurring at the main vent in the center of NSEC.
2013 Feb 28	- - - -	Ash Plume	Weak explosive activity and sporadic weak ash emissions at New SE Crater (NSEC) were observed during the early morning hours. Activity during 0930-1030 generated a dense gas plume containing modest quantities of ash.
2013 Feb 28	- - - -	Incandescent ejecta	Weak explosive activity and sporadic weak ash emissions at New SE Crater (NSEC) were observed during the early morning hours. Weak Strombolian activity in the W part of the NSEC appeared at 0917. Thirteen minutes later Strombolian activity was occurring at the main vent in the center of NSEC. At 1030, at least three vents were erupting including the former "pittino" to the W, in the saddle between the old SEC cone and NSEC cone.
2013 Feb 28	- - - -	Seismicity (tremor)	Around 0930, the volcanic tremor amplitude started to rise. During the following hour, eruptive activity gradually increased, while the volcanic tremor amplitude increased rapidly.
2013 Feb 28	- - - -	Lava flow	At 1040 lava flowed through the through the deep breach cutting the SE crater rim.
2013 Feb 28	- - - -	Lava fountains	At 1105, explosive activity increased dramatically and lava fountains rose about 100 m above the crater rim.
2013 Feb 28	- - - -	Explosion	From 1115 on, frequent powerful explosions generated visible shock waves and heavily showered the NSEC cone with large volcanic bombs.
2013 Feb 28	- - - -	Bombs	From 1115 on, frequent powerful explosions generated visible shock waves and heavily showered the NSEC cone with large volcanic bombs.
2013 Feb 28	- - - -	Ash Plume	The activity intensified further between 1117 and 1122, accompanied by a conspicuous cloud of vapor and brown ash issued from the saddle between the two SEC cones. This cloud marked the progressive collapse of a large portion of the saddle, which destroyed nearly all of the SW flank of the NSEC cone, and parts of the E flank of the old SEC cone.
2013 Feb 28	- - - -	Collapse	This cloud marked the progressive collapse of a large portion of the saddle, which destroyed nearly all of the SW flank of the NSEC cone, and parts of the E flank of the old SEC cone.
2013 Feb 28	2013 Mar 1	Lava flow	Voluminous amounts of lava flowed from the deep notch left by the collapse, expanding first S and then SE, in the direction of the Belvedere monitoring station. Lava was also emitted from the eruptive vents at the base of the NSEC cone; this lava mixed with the flow emitted directly from the NSEC toward SE. Lava emission continued from the collapsed saddle area as well as from the SE flank of the NSEC cone, at a slowly diminishing rate. The lava flows continued to advance during the night of 28 February-1 March, and ceased sometime during 1 March.
2013 Feb 28	- - - -	Lava fountains	Sustained lava fountaining, with intense pyroclastic fallout and the generation of a huge cloud of gas and ash, continued at maximum intensity for about 20 minutes. Shortly after 1200, explosive activity at the NSEC ceased.
2013 Feb 28	- - - -	Ash Plume	Sustained lava fountaining, with intense pyroclastic fallout and the generation of a huge cloud of gas and ash, continued at maximum intensity for about 20 minutes. The ash cloud drifted E, leading to abundant ash and scoria fall in the Milo-Fornazzo and Giarre-Riposto areas. At 1142 the activity started to diminish, although dense clouds of vapor and grayish-brown ash were emitted from the collapsed saddle area.
2013 Feb 28	- - - -	Ashfall	The ash cloud drifted E, leading to abundant ash and scoria fall in the Milo-Fornazzo and Giarre-Riposto areas.
2013 Feb 28	- - - -	Phreatomagmatic	At about 1150, the activity at the "pittino" became phreatomagmatic; vapor and ash were emitted and hot, wet blocks that formed spectacular vapor trails were ejected.
2013 Feb 28	2013 Mar 1	Thermal Anomaly	Seven MODVOLC thermal alerts were issued.
2013 Mar 4	2013 Mar 8	Thermal Anomaly	Eighteen MODVOLC thermal alerts were issued.
2013 Mar 5	- - - -	Explosion	An explosion from the vent in the W part of NSEC was detected at 1854 and ejected incandescent bombs several tens of meters above the crater rim. This explosion was followed by similar ones, initially separated by intervals of 15-20 minutes, but then gradually became more frequent. As the evening went on, the activity at NSEC progressively intensified.
2013 Mar 5	2013 Mar 9	Incandescent ejecta	Sezione di Catania - Osservatorio Etneo reported that a new episode of lava fountaining occurred at Etna's New Southeast Crater (NSEC). An explosion from the vent in the W part of NSEC was detected at 1854 and ejected incandescent bombs several tens of meters above the crater rim. Just after 0100 on 6 March, and within a few minutes, explosive activity nearly ceased, with only a few weak Strombolian explosions. During the same time, however, an eruptive vent opened on the lower E flank of the NSEC cone, which produced vigorous spattering and a well-fed lava flow that advanced SE. This activity continued at a slowly decreasing rate for a few days and ceased altogether on 9 March.
2013 Mar 5	- - - -	Bombs	An explosion from the vent in the W part of NSEC was detected at 1854 and ejected incandescent bombs several tens of meters above the crater rim.
2013 Mar 5	- - - -	Seismicity (tremor)	As the evening went on, the activity at NSEC progressively intensified; the volcanic tremor amplitude started to rise.
2013 Mar 6	2013 Mar 9	Lava flow	Around 0012, lava started to flow from the saddle between the two SEC cones. Various vents were active within the NSEC, in the saddle area, and at the base of the saddle, from where a voluminous lava flow expanded S and SE. Around 0100 this lava flow had reached the area of Belvedere station. Lava also flowed through the breach in the SE rim of NSEC. Just after 0100, an eruptive vent opened on the lower E flank of the NSEC cone, which produced vigorous spattering and a well-fed lava flow that advanced SE. This activity continued at a slowly decreasing rate for a few days and ceased altogether on 9 March.
2013 Mar 6	- - - -	Fissure	A few minutes later, an eruptive fissure with several vents opened in the lower portion of the saddle.
2013 Mar 6	- - - -	Lava fountains	Lava jets became continuous around 0017, forming a fountain that rose 200-300 m above the crater rim. For the next 30 minutes, lava fountaining continued with jets rising 600 to 800 m above the crater.
2013 Mar 6	- - - -	Ash Plume	An eruption column heavily laden with pyroclastic material rose several kilometers above the summit and drifted NE.
2013 Mar 6	- - - -	Bombs	Deposition was intense on the upper NE flank of Etna, covering the area of the Valle del Leone, Pizzi Deneri, and Serra delle Concazze with incandescent bombs and scoriae.
2013 Mar 6	- - - -	Scoria	Deposition was intense on the upper NE flank of Etna, covering the area of the Valle del Leone, Pizzi Deneri, and Serra delle Concazze with incandescent bombs and scoriae. Further downslope, at Linguaglossa, scoria with diameters of several centimeters fell, and ash and lapilli fall was also observed at Piedimonte Etneo, Fiumefreddo, Taormina, and other towns along the Messinian Ionian coast.
2013 Mar 6	- - - -	Lapilli	Further downslope, at Linguaglossa, scoria with diameters of several centimeters fell, and ash and lapilli fall was also observed at Piedimonte Etneo, Fiumefreddo, Taormina, and other towns along the Messinian Ionian coast.
2013 Mar 6	- - - -	Ashfall	Further downslope, at Linguaglossa, scoria with diameters of several centimeters fell, and ash and lapilli fall was also observed at Piedimonte Etneo, Fiumefreddo, Taormina, and other towns along the Messinian Ionian coast.
2013 Mar 15	2013 Mar 16	Explosion	Sometime during the afternoon of 15 March, numerous explosion signals were detected, and the volcanic tremor amplitude increased through the evening. After nightfall, incandescence from the NSEC was visible, and nearby residents (on the SE flank) heard loud bangs coming from the crater. This activity continued during the night and through the following morning. At daybreak on 16 March, numerous gas rings formed by the more powerful explosions were recorded by the monitoring cameras and photographed by observers in the field.
2013 Mar 15	- - - -	Seismicity (tremor)	Sometime during the afternoon of 15 March, numerous explosion signals were detected, and the volcanic tremor amplitude increased through the evening.
2013 Mar 15	2013 Mar 16	Incandescence	After nightfall, incandescence from the NSEC was visible, and nearby residents (on the SE flank) heard loud bangs coming from the crater. This activity continued during the night and through the following morning.
2013 Mar 15	2013 Mar 16	Audible Sounds	After nightfall, incandescence from the NSEC was visible, and nearby residents (on the SE flank) heard loud bangs coming from the crater. This activity continued during the night and through the following morning.
2013 Mar 16	- - - -	Incandescent ejecta	During the early afternoon, activity started to intensify more rapidly, and frequent jets of incandescent lava were launched up to150 m above the crater rim. At about 1800 lava started to flow through the deep breach in the SE rim of NSEC. Approximately 15 minutes later, explosions became progressively more energetic, ejecting incandescent bombs onto the outer flanks of the cone; contemporaneously, the quantity of pyroclastic material (ash and lapilli) in the eruptive plume increased. Between 1830 and 1845, the eruptive activity changed from Strombolian explosions to lava fountaining, with the highest jets rising 600-800 m above the crater rim. The activity started to decrease around 1904. A few weaker Strombolian explosions occurred shortly after 1930.
2013 Mar 16	- - - -	Lava fountains	During the early afternoon, activity started to intensify more rapidly, and frequent jets of incandescent lava were launched up to 150 m above the crater rim.
2013 Mar 16	- - - -	Lava flow	At about 1800 lava started to flow through the deep breach in the SE rim of NSEC. Observations made after the end of the paroxysm revealed that a lava flow was emitted from the area of the saddle between the SEC cones.
2013 Mar 16	- - - -	Explosion	About 1815, explosions became progressively more energetic, ejecting incandescent bombs onto the outer flanks of the cone.
2013 Mar 16	- - - -	Bombs	About 1815, explosions became progressively more energetic, ejecting incandescent bombs onto the outer flanks of the cone. Large, incandescent bombs and scoriae were deposited on the entire cone of the NSEC and the adjacent areas to the S and SE. During the phase of most intense lava fountaining, numerous volcanic bombs fell onto the pyroclastic cones formed during the 2002-2003 eruption, up to 2 km from the NSEC. The activity started to decrease around 1904, and at 1910 the activity evolved into violent explosions that ejected broad fans of large, incandescent bombs, accompanied by loud bangs and detonations. These explosions ceased at 1920, but at 1927 two particularly powerful explosions ejected large incandescent rock fragments towards the SW at least 1.5 km from the crater.
2013 Mar 16	- - - -	Ash Plume	At the same time, around 1815, the quantity of pyroclastic material (ash and lapilli) in the eruptive plume increased. Ash plumes drifted SE. The eruption column rose about 2 km above the summit of Etna before it was blown SE by the strong winds. Based on INGV information and satellite imagery, the Toulouse VAAC reported an ash plume dissipating at 9.1 km altitude from a brief eruption during the afternoon.
2013 Mar 16	- - - -	Lava fountains	Between 1830 and 1845, the eruptive activity changed from Strombolian explosions to lava fountaining, with the highest jets rising 600-800 m above the crater rim. During the phase of most intense lava fountaining, numerous volcanic bombs fell onto the pyroclastic cones formed during the 2002-2003 eruption, up to 2 km from the NSEC. In this phase, the lava fountains were also spectacularly visible from the town of Randazzo, on the NNE flank, about 15 km from the NSEC.
2013 Mar 16	- - - -	Lightning	Around 1900, several lightning flashes within the eruptive cloud were observed.
2013 Mar 16	- - - -	Scoria	Large, incandescent bombs and scoriae were deposited on the entire cone of the NSEC and the adjacent areas to the S and SE.
2013 Mar 16	- - - -	Tephra	Heavy tephra fall, mostly in the form of scoriaceous lapilli, affected the SE flank; on the W headwall of the Valle del Bove this material was still incandescent.
2013 Mar 16	- - - -	Lapilli	Further downslope, in the towns of Zafferana Etnea, Santa Venerina, and a number of villages to the N of Acireale, the tephra fallout formed a continuous deposit of scoriaceous lapilli, which in the N portion of Zafferana Etnea locally was up to 10 cm thick. Many clasts in this area had diameters from 5 to 8 cm, and more rarely up to 10 cm.
2013 Mar 16	- - - -	Ashfall	Even on the Ionian coast, the deposit consisted largely of lapilli, with only a minor fraction of ash.
2013 Mar 16	- - - -	Property Damage	Numerous car windshields, skylights, and roof tiles were broken.
2013 Mar 16	- - - -	Thermal Anomaly	A MODVOLC thermal alert was issued.
2013 Mar 16	- - - -	VEI (Explosivity Index)	VEI 3
2013 Mar 17	- - - -	Collapse	There were small collapses and slides of still hot material from unstable portions on the NSEC cone, which generated minor quantities of ash.
2013 Apr 2	- - - -	Ash Plume	Activity increased when small grayish-brown puffs rose from NSEC.
2013 Apr 2	- - - -	Incandescent ejecta	Sporadic glow suggested Strombolian activity.
2013 Apr 3	- - - -	Seismicity (tremor)	In the morning, the volcanic tremor amplitude slowly increased and was accompanied by numerous explosion signals. At around 1540 ash emissions progressively increased and the volcanic tremor amplitude showed a rapid rise.
2013 Apr 3	- - - -	Explosion	In the morning, the volcanic tremor amplitude slowly increased and was accompanied by numerous explosion signals. The activity progressively intensified between 1400 and 1430, with frequent, powerful Strombolian explosions often generating loud bangs and launching great quantities of incandescent bombs (with diameters of many meters) onto the flanks of the cone. Shortly after 1435, ash emission started from the saddle vent (SV), followed a few minutes later by Strombolian explosions from the same vent. At 1450, a continuous jet of incandescent lava fountained up to 100 m, whereas the vents within NSEC continued to produced powerful loud explosions. At 1615 explosions from the vents within NSEC continued, producing loud detonations every 1-2 seconds. Between 1630 and 1640, the eruptive activity reached a new peak of intensity with sustained lava fountains from SV and powerful explosions from the vents within the NSEC.
2013 Apr 3	- - - -	Incandescent ejecta	Field observations revealed that at 1330 vigorous Strombolian activity was occurring at one or two NSEC vents, with jets of pyroclastic material rising up to a few tens of meters above the crater rim. The activity progressively intensified between 1400 and 1430, with frequent, powerful Strombolian explosions often generating loud bangs and launching great quantities of incandescent bombs (with diameters of many meters) onto the flanks of the cone. Shortly after 1435, ash emission started from the saddle vent (SV), followed a few minutes later by Strombolian explosions from the same vent.
2013 Apr 3	- - - -	Lava fountains	Field observations revealed that at 1330 vigorous Strombolian activity was occurring at one or two NSEC vents, with jets of pyroclastic material rising up to a few tens of meters above the crater rim. At 1450, a continuous jet of incandescent lava fountained up to 100 m, whereas the vents within NSEC continued to produce powerful loud explosions. Between 1540 and 1615 low lava fountaining continued from the Saddle Vent (SV), whereas the vents within NSEC emitted intermittent, pulsating lava fountains. The incandescent jets from the vents within NSEC rose up to 400 m above the crater rim. At 1615, lava fountaining at the Saddle vent (SV) intensified, with jets rising 400-500 m high. Lava fountaining significantly decreased between 1625 and 1628 when a new eruptive vent (NV) opened a few tens of meters to the W of the Saddle Vent (SV), on the E slope of the old SEC cone, and emitted grayish-brown ash. Between 1630 and 1640, the eruptive activity reached a new peak of intensity with sustained lava fountains from the Saddle Vent (SV) and powerful explosions from the vents within the NSEC.
2013 Apr 3	- - - -	Audible Sounds	The activity progressively intensified between 1400 and 1430, with frequent, powerful Strombolian explosions often generating loud bangs and launching great quantities of incandescent bombs (with diameters of many meters) onto the flanks of the cone. At 1450, the vents within NSEC continued to produce powerful loud explosions. At 1615 explosions from the vents within NSEC continued, producing loud detonations every 1-2 seconds.
2013 Apr 3	- - - -	Bombs	The activity progressively intensified between 1400 and 1430, with frequent, powerful Strombolian explosions often generating loud bangs and launching great quantities of incandescent bombs (with diameters of many meters) onto the flanks of the cone.
2013 Apr 3	- - - -	Ash Plume	Shortly after 1435, ash emission started from the saddle vent (SV), followed a few minutes later by Strombolian explosions from the same vent. After 1430 the eruptive plume drifted SE and contained modest amounts of volcanic ash. At around 1540 ash emissions progressively increased and the volcanic tremor amplitude showed a rapid rise. Lava fountaining significantly decreased between 1625 and 1628 when a new eruptive vent (NV) opened a few tens of meters to the W of the Saddle Vent (SV), on the E slope of the old SEC cone, and emitted grayish-brown ash.
2013 Apr 3	- - - -	Lava flow	At around 1505 a lava flow moved through the deep breach in the SE rim of NSEC and then traveled over the W rim of the Valle del Bove. During the same time interval, lava emissions started from the Saddle Vent (SV), feeding a flow that went S. Around 1637 two lava flows emerged from the NE flank of the NSEC cone and traveled toward the Valle del Bove.
2013 Apr 3	- - - -	Tephra	A dense cloud of pyroclastic material emitted by NSEC vents and SV rose about 2 km high and drifted SE. Fallout of pyroclastic material affected almost the same area that had already been subjected to the heavy shower of lapilli on 16 March: Zafferana Etnea and Santa Venerina on the SE flank, and the N part of Acireale plus a number of smaller villages to the N at the S margin of Giarre, in the Ionian area.
2013 Apr 3	- - - -	Lapilli	A dense cloud of pyroclastic material emitted by NSEC vents and SV rose about 2 km high and drifted SE. Fallout of pyroclastic material affected almost the same area that had already been subjected to the heavy shower of lapilli on 16 March: Zafferana Etnea and Santa Venerina on the SE flank, and the N part of Acireale plus a number of smaller villages to the N at the S margin of Giarre, in the Ionian area. The deposit was thinner than that of 16 March, and the dimensions of the lapilli were notably smaller.
2013 Apr 3	- - - -	Pyroclastic flow	At 1637 a thermal surveillance camera recorded a pyroclastic flow from the NE flank of the NSEC cone.
2013 Apr 3	2013 Apr 4	Thermal Anomaly	Nine MODVOLC thermal alerts were issued.
2013 Apr 8	2013 Apr 10	Ash Plume	Sezione di Catania - Osservatorio Etneo reported that the tenth eruptive episode of 2013 began at Etna's New Southeast Crater (NSEC) on 8 April with sporadic ash emissions occasionally accompanied by incandescent material. The ash emissions continued for about 48 hours.
2013 Apr 8	- - - -	Incandescent ejecta	Sezione di Catania - Osservatorio Etneo reported that the tenth eruptive episode of 2013 began at Etna's New Southeast Crater (NSEC) on 8 April with sporadic ash emissions occasionally accompanied by incandescent material.
2013 Apr 8	- - - -	Explosion	A large explosion at 2252 was heard up to 15 km away.
2013 Apr 8	- - - -	Audible Sounds	A large explosion at 2252 was heard up to 15 km away.
2013 Apr 9	2013 Apr 14	Thermal Anomaly	Multiple near-daily MODVOLC thermal alerts were issued.
2013 Apr 10	- - - -	Incandescent ejecta	In the late afternoon Strombolian activity began, producing minor ash emissions during some of the explosions.
2013 Apr 10	- - - -	Ash Plume	In the late afternoon Strombolian activity began, producing minor ash emissions during some of the explosions.
2013 Apr 10	- - - -	Explosion	In the late afternoon Strombolian activity began, producing minor ash emissions during some of the explosions.
2013 Apr 11	- - - -	Incandescent ejecta	In the morning, Strombolian explosions occurred about every 2-5 seconds, ejecting incandescent pyroclastics several tens of meters above the crater rim. Strombolian activity increased slowly in intensity and frequency of explosions throughout the day; contemporaneously the volcanic tremor amplitude continued to show a gradual rise. Late in the afternoon frequent and very powerful Strombolian explosions occurred every 1-2 seconds and were widely audible around the volcano.
2013 Apr 11	- - - -	Explosion	In the morning, Strombolian explosions occurred about every 2-5 seconds, ejecting incandescent pyroclastics several tens of meters above the crater rim. Strombolian activity increased slowly in intensity and frequency of explosions throughout the day; contemporaneously the volcanic tremor amplitude continued to show a gradual rise. Late in the afternoon frequent and very powerful Strombolian explosions occurred every 1-2 seconds and were widely audible around the volcano.
2013 Apr 11	- - - -	Seismicity (tremor)	Strombolian activity increased slowly in intensity and frequency of explosions throughout the day; contemporaneously the volcanic tremor amplitude continued to show a gradual rise.
2013 Apr 11	- - - -	Audible Sounds	Late in the afternoon frequent and very powerful Strombolian explosions occurred every 1-2 seconds and were widely audible around the volcano.
2013 Apr 11	- - - -	Lava fountains	Late in the afternoon, jets of incandescent pyroclastics often rose 200 m above the crater rim and generally contained minor amounts of ash.
2013 Apr 11	- - - -	Ash Plume	Late in the afternoon, jets of incandescent pyroclastics often rose 200 m above the crater rim and generally contained minor amounts of ash. Based on INGV information and a pilot report, the Toulouse VAAC reported an ash plume 55 km E of the summit at 4.6 km altitude.
2013 Apr 11	- - - -	Lava flow	Around 1840, a small amount of lava flowed over the deep breach in the SE rim of the crater. In the late evening it stopped and showed evidence of cooling.
2013 Apr 12	- - - -	Lava flow	Around 0110 another small lava flow traveled S then SE from the saddle between the two cones of the Southeast Crater (SEC).
2013 Apr 12	- - - -	Incandescent ejecta	Throughout the night powerful explosions alternated with intermittent, low lava fountains. Until about 1025, all eruptive activity occurred exclusively at one or two closely spaced vents within the NSEC, then lava was emitted from two vents at the NE base of the NSEC cone. Eruptive activity continued at the NSEC with frequent, powerful Strombolian explosions and emission of modest quantities of volcanic ash, which was rapidly dispersed. Shortly before 1200, the eruptive activity changed from low lava fountains to Strombolian explosions and intermittent ash emissions. Sustained lava fountaining continued for about one hour from 1300; a few minutes after 1400 the activity switched to sporadic Strombolian explosions and ash emissions, which gradually diminished in vigor.
2013 Apr 12	- - - -	Explosion	Throughout the night powerful explosions alternated with intermittent, low lava fountains. Eruptive activity continued during the morning at the NSEC with frequent, powerful Strombolian explosions and emission of modest quantities of volcanic ash, which was rapidly dispersed. Shortly before 1200, the eruptive activity changed from low lava fountains to Strombolian explosions and intermittent ash emissions. After 1400 sporadic Strombolian explosions and ash emissions gradually diminished in vigor. Explosive activity progressively diminished and completely ceased around 1700.
2013 Apr 12	- - - -	Lava fountains	Throughout the night powerful explosions alternated with intermittent, low lava fountains. Lava emission from the SSE rim of the NSEC, the saddle, and the NE base of the cone remained active. Shortly before 1200, the eruptive activity changed from low lava fountains to Strombolian explosions and intermittent ash emissions. The activity shifted back entirely to NSEC, entering into the true paroxysmal phase of this episode at 1250 with sustained lava fountaining, accompanied by a return to high levels of the volcanic tremor amplitude. Sustained lava fountaining continued for about one hour; a few minutes after 1400 the activity switched to sporadic Strombolian explosions and ash emissions, which gradually diminished in vigor.
2013 Apr 12	- - - -	Ash Plume	At daybreak a dense eruption plume containing relatively minor amounts of pyroclastic material drifted ESE. The Toulouse VAAC initially reported the ash plume at 3.9 km altitude drifting 45 km ESE. Eruptive activity continued throughout the morning at the NSEC with frequent, powerful Strombolian explosions and emission of modest quantities of volcanic ash, which was rapidly dispersed. Shortly before 1200, the eruptive activity changed from low lava fountains to Strombolian explosions and intermittent ash emissions. Vigorous ash emissions resumed at 1214 both from the main vent of the NSEC and from the saddle vent. Expulsion of blocks, bombs and ash from the saddle vent continued until 1234, when the main vent of the NSEC reactivated, and for the next nearly 20 minutes both vents were the source intense ash emissions. The Toulouse VAAC reported ash emissions at 6.1 km altitude during the middle of the day. A few minutes after 1400 the activity switched to sporadic Strombolian explosions and ash emissions, which gradually diminished in vigor.
2013 Apr 12	- - - -	Pyroclastic flow	At 1024 a flow of hot pyroclastic material from the area of two vents at the NE base of the NSEC cone traveled about 2 km NE in less than 1 minute.
2013 Apr 12	- - - -	Bombs	Expulsion of blocks, bombs and ash from the saddle vent (SV) continued until 1234, when the main vent of the NSEC reactivated, and for the next nearly 20 minutes both vents were the source intense ash emissions.
2013 Apr 12	- - - -	Seismicity (tremor)	The activity shifted back entirely to NSEC, entering into the true paroxysmal phase of this episode at 1250 with sustained lava fountaining, accompanied by a return to high levels of the volcanic tremor amplitude.
2013 Apr 12	- - - -	Tephra	Between 1250 and 1300, there was a considerable increase in the quantity of pyroclastic material in the plume, which drifted ESE. Tephra fall (ash and small lapilli) affected Fleri, Zafferana Etnea, Milo and S. Maria la Scala, although the quantity of fallout was much smaller compared to those of the previous paroxysms.
2013 Apr 12	- - - -	Lapilli	Tephra fall (ash and small lapilli) affected Fleri, Zafferana Etnea, Milo and S. Maria la Scala, although the quantity of fallout was much smaller compared to those of the previous paroxysms.
2013 Apr 12	- - - -	Collapse	During 1400 and 1410, repeated collapses occurred on the SE flank of the NSEC cone, possibly from new vents at the base of the cone, from which a new lava flow traveled toward the Valle del Bove. The collapses generated avalanches and ash clouds.
2013 Apr 12	- - - -	Lava flow	During 1400 and 1410, repeated collapses occurred on the SE flank of the NSEC cone, possibly from new vents at the base of the cone, from which a new lava flow traveled toward the Valle del Bove. During the evening, the lava flows emitted from the saddle and from the various vents on the flanks of the cone were incandescent and slowly moving; during the night, the surveillance cameras showed the cessation of all lava emission and the cooling of the flows.
2013 Apr 13	2013 Apr 14	Lava flow	In the morning, slow lava effusion resumed from the lower of the vents and a small flow advanced a few hundred meters. This flow ceased in the early morning hours the following day. Once more, on the evening of 14 April, there was a rather weak resumption of effusive activity from this vent, which ceased after a few hours.
2013 Apr 16	- - - -	Incandescent ejecta	Activity increased with ejected incandescent tephra and small ash puffs from a vent inside NSEC, followed by weak Strombolian explosions.
2013 Apr 16	- - - -	Ash Plume	Activity increased with ejected incandescent tephra and small ash puffs from a vent inside NSEC, followed by weak Strombolian explosions.
2013 Apr 16	2013 Apr 21	Thermal Anomaly	Multiple near-daily MODVOLC thermal alerts were issued.
2013 Apr 18	- - - -	Incandescent ejecta	Strombolian explosions became more frequent and intense in the morning and then were almost continuous by 1300.
2013 Apr 18	- - - -	Lava fountains	During the next two hours lava fountains developed and a dense plume drifted SSW. After the lava fountains ceased, strong explosions were heard the rest of the day.
2013 Apr 18	- - - -	Ash Plume	During the next two hours lava fountains developed and a dense plume drifted SSW. Based on INGV webcam images and satellite data, the Toulouse VAAC reported an ash emission at 6.1 km altitude.
2013 Apr 18	- - - -	Ashfall	Ash and lapilli affected Ragalna, Belper, and Paterno, as well as the tourist area "Etna Sud."
2013 Apr 18	- - - -	Lapilli	Ash and lapilli fell in between the villages of Ragalna, Belper, and Paterno, as well as the tourist area "Etna Sud." Lapilli-fall was a few centimeters deep and clasts were at most 5 cm in diameter.
2013 Apr 18	- - - -	Lava flow	Three lava flows were produced; the largest flowed through the deep notch in the SE rim of the crater and traveled 4 km towards the Valle del Bove. The interaction of the lava with snow led to rapid melting, generating small lahars. The two other lava flows originated in the saddle between the two SEC cones; one traveled N and the other S.
2013 Apr 18	- - - -	Lahar or Mudflow	The interaction of the lava with snow led to rapid melting, generating small lahars.
2013 Apr 18	- - - -	Explosion	After the lava fountains ceased, strong explosions were heard the rest of the day.
2013 Apr 18	- - - -	Audible Sounds	After the lava fountains ceased, strong explosions were heard the rest of the day.
2013 Apr 19	- - - -	Explosion	Intermittent explosions ejected incandescent tephra and generated small ash puffs.
2013 Apr 19	- - - -	Incandescent ejecta	Intermittent explosions ejected incandescent tephra and generated small ash puffs.
2013 Apr 19	- - - -	Ash Plume	Intermittent explosions ejected incandescent tephra and generated small ash puffs.
2013 Apr 20	- - - -	Ash Plume	Around 1700 ash puffs rose from the crater, followed by incandescent tephra ejected at 1713. Within a few minutes sustained lava fountains were observed, along with a tall eruption plume that drifted E. Around 1815 lava-fountain activity decreased and turned into explosions and ash emissions. At 1840 the paroxysm was over. Based on INGV information, satellite data and a pilot report, the Toulouse VAAC reported that an ash emission was drifting E at 9.1 km altitude.
2013 Apr 20	- - - -	Incandescent ejecta	Around 1700 ash puffs rose from the crater, followed by sporadic Strombolian explosions beginning at 1713. Around 1815 lava-fountain activity decreased and turned into explosions and ash emissions. At 1840 the paroxysm was over.
2013 Apr 20	- - - -	Lava fountains	Within a few minutes of 1713 sustained lava fountains were observed, along with a tall eruption plume that drifted E. Lava fountains reached heights of 800-1000 m above the crater. Around 1815 lava-fountain activity decreased and turned into explosions and ash emissions.
2013 Apr 20	- - - -	Ashfall	Ash and lapilli fell over a wide area to the E, including along the Ionian coastline, just S of Guardia Mangano, up to Fiumefreddo, including the towns of Taormina, Ripon, and Mascali, and further upstream, including Santa Venerina, Zafferana, Milo, and Sant'Alfio.
2013 Apr 20	- - - -	Lapilli	Ash and lapilli fell over a wide area to the E, including along the Ionian coastline, just S of Guardia Mangano, up to Fiumefreddo, including the towns of Taormina, Ripon, and Mascali, and further upstream, including Santa Venerina, Zafferana, Milo, and Sant'Alfio.
2013 Apr 20	- - - -	Lava flow	The explosive activity ceased in the late evening, but shortly afterwards, the lower of the two effusive vents at the base of the NSEC cone produced a well-fed lava flow that traveled 1.5 km towards the Valle del Bove.
2013 Apr 20	- - - -	Lahar or Mudflow	Several lava flows on the W wall of the Valle del Bove interacted with the snow, generating explosions and lahars.
2013 Apr 20	- - - -	VEI (Explosivity Index)	VEI 3
2013 Apr 21	- - - -	Incandescent ejecta	Poor weather conditions prevented visual observations until the evening of 21 April, when surveillance videos showed sporadic Strombolian explosions accompanied by small ash puffs at the NSEC, and the emission of a small lava flow from the base of the cone.
2013 Apr 21	- - - -	Ash Plume	Poor weather conditions prevented visual observations until the evening of 21 April, when surveillance videos showed sporadic Strombolian explosions accompanied by small ash puffs at the NSEC, and the emission of a small lava flow from the base of the cone.
2013 Apr 21	- - - -	Lava flow	Poor weather conditions prevented visual observations until the evening of 21 April, when surveillance videos showed sporadic Strombolian explosions accompanied by small ash puffs at the NSEC, and the emission of a small lava flow from the base of the cone.
2013 Apr 23	- - - -	Thermal Anomaly	A MODVOLC thermal alert was issued.
2013 Apr 25	2013 Apr 30	Thermal Anomaly	Multiple near-daily MODVOLC thermal alerts were issued.
2013 Apr 26	- - - -	Seismicity (tremor)	Eruptive activity and the volcanic tremor amplitude gradually increased in the evening.
2013 Apr 27	- - - -	Lava fountains	Just after sunset lava fountains rose 300-500 m high.
2013 Apr 27	- - - -	Lava flow	Lava flows from the SE and NE flanks of the NSEC cone and from the saddle between the two Southeast Crater (SEC) cones traveled S and N.
2013 May 9	- - - -	Degassing	Based on webcams and satellite data, the Toulouse VAAC reported an emission of primarily steam at 3.7 km altitude.
2013 Jun 16	- - - -	Degassing	Based on webcams and satellite data, the Toulouse VAAC reported an emission of primarily steam at 3.9 km altitude.

Episode 7 | Eruption

Bocca Nuova (BN)

2013 Jan 9 - 2013 Feb 28

Evidence from Observations: Reported

Vigorous Strombolian activity at Bocca Nuova (BN) Crater began at night on 9 January 2013 three months after the last activity at that vent. Explosions, lava fountains, and lava flows recurred multiple times during January-February. On 2 February jets of lava rose many tens of meters above the rim. Ash emissions were weak and intermittent. A pyroclastic cone was built around the eruptive vent in the SE portion of the BN crater. Strombolian activity was intermittent through 28 February 2013.

List of 33 Events for Episode 7 at Bocca Nuova (BN)

Start Date	End Date	Event Type	Event Remarks
2013 Jan 9	2013 Jan 15	Incandescent ejecta	Vigorous Strombolian activity at Bocca Nuova Crater began at night three months after the last episode. Ten minutes after midnight a video camera recorded the first burst in the E part of the crater, which progressively became stronger and more frequent. At 0350 jets of incandescent fragments rose significantly higher than the crater rim. In the early morning of 15 January volcanic tremor amplitude rapidly decreased, marking the cessation of Strombolian activity in the Bocca Nuova Crater.
2013 Jan 10	2013 Jan 15	Seismicity (tremor)	At 0000 a rapid rise in tremor amplitude was detected. the volcanic tremor amplitude remained elevated but started to decrease around 1200. In the early morning of 15 January volcanic tremor amplitude rapidly decreased.
2013 Jan 10	2013 Jan 15	Thermal Anomaly	Fourteen MODVOLC thermal alerts were issued.
2013 Jan 16	2013 Jan 18	Incandescent ejecta	Two episodes of Strombolian activity from Etna's Bocca Nuova Crater occurred during the evenings of 16 and 18 January. Both began with a sudden increase in volcanic tremor amplitude. Poor weather conditions prevented direct observations; the only visible evidence was a bright glow illuminating the clouds covering the summit. On 18 January some clasts were ejected onto the S outer slope of the central summit cone.
2013 Jan 28	2013 Feb 2	Thermal Anomaly	Eight MODVOLC thermal alerts were issued.
2013 Jan 30	2013 Jan 31	Incandescent ejecta	Intense Strombolian activity at Etna's Bocca Nuova Crater began on the evening of 30 January. Weak glow from a vent on the SE part of the crater floor was first observed at 1807. The glow became stronger and was visible to nearby residents. Between 1900 and 1915 the activity intensified, and from 1920 onward jets of incandescent volcanic bombs and scoria nearly continuously rose higher than the crater rim. Some tephra was ejected 150 m above the rim. During the night weak eruptive activity continued on the crater floor, evident from a dull glow emanating from the crater.
2013 Jan 30	- - - -	Seismicity (tremor)	Volcanic tremor amplitude rapidly increased along with the explosive activitiy, and shifted from below the New Southeast Crater (NSEC) toward Bocca Nuova. The volcanic tremor amplitude rapidly decreased and returned to normal levels in the late evening.
2013 Jan 30	- - - -	Bombs	From 1920 onward jets of incandescent volcanic bombs and scoria nearly continuously rose higher than the crater rim. Shortly after 2000, the fountain leaned SW and produced heavy fallout of incandescent bombs and scoria on the outer SW flank of the central summit cone, down to its base.
2013 Jan 30	- - - -	Scoria	From 1920 onward jets of incandescent volcanic bombs and scoria nearly continuously rose higher than the crater rim. Shortly after 2000, the fountain leaned SW and produced heavy fallout of incandescent bombs and scoria on the outer SW flank of the central summit cone, down to its base.
2013 Jan 30	- - - -	Lava fountains	During 1930-2000, lava fountains rose 100 m above the rim. Shortly after 2000, the fountain leaned SW and produced heavy fallout of incandescent bombs and scoria on the outer SW flank of the central summit cone, down to its base. At 2016 the fountain rose vertically and pyroclastic fallout outside the crater diminished. Around 2030 the lava fountain started to wane; the incandescent jets became discontinuous and only rarely rose more than 100 m above the crater rim, except for one jet, at 2100, which rose 150 m above the rim. After 2200, the incandescent pyroclastic jets no longer rose above the crater rim, and the glow became progressively less brilliant.
2013 Jan 31	- - - -	Ash Plume	The episode ended with a series of sporadic, small ash emissions, the last of which was seen around 0641.
2013 Feb 1	- - - -	Ash Plume	Small discrete "puffs" of ash rose from Bocca Nuova. Ash plumes rose no higher than 100 m above the crater rim.
2013 Feb 2	- - - -	Lava fountains	At 0450 jets of lava rose above the rim of Bocca Nuova; at 0500 Strombolian activity became continuous, producing jets that rose many tens of meters above the rim. Just after 0515 activity at Bocca Nuova started to increase rapidly; contemporaneously, the volcanic tremor amplitude showed a sharp rise. Lava fountains rose 120-150 m above the rim. Activity at Bocca Nuova decreased markedly between 0620 and 0630.
2013 Feb 3 (?)	2013 Feb 5 (?)	Ash Plume	During the days following the 2 February eruptive episode at Etna intermittent emissions of small quantities of ash were repeatedly observed.
2013 Feb 5	- - - -	Cinder Cone	Volcanologists observed the recent changes that had taken place at Bocca Nuova Crater, notably the growth of a pyroclastic cone surrounding the eruptive vent in the SE portion of the crater. This cone had grown at least 50-70 m, about halfway up the inner crater wall, and was leaning into the wall. The entire crater floor was covered with recent lava.
2013 Feb 8	- - - -	Lava fountains	At 2100 a webcam recorded fluctuating glow from within Bocca Nuova which became more intense over the next 10 minutes. Around 2125 jets of incandescent lava were repeatedly seen rising above a thick blanket of clouds drifting over the summit area of Etna.
2013 Feb 8	- - - -	Seismicity (tremor)	Volcanic tremor amplitude rose sharply. After 2200 the volcanic tremor amplitude began to decrease, whereas the eruptive activity continued without showing signs of diminishing until about 30 minutes later.
2013 Feb 9	- - - -	Thermal Anomaly	Two MODVOLC thermal alerts were issued.
2013 Feb 10	- - - -	Ash Plume	A brief ash emission was observed.
2013 Feb 19	- - - -	Ash Plume	At 0622 a puff of ash was emitted from the Bocca Nuova. During the late afternoon, small ash puffs were again emitted from the Bocca Nuova.
2013 Feb 22	- - - -	Seismicity (tremor)	At about 0700, rising tremor amplitude signaled the onset of a new episode from Bocca Nuova. Between 0730 and 0815 many vapor puffs and thermal anomalies were observed. Cloud cover prevented clear views, but mild Strombolian activity was likely occurring within the crater. At about 0815 the volcanic tremor amplitude started decreasing and the gas emissions from Bocca Nuova became less conspicuous.
2013 Feb 22	- - - -	Degassing	At about 0700, rising tremor amplitude signaled the onset of a new episode, but from Bocca Nuova. Between 0730 and 0815 many vapor puffs and thermal anomalies were observed. Cloud cover prevented clear views, but mild Strombolian activity was likely occurring within the crater. At about 0815 the volcanic tremor amplitude started decreasing and the gas emissions from Bocca Nuova became less conspicuous.
2013 Feb 22	- - - -	Thermal Anomaly	Between 0730 and 0815 many vapor puffs and thermal anomalies were observed. Cloud cover prevented clear views, but mild Strombolian activity was likely occurring within the crater.
2013 Feb 26	2013 Feb 27	Seismicity (volcanic)	Sezione di Catania - Osservatorio Etneo reported that seismic activity at Etna's Bocca Nuova Crater (BN) gradually increased at night during 26-27 February.
2013 Feb 27	- - - -	Degassing	Copious, puffing emission of dense vapor from BN observed at sunrise slowly grew more energetic over the next few hours.
2013 Feb 27	- - - -	Seismicity (tremor)	Between 1030 and 1045, the volcanic tremor amplitude rapidly rose.
2013 Feb 27	- - - -	Incandescent ejecta	At the same time an eruption column largely composed of vapor formed and hot material was ejected.
2013 Feb 27	- - - -	Ash Plume	The plume contained moderate amounts of reddish-brown volcanic ash, mostly during 1215-1220 and 1314-1316. The Toulouse VAAC reported an ash plume that rose to 3.7 km altitude.
2013 Feb 27	- - - -	Ashfall	The plume contained moderate amounts of reddish-brown volcanic ash, mostly during 1215-1220 and 1314-1316, which led to the fall of small quantities of very fine ash on the SE flank between Zafferana and Santa Venerina.
2013 Feb 27	- - - -	Collapse	These ash emissions likely resulted from collapse or sliding of unstable material on the steep inner crater wall; the eruptive vent, which lies in the SE part of the crater, is leaning against the wall and the rapid accumulation of pyroclastic deposits in that area might have facilitated collapses.
2013 Feb 27	- - - -	Bombs	During the phase of most intense eruptive activity, INGV staff carrying out fieldwork in the summit area, noted that volcanic bombs fell outside the crater rim onto the SW flank of the central cone.
2013 Feb 27	2013 Feb 28	Incandescent ejecta	During the evening minor and discontinuous Strombolian activity occurred at BN which often launched incandescent volcanic bombs up to 150 m above the crater rim. The activity continued through the night, into at least early 28 February.
2013 Feb 27	- - - -	VEI (Explosivity Index)	VEI 1

Episode 8 | Eruption

Voragine Crater (VOR)

2013 Feb 27 - 2013 Mar 17

Evidence from Observations: Reported

Intense explosions was observed within the Voragine (VOR) on 27 February 2013, the first such activity there since early October 1999. Multiple pulses of Strombolian activity were recorded through 17 March 2013.

List of 8 Events for Episode 8 at Voragine Crater (VOR)

Start Date	End Date	Event Type	Event Remarks
2013 Feb 27	2013 Mar 3	Incandescent ejecta	Intense explosive activity was also observed within the Voragine (VOR), which since early October 1999 had not exhibited magmatic activity. The activity began to diminish around 1320, evident from a reduction in the volcanic tremor amplitude; at 1430, the episode was essentially over, even though strong degassing continued at both BN and VOR. During the evening of vigorous Strombolian activity in VOR was reported by observers on the W and E flanks. The activity continued through the night, into at least early 28 February. Strombolian activity within the VOR continued without significant variations, and was observed by INGV staff during a field visit on the morning of 1 March, and at least through 1500 on 3 March.
2013 Feb 27	- - - -	Thermal Anomaly	Six MODVOLC thermal alerts were issued.
2013 Feb 27	- - - -	VEI (Explosivity Index)	VEI 1
2013 Mar 6	2013 Mar 14	Incandescent ejecta	At the Voragine (VOR), Strombolian activity continued after the 5-6 March paroxysm at NSEC, but then alternated with short episodes of intense Strombolian activity and nearly totally quiet intervals. They were rarely detected by 14 March.
2013 Mar 6	2013 Mar 7	Seismicity (tremor)	These oscillations were reflected in the volcanic tremor amplitude, which during the 24 hours following the paroxysmal episode at the NSEC showed about twenty small peaks.
2013 Mar 17	- - - -	Explosion	At 0449, a series of explosions started at Voragine, which continued for about 5 minutes, generating strong thermal anomalies that were recorded by the thermal surveillance camera, and probably produced small ash puffs.
2013 Mar 17	- - - -	Thermal Anomaly	At 0449, a series of explosions started at Voragine, which continued for about 5 minutes, generating strong thermal anomalies that were recorded by the thermal surveillance camera, and probably produced small ash puffs.
2013 Mar 17	- - - -	Incandescence	During the next few hours, weak glow coming from Voragine was recorded by a monitoring camera.

2010 Apr 8 - 2010 Apr 8 Confirmed Eruption VEI: 1

Episode 1 | Eruption

SEC (South-East Crater)

2010 Apr 8 - 2010 Apr 8

Evidence from Observations: Reported

List of 12 Events for Episode 1 at SEC (South-East Crater)

Start Date	End Date	Event Type	Event Remarks
2010 Apr 8	- - - -	Seismicity (volcanic)	INGV-CT reported that twelve low-frequency events located near the summit were detected by the seismic network.
2010 Apr 8	- - - -	Explosion	A small explosion from the pit crater located at the E base of the Southeast Crater (SEC) widened the crater from ~40 m to ~80 m in diameter.
2010 Apr 8	- - - -	Ash Plume	A dark-colored ash plume rose 1 km above the pit crater at the eastern base of the South-East Crater (SEC) after it collapsed, and drifted NE at the same time that 12 seismic events were recorded.
2010 Apr 8	- - - -	Ash Plume	Dark emissions from the central crater, (BN and VOR), Bocca Nuova and Voragine, were seen a short time after the emissions from the SEC flank pit crater.
2010 Apr 8	- - - -	Pyroclastic flow	A small pyroclastic density current moved a few hundred meters to the NE from the pit.
2010 Apr 8	- - - -	Ashfall	Mainly lithic ash fell at distances of up to 6 km from the volcano.
2010 Apr 8	- - - -	Ashfall	Fallout of ash in the Rocca Campana area, between Milo and Fornazzo was noted after the emission from the central crater (BN and VOR).
2010 Apr 8	- - - -	Crater	A small explosion from the pit crater located at the E base of the Southeast Crater (SEC) widened the crater from ~40 m to ~80 m in diameter.
2010 Apr 8	- - - -	VEI (Explosivity Index)	VEI 1
2010 Apr 9	- - - -	Degassing	Intense gas emissions were noted at the pit crater, but without ash emission.
2010 Jun 19	- - - -	Thermal Anomaly	Data from a fixed thermal monitoring camera showed thermal anomalies over 180°C, indicating that the landslide material was hot.
2010 Jun 19	- - - -	Crater	INGV-OE reported a series of landslides from the NW rim of the pit crater located on the lower E side of the SEC. The collapses generated small ash clouds that drifted NE and changed the pit crater's morphology.

2007 Mar 19 - 2009 Jul 4 Confirmed Eruption VEI: 2

Episode 1 | Eruption

Bocca Nuova, SE Crater and flank vents

2007 Mar 19 - 2008 May 16 (?) ± 15 days

Evidence from Observations: Reported

List of 12 Events for Episode 1 at Bocca Nuova, SE Crater and flank vents

Start Date	End Date	Event Type
- - - -	- - - -	Seismicity (tremor)
- - - -	- - - -	Explosion
- - - -	- - - -	Lava fountains
- - - -	- - - -	Lava flow
- - - -	- - - -	Ash
- - - -	- - - -	Lapilli
- - - -	- - - -	Blocks
- - - -	- - - -	Scoria
2007 Mar 19	- - - -	VEI (Explosivity Index)
2007 Apr 29	- - - -	VEI (Explosivity Index)
2007 Sep 4	- - - -	VEI (Explosivity Index)
2007 Nov 23	- - - -	VEI (Explosivity Index)

Episode 2 | Eruption

East base of NE Crater (3000-2650 m)

2008 May 13 - 2009 Jul 4

Evidence from Observations: Reported

List of 7 Events for Episode 2 at East base of NE Crater (3000-2650 m)

Start Date	End Date	Event Type	Event Remarks
- - - -	- - - -	Explosion
- - - -	- - - -	Lava fountains
- - - -	- - - -	Lava flow
- - - -	- - - -	Ash
- - - -	- - - -	Scoria
- - - -	- - - -	Earthquakes (undefined)	Before.
2008 May 13	- - - -	VEI (Explosivity Index)

2006 Jul 14 - 2006 Dec 15 Confirmed Eruption VEI: 2

Episode 1 | Eruption

SE Crater & flank vents; NE Crater

2006 Jul 14 - 2006 Dec 15

Evidence from Observations: Reported

List of 13 Events for Episode 1 at SE Crater & flank vents; NE Crater

Start Date	End Date	Event Type
- - - -	- - - -	Seismicity (tremor)
- - - -	- - - -	Explosion
- - - -	- - - -	Phreatic activity
- - - -	- - - -	Pyroclastic flow
- - - -	- - - -	Lava fountains
- - - -	- - - -	Lava flow
- - - -	- - - -	Cinder Cone
- - - -	- - - -	Ash
- - - -	- - - -	Lapilli
- - - -	- - - -	Bombs
- - - -	- - - -	Blocks
2006 Jul 14	- - - -	VEI (Explosivity Index)
2006 Aug 31	- - - -	VEI (Explosivity Index)

2005 Dec 16 - 2005 Dec 22 Confirmed Eruption VEI: 1

Episode 1 | Eruption

Bocca Nuova

2005 Dec 16 - 2005 Dec 22

Evidence from Observations: Reported

List of 3 Events for Episode 1 at Bocca Nuova

Start Date	End Date	Event Type	Event Remarks
- - - -	- - - -	Explosion	weak or small
- - - -	- - - -	Earthquakes (undefined)
2005 Dec 16	- - - -	VEI (Explosivity Index)

2004 Sep 7 - 2005 Mar 8 Confirmed Eruption VEI: 1

Episode 1 | Eruption

SE Crater, SE flank (3000-2320 m)

2004 Sep 7 - 2005 Mar 8

Evidence from Observations: Reported

List of 6 Events for Episode 1 at SE Crater, SE flank (3000-2320 m)

Start Date	End Date	Event Type	Event Remarks
- - - -	- - - -	Explosion
- - - -	- - - -	Lava flow
- - - -	- - - -	Avalanche	weak or small
- - - -	- - - -	Ash
2004 Sep 7	- - - -	VEI (Explosivity Index)
2005 Jan 8	- - - -	VEI (Explosivity Index)

2004 Feb 12 - 2004 Feb 14 Confirmed Eruption VEI: 1 (?)

Episode 1 | Eruption

Central Crater

2004 Feb 12 - 2004 Feb 14

Evidence from Observations: Reported

List of 3 Events for Episode 1 at Central Crater

Start Date	End Date	Event Type	Event Remarks
- - - -	- - - -	Explosion
- - - -	- - - -	Ash	weak or small
2004 Feb 12	- - - -	VEI (Explosivity Index)

2001 Dec 16 (?) ± 15 days - 2003 Nov 9 Confirmed Eruption VEI: 3

Episode 1 | Eruption

Central Crater, NE Crater

2001 Dec 16 (?) ± 15 days - 2002 Oct 30 (?)

Evidence from Observations: Reported

List of 4 Events for Episode 1 at Central Crater, NE Crater

Start Date	End Date	Event Type
- - - -	- - - -	Explosion
- - - -	- - - -	Ash
- - - -	- - - -	Earthquakes (undefined)
2001 Dec (?)	- - - -	VEI (Explosivity Index)

Episode 2 | Eruption

NE Rift (3100-1900 m), S flank (2850-2600 m)

2002 Oct 26 - 2003 Jan 28

Evidence from Observations: Reported

List of 12 Events for Episode 2 at NE Rift (3100-1900 m), S flank (2850-2600 m)

Start Date	End Date	Event Type	Event Remarks
- - - -	- - - -	Explosion
- - - -	- - - -	Phreatomagmatic
- - - -	- - - -	Lava fountains
- - - -	- - - -	Lava flow
- - - -	- - - -	Cinder Cone
- - - -	- - - -	Ash
- - - -	- - - -	Lapilli
- - - -	- - - -	Earthquakes (undefined)	Before.
- - - -	- - - -	Earthquakes (undefined)
- - - -	- - - -	Property Damage
- - - -	- - - -	Evacuations
2002 Oct 26	- - - -	VEI (Explosivity Index)

Episode 3 | Eruption

NE Crater

2003 Mar 8 ± 3 days - 2003 Nov 9

Evidence from Observations: Reported

List of 4 Events for Episode 3 at NE Crater

Start Date	End Date	Event Type
- - - -	- - - -	Explosion
- - - -	- - - -	Ash
- - - -	- - - -	Earthquakes (undefined)
2003 Mar 8 ± 3 days	- - - -	VEI (Explosivity Index)

1994 Jun 17 - 2001 Aug 9 Confirmed Eruption VEI: 3

Episode 1 | Eruption

Central Crater, NE Crater, SE Crater

1994 Jun 17 - 2001 Jul 17

Evidence from Observations: Reported

List of 20 Events for Episode 1 at Central Crater, NE Crater, SE Crater

Start Date	End Date	Event Type
- - - -	- - - -	Seismicity (tremor)
- - - -	- - - -	Explosion
- - - -	- - - -	Pyroclastic flow
- - - -	- - - -	Lava fountains
- - - -	- - - -	Lava flow
- - - -	- - - -	Lava dome
- - - -	- - - -	Ash
- - - -	- - - -	Lapilli
- - - -	- - - -	Bombs
- - - -	- - - -	Blocks
- - - -	- - - -	Earthquakes (undefined)
- - - -	- - - -	Deformation (deflation)
- - - -	- - - -	Property Damage
1994 Jun 17	- - - -	VEI (Explosivity Index)
1995 Dec 23	- - - -	VEI (Explosivity Index)
1996 Jun 25	- - - -	VEI (Explosivity Index)
1998 Jul 22	- - - -	VEI (Explosivity Index)
1998 Sep 15	- - - -	VEI (Explosivity Index)
1999 Feb 4	- - - -	VEI (Explosivity Index)
1999 Sep 4	- - - -	VEI (Explosivity Index)

Episode 2 | Eruption

S to NE flanks (3100-2100 m)

2001 Jul 17 - 2001 Aug 9

Evidence from Observations: Reported

List of 13 Events for Episode 2 at S to NE flanks (3100-2100 m)

Start Date	End Date	Event Type	Event Remarks
- - - -	- - - -	Explosion
- - - -	- - - -	Phreatomagmatic
- - - -	- - - -	Lava fountains
- - - -	- - - -	Lava flow
- - - -	- - - -	Cinder Cone
- - - -	- - - -	Bombs
- - - -	- - - -	Blocks
- - - -	- - - -	Earthquakes (undefined)	Before.
- - - -	- - - -	Earthquakes (undefined)
- - - -	- - - -	Deformation (inflation)
- - - -	- - - -	Property Damage
2001 Jul 17	- - - -	VEI (Explosivity Index)
2001 Jul 21	- - - -	VEI (Explosivity Index)

1993 Aug 3 - 1993 Oct 13 Confirmed Eruption VEI: 1

Episode 1 | Eruption

Central Crater, NE Crater

1993 Aug 3 - 1993 Oct 13

Evidence from Observations: Reported

List of 7 Events for Episode 1 at Central Crater, NE Crater

Start Date	End Date	Event Type	Event Remarks
- - - -	- - - -	Explosion
- - - -	- - - -	Ash
- - - -	- - - -	Bombs
- - - -	- - - -	Earthquakes (undefined)	Before.
- - - -	- - - -	Earthquakes (undefined)
- - - -	- - - -	Earthquakes (undefined)	After.
1993 Aug 3	- - - -	VEI (Explosivity Index)

1979 Jul 3 - 1993 Mar 30 Confirmed Eruption VEI: 3 (?)

Episode 1 | Eruption

Central Crater

1979 Jul 3 - 1992 Dec 16 ± 15 days

Evidence from Observations: Reported

List of 10 Events for Episode 1 at Central Crater

Start Date	End Date	Event Type
- - - -	- - - -	Explosion
- - - -	- - - -	Phreatic activity
- - - -	- - - -	Directed Explosion
- - - -	- - - -	Ash
- - - -	- - - -	Blocks
- - - -	- - - -	Earthquakes (undefined)
- - - -	- - - -	Property Damage
1979 Jul 3	- - - -	VEI (Explosivity Index)
1979 Sep 12	- - - -	Fatalities
1979 Sep 12	- - - -	VEI (Explosivity Index)

Episode 2 | Eruption

SE Crater, SE, E and NE flanks

1979 Jul 16 - 1980 Sep 1 ± 5 days

Evidence from Observations: Reported

List of 7 Events for Episode 2 at SE Crater, SE, E and NE flanks

Start Date	End Date	Event Type
- - - -	- - - -	Explosion
- - - -	- - - -	Lava flow
- - - -	- - - -	Ash
- - - -	- - - -	Blocks
- - - -	- - - -	Property Damage
1979 Jul 16	- - - -	VEI (Explosivity Index)
1979 Aug 3	- - - -	VEI (Explosivity Index)

Episode 3 | Eruption

NE Crater

1980 Jul 8 - 1980 Sep 26

Evidence from Observations: Reported

List of 10 Events for Episode 3 at NE Crater

Start Date	End Date	Event Type
- - - -	- - - -	Explosion
- - - -	- - - -	Eruption cloud
- - - -	- - - -	Lava fountains
- - - -	- - - -	Lava flow
- - - -	- - - -	Ash
- - - -	- - - -	Bombs
- - - -	- - - -	Blocks
- - - -	- - - -	Earthquakes (undefined)
1980 Jul 8	- - - -	VEI (Explosivity Index)
1980 Sep 1	- - - -	VEI (Explosivity Index)

Episode 4 | Eruption

NE Crater

1981 Jan 26 ± 5 days - 1981 Mar 5 ± 4 days

Evidence from Observations: Reported

List of 6 Events for Episode 4 at NE Crater

Start Date	End Date	Event Type
- - - -	- - - -	Explosion
- - - -	- - - -	Lava flow
- - - -	- - - -	Ash
- - - -	- - - -	Bombs
- - - -	- - - -	Scoria
1981 Jan 26 ± 5 days	- - - -	VEI (Explosivity Index)

Episode 5 | Eruption

NNW flank (2550-1140 m)

1981 Mar 17 - 1981 Mar 23

Evidence from Observations: Reported

List of 12 Events for Episode 5 at NNW flank (2550-1140 m)

Start Date	End Date	Event Type	Event Remarks
- - - -	- - - -	Seismicity (volcanic)	Before eruption.
- - - -	- - - -	Seismicity (volcanic)
- - - -	- - - -	Explosion
- - - -	- - - -	Lava flow
- - - -	- - - -	Ash
- - - -	- - - -	Lapilli
- - - -	- - - -	Bombs
- - - -	- - - -	Blocks
- - - -	- - - -	Deformation (inflation)
- - - -	- - - -	Property Damage
- - - -	- - - -	Evacuations
1981 Mar 17	- - - -	VEI (Explosivity Index)

Episode 6 | Eruption

NE Crater

1981 Nov 26 - 1981 Nov 26

Evidence from Observations: Reported

List of 3 Events for Episode 6 at NE Crater

Start Date	End Date	Event Type
- - - -	- - - -	Explosion
- - - -	- - - -	Ash
1981 Nov 26	- - - -	VEI (Explosivity Index)

Episode 7 | Eruption

South flank (2680-2250 m)

1983 Mar 28 - 1983 Aug 6

Evidence from Observations: Reported

List of 10 Events for Episode 7 at South flank (2680-2250 m)

Start Date	End Date	Event Type	Event Remarks
- - - -	- - - -	Explosion
- - - -	- - - -	Phreatic activity
- - - -	- - - -	Lava flow	violent, strong, or large
- - - -	- - - -	Ash
- - - -	- - - -	Earthquakes (undefined)	Before.
- - - -	- - - -	Earthquakes (undefined)
- - - -	- - - -	Deformation (inflation)
- - - -	- - - -	Deformation (deflation)
- - - -	- - - -	Property Damage
1983 Mar 28	- - - -	VEI (Explosivity Index)

Episode 8 | Eruption

SE Crater

1984 Apr 28 - 1984 Oct 18

Evidence from Observations: Reported

List of 8 Events for Episode 8 at SE Crater

Start Date	End Date	Event Type
- - - -	- - - -	Explosion
- - - -	- - - -	Eruption cloud
- - - -	- - - -	Lava flow
- - - -	- - - -	Cinder Cone
- - - -	- - - -	Ash
- - - -	- - - -	Bombs
- - - -	- - - -	Earthquakes (undefined)
1984 Apr 28	- - - -	VEI (Explosivity Index)

Episode 9 | Eruption

NE Crater

1984 Jul 20 - 1986 Sep 24

Evidence from Observations: Reported

List of 17 Events for Episode 9 at NE Crater

Start Date	End Date	Event Type	Event Remarks
- - - -	- - - -	Seismicity (tremor)
- - - -	- - - -	Explosion	moderate
- - - -	- - - -	Eruption cloud
- - - -	- - - -	Pyroclastic flow
- - - -	- - - -	Lava fountains
- - - -	- - - -	Lava flow	moderate
- - - -	- - - -	Cinder Cone
- - - -	- - - -	Ash
- - - -	- - - -	Lapilli
- - - -	- - - -	Bombs
- - - -	- - - -	Blocks
- - - -	- - - -	Scoria
- - - -	- - - -	Lightning
- - - -	- - - -	Property Damage
1984 Jul 20	- - - -	VEI (Explosivity Index)
1984 Oct 16	- - - -	Fatalities
1986 Sep 24	- - - -	VEI (Explosivity Index)

Episode 10 | Eruption

SE Crater, south flank (2620-2480 m)

1985 Mar 8 - 1985 Jul 13

Evidence from Observations: Reported

List of 12 Events for Episode 10 at SE Crater, south flank (2620-2480 m)

Start Date	End Date	Event Type	Event Remarks
- - - -	- - - -	Seismicity (tremor)	Before eruption.
- - - -	- - - -	Seismicity (tremor)
- - - -	- - - -	Explosion
- - - -	- - - -	Phreatic activity
- - - -	- - - -	Lava flow
- - - -	- - - -	Ash
- - - -	- - - -	Lapilli
- - - -	- - - -	Scoria
- - - -	- - - -	Deformation (inflation)
- - - -	- - - -	Lahar or Mudflow
- - - -	- - - -	Property Damage
1985 Mar 8	- - - -	VEI (Explosivity Index)

Episode 11 | Eruption

SE Crater and SE flank (2750-2420 m)

1985 Dec 19 - 1985 Dec 31

Evidence from Observations: Reported

List of 9 Events for Episode 11 at SE Crater and SE flank (2750-2420 m)

Start Date	End Date	Event Type	Event Remarks
- - - -	- - - -	Explosion
- - - -	- - - -	Lava flow
- - - -	- - - -	Ash
- - - -	- - - -	Lapilli
- - - -	- - - -	Earthquakes (undefined)
- - - -	- - - -	Earthquakes (undefined)	After.
- - - -	- - - -	Deformation (inflation)
1985 Dec 19 (in or before)	- - - -	Fatalities
1985 Dec 19	- - - -	VEI (Explosivity Index)

Episode 12 | Eruption

SE Crater

1986 Mar 16 ± 15 days - 1986 Oct 31 (?)

Evidence from Observations: Reported

List of 6 Events for Episode 12 at SE Crater

Start Date	End Date	Event Type
- - - -	- - - -	Explosion
- - - -	- - - -	Lava fountains
- - - -	- - - -	Lava flow
- - - -	- - - -	Scoria
1986 Mar	- - - -	VEI (Explosivity Index)
1986 Oct 31	- - - -	VEI (Explosivity Index)

Episode 13 | Eruption

Valle del Bove (3050-2180 m)

1986 Oct 30 - 1987 Mar 1

Evidence from Observations: Reported

List of 8 Events for Episode 13 at Valle del Bove (3050-2180 m)

Start Date	End Date	Event Type	Event Remarks
- - - -	- - - -	Explosion
- - - -	- - - -	Lava flow
- - - -	- - - -	Cinder Cone
- - - -	- - - -	Ash
- - - -	- - - -	Scoria
- - - -	- - - -	Earthquakes (undefined)	Before.
- - - -	- - - -	Earthquakes (undefined)
1986 Oct 30	- - - -	VEI (Explosivity Index)

Episode 14 | Eruption

NE and SE Craters

1987 Mar 8 ± 8 days - 1987 May 16

Evidence from Observations: Reported

List of 8 Events for Episode 14 at NE and SE Craters

Start Date	End Date	Event Type
- - - -	- - - -	Seismicity (tremor)
- - - -	- - - -	Phreatic activity
- - - -	- - - -	Tephra
- - - -	- - - -	Ash
- - - -	- - - -	Blocks
1987 Mar 8 ± 8 days	- - - -	VEI (Explosivity Index)
1987 Apr 17	- - - -	Fatalities
1987 Apr 17	- - - -	VEI (Explosivity Index)

Episode 15 | Eruption

SE Crater

1988 Oct 2 - 1989 Jun 30

Evidence from Observations: Reported

List of 12 Events for Episode 15 at SE Crater

Start Date	End Date	Event Type	Event Remarks
- - - -	- - - -	Explosion
- - - -	- - - -	Lava fountains
- - - -	- - - -	Lava flow	weak or small
- - - -	- - - -	Ash
- - - -	- - - -	Lapilli
- - - -	- - - -	Bombs
- - - -	- - - -	Blocks
- - - -	- - - -	Scoria
- - - -	- - - -	Earthquakes (undefined)
- - - -	- - - -	Deformation (inflation)
- - - -	- - - -	Deformation (deflation)
1988 Oct 2	- - - -	VEI (Explosivity Index)

Episode 16 | Eruption

SE Crater, SE and NE flanks

1989 Sep 11 - 1989 Oct 9

Evidence from Observations: Reported

List of 15 Events for Episode 16 at SE Crater, SE and NE flanks

Start Date	End Date	Event Type	Event Remarks
- - - -	- - - -	Seismicity (tremor)
- - - -	- - - -	Explosion
- - - -	- - - -	Lava flow
- - - -	- - - -	Lava lake
- - - -	- - - -	Ash
- - - -	- - - -	Bombs
- - - -	- - - -	Blocks
- - - -	- - - -	Scoria
- - - -	- - - -	Earthquakes (undefined)	Before.
- - - -	- - - -	Earthquakes (undefined)
- - - -	- - - -	Earthquakes (undefined)	After.
- - - -	- - - -	Deformation (inflation)
- - - -	- - - -	Deformation (deflation)
- - - -	- - - -	Property Damage
1989 Sep 11	- - - -	VEI (Explosivity Index)

Episode 17 | Eruption

SE and NE Craters

1989 Dec 16 - 1992 May 23

Evidence from Observations: Reported

List of 9 Events for Episode 17 at SE and NE Craters

Start Date	End Date	Event Type
- - - -	- - - -	Seismicity (tremor)
- - - -	- - - -	Explosion
- - - -	- - - -	Lava flow
- - - -	- - - -	Ash
- - - -	- - - -	Bombs
- - - -	- - - -	Blocks
- - - -	- - - -	Scoria
1989 Dec 16	- - - -	VEI (Explosivity Index)
1990 Jan 4	- - - -	VEI (Explosivity Index)

Episode 18 | Eruption

SE flank (3100-2800 m and 2400-2100 m)

1991 Dec 14 - 1993 Mar 30

Evidence from Observations: Reported

List of 11 Events for Episode 18 at SE flank (3100-2800 m and 2400-2100 m)

Start Date	End Date	Event Type	Event Remarks
- - - -	- - - -	Seismicity (tremor)
- - - -	- - - -	Explosion
- - - -	- - - -	Lava fountains
- - - -	- - - -	Lava flow
- - - -	- - - -	Cinder Cone
- - - -	- - - -	Earthquakes (undefined)	Before.
- - - -	- - - -	Earthquakes (undefined)
- - - -	- - - -	Deformation (inflation)
- - - -	- - - -	Deformation (deflation)
- - - -	- - - -	Property Damage
1991 Dec 14	- - - -	VEI (Explosivity Index)

Episode 19 | Eruption

NE Crater

1993 Feb 3 - 1993 Feb 3

Evidence from Observations: Reported

List of 4 Events for Episode 19 at NE Crater

Start Date	End Date	Event Type
- - - -	- - - -	Phreatic activity
- - - -	- - - -	Ash
- - - -	- - - -	Blocks
1993 Feb 3	- - - -	VEI (Explosivity Index)

1971 Sep 19 - 1979 Mar 16 (?) ± 15 days Confirmed Eruption VEI: 2

Episode 1 | Eruption

Central Crater

1971 Sep 19 - 1979 Mar 16 (?) ± 15 days

Evidence from Observations: Reported

List of 3 Events for Episode 1 at Central Crater

Start Date	End Date	Event Type
- - - -	- - - -	Explosion
- - - -	- - - -	Ash
1971 Sep 19	- - - -	VEI (Explosivity Index)

Episode 2 | Eruption

West flank (1670 m and 1650 m)

1974 Jan 30 - 1974 Mar 29

Evidence from Observations: Reported

List of 11 Events for Episode 2 at West flank (1670 m and 1650 m)

Start Date	End Date	Event Type	Event Remarks
- - - -	- - - -	Explosion	moderate
- - - -	- - - -	Fissure
- - - -	- - - -	Lava flow	moderate
- - - -	- - - -	Cinder Cone
- - - -	- - - -	Ash
- - - -	- - - -	Bombs
- - - -	- - - -	Blocks
- - - -	- - - -	Earthquakes (undefined)	Before.
- - - -	- - - -	Earthquakes (undefined)
- - - -	- - - -	Property Damage
1974 Jan 30	- - - -	VEI (Explosivity Index)

Episode 3 | Eruption

NE Crater

1974 Sep 29 (?) - 1978 Mar 29

Evidence from Observations: Reported

List of 8 Events for Episode 3 at NE Crater

Start Date	End Date	Event Type	Event Remarks
- - - -	- - - -	Explosion	moderate
- - - -	- - - -	Lava fountains
- - - -	- - - -	Lava flow	violent, strong, or large
- - - -	- - - -	Ash
- - - -	- - - -	Bombs
- - - -	- - - -	Scoria
- - - -	- - - -	Earthquakes (undefined)
1974 Sep 29 (?)	- - - -	VEI (Explosivity Index)

Episode 4 | Eruption

North flank (2625 m)

1975 Feb 24 - 1975 Aug 29

Evidence from Observations: Reported

List of 4 Events for Episode 4 at North flank (2625 m)

Start Date	End Date	Event Type	Event Remarks
- - - -	- - - -	Explosion	weak or small
- - - -	- - - -	Lava flow	violent, strong, or large
- - - -	- - - -	Scoria
1975 Feb 24	- - - -	VEI (Explosivity Index)

Episode 5 | Eruption

SE Crater, SE and ENE flanks (3050-1675 m)

1978 Apr 29 - 1978 Nov 30

Evidence from Observations: Reported

List of 9 Events for Episode 5 at SE Crater, SE and ENE flanks (3050-1675 m)

Start Date	End Date	Event Type	Event Remarks
- - - -	- - - -	Explosion
- - - -	- - - -	Lava fountains
- - - -	- - - -	Lava flow
- - - -	- - - -	Ash
- - - -	- - - -	Bombs
- - - -	- - - -	Crater	Parasitic.
1978 Apr 29	- - - -	VEI (Explosivity Index)
1978 Aug 22	- - - -	VEI (Explosivity Index)
1978 Nov 18	- - - -	VEI (Explosivity Index)

1966 Jan 10 - 1971 Jun 12 Confirmed Eruption VEI: 2

Episode 1 | Eruption

NE Crater, Central Crater

1966 Jan 10 - 1971 Mar 16 (?) ± 15 days

Evidence from Observations: Reported

List of 6 Events for Episode 1 at NE Crater, Central Crater

Start Date	End Date	Event Type
- - - -	- - - -	Explosion
- - - -	- - - -	Lava flow
- - - -	- - - -	Ash
- - - -	- - - -	Scoria
- - - -	- - - -	Earthquake (tectonic)
1966 Jan 10	- - - -	VEI (Explosivity Index)

Episode 2 | Eruption

SE flank (2550 m)

1968 Jan 7 - 1968 May 4

Evidence from Observations: Reported

List of 2 Events for Episode 2 at SE flank (2550 m)

	Start Date	End Date	Event Type	Event Remarks
	- - - -	- - - -	Lava flow
	1968 Jan 7	- - - -	VEI (Explosivity Index)

Episode 3 | Eruption

SE flank (3050 m), E flank (2880-1800 m)

1971 Apr 5 - 1971 Jun 12

Evidence from Observations: Reported

List of 9 Events for Episode 3 at SE flank (3050 m), E flank (2880-1800 m)

Start Date	End Date	Event Type	Event Remarks
- - - -	- - - -	Explosion
- - - -	- - - -	Phreatomagmatic
- - - -	- - - -	Lava flow	violent, strong, or large
- - - -	- - - -	Cinder Cone
- - - -	- - - -	Ash
- - - -	- - - -	Blocks
- - - -	- - - -	Scoria
- - - -	- - - -	Property Damage
1971 Apr 5	- - - -	VEI (Explosivity Index)

1959 Oct 17 - 1964 Dec 31 Confirmed Eruption VEI: 3

Episode 1 | Eruption

Central and NE Craters, NNE (3100 m)

1959 Oct 17 - 1964 Dec 31

Evidence from Observations: Reported

List of 10 Events for Episode 1 at Central and NE Craters, NNE (3100 m)

Start Date	End Date	Event Type
- - - -	- - - -	Explosion
- - - -	- - - -	Lava fountains
- - - -	- - - -	Lava flow
- - - -	- - - -	Ash
- - - -	- - - -	Blocks
- - - -	- - - -	Earthquakes (undefined)
- - - -	- - - -	Property Damage
1959 Oct 17	- - - -	VEI (Explosivity Index)
1960 Jul 17	- - - -	VEI (Explosivity Index)
1964 Feb 1	- - - -	VEI (Explosivity Index)

1959 Mar 23 - 1959 Apr 25 ± 5 days Confirmed Eruption VEI: 1

Episode 1 | Eruption

Central Crater

1959 Mar 23 - 1959 Apr 25 ± 5 days

Evidence from Observations: Reported

List of 3 Events for Episode 1 at Central Crater

Start Date	End Date	Event Type
- - - -	- - - -	Explosion
- - - -	- - - -	Ash
1959 Mar 23	- - - -	VEI (Explosivity Index)

1958 Nov 16 ± 15 days - 1958 Dec 16 ± 15 days Confirmed Eruption VEI: 1

Episode 1 | Eruption

NE Crater, Central Crater

1958 Nov 16 ± 15 days - 1958 Dec 16 ± 15 days

Evidence from Observations: Reported

List of 2 Events for Episode 1 at NE Crater, Central Crater

	Start Date	End Date	Event Type	Event Remarks
	- - - -	- - - -	Explosion	weak or small
	1958 Nov	- - - -	VEI (Explosivity Index)

1957 Aug 25 - 1958 May 3 Confirmed Eruption VEI: 2

Episode 1 | Eruption

NE Crater

1957 Aug 25 - 1958 May 3

Evidence from Observations: Reported

List of 6 Events for Episode 1 at NE Crater

Start Date	End Date	Event Type
- - - -	- - - -	Explosion
- - - -	- - - -	Lava flow
- - - -	- - - -	Ash
- - - -	- - - -	Blocks
- - - -	- - - -	Scoria
1957 Aug 25	- - - -	VEI (Explosivity Index)

1957 Feb 5 - 1957 May 7 Confirmed Eruption VEI: 2

Episode 1 | Eruption

NE Crater

1957 Feb 5 - 1957 May 7

Evidence from Observations: Reported

List of 6 Events for Episode 1 at NE Crater

Start Date	End Date	Event Type
- - - -	- - - -	Explosion
- - - -	- - - -	Lava flow
- - - -	- - - -	Ash
- - - -	- - - -	Scoria
- - - -	- - - -	Earthquakes (undefined)
1957 Feb 5	- - - -	VEI (Explosivity Index)

1955 Apr 5 - 1956 Apr 7 Confirmed Eruption VEI: 2

Episode 1 | Eruption

NE Crater, Central Crater

1955 Apr 5 - 1956 Apr 7

Evidence from Observations: Reported

List of 8 Events for Episode 1 at NE Crater, Central Crater

Start Date	End Date	Event Type
- - - -	- - - -	Explosion
- - - -	- - - -	Lava flow
- - - -	- - - -	Ash
- - - -	- - - -	Lapilli
- - - -	- - - -	Blocks
- - - -	- - - -	Scoria
1955 Apr 5	- - - -	VEI (Explosivity Index)
1956 Feb 28	- - - -	VEI (Explosivity Index)

[ 1953 Jul 30 ] Uncertain Eruption

Episode 1 | Eruption

1953 Jul 30 - Unknown

Evidence from Unknown

List of 3 Events for Episode 1

Start Date	End Date	Event Type	Event Remarks
- - - -	- - - -	Explosion	Uncertain
- - - -	- - - -	Ash	Uncertain
1953 Jul 30	- - - -	VEI (Explosivity Index)

1949 Dec 2 - 1952 May 30 Confirmed Eruption VEI: 2

Episode 1 | Eruption

Central Crater and NW flank (2420-1900 m)

1949 Dec 2 - 1949 Dec 5

Evidence from Observations: Reported

List of 9 Events for Episode 1 at Central Crater and NW flank (2420-1900 m)

Start Date	End Date	Event Type	Event Remarks
- - - -	- - - -	Explosion
- - - -	- - - -	Phreatic activity
- - - -	- - - -	Lava flow
- - - -	- - - -	Ash
- - - -	- - - -	Flames
- - - -	- - - -	Earthquakes (undefined)
- - - -	- - - -	Earthquakes (undefined)	Before.
- - - -	- - - -	Property Damage
1949 Dec 2	- - - -	VEI (Explosivity Index)

Episode 2 | Eruption

NE Crater

1949 Dec 3 - 1950 Nov 16 ± 15 days

Evidence from Observations: Reported

List of 3 Events for Episode 2 at NE Crater

Start Date	End Date	Event Type
- - - -	- - - -	Explosion
- - - -	- - - -	Ash
1949 Dec 3	- - - -	VEI (Explosivity Index)

Episode 3 | Eruption

East flank (2820-2200 m)

1950 Nov 25 - 1951 Dec 2

Evidence from Observations: Reported

List of 13 Events for Episode 3 at East flank (2820-2200 m)

Start Date	End Date	Event Type	Event Remarks
- - - -	- - - -	Explosion
- - - -	- - - -	Phreatic activity
- - - -	- - - -	Lava flow
- - - -	- - - -	Cinder Cone
- - - -	- - - -	Ash
- - - -	- - - -	Bombs
- - - -	- - - -	Scoria
- - - -	- - - -	Earthquakes (undefined)	Before.
- - - -	- - - -	Earthquakes (undefined)
- - - -	- - - -	Earthquakes (undefined)	After.
- - - -	- - - -	Property Damage
- - - -	- - - -	Evacuations
1950 Nov 25	- - - -	VEI (Explosivity Index)

Episode 4 | Eruption

NE Crater

1951 Sep 21 - 1952 May 30

Evidence from Observations: Reported

List of 2 Events for Episode 4 at NE Crater

	Start Date	End Date	Event Type	Event Remarks
	- - - -	- - - -	Explosion
	1951 Sep 21	- - - -	VEI (Explosivity Index)

1947 Jan 29 - 1947 Mar 10 Confirmed Eruption VEI: 3 (?)

Episode 1 | Eruption

NE Crater, Central Crater

1947 Jan 29 - 1947 Feb 24

Evidence from Observations: Reported

List of 7 Events for Episode 1 at NE Crater, Central Crater

Start Date	End Date	Event Type
- - - -	- - - -	Explosion
- - - -	- - - -	Lava fountains
- - - -	- - - -	Ash
- - - -	- - - -	Lapilli
- - - -	- - - -	Bombs
1947 Jan 29	- - - -	VEI (Explosivity Index)
1947 Feb 5	- - - -	VEI (Explosivity Index)

Episode 2 | Eruption

NE flank (3050-2150 m)

1947 Feb 24 - 1947 Mar 10

Evidence from Observations: Reported

List of 5 Events for Episode 2 at NE flank (3050-2150 m)

Start Date	End Date	Event Type
- - - -	- - - -	Explosion
- - - -	- - - -	Lava flow
- - - -	- - - -	Tephra
- - - -	- - - -	Property Damage
1947 Feb 24	- - - -	VEI (Explosivity Index)

1946 Feb - 1946 Oct Confirmed Eruption VEI: 1

Episode 1 | Eruption

NE Crater

1946 Feb - 1946 Oct

Evidence from Observations: Reported

List of 2 Events for Episode 1 at NE Crater

	Start Date	End Date	Event Type	Event Remarks
	- - - -	- - - -	Explosion
	1946 Feb	- - - -	VEI (Explosivity Index)

1945 Jun 5 ± 4 days - 1945 Oct Confirmed Eruption VEI: 1

Episode 1 | Eruption

NE Crater

1945 Jun 5 ± 4 days - 1945 Oct

Evidence from Observations: Reported

List of 2 Events for Episode 1 at NE Crater

	Start Date	End Date	Event Type	Event Remarks
	- - - -	- - - -	Explosion
	1945 Jun 5 ± 4 days	- - - -	VEI (Explosivity Index)

1941 Oct (?) - 1944 Apr 26 ± 4 days Confirmed Eruption VEI: 2

Episode 1 | Eruption

Central Crater, NE Crater

1941 Oct (?) - 1944 Apr 26 ± 4 days

Evidence from Observations: Reported

List of 4 Events for Episode 1 at Central Crater, NE Crater

Start Date	End Date	Event Type
- - - -	- - - -	Explosion
- - - -	- - - -	Lava fountains
- - - -	- - - -	Ash
1941 Oct (?)	- - - -	VEI (Explosivity Index)

Episode 2 | Eruption

SW flank (2780-2240 m)

1942 Jun 30 - 1942 Jul 1

Evidence from Observations: Reported

List of 4 Events for Episode 2 at SW flank (2780-2240 m)

Start Date	End Date	Event Type
- - - -	- - - -	Explosion
- - - -	- - - -	Lava flow
- - - -	- - - -	Earthquakes (undefined)
1942 Jun 30	- - - -	VEI (Explosivity Index)

1935 Jul 7 - 1941 Jan 27 (?) Confirmed Eruption VEI: 3

Episode 1 | Eruption

Central Crater, NE Crater

1935 Jul 7 - 1941 Jan 27 (?)

Evidence from Observations: Reported

List of 8 Events for Episode 1 at Central Crater, NE Crater

Start Date	End Date	Event Type	Event Remarks
- - - -	- - - -	Explosion
- - - -	- - - -	Lava fountains
- - - -	- - - -	Lava flow	moderate
- - - -	- - - -	Ash
- - - -	- - - -	Lapilli
- - - -	- - - -	Property Damage
1935 Jul 7	- - - -	VEI (Explosivity Index)
1940 Mar 16	- - - -	VEI (Explosivity Index)

1934 Jan 5 - 1934 Mar Confirmed Eruption VEI: 1

Episode 1 | Eruption

NE Crater

1934 Jan 5 - 1934 Mar

Evidence from Observations: Reported

List of 2 Events for Episode 1 at NE Crater

	Start Date	End Date	Event Type	Event Remarks
	- - - -	- - - -	Explosion
	1934 Jan 5	- - - -	VEI (Explosivity Index)

1931 Jul 26 ± 5 days - 1933 Sep Confirmed Eruption VEI: 2

Episode 1 | Eruption

Central Crater, NE Crater

1931 Jul 26 ± 5 days - 1933 Sep

Evidence from Observations: Reported

List of 2 Events for Episode 1 at Central Crater, NE Crater

	Start Date	End Date	Event Type	Event Remarks
	- - - -	- - - -	Explosion
	1931 Jul 26 ± 5 days	- - - -	VEI (Explosivity Index)

1930 Nov 1 Confirmed Eruption VEI: 1

Episode 1 | Eruption

NE Crater

1930 Nov 1 - Unknown

Evidence from Observations: Reported

List of 2 Events for Episode 1 at NE Crater

	Start Date	End Date	Event Type	Event Remarks
	- - - -	- - - -	Explosion
	1930 Nov 1	- - - -	VEI (Explosivity Index)

1929 Aug 2 Confirmed Eruption VEI: 1

Episode 1 | Eruption

NE Crater

1929 Aug 2 - Unknown

Evidence from Observations: Reported

List of 3 Events for Episode 1 at NE Crater

Start Date	End Date	Event Type
- - - -	- - - -	Explosion
1929 Aug 2	- - - -	Fatalities
1929 Aug 2	- - - -	VEI (Explosivity Index)

1928 Jul 31 - 1928 Nov 20 Confirmed Eruption VEI: 1

Episode 1 | Eruption

Central Crater

1928 Jul 31 - 1928 Aug 20

Evidence from Observations: Reported

List of 2 Events for Episode 1 at Central Crater

	Start Date	End Date	Event Type	Event Remarks
	- - - -	- - - -	Explosion
	1928 Jul 31	- - - -	VEI (Explosivity Index)

Episode 2 | Eruption

East flank (3000-1200 m), NE Crater

1928 Nov 2 - 1928 Nov 20

Evidence from Observations: Reported

List of 11 Events for Episode 2 at East flank (3000-1200 m), NE Crater

Start Date	End Date	Event Type	Event Remarks
- - - -	- - - -	Seismicity (volcanic)
- - - -	- - - -	Explosion
- - - -	- - - -	Lava flow
- - - -	- - - -	Ash
- - - -	- - - -	Scoria
- - - -	- - - -	Audible Sounds
- - - -	- - - -	Collapse	Event was "Partial collapse at end of eruption"
- - - -	- - - -	Property Damage
- - - -	- - - -	Evacuations
1928 Nov 2	- - - -	VEI (Explosivity Index)
1928 Nov 8	- - - -	Fatalities

1926 Jan 2 - 1926 Jun Confirmed Eruption VEI: 1

Episode 1 | Eruption

NE Crater

1926 Jan 2 - 1926 Jun

Evidence from Observations: Reported

List of 2 Events for Episode 1 at NE Crater

	Start Date	End Date	Event Type	Event Remarks
	- - - -	- - - -	Explosion
	1926 Jan 2	- - - -	VEI (Explosivity Index)

1919 Mar 15 - 1925 Feb Confirmed Eruption VEI: 2

Episode 1 | Eruption

Central Crater, NE Crater

1919 Mar 15 - 1923 Jul (?)

Evidence from Observations: Reported

List of 5 Events for Episode 1 at Central Crater, NE Crater

Start Date	End Date	Event Type
- - - -	- - - -	Explosion
- - - -	- - - -	Lava flow
- - - -	- - - -	Cinder Cone
- - - -	- - - -	Ash
1919 Mar 15	- - - -	VEI (Explosivity Index)

Episode 2 | Eruption

NE flank (2500-1800 m)

1923 Jun 17 - 1923 Jul 18

Evidence from Observations: Reported

List of 6 Events for Episode 2 at NE flank (2500-1800 m)

Start Date	End Date	Event Type	Event Remarks
- - - -	- - - -	Explosion
- - - -	- - - -	Lava flow
- - - -	- - - -	Earthquakes (undefined)	Before.
- - - -	- - - -	Earthquakes (undefined)
- - - -	- - - -	Property Damage
1923 Jun 17	- - - -	VEI (Explosivity Index)

Episode 3 | Eruption

Central Crater

1923 Oct 9 - 1925 Feb

Evidence from Observations: Reported

List of 4 Events for Episode 3 at Central Crater

Start Date	End Date	Event Type	Event Remarks
- - - -	- - - -	Explosion
- - - -	- - - -	Ash
- - - -	- - - -	Collapse	Event was "Partial collapse at end of eruption"
1923 Oct 9	- - - -	VEI (Explosivity Index)

1918 Mar - 1918 Dec 1 (?) Confirmed Eruption VEI: 2

Episode 1 | Eruption

NE Crater, Central Crater

1918 Mar - 1918 Nov

Evidence from Observations: Reported

List of 4 Events for Episode 1 at NE Crater, Central Crater

Start Date	End Date	Event Type
- - - -	- - - -	Explosion
- - - -	- - - -	Lava flow
1918 Mar	- - - -	VEI (Explosivity Index)
1918 Oct 7	- - - -	VEI (Explosivity Index)

Episode 2 | Eruption

North flank (3110-2025 m)

1918 Nov 30 (?) - 1918 Dec 1 (?)

Evidence from Observations: Reported

List of 3 Events for Episode 2 at North flank (3110-2025 m)

Start Date	End Date	Event Type
- - - -	- - - -	Explosion
- - - -	- - - -	Lava flow
1918 Nov 30 (?)	- - - -	VEI (Explosivity Index)

1917 Jun 24 - 1917 Jul 5 ± 4 days Confirmed Eruption VEI: 2

Episode 1 | Eruption

NE Crater, Central Crater

1917 Jun 24 - 1917 Jul 5 ± 4 days

Evidence from Observations: Reported

List of 6 Events for Episode 1 at NE Crater, Central Crater

Start Date	End Date	Event Type	Event Remarks
- - - -	- - - -	Explosion
- - - -	- - - -	Lava flow	weak or small
- - - -	- - - -	Ash
- - - -	- - - -	Lapilli
- - - -	- - - -	Property Damage
1917 Jun 24	- - - -	VEI (Explosivity Index)

1913 Nov 13 - 1917 Mar Confirmed Eruption VEI: 2

Episode 1 | Eruption

Central Crater, NE Crater

1913 Nov 13 - 1917 Mar

Evidence from Observations: Reported

List of 3 Events for Episode 1 at Central Crater, NE Crater

Start Date	End Date	Event Type
- - - -	- - - -	Explosion
- - - -	- - - -	Lava flow
1913 Nov 13	- - - -	VEI (Explosivity Index)

1912 Aug 4 - 1912 Aug Confirmed Eruption VEI: 3

Episode 1 | Eruption

Central Crater

1912 Aug 4 - 1912 Aug

Evidence from Observations: Reported

List of 3 Events for Episode 1 at Central Crater

Start Date	End Date	Event Type
- - - -	- - - -	Explosion
- - - -	- - - -	Lava flow
1912 Aug 4	- - - -	VEI (Explosivity Index)

1911 Aug - 1911 Sep 26 ± 4 days Confirmed Eruption VEI: 2

Episode 1 | Eruption

Central Crater, NE Crater?

1911 Aug - 1911 Sep 26 ± 4 days

Evidence from Observations: Reported

List of 3 Events for Episode 1 at Central Crater, NE Crater?

Start Date	End Date	Event Type
- - - -	- - - -	Explosion
- - - -	- - - -	Ash
1911 Aug	- - - -	VEI (Explosivity Index)

Episode 2 | Eruption

NE flank (2550-1625 m)

1911 Sep 10 - 1911 Sep 22

Evidence from Observations: Reported

List of 7 Events for Episode 2 at NE flank (2550-1625 m)

Start Date	End Date	Event Type	Event Remarks
- - - -	- - - -	Explosion
- - - -	- - - -	Lava flow
- - - -	- - - -	Tephra
- - - -	- - - -	Earthquakes (undefined)	Before.
- - - -	- - - -	Earthquakes (undefined)
- - - -	- - - -	Property Damage
1911 Sep 10	- - - -	VEI (Explosivity Index)

[ 1911 May 27 ] Discredited Eruption

A collapse event formed NE Crater; no eruption (CAVW; Tanguy, 1981).

1910 Dec 27 - 1911 Feb 17 Confirmed Eruption VEI: 2

Episode 1 | Eruption

Central Crater

1910 Dec 27 - 1911 Feb 17

Evidence from Observations: Reported

List of 5 Events for Episode 1 at Central Crater

Start Date	End Date	Event Type	Event Remarks
- - - -	- - - -	Explosion
- - - -	- - - -	Lava flow	Uncertain
- - - -	- - - -	Ash
- - - -	- - - -	Lapilli
1910 Dec 27	- - - -	VEI (Explosivity Index)

1910 Feb 21 - 1910 Apr 18 Confirmed Eruption VEI: 2

Episode 1 | Eruption

Central Crater

1910 Feb 21 - 1910 Feb 21

Evidence from Observations: Reported

List of 3 Events for Episode 1 at Central Crater

Start Date	End Date	Event Type	Event Remarks
- - - -	- - - -	Explosion	weak or small
- - - -	- - - -	Ash
1910 Feb 21	- - - -	VEI (Explosivity Index)

Episode 2 | Eruption

South flank (2300-1900 m, Mt. Ricco)

1910 Mar 23 - 1910 Apr 18

Evidence from Observations: Reported

List of 9 Events for Episode 2 at South flank (2300-1900 m, Mt. Ricco)

Start Date	End Date	Event Type	Event Remarks
- - - -	- - - -	Explosion
- - - -	- - - -	Lava flow
- - - -	- - - -	Cinder Cone
- - - -	- - - -	Ash
- - - -	- - - -	Scoria
- - - -	- - - -	Earthquakes (undefined)	Before.
- - - -	- - - -	Earthquakes (undefined)
- - - -	- - - -	Property Damage
1910 Mar 23	- - - -	VEI (Explosivity Index)

1908 Apr 29 - 1909 Sep 28 Confirmed Eruption VEI: 2

Episode 1 | Eruption

SE flank (Valle del Bove 2800-2275 m)

1908 Apr 29 - 1908 May 1 ± 1 days

Evidence from Observations: Reported

List of 6 Events for Episode 1 at SE flank (Valle del Bove 2800-2275 m)

Start Date	End Date	Event Type	Event Remarks
- - - -	- - - -	Explosion
- - - -	- - - -	Lava flow
- - - -	- - - -	Tephra
- - - -	- - - -	Earthquakes (undefined)	Before.
- - - -	- - - -	Earthquakes (undefined)
1908 Apr 29	- - - -	VEI (Explosivity Index)

Episode 2 | Eruption

Central Crater

1908 May 20 - 1909 Sep 28

Evidence from Observations: Reported

List of 2 Events for Episode 2 at Central Crater

	Start Date	End Date	Event Type	Event Remarks
	- - - -	- - - -	Explosion
	1908 May 20	- - - -	VEI (Explosivity Index)

1899 Nov 15 - 1907 Aug Confirmed Eruption VEI: 2

Episode 1 | Eruption

1899 Nov 15 - 1907 Aug

Evidence from Observations: Reported

List of 6 Events for Episode 1

Start Date	End Date	Event Type
- - - -	- - - -	Explosion
- - - -	- - - -	Phreatomagmatic
- - - -	- - - -	Lava flow
- - - -	- - - -	Ash
1899 Nov 15	- - - -	VEI (Explosivity Index)
1906 Jan 5	- - - -	VEI (Explosivity Index)

1899 Jul 19 - 1899 Aug 5 Confirmed Eruption VEI: 3

Episode 1 | Eruption

Central Crater

1899 Jul 19 - 1899 Aug 5

Evidence from Observations: Reported

List of 7 Events for Episode 1 at Central Crater

Start Date	End Date	Event Type
- - - -	- - - -	Explosion
- - - -	- - - -	Phreatic activity
- - - -	- - - -	Ash
- - - -	- - - -	Lapilli
- - - -	- - - -	Earthquakes (undefined)
- - - -	- - - -	Property Damage
1899 Jul 19	- - - -	VEI (Explosivity Index)

1893 Apr 26 - 1898 Jun Confirmed Eruption VEI: 1

Episode 1 | Eruption

Central Crater

1893 Apr 26 - 1898 Jun

Evidence from Observations: Reported

List of 4 Events for Episode 1 at Central Crater

Start Date	End Date	Event Type	Event Remarks
- - - -	- - - -	Explosion
- - - -	- - - -	Lava flow
- - - -	- - - -	Earthquakes (undefined)	Before.
1893 Apr 26	- - - -	VEI (Explosivity Index)

1892 Jun 20 - 1892 Dec 29 Confirmed Eruption VEI: 2

Episode 1 | Eruption

Central Crater

1892 Jun 20 - 1892 Jul 8 (?)

Evidence from Observations: Reported

List of 4 Events for Episode 1 at Central Crater

Start Date	End Date	Event Type
- - - -	- - - -	Explosion
- - - -	- - - -	Ash
1892 Jun 20	- - - -	VEI (Explosivity Index)
1892 Jul 8	- - - -	VEI (Explosivity Index)

Episode 2 | Eruption

South flank (2045-1800 m), Mt. Silvestri

1892 Jul 9 - 1892 Dec 29

Evidence from Observations: Reported

List of 10 Events for Episode 2 at South flank (2045-1800 m), Mt. Silvestri

Start Date	End Date	Event Type	Event Remarks
- - - -	- - - -	Explosion
- - - -	- - - -	Lava fountains
- - - -	- - - -	Lava flow
- - - -	- - - -	Cinder Cone
- - - -	- - - -	Ash
- - - -	- - - -	Scoria
- - - -	- - - -	Earthquakes (undefined)	Before.
- - - -	- - - -	Earthquakes (undefined)
- - - -	- - - -	Property Damage
1892 Jul 9	- - - -	VEI (Explosivity Index)

1891 Feb 20 - 1891 Dec Confirmed Eruption VEI: 2

Episode 1 | Eruption

Central Crater

1891 Feb 20 - 1891 Dec

Evidence from Observations: Reported

List of 6 Events for Episode 1 at Central Crater

Start Date	End Date	Event Type	Event Remarks
- - - -	- - - -	Explosion
- - - -	- - - -	Lava fountains
- - - -	- - - -	Lava flow	Uncertain
- - - -	- - - -	Ash
1891 Feb 20	- - - -	VEI (Explosivity Index)
1891 Dec 8	- - - -	VEI (Explosivity Index)

1890 May - 1890 Oct 17 (?) Confirmed Eruption VEI: 2

Episode 1 | Eruption

Central Crater

1890 May - 1890 Oct 17 (?)

Evidence from Observations: Reported

List of 5 Events for Episode 1 at Central Crater

Start Date	End Date	Event Type
- - - -	- - - -	Explosion
- - - -	- - - -	Lava fountains
- - - -	- - - -	Ash
1890 May	- - - -	VEI (Explosivity Index)
1890 Oct 17	- - - -	VEI (Explosivity Index)

1888 Apr 13 (in or before) - 1889 Aug Confirmed Eruption VEI: 2

Episode 1 | Eruption

Central Crater

1888 Apr 13 (in or before) - 1889 Aug

Evidence from Observations: Reported

List of 5 Events for Episode 1 at Central Crater

Start Date	End Date	Event Type
- - - -	- - - -	Explosion
- - - -	- - - -	Lava fountains
- - - -	- - - -	Ash
- - - -	- - - -	Lapilli
1888 Apr 13 (in or before)	- - - -	VEI (Explosivity Index)

1887 May 31 - 1887 Aug Confirmed Eruption VEI: 1

Episode 1 | Eruption

Central Crater

1887 May 31 - 1887 Aug

Evidence from Observations: Reported

List of 3 Events for Episode 1 at Central Crater

Start Date	End Date	Event Type
- - - -	- - - -	Explosion
- - - -	- - - -	Ash
1887 May 31	- - - -	VEI (Explosivity Index)

1884 - 1886 Jun 7 Confirmed Eruption VEI: 3

Episode 1 | Eruption

Central Crater

1884 - 1886 Apr

Evidence from Observations: Reported

List of 3 Events for Episode 1 at Central Crater

Start Date	End Date	Event Type	Event Remarks
- - - -	- - - -	Explosion	weak or small
- - - -	- - - -	Ash
1884	- - - -	VEI (Explosivity Index)

Episode 2 | Eruption

S flank (1525-1320 m), Mt. Gemmellaro

1886 May 18 - 1886 Jun 7

Evidence from Observations: Reported

List of 8 Events for Episode 2 at S flank (1525-1320 m), Mt. Gemmellaro

Start Date	End Date	Event Type	Event Remarks
- - - -	- - - -	Explosion
- - - -	- - - -	Lava flow
- - - -	- - - -	Cinder Cone
- - - -	- - - -	Ash
- - - -	- - - -	Earthquakes (undefined)	Before.
- - - -	- - - -	Earthquakes (undefined)
- - - -	- - - -	Property Damage
1886 May 18	- - - -	VEI (Explosivity Index)

1878 Dec 23 - 1883 Mar 31 (in or after) Confirmed Eruption VEI: 3

Episode 1 | Eruption

Central Crater

1878 Dec 23 - 1883 Mar 31 (in or after)

Evidence from Observations: Reported

List of 6 Events for Episode 1 at Central Crater

Start Date	End Date	Event Type	Event Remarks
- - - -	- - - -	Explosion
- - - -	- - - -	Lava flow
- - - -	- - - -	Earthquakes (undefined)	Before.
- - - -	- - - -	Earthquakes (undefined)
- - - -	- - - -	Property Damage
1878 Dec 23	- - - -	VEI (Explosivity Index)

Episode 2 | Eruption

SSW (2650-2300 m), NNE (2450-1690 m)

1879 May 26 - 1879 Jun 7

Evidence from Observations: Reported

List of 8 Events for Episode 2 at SSW (2650-2300 m), NNE (2450-1690 m)

Start Date	End Date	Event Type	Event Remarks
- - - -	- - - -	Explosion
- - - -	- - - -	Lava flow
- - - -	- - - -	Cinder Cone
- - - -	- - - -	Tephra
- - - -	- - - -	Earthquakes (undefined)	Before.
- - - -	- - - -	Earthquakes (undefined)
- - - -	- - - -	Property Damage
1879 May 26	- - - -	VEI (Explosivity Index)

Episode 3 | Eruption

South flank (1200-950 m, Mt. Leone)

1883 Mar 22 - 1883 Mar 24

Evidence from Observations: Reported

List of 5 Events for Episode 3 at South flank (1200-950 m, Mt. Leone)

Start Date	End Date	Event Type	Event Remarks
- - - -	- - - -	Explosion
- - - -	- - - -	Lava flow
- - - -	- - - -	Tephra
- - - -	- - - -	Earthquakes (undefined)	Time and Type Unknown.
1883 Mar 22	- - - -	VEI (Explosivity Index)

1874 Aug 29 - 1874 Aug 31 Confirmed Eruption VEI: 2

Episode 1 | Eruption

North flank (2520-2110 m), Central Crater

1874 Aug 29 - 1874 Aug 31

Evidence from Observations: Reported

List of 9 Events for Episode 1 at North flank (2520-2110 m), Central Crater

Start Date	End Date	Event Type	Event Remarks
- - - -	- - - -	Explosion
- - - -	- - - -	Lava fountains
- - - -	- - - -	Lava flow
- - - -	- - - -	Ash
- - - -	- - - -	Lapilli
- - - -	- - - -	Scoria
- - - -	- - - -	Earthquakes (undefined)
- - - -	- - - -	Crater	Parasitic.
1874 Aug 29	- - - -	VEI (Explosivity Index)

1874 May Confirmed Eruption VEI: 2

Episode 1 | Eruption

Central Crater

1874 May - Unknown

Evidence from Observations: Reported

List of 2 Events for Episode 1 at Central Crater

	Start Date	End Date	Event Type	Event Remarks
	- - - -	- - - -	Explosion
	1874 May	- - - -	VEI (Explosivity Index)

1869 Sep 26 - 1869 Sep 26 Confirmed Eruption VEI: 0

Episode 1 | Eruption

East flank (W wall of Valle del Bove)

1869 Sep 26 - 1869 Sep 26

Evidence from Observations: Reported

List of 2 Events for Episode 1 at East flank (W wall of Valle del Bove)

	Start Date	End Date	Event Type	Event Remarks
	- - - -	- - - -	Lava flow
	1869 Sep 26	- - - -	VEI (Explosivity Index)

1868 Nov 26 (?) - 1868 Dec 8 Confirmed Eruption VEI: 3

Episode 1 | Eruption

Central Crater

1868 Nov 26 (?) - 1868 Dec 8

Evidence from Observations: Reported

List of 3 Events for Episode 1 at Central Crater

Start Date	End Date	Event Type
- - - -	- - - -	Explosion
- - - -	- - - -	Lava fountains
1868 Nov 26 (?)	- - - -	VEI (Explosivity Index)

1865 Jan 30 - 1865 Jun 28 Confirmed Eruption VEI: 2

Episode 1 | Eruption

NE flank (1865-1690 m, Mt. Sartorius)

1865 Jan 30 - 1865 Jun 28

Evidence from Observations: Reported

List of 9 Events for Episode 1 at NE flank (1865-1690 m, Mt. Sartorius)

Start Date	End Date	Event Type	Event Remarks
- - - -	- - - -	Explosion
- - - -	- - - -	Lava flow
- - - -	- - - -	Cinder Cone
- - - -	- - - -	Ash
- - - -	- - - -	Lapilli
- - - -	- - - -	Earthquakes (undefined)	Before.
- - - -	- - - -	Earthquakes (undefined)
- - - -	- - - -	Property Damage
1865 Jan 30	- - - -	VEI (Explosivity Index)

1864 Aug 5 ± 4 days - 1864 Sep 19 Confirmed Eruption VEI: 2

Episode 1 | Eruption

Central Crater

1864 Aug 5 ± 4 days - 1864 Sep 19

Evidence from Observations: Reported

List of 3 Events for Episode 1 at Central Crater

Start Date	End Date	Event Type
- - - -	- - - -	Explosion
- - - -	- - - -	Lava flow
1864 Aug 5 ± 4 days	- - - -	VEI (Explosivity Index)

1863 May 1 - 1863 Jul 25 (?) Confirmed Eruption VEI: 3 (?)

Episode 1 | Eruption

Central Crater

1863 May 1 - 1863 Jul 25 (?)

Evidence from Observations: Reported

List of 9 Events for Episode 1 at Central Crater

Start Date	End Date	Event Type
- - - -	- - - -	Explosion
- - - -	- - - -	Lava fountains
- - - -	- - - -	Lava flow
- - - -	- - - -	Ash
- - - -	- - - -	Lapilli
- - - -	- - - -	Bombs
- - - -	- - - -	Property Damage
1863 May 1	- - - -	VEI (Explosivity Index)
1863 Jul 7	- - - -	VEI (Explosivity Index)

[ 1857 Sep 6 ] Uncertain Eruption

Episode 1 | Eruption

Central Crater

1857 Sep 6 - Unknown

Evidence from Unknown

List of 2 Events for Episode 1 at Central Crater

	Start Date	End Date	Event Type	Event Remarks
	- - - -	- - - -	Explosion	Uncertain
	1857 Sep 6	- - - -	VEI (Explosivity Index)

1852 Aug 20 - 1853 May 27 Confirmed Eruption VEI: 2

Episode 1 | Eruption

East (Valle del Bove 1950-1700 m)

1852 Aug 20 - 1853 May 27

Evidence from Observations: Reported

List of 8 Events for Episode 1 at East (Valle del Bove 1950-1700 m)

Start Date	End Date	Event Type
- - - -	- - - -	Explosion
- - - -	- - - -	Lava flow
- - - -	- - - -	Cinder Cone
- - - -	- - - -	Ash
- - - -	- - - -	Scoria
- - - -	- - - -	Earthquakes (undefined)
- - - -	- - - -	Property Damage
1852 Aug 20	- - - -	VEI (Explosivity Index)

1843 Nov 17 - 1843 Dec 16 (?) Confirmed Eruption VEI: 2

Episode 1 | Eruption

West flank (2400-1900 m), Central Crater

1843 Nov 17 - 1843 Dec 16 (?)

Evidence from Observations: Reported

List of 10 Events for Episode 1 at West flank (2400-1900 m), Central Crater

Start Date	End Date	Event Type	Event Remarks
- - - -	- - - -	Explosion
- - - -	- - - -	Lava flow
- - - -	- - - -	Ash
- - - -	- - - -	Scoria
- - - -	- - - -	Earthquakes (undefined)	Before.
- - - -	- - - -	Earthquakes (undefined)
- - - -	- - - -	Collapse	Event was "Partial collapse at end of eruption"
- - - -	- - - -	Property Damage
1843 Nov 17	- - - -	VEI (Explosivity Index)
1843 Nov 25	- - - -	Fatalities

1842 Nov 18 - 1842 Dec 29 (?) Confirmed Eruption VEI: 2

Episode 1 | Eruption

Central Crater (south & east slopes)

1842 Nov 18 - 1842 Dec 29 (?)

Evidence from Observations: Reported

List of 7 Events for Episode 1 at Central Crater (south & east slopes)

Start Date	End Date	Event Type
- - - -	- - - -	Explosion
- - - -	- - - -	Lava fountains
- - - -	- - - -	Lava flow
- - - -	- - - -	Cinder Cone
- - - -	- - - -	Ash
- - - -	- - - -	Scoria
1842 Nov 18	- - - -	VEI (Explosivity Index)

1838 Jul 8 - 1839 Feb Confirmed Eruption VEI: 2

Episode 1 | Eruption

Central Crater

1838 Jul 8 - 1839 Feb

Evidence from Observations: Reported

List of 4 Events for Episode 1 at Central Crater

Start Date	End Date	Event Type
- - - -	- - - -	Explosion
- - - -	- - - -	Lava flow
- - - -	- - - -	Earthquakes (undefined)
1838 Jul 8	- - - -	VEI (Explosivity Index)

1832 Oct 31 - 1832 Nov 22 Confirmed Eruption VEI: 2

Episode 1 | Eruption

SSE, W flanks (3000-1700? m), Mt. Nunziata

1832 Oct 31 - 1832 Nov 22

Evidence from Observations: Reported

List of 7 Events for Episode 1 at SSE, W flanks (3000-1700? m), Mt. Nunziata

Start Date	End Date	Event Type
- - - -	- - - -	Explosion
- - - -	- - - -	Lava flow
- - - -	- - - -	Tephra
- - - -	- - - -	Earthquakes (undefined)
- - - -	- - - -	Property Damage
1832	- - - -	Fatalities
1832 Oct 31	- - - -	VEI (Explosivity Index)

1820 Dec (?) - 1833 Confirmed Eruption VEI: 2

Episode 1 | Eruption

Central Crater

1820 Dec (?) - 1833

Evidence from Observations: Reported

List of 13 Events for Episode 1 at Central Crater

Start Date	End Date	Event Type	Event Remarks
- - - -	- - - -	Explosion
- - - -	- - - -	Lava flow
- - - -	- - - -	Ash
- - - -	- - - -	Earthquakes (undefined)
- - - -	- - - -	Collapse	Event was "Partial collapse at end of eruption"
1820 Dec (?)	- - - -	VEI (Explosivity Index)
1822 Jun 21	- - - -	VEI (Explosivity Index)
1823 Dec 27	- - - -	VEI (Explosivity Index)
1827 Oct 10	- - - -	VEI (Explosivity Index)
1828 Aug 23	- - - -	VEI (Explosivity Index)
1829 Nov 11	- - - -	VEI (Explosivity Index)
1830 Mar	- - - -	VEI (Explosivity Index)
1831 Mar 4	- - - -	VEI (Explosivity Index)

1819 May 27 - 1819 Aug 5 Confirmed Eruption VEI: 2 (?)

Episode 1 | Eruption

Valle del Bove 2850-2375 m, Central Crater

1819 May 27 - 1819 Aug 5

Evidence from Observations: Reported

List of 6 Events for Episode 1 at Valle del Bove 2850-2375 m, Central Crater

Start Date	End Date	Event Type
- - - -	- - - -	Explosion
- - - -	- - - -	Lava flow
- - - -	- - - -	Ash
- - - -	- - - -	Earthquakes (undefined)
1819 May 27	- - - -	VEI (Explosivity Index)
1819 Jun 13	- - - -	VEI (Explosivity Index)

[ 1816 Mar 6 ] Uncertain Eruption

Episode 1 | Eruption

Offshore from Aci-Castello

1816 Mar 6 - Unknown

Evidence from Unknown

List of 1 Events for Episode 1 at Offshore from Aci-Castello

	Start Date	End Date	Event Type	Event Remarks
	1816 Mar 6	- - - -	VEI (Explosivity Index)

1811 Oct 27 - 1812 May (?) Confirmed Eruption VEI: 2

Episode 1 | Eruption

East (Valle del Bove 3000-1975 m)

1811 Oct 27 - 1812 May (?)

Evidence from Observations: Reported

List of 7 Events for Episode 1 at East (Valle del Bove 3000-1975 m)

Start Date	End Date	Event Type	Event Remarks
- - - -	- - - -	Explosion
- - - -	- - - -	Lava flow
- - - -	- - - -	Cinder Cone
- - - -	- - - -	Scoria
- - - -	- - - -	Earthquakes (undefined)	Time and Type Unknown.
1811 Oct 27	- - - -	VEI (Explosivity Index)
1811 Oct 31	- - - -	VEI (Explosivity Index)

1809 Mar 27 - 1809 Apr 9 Confirmed Eruption VEI: 2

Episode 1 | Eruption

Central Crater, N & NE flanks (3000-1325 m)

1809 Mar 27 - 1809 Apr 9

Evidence from Observations: Reported

List of 10 Events for Episode 1 at Central Crater, N & NE flanks (3000-1325 m)

Start Date	End Date	Event Type	Event Remarks
- - - -	- - - -	Explosion
- - - -	- - - -	Lava flow
- - - -	- - - -	Cinder Cone
- - - -	- - - -	Ash
- - - -	- - - -	Scoria
- - - -	- - - -	Audible Sounds
- - - -	- - - -	Earthquakes (undefined)
- - - -	- - - -	Crater	Summit.
- - - -	- - - -	Property Damage
1809 Mar 27	- - - -	VEI (Explosivity Index)

1803 Jan 1 - 1819 (?) Confirmed Eruption VEI: 2

Episode 1 | Eruption

Central Crater

1803 Jan 1 - 1819 (?)

Evidence from Observations: Reported

List of 9 Events for Episode 1 at Central Crater

Start Date	End Date	Event Type
- - - -	- - - -	Explosion
- - - -	- - - -	Lava fountains
- - - -	- - - -	Lava flow
1803 Jan 1	- - - -	VEI (Explosivity Index)
1805 Mar 11	- - - -	VEI (Explosivity Index)
1805 Jul 11	- - - -	VEI (Explosivity Index)
1807 Jan 12	- - - -	VEI (Explosivity Index)
1808 Jul	- - - -	VEI (Explosivity Index)
1810 Dec 26 ± 5 days	- - - -	VEI (Explosivity Index)

1802 Nov 15 - 1802 Nov 18 Confirmed Eruption VEI: 2

Episode 1 | Eruption

Central Crater, E flank (1950-1700 m)

1802 Nov 15 - 1802 Nov 18

Evidence from Observations: Reported

List of 3 Events for Episode 1 at Central Crater, E flank (1950-1700 m)

Start Date	End Date	Event Type
- - - -	- - - -	Explosion
- - - -	- - - -	Lava flow
1802 Nov 15	- - - -	VEI (Explosivity Index)

1793 (?) - 1802 (?) Confirmed Eruption VEI: 3 (?)

Episode 1 | Eruption

Central Crater

1793 (?) - 1802 (?)

Evidence from Observations: Reported

List of 10 Events for Episode 1 at Central Crater

Start Date	End Date	Event Type
- - - -	- - - -	Explosion
- - - -	- - - -	Lava fountains
- - - -	- - - -	Lava flow
- - - -	- - - -	Ash
- - - -	- - - -	Scoria
- - - -	- - - -	Lightning
- - - -	- - - -	Earthquakes (undefined)
1793 (?)	- - - -	VEI (Explosivity Index)
1797 Jan	- - - -	VEI (Explosivity Index)
1800 Mar 4	- - - -	VEI (Explosivity Index)

1792 Mar - 1793 May 26 ± 5 days Confirmed Eruption VEI: 3

Episode 1 | Eruption

Central Crater, west slope

1792 Mar - 1792 May 24

Evidence from Observations: Reported

List of 6 Events for Episode 1 at Central Crater, west slope

Start Date	End Date	Event Type	Event Remarks
- - - -	- - - -	Explosion
- - - -	- - - -	Lava fountains
- - - -	- - - -	Lava flow
- - - -	- - - -	Earthquakes (undefined)	Before.
- - - -	- - - -	Earthquakes (undefined)
1792 Mar	- - - -	VEI (Explosivity Index)

Episode 2 | Eruption

Summit, SE flank (2825-1500 m)

1792 May 25 - 1793 May 26 ± 5 days

Evidence from Observations: Reported

List of 8 Events for Episode 2 at Summit, SE flank (2825-1500 m)

Start Date	End Date	Event Type
- - - -	- - - -	Explosion
- - - -	- - - -	Phreatic activity
- - - -	- - - -	Lava flow
- - - -	- - - -	Ash
- - - -	- - - -	Blocks
- - - -	- - - -	Earthquakes (undefined)
- - - -	- - - -	Property Damage
1792 May 25	- - - -	VEI (Explosivity Index)

1791 Feb - 1791 Sep Confirmed Eruption VEI: 2

Episode 1 | Eruption

Central Crater

1791 Feb - 1791 Sep

Evidence from Observations: Reported

List of 3 Events for Episode 1 at Central Crater

Start Date	End Date	Event Type
- - - -	- - - -	Explosion
- - - -	- - - -	Audible Sounds
1791 Feb	- - - -	VEI (Explosivity Index)

1787 Jun 4 ± 4 days - 1787 Aug 11 Confirmed Eruption VEI: 4

Episode 1 | Eruption

Central Crater

1787 Jun 4 ± 4 days - 1787 Aug 11

Evidence from Observations: Reported

List of 10 Events for Episode 1 at Central Crater

Start Date	End Date	Event Type
- - - -	- - - -	Explosion
- - - -	- - - -	Lava flow
- - - -	- - - -	Ash
- - - -	- - - -	Lapilli
- - - -	- - - -	Bombs
- - - -	- - - -	Scoria
- - - -	- - - -	Earthquakes (undefined)
- - - -	- - - -	Property Damage
1787 Jun 4 ± 4 days	- - - -	VEI (Explosivity Index)
1787 Jul 18	- - - -	VEI (Explosivity Index)

1781 Mar - 1781 May 10 Confirmed Eruption VEI: 2

Episode 1 | Eruption

Central Crater

1781 Mar - 1781 May 10

Evidence from Observations: Reported

List of 6 Events for Episode 1 at Central Crater

Start Date	End Date	Event Type
- - - -	- - - -	Explosion
- - - -	- - - -	Lava fountains
- - - -	- - - -	Lava flow
- - - -	- - - -	Ash
- - - -	- - - -	Earthquakes (undefined)
1781 Mar	- - - -	VEI (Explosivity Index)

1780 Apr 20 (?) - 1780 Jul (?) Confirmed Eruption VEI: 2

Episode 1 | Eruption

Summit, S & SSW flanks (2360-1850 m)

1780 Apr 20 (?) - 1780 Jul (?)

Evidence from Observations: Reported

List of 7 Events for Episode 1 at Summit, S & SSW flanks (2360-1850 m)

Start Date	End Date	Event Type	Event Remarks
- - - -	- - - -	Explosion
- - - -	- - - -	Lava flow
- - - -	- - - -	Earthquakes (undefined)
- - - -	- - - -	Earthquakes (undefined)	After.
- - - -	- - - -	Property Damage
1780 Apr 20 (?)	- - - -	VEI (Explosivity Index)
1780 May 18	- - - -	VEI (Explosivity Index)

1776 Confirmed Eruption

Episode 1 | Eruption

Central Crater

1776 - Unknown

Evidence from Observations: Reported

List of 1 Events for Episode 1 at Central Crater

	Start Date	End Date	Event Type	Event Remarks
	- - - -	- - - -	Explosion

[ 1770 May 28 ± 1 days ] Uncertain Eruption

Episode 1 | Eruption

Central Crater

1770 May 28 ± 1 days - Unknown

Evidence from Unknown

List of 1 Events for Episode 1 at Central Crater

	Start Date	End Date	Event Type	Event Remarks
	- - - -	- - - -	Explosion	Uncertain

1767 May 2 Confirmed Eruption

Episode 1 | Eruption

Central Crater

1767 May 2 - Unknown

Evidence from Observations: Reported

List of 1 Events for Episode 1 at Central Crater

	Start Date	End Date	Event Type	Event Remarks
	- - - -	- - - -	Explosion

1766 Apr 27 - 1766 Nov 6 Confirmed Eruption VEI: 2

Episode 1 | Eruption

South flank (2100-1950 m, M. Calcarazzi)

1766 Apr 27 - 1766 Nov 6

Evidence from Observations: Reported

List of 8 Events for Episode 1 at South flank (2100-1950 m, M. Calcarazzi)

Start Date	End Date	Event Type	Event Remarks
- - - -	- - - -	Explosion
- - - -	- - - -	Phreatic activity	Uncertain
- - - -	- - - -	Lava flow
- - - -	- - - -	Cinder Cone
- - - -	- - - -	Earthquakes (undefined)	Before.
- - - -	- - - -	Earthquakes (undefined)
- - - -	- - - -	Property Damage
1766 Apr 27	- - - -	VEI (Explosivity Index)

1732 Dec 9 - 1765 Confirmed Eruption VEI: 3

Episode 1 | Eruption

Central Crater

1732 Dec 9 - 1765

Evidence from Observations: Reported

List of 16 Events for Episode 1 at Central Crater

Start Date	End Date	Event Type
- - - -	- - - -	Explosion
- - - -	- - - -	Lava fountains
- - - -	- - - -	Lava flow
- - - -	- - - -	Cinder Cone
- - - -	- - - -	Ash
- - - -	- - - -	Scoria
- - - -	- - - -	Earthquakes (undefined)
- - - -	- - - -	Property Damage
1732 Dec 9	- - - -	VEI (Explosivity Index)
1735 Oct 4	- - - -	VEI (Explosivity Index)
1744 Apr (?)	- - - -	VEI (Explosivity Index)
1747 Sep	- - - -	VEI (Explosivity Index)
1752	- - - -	VEI (Explosivity Index)
1755 Mar 2	- - - -	VEI (Explosivity Index)
1758 Oct	- - - -	VEI (Explosivity Index)
1759 Apr 14	- - - -	VEI (Explosivity Index)

Episode 2 | Eruption

East flank (Valle del Bove, 1750 m)

1755 Mar 9 - 1755 Mar 15

Evidence from Observations: Reported

List of 8 Events for Episode 2 at East flank (Valle del Bove, 1750 m)

Start Date	End Date	Event Type
- - - -	- - - -	Explosion
- - - -	- - - -	Lava flow
- - - -	- - - -	Scoria
- - - -	- - - -	Audible Sounds
- - - -	- - - -	Lightning
- - - -	- - - -	Lahar or Mudflow
- - - -	- - - -	Property Damage
1755 Mar 9	- - - -	VEI (Explosivity Index)

Episode 3 | Eruption

Central Crater, south flank (3000 m)

1758 Nov 3 (?) - 1759 Aug 1

Evidence from Observations: Reported

List of 6 Events for Episode 3 at Central Crater, south flank (3000 m)

Start Date	End Date	Event Type	Event Remarks
- - - -	- - - -	Explosion
- - - -	- - - -	Lava flow
- - - -	- - - -	Earthquakes (undefined)
- - - -	- - - -	Collapse	Event was "Partial collapse at end of eruption"
1758 Nov 3 (?)	- - - -	VEI (Explosivity Index)
1759 Apr 19	- - - -	VEI (Explosivity Index)

Episode 4 | Eruption

West flank (1725-1580 m, Mt. Nuovo)

1763 Feb 6 - 1763 Mar 10 (?)

Evidence from Observations: Reported

List of 8 Events for Episode 4 at West flank (1725-1580 m, Mt. Nuovo)

Start Date	End Date	Event Type	Event Remarks
- - - -	- - - -	Explosion
- - - -	- - - -	Lava flow
- - - -	- - - -	Cinder Cone
- - - -	- - - -	Earthquakes (undefined)	Before.
- - - -	- - - -	Earthquakes (undefined)
- - - -	- - - -	Crater	Parasitic.
- - - -	- - - -	Property Damage
1763 Feb 6	- - - -	VEI (Explosivity Index)

Episode 5 | Eruption

South flank (2500-1925 m, Montagnola)

1763 Jun 18 - 1763 Sep 10

Evidence from Observations: Reported

List of 8 Events for Episode 5 at South flank (2500-1925 m, Montagnola)

Start Date	End Date	Event Type	Event Remarks
- - - -	- - - -	Explosion
- - - -	- - - -	Lava fountains
- - - -	- - - -	Lava flow
- - - -	- - - -	Cinder Cone
- - - -	- - - -	Ash
- - - -	- - - -	Earthquakes (undefined)	Before.
- - - -	- - - -	Property Damage
1763 Jun 18	- - - -	VEI (Explosivity Index)

Episode 6 | Eruption

NW flank (3125-2500 m?)

1764 - 1765 (?)

Evidence from Observations: Reported

List of 3 Events for Episode 6 at NW flank (3125-2500 m?)

Start Date	End Date	Event Type
- - - -	- - - -	Explosion
- - - -	- - - -	Lava flow
1764	- - - -	VEI (Explosivity Index)

1727 Nov 22 - 1728 May 10 (?) Confirmed Eruption VEI: 2 (?)

Episode 1 | Eruption

Central Crater (SW slope)

1727 Nov 22 - 1728 May 10 (?)

Evidence from Observations: Reported

List of 4 Events for Episode 1 at Central Crater (SW slope)

Start Date	End Date	Event Type
- - - -	- - - -	Explosion
- - - -	- - - -	Lava flow
- - - -	- - - -	Property Damage
1727 Nov 22	- - - -	VEI (Explosivity Index)

[ 1723 Nov 22 - 1724 May (?) ] Uncertain Eruption

Episode 1 | Eruption

1723 Nov 22 - 1724 May (?)

Evidence from Unknown

List of 5 Events for Episode 1

Start Date	End Date	Event Type	Event Remarks
- - - -	- - - -	Explosion
- - - -	- - - -	Lava flow
- - - -	- - - -	Earthquakes (undefined)	Before.
- - - -	- - - -	Property Damage
1723 Nov 22	- - - -	VEI (Explosivity Index)

1702 Mar 8 - 1702 May 8 Confirmed Eruption VEI: 1

Episode 1 | Eruption

East flank (Valle del Bove, 2075-1875 m)

1702 Mar 8 - 1702 May 8

Evidence from Observations: Reported

List of 5 Events for Episode 1 at East flank (Valle del Bove, 2075-1875 m)

Start Date	End Date	Event Type
- - - -	- - - -	Explosion
- - - -	- - - -	Lava flow
- - - -	- - - -	Earthquakes (undefined)
- - - -	- - - -	Property Damage
1702 Mar 8	- - - -	VEI (Explosivity Index)

1693 Dec - 1694 Nov (?) Confirmed Eruption VEI: 3 (?)

Episode 1 | Eruption

Central Crater

1693 Dec - 1694 Nov (?)

Evidence from Observations: Reported

List of 6 Events for Episode 1 at Central Crater

Start Date	End Date	Event Type
- - - -	- - - -	Explosion
- - - -	- - - -	Ash
- - - -	- - - -	Earthquakes (undefined)
- - - -	- - - -	Property Damage
1693 Dec	- - - -	VEI (Explosivity Index)
1694 Mar	- - - -	VEI (Explosivity Index)

[ 1693 Jan 9 ] Uncertain Eruption

Episode 1 | Eruption

1693 Jan 9 - Unknown

Evidence from Unknown

List of 3 Events for Episode 1

Start Date	End Date	Event Type	Event Remarks
- - - -	- - - -	Explosion	Uncertain
- - - -	- - - -	Lava flow	Uncertain
- - - -	- - - -	Earthquakes (undefined)	Time and Type Unknown.

1689 Mar 14 Confirmed Eruption VEI: 1

Episode 1 | Eruption

East flank (Valle del Bove, 2300 m?)

1689 Mar 14 - Unknown

Evidence from Observations: Reported

List of 6 Events for Episode 1 at East flank (Valle del Bove, 2300 m?)

Start Date	End Date	Event Type
- - - -	- - - -	Explosion
- - - -	- - - -	Lava flow
- - - -	- - - -	Ash
- - - -	- - - -	Property Damage
1689 Mar 14	- - - -	VEI (Explosivity Index)
1689 Mar 19	- - - -	Fatalities

1688 Confirmed Eruption VEI: 1

Episode 1 | Eruption

East slope of Central Crater

1688 - Unknown

Evidence from Observations: Reported

List of 3 Events for Episode 1 at East slope of Central Crater

Start Date	End Date	Event Type
- - - -	- - - -	Explosion
- - - -	- - - -	Lava flow
1688	- - - -	VEI (Explosivity Index)

1682 Sep 1 - 1682 Oct (?) Confirmed Eruption VEI: 2

Episode 1 | Eruption

East flank (Valle del Bove, 2900 m)

1682 Sep 1 - 1682 Oct (?)

Evidence from Observations: Reported

List of 3 Events for Episode 1 at East flank (Valle del Bove, 2900 m)

Start Date	End Date	Event Type	Event Remarks
- - - -	- - - -	Explosion	Uncertain
- - - -	- - - -	Lava flow
1682 Sep 1	- - - -	VEI (Explosivity Index)

1669 Mar 11 - 1669 Jul 11 (?) Confirmed Eruption VEI: 3 (?)

Episode 1 | Eruption

S flank (950-625 m, Monti Rossi)

1669 Mar 11 - 1669 Jul 11 (?)

Evidence from Observations: Reported

List of 14 Events for Episode 1 at S flank (950-625 m, Monti Rossi)

Start Date	End Date	Event Type	Event Remarks
- - - -	- - - -	Seismicity (volcanic)	Before eruption.
- - - -	- - - -	Seismicity (volcanic)
- - - -	- - - -	Explosion
- - - -	- - - -	Lava flow
- - - -	- - - -	Lava flow	Entered water.
- - - -	- - - -	Cinder Cone
- - - -	- - - -	Ash
- - - -	- - - -	Lapilli
- - - -	- - - -	Blocks
- - - -	- - - -	Scoria
- - - -	- - - -	Property Damage
- - - -	- - - -	Evacuations
1669	- - - -	Fatalities
1669 Mar 11	- - - -	VEI (Explosivity Index)

1654 Jan 1 - 1656 (?) Confirmed Eruption VEI: 1

Episode 1 | Eruption

Central Crater

1654 Jan 1 - 1656 (?)

Evidence from Observations: Reported

List of 3 Events for Episode 1 at Central Crater

Start Date	End Date	Event Type
- - - -	- - - -	Explosion
- - - -	- - - -	Lava flow
1654 Jan 1	- - - -	VEI (Explosivity Index)

1651 Jan 17 - 1653 Jul (?) Confirmed Eruption VEI: 1

Episode 1 | Eruption

West (2600-1770 m), east (1875-1815 m)

1651 Jan 17 - 1653 Jul (?)

Evidence from Observations: Reported

List of 6 Events for Episode 1 at West (2600-1770 m), east (1875-1815 m)

Start Date	End Date	Event Type
- - - -	- - - -	Explosion
- - - -	- - - -	Lava flow
- - - -	- - - -	Cinder Cone
- - - -	- - - -	Earthquakes (undefined)
- - - -	- - - -	Property Damage
1651 Jan 17	- - - -	VEI (Explosivity Index)

1646 Nov 20 - 1647 Jan 17 Confirmed Eruption VEI: 2

Episode 1 | Eruption

NNE (2000 m, 1800 m), Mt. Nero

1646 Nov 20 - 1647 Jan 17

Evidence from Observations: Reported

List of 5 Events for Episode 1 at NNE (2000 m, 1800 m), Mt. Nero

Start Date	End Date	Event Type
- - - -	- - - -	Explosion
- - - -	- - - -	Lava flow
- - - -	- - - -	Cinder Cone
- - - -	- - - -	Property Damage
1646 Nov 20	- - - -	VEI (Explosivity Index)

1643 Feb 20 - 1643 Feb 28 Confirmed Eruption VEI: 1

Episode 1 | Eruption

N flank (2100-1275 m), Monte Pomiciaro

1643 Feb 20 - 1643 Feb 28

Evidence from Observations: Reported

List of 5 Events for Episode 1 at N flank (2100-1275 m), Monte Pomiciaro

Start Date	End Date	Event Type
- - - -	- - - -	Explosion
- - - -	- - - -	Lava flow
- - - -	- - - -	Cinder Cone
- - - -	- - - -	Scoria
1643 Feb 20	- - - -	VEI (Explosivity Index)

[ 1640 ] Discredited Eruption

The 1640 date is a typographical error in Alessi, corresponding to the 1643 eruption in his table (Tanguy, 1981).

1634 Dec 19 (?) - 1638 Apr 27 Confirmed Eruption VEI: 1

Episode 1 | Eruption

SE (2100-1950 m), Little Mt. Pecorara

1634 Dec 19 (?) - 1638 Apr 27

Evidence from Observations: Reported

List of 6 Events for Episode 1 at SE (2100-1950 m), Little Mt. Pecorara

Start Date	End Date	Event Type
- - - -	- - - -	Explosion
- - - -	- - - -	Lava flow
- - - -	- - - -	Cinder Cone
- - - -	- - - -	Earthquakes (undefined)
- - - -	- - - -	Property Damage
1634 Dec 19 (?)	- - - -	VEI (Explosivity Index)

[ 1633 Feb 21 ] Uncertain Eruption

Episode 1 | Eruption

Central Crater

1633 Feb 21 - Unknown

Evidence from Unknown

List of 3 Events for Episode 1 at Central Crater

Start Date	End Date	Event Type	Event Remarks
- - - -	- - - -	Explosion	Uncertain
- - - -	- - - -	Lava flow	Uncertain
- - - -	- - - -	Earthquakes (undefined)

1614 Jul 1 (?) - 1624 Confirmed Eruption VEI: 2

Episode 1 | Eruption

NNE flank (2800-2400 m), Monti Deserti

1614 Jul 1 (?) - 1624

Evidence from Observations: Reported

List of 6 Events for Episode 1 at NNE flank (2800-2400 m), Monti Deserti

Start Date	End Date	Event Type
- - - -	- - - -	Explosion
- - - -	- - - -	Lava flow
- - - -	- - - -	Cinder Cone
- - - -	- - - -	Earthquakes (undefined)
- - - -	- - - -	Property Damage
1614 Jul 1 (?)	- - - -	VEI (Explosivity Index)

1610 Feb 6 - 1610 Aug 15 Confirmed Eruption VEI: 2

Episode 1 | Eruption

SW flank (2500-1700 m)

1610 Feb 6 - 1610 Aug 15

Evidence from Observations: Reported

CAVW (Imbo, 1965) lists an eruption from the NNW(?) side, other sources list SW flank activity. The first phase, from 6 February to 3 May 1610, occurred from vents between 2,500 and 2,200 m elevation on the SW flank; the second phase, from 3 May to 15 August 1610, occurred from vents at 2,275-1,700 m on the SW flank (Behncke et al., 2005).

List of 4 Events for Episode 1 at SW flank (2500-1700 m)

Start Date	End Date	Event Type
- - - -	- - - -	Explosion
- - - -	- - - -	Lava flow
- - - -	- - - -	Property Damage
1610 Feb 6	- - - -	VEI (Explosivity Index)

[ 1609 Jul ] Discredited Eruption

Possible confusion with the 1607 eruption (Romano, 1982). No 1609 eruption, confused with the 1607 eruption (Tanguy 1981, 1982).

1607 Jun 28 - 1608 (?) Confirmed Eruption VEI: 2

Episode 1 | Eruption

SW flank (2250-1950 m)?

1607 Jun 28 - 1608 (?)

Evidence from Observations: Reported

A SW flank eruption began on 28 June 1607 (Romano, 1982). Tanguy (1981) assigns this date to a vent at 1,500 m elevation on the NW flank on the basis of paleomagnetic evidence. Neither source lists activity in 1608 (CAVW), but Behncke et al. (2005) noted possible activity into that year.

List of 4 Events for Episode 1 at SW flank (2250-1950 m)?

Start Date	End Date	Event Type
- - - -	- - - -	Explosion
- - - -	- - - -	Lava flow
- - - -	- - - -	Tephra
1607 Jun 28	- - - -	VEI (Explosivity Index)

1603 Jul - 1610 Confirmed Eruption VEI: 2

Episode 1 | Eruption

Central Crater (SW and S slope)

1603 Jul - 1610

Evidence from Observations: Reported

Romano (1982) lists Central Crater activity from the SW slope in 1603. Sapper (1917) mentions eruptions in 1603 and following years. Behncke et al. (2005) listed a 24-25 February 1607 lava flow from the Central Crater with a volume of 0.001 km³. A N-flank eruption on 22 April 1607 noted by Romano (1982) consisted of only normal persistent activity on the north rim of the Central Crater according to Recupero (Tanguy, 1984 pers. comm.). Tanguy (pers. comm.) listed summit explosive (VEI 2) and effusive activity from 1603-1610.

List of 4 Events for Episode 1 at Central Crater (SW and S slope)

Start Date	End Date	Event Type
- - - -	- - - -	Explosion
- - - -	- - - -	Lava flow
- - - -	- - - -	Ash
1603 Jul	- - - -	VEI (Explosivity Index)

[ 1595 ] Discredited Eruption

Map in Sartorius (1848) shows a 1595 lava flow, but other sources do not mention 1595 activity and the date must be considered as uncertain. The description of a 1579 eruption may represent this major eruption low on the SW flank (Wadge 1977). Romano (1982) considered the eruption to have taken place sometime around 1595. Tanguy et al. (1981) suggested that 1595 may have been a printing error for 1535 (which is confused with the 1536 eruption), and considered the lava flows in question to have been erupted in 1225 ± 30 CE on the basis of paleomagnetic evidence. Tanguy et al. (2007) considered the flow in question to represent two events, one probably correlating to the 1062 CE eruption.

1579 Sep 9 (?) - 1580 (?) Confirmed Eruption

Episode 1 | Eruption

SE flank

1579 Sep 9 (?) - 1580 (?)

Evidence from Observations: Reported

List of 4 Events for Episode 1 at SE flank

Start Date	End Date	Event Type
- - - -	- - - -	Explosion
- - - -	- - - -	Lava flow
- - - -	- - - -	Earthquakes (undefined)
- - - -	- - - -	Property Damage

[ 1578 ] Uncertain Eruption

Episode 1 \| Eruption
1578 - Unknown				Evidence from Unknown

1566 Nov 1 (?) - 1566 Dec Confirmed Eruption VEI: 2

Episode 1 | Eruption

NE flank

1566 Nov 1 (?) - 1566 Dec

Evidence from Observations: Reported

List of 4 Events for Episode 1 at NE flank

Start Date	End Date	Event Type
- - - -	- - - -	Explosion
- - - -	- - - -	Lava flow
- - - -	- - - -	Property Damage
1566 Nov 1 (?)	- - - -	VEI (Explosivity Index)

[ 1554 ] Uncertain Eruption

Episode 1 | Eruption

1554 - Unknown

Evidence from Unknown

List of 1 Events for Episode 1

	Start Date	End Date	Event Type	Event Remarks
	1554	- - - -	VEI (Explosivity Index)

[ 1550 ] Discredited Eruption

No eruption in 1550 (Tanguy, 1982 p.c.).

1541 Jul (?) Confirmed Eruption VEI: 2

Episode 1 | Eruption

1541 Jul (?) - Unknown

Evidence from Observations: Reported

List of 2 Events for Episode 1

	Start Date	End Date	Event Type	Event Remarks
	- - - -	- - - -	Explosion
	1541 Jul (?)	- - - -	VEI (Explosivity Index)

1540 Jul Confirmed Eruption VEI: 1

Episode 1 | Eruption

1540 Jul - Unknown

Evidence from Observations: Reported

List of 2 Events for Episode 1

	Start Date	End Date	Event Type	Event Remarks
	- - - -	- - - -	Explosion
	1540 Jul	- - - -	VEI (Explosivity Index)

1537 Mar (?) - 1537 Jul Confirmed Eruption VEI: 2

Episode 1 | Eruption

Summit, south flank (1800-1500 m)

1537 Mar (?) - 1537 Jul

Evidence from Observations: Reported

List of 9 Events for Episode 1 at Summit, south flank (1800-1500 m)

Start Date	End Date	Event Type	Event Remarks
- - - -	- - - -	Explosion
- - - -	- - - -	Lava flow
- - - -	- - - -	Ash
- - - -	- - - -	Audible Sounds
- - - -	- - - -	Earthquakes (undefined)
- - - -	- - - -	Crater	Parasitic.
- - - -	- - - -	Collapse	Event was "Partial collapse at end of eruption"
- - - -	- - - -	Property Damage
1537 Mar (?)	- - - -	VEI (Explosivity Index)

1536 Mar 22 - 1536 Dec (?) Confirmed Eruption VEI: 3

Episode 1 | Eruption

Summit, S, N & W flanks (1400-2500 m)

1536 Mar 22 - 1536 Dec (?)

Evidence from Observations: Reported

List of 10 Events for Episode 1 at Summit, S, N & W flanks (1400-2500 m)

Start Date	End Date	Event Type	Event Remarks
- - - -	- - - -	Explosion	violent, strong, or large
- - - -	- - - -	Lava flow
- - - -	- - - -	Cinder Cone
- - - -	- - - -	Ash
- - - -	- - - -	Earthquakes (undefined)
- - - -	- - - -	Crater	Parasitic.
- - - -	- - - -	Lahar or Mudflow
- - - -	- - - -	Property Damage
1536 Mar 22	- - - -	VEI (Explosivity Index)
1536 Mar 26	- - - -	Fatalities

[ 1535 ] Discredited Eruption

The 1535 eruption listed in several sources is due to an incorrect assignment of an eruption by Sartorius (Tanguy, 1981). Romano (1982) states that in all probability lavas from Mt. Nero Degli Zappini should be attributed to 1536 eruption.

[ 1533 ] Discredited Eruption

Sartorius incorrectly assigned an eruption to 1533 (Tanguy, 1981). CAVW notes summit explosive activity from 1494-1533, but Tanguy indicates that there are no records of activity for these years.

1493 (?) - 1500 (?) Confirmed Eruption VEI: 1

Episode 1 | Eruption

1493 (?) - 1500 (?)

Evidence from Observations: Reported

List of 3 Events for Episode 1

Start Date	End Date	Event Type	Event Remarks
- - - -	- - - -	Explosion	Uncertain
- - - -	- - - -	Lava flow	Uncertain
1493 (?)	- - - -	VEI (Explosivity Index)

[ 1470 ] Discredited Eruption

Eruption cited by Alessi without good evidence (Tanguy, 1981).

1447 Sep 21 Confirmed Eruption VEI: 1

Episode 1 | Eruption

1447 Sep 21 - Unknown

Evidence from Observations: Reported

List of 3 Events for Episode 1

Start Date	End Date	Event Type
- - - -	- - - -	Explosion
- - - -	- - - -	Lava flow
1447 Sep 21	- - - -	VEI (Explosivity Index)

1446 Sep 25 Confirmed Eruption VEI: 1

Episode 1 | Eruption

East (Valle del Bove, 1630 or 1825 m)

1446 Sep 25 - Unknown

Evidence from Observations: Reported

List of 2 Events for Episode 1 at East (Valle del Bove, 1630 or 1825 m)

	Start Date	End Date	Event Type	Event Remarks
	- - - -	- - - -	Lava flow
	1446 Sep 25	- - - -	VEI (Explosivity Index)

1444 Confirmed Eruption VEI: 2

Episode 1 | Eruption

South (N of Mt. Arso and 950 m)

1444 - Unknown

Evidence from Observations: Reported

List of 6 Events for Episode 1 at South (N of Mt. Arso and 950 m)

Start Date	End Date	Event Type	Event Remarks
- - - -	- - - -	Explosion
- - - -	- - - -	Lava flow
- - - -	- - - -	Earthquakes (undefined)
- - - -	- - - -	Collapse	Event was "Partial collapse at end of eruption"
- - - -	- - - -	Property Damage
1444	- - - -	VEI (Explosivity Index)

1408 Nov 8 - 1408 Nov 25 (?) Confirmed Eruption VEI: 3

Episode 1 | Eruption

Summit, south flank (M. Piniteddu)

1408 Nov 8 - 1408 Nov 25 (?)

Evidence from Observations: Reported

List of 6 Events for Episode 1 at Summit, south flank (M. Piniteddu)

Start Date	End Date	Event Type
- - - -	- - - -	Explosion
- - - -	- - - -	Lava flow
- - - -	- - - -	Ash
- - - -	- - - -	Earthquakes (undefined)
- - - -	- - - -	Property Damage
1408 Nov 8	- - - -	VEI (Explosivity Index)

1381 Aug 6 (?) (?) Confirmed Eruption VEI: 2

Episode 1 | Eruption

SSE (370 m), Mts. Pomiciari, Arsi?

1381 Aug 6 (?) (?) - Unknown

Evidence from Observations: Reported

List of 5 Events for Episode 1 at SSE (370 m), Mts. Pomiciari, Arsi?

Start Date	End Date	Event Type	Event Remarks
- - - -	- - - -	Explosion	Uncertain
- - - -	- - - -	Lava flow
- - - -	- - - -	Lava flow	Entered water.
- - - -	- - - -	Property Damage
1381 Aug 6 (?) (?)	- - - -	VEI (Explosivity Index)

1350 Confirmed Eruption VEI: 2

Episode 1 | Eruption

1350 - Unknown

Evidence from Observations: Reported

List of 2 Events for Episode 1

	Start Date	End Date	Event Type	Event Remarks
	- - - -	- - - -	Explosion	violent, strong, or large
	1350	- - - -	VEI (Explosivity Index)

[ 1334 ] Discredited Eruption

Romano (1982) assigns the Monte Rosso eruption to 1334 CE on the basis of lava petrography, rather than 1329 CE as do other sources (CAVW; Tanguy, 1981). Tanguy considered the 1334 date to have been confused with the 1329 eruption as a result of a transcription error by Recupero that was repeated by later sources.

1333 Confirmed Eruption VEI: 2

Episode 1 | Eruption

1333 - Unknown

Evidence from Observations: Reported

List of 3 Events for Episode 1

Start Date	End Date	Event Type
- - - -	- - - -	Explosion
- - - -	- - - -	Lava flow
1333	- - - -	VEI (Explosivity Index)

1329 Jun 28 - 1329 Aug 4 ± 4 days Confirmed Eruption VEI: 3 (?)

Episode 1 | Eruption

SE flank

1329 Jun 28 - 1329 Aug 4 ± 4 days

Evidence from Observations: Reported

List of 11 Events for Episode 1 at SE flank

Start Date	End Date	Event Type	Event Remarks
- - - -	- - - -	Lava flow
- - - -	- - - -	Lava flow	Entered water.
- - - -	- - - -	Ash
- - - -	- - - -	Bombs
- - - -	- - - -	Earthquakes (undefined)
- - - -	- - - -	Crater	Parasitic.
- - - -	- - - -	Tsunami
- - - -	- - - -	Fauna Kill	Terrestrial.
- - - -	- - - -	Property Damage
1329 Jun 28	- - - -	VEI (Explosivity Index)
1329 Jul 15 (?)	- - - -	Fatalities	Uncertain

[ 1321 - 1328 ] Discredited Eruption

Reports of eruptions in 1321 and 1323-1328 CE are confused with the 1329 CE eruption (Tanguy, 1981).

1284 - 1285 Jan (?) Confirmed Eruption

Episode 1 | Eruption

East flank (Valle del Bove)

1284 - 1285 Jan (?)

Evidence from Observations: Reported

List of 2 Events for Episode 1 at East flank (Valle del Bove)

	Start Date	End Date	Event Type	Event Remarks
	- - - -	- - - -	Lava flow
	- - - -	- - - -	Earthquakes (undefined)

1250 Confirmed Eruption VEI: 2 (?)

Episode 1 | Eruption

1250 - Unknown

Evidence from Observations: Reported

List of 1 Events for Episode 1

	Start Date	End Date	Event Type	Event Remarks
	1250	- - - -	VEI (Explosivity Index)

1224 Aug (?) Confirmed Eruption

Episode 1 | Eruption

SE flank

1224 Aug (?) - Unknown

Evidence from Observations: Reported

List of 3 Events for Episode 1 at SE flank

Start Date	End Date	Event Type	Event Remarks
- - - -	- - - -	Lava flow
- - - -	- - - -	Lava flow	Entered water.
- - - -	- - - -	Property Damage

[ 1222 ] Discredited Eruption

Both CAVW and Sapper (1917) listed a 1222 CE eruption. Tanguy (1981) assigned the 1595 eruption to this period (1225 ± 30 CE) on paleomagnetism evidence. Guidoboni and Ciucarelli (2008) indicated that the 1222 date originated from inferences of Alessi (1829-1835), who assigned the date from the inferred date of the account of the monk Cesarius, and that the 1222 date should be discredited.

1194 Confirmed Eruption VEI: 2 (?)

Episode 1 | Eruption

1194 - Unknown

Evidence from Observations: Reported

List of 1 Events for Episode 1

	Start Date	End Date	Event Type	Event Remarks
	1194	- - - -	VEI (Explosivity Index)

[ 1175 ] Discredited Eruption

A report of an eruption in 1175 CE is probably confused with the events of 1169 CE (Sapper, 1917; Tanguy, 1981).

[ 1169 Feb 4 ] Uncertain Eruption

Episode 1 | Eruption

1169 Feb 4 - Unknown

Evidence from Unknown

List of 5 Events for Episode 1

Start Date	End Date	Event Type	Event Remarks
- - - -	- - - -	Explosion	Uncertain
- - - -	- - - -	Lava flow	Uncertain
- - - -	- - - -	Earthquakes (undefined)
- - - -	- - - -	Property Damage	Uncertain
1169 Feb	- - - -	Fatalities

1164 (?) Confirmed Eruption VEI: 2 (?)

Episode 1 | Eruption

1164 (?) - Unknown

Evidence from Observations: Reported

List of 1 Events for Episode 1

	Start Date	End Date	Event Type	Event Remarks
	1164 (?)	- - - -	VEI (Explosivity Index)

1160 Confirmed Eruption VEI: 2 (?)

Episode 1 | Eruption

1160 - Unknown

Evidence from Observations: Reported

List of 1 Events for Episode 1

	Start Date	End Date	Event Type	Event Remarks
	1160	- - - -	VEI (Explosivity Index)

1157 Confirmed Eruption VEI: 2 (?)

Episode 1 | Eruption

1157 - Unknown

Evidence from Observations: Reported

List of 1 Events for Episode 1

	Start Date	End Date	Event Type	Event Remarks
	1157	- - - -	VEI (Explosivity Index)

1063 ± 1 years Confirmed Eruption

Episode 1 | Eruption

WSW flank (1500 m) ?

1063 ± 1 years - Unknown

Evidence from Observations: Reported

List of 2 Events for Episode 1 at WSW flank (1500 m) ?

	Start Date	End Date	Event Type	Event Remarks
	- - - -	- - - -	Explosion
	- - - -	- - - -	Lava flow

[ 1044 ] Uncertain Eruption

Episode 1 \| Eruption
1044 - Unknown				Evidence from Unknown

[ 1004 ] Uncertain Eruption

Episode 1 \| Eruption
1004 - Unknown				Evidence from Unknown

[ 0911 ] Uncertain Eruption

Episode 1 \| Eruption
0911 - Unknown				Evidence from Unknown

[ 0859 ] Uncertain Eruption

Episode 1 \| Eruption
0859 - Unknown				Evidence from Unknown

[ 0814 ] Uncertain Eruption

Episode 1 \| Eruption
0814 - Unknown				Evidence from Unknown

[ 0812 (?) ] Uncertain Eruption

Episode 1 | Eruption

South flank (1200 m, S of Mt. Sona)

0812 (?) - Unknown

Evidence from Unknown

List of 2 Events for Episode 1 at South flank (1200 m, S of Mt. Sona)

	Start Date	End Date	Event Type	Event Remarks
	- - - -	- - - -	Explosion
	- - - -	- - - -	Lava flow

[ 0644 ] Uncertain Eruption

Episode 1 \| Eruption
0644 - Unknown				Evidence from Unknown

[ 0604 ] Discredited Eruption

The year of this eruption, 604 CE, appears to be only a reference number to a text of Gregory the Great cited by Sartorius von Waltershausen (1880) (Stothers and Rampino, 1983).

[ 0560 ] Discredited Eruption

The original Procopius source does not describe specific eruptions during 500-560 CE (Stothers and Rampino, 1983).

[ 0500 ] Discredited Eruption

The original Procopius source does not describe specific eruptions during 500-560 CE (Stothers and Rampino, 1983).

0417 (?) Confirmed Eruption

Episode 1 | Eruption

0417 (?) - Unknown

Evidence from Observations: Reported

List of 2 Events for Episode 1

	Start Date	End Date	Event Type	Event Remarks
	- - - -	- - - -	Explosion
	- - - -	- - - -	Ash

[ 0410 ] Discredited Eruption

Accounts of late Roman writers have been incorrectly interpreted by Alessi as references to eruptive activity in 400, 410, and 420 CE (Clover, 1983).

[ 0400 ] Discredited Eruption

Accounts of late Roman writers have been incorrectly interpreted by Alessi as references to eruptive activity in 400, 410, and 420 CE (Clover, 1983).

0252 Feb 1 - 0252 Feb 9 Confirmed Eruption VEI: 3 (?)

Episode 1 | Eruption

South flank (Monpeloso)

0252 Feb 1 - 0252 Feb 9

Evidence from Observations: Reported

List of 7 Events for Episode 1 at South flank (Monpeloso)

Start Date	End Date	Event Type	Event Remarks
- - - -	- - - -	Explosion	Uncertain
- - - -	- - - -	Lava flow
- - - -	- - - -	Lava flow	Entered water.
- - - -	- - - -	Cinder Cone
- - - -	- - - -	Earthquakes (undefined)
- - - -	- - - -	Property Damage
0252 Feb 1	- - - -	VEI (Explosivity Index)

[ 0165 ] Discredited Eruption

Stothers and Rampino (1983) note that there is no justification for a 165 CE eruption. Tanguy (1982, p.c.) described this as a questionable eruption.

0100 ± 100 years Confirmed Eruption

Episode 1 | Eruption

FV tephra

0100 ± 100 years - Unknown

Evidence from Correlation: Tephrochronology

List of 3 Events for Episode 1 at FV tephra

Start Date	End Date	Event Type
- - - -	- - - -	Explosion
- - - -	- - - -	Lapilli
- - - -	- - - -	Scoria

[ 0080 (?) ] Uncertain Eruption

Episode 1 | Eruption

0080 (?) - Unknown

Evidence from Unknown

List of 2 Events for Episode 1

	Start Date	End Date	Event Type	Event Remarks
	- - - -	- - - -	Explosion
	- - - -	- - - -	Lava flow	Uncertain

[ 0072 ] Discredited Eruption

This incorrect eruption date was caused by the accidental combination of two unrelated passages dealing with the 70 CE reign of Vespasian and the 425 BCE eruption of Etna (Stothers and Rampino, 1983).

[ 0050 ] Discredited Eruption

Stothers and Rampino (1983) stated that the report of a 50 CE eruption was simply an exaggeration of a standard description of Etna. Tanguy (1982, p.c.) also described it as a questionable eruption.

0039 ± 1 years Confirmed Eruption

Episode 1 | Eruption

0039 ± 1 years - Unknown

Evidence from Observations: Reported

List of 1 Events for Episode 1

	Start Date	End Date	Event Type	Event Remarks
	- - - -	- - - -	Explosion

0010 (?) - 0020 (?) Confirmed Eruption

Episode 1 | Eruption

0010 (?) - 0020 (?)

Evidence from Observations: Reported

List of 1 Events for Episode 1

	Start Date	End Date	Event Type	Event Remarks
	- - - -	- - - -	Explosion

[ 0010 BCE (?) ] Uncertain Eruption

Episode 1 | Eruption

0010 BCE (?) - Unknown

Evidence from Unknown

List of 2 Events for Episode 1

	Start Date	End Date	Event Type	Event Remarks
	- - - -	- - - -	Explosion	Uncertain
	- - - -	- - - -	Lava flow	Uncertain

0032 Dec 31 BCE ± 365 days Confirmed Eruption

Episode 1 | Eruption

0032 Dec 31 BCE ± 365 days - Unknown

Evidence from Observations: Reported

List of 1 Events for Episode 1

	Start Date	End Date	Event Type	Event Remarks
	- - - -	- - - -	Lava flow	Uncertain

0036 Jul 15 BCE ± 45 days - 0035 BCE Confirmed Eruption

Episode 1 | Eruption

East side ?

0036 Jul 15 BCE ± 45 days - 0035 BCE

Evidence from Observations: Reported

List of 3 Events for Episode 1 at East side ?

Start Date	End Date	Event Type
- - - -	- - - -	Explosion
- - - -	- - - -	Lava flow
- - - -	- - - -	Earthquakes (undefined)

0044 Mar BCE (?) Confirmed Eruption VEI: 3 (?)

Episode 1 | Eruption

FF tephra layer

0044 Mar BCE (?) - Unknown

Evidence from Observations: Reported

List of 8 Events for Episode 1 at FF tephra layer

Start Date	End Date	Event Type	Event Remarks
- - - -	- - - -	Explosion
- - - -	- - - -	Eruption cloud
- - - -	- - - -	Lava flow
- - - -	- - - -	Lava flow	Entered water.
- - - -	- - - -	Ash
- - - -	- - - -	Earthquakes (undefined)
- - - -	- - - -	Property Damage
0044 Mar BCE (?)	- - - -	VEI (Explosivity Index)

0049 BCE Confirmed Eruption

Episode 1 | Eruption

West flank and summit ?

0049 BCE - Unknown

Evidence from Observations: Reported

List of 3 Events for Episode 1 at West flank and summit ?

Start Date	End Date	Event Type
- - - -	- - - -	Explosion
- - - -	- - - -	Lava flow
- - - -	- - - -	Lightning

[ 0056 BCE ] Uncertain Eruption

Episode 1 \| Eruption
0056 BCE - Unknown				Evidence from Unknown

[ 0061 BCE ] Uncertain Eruption

Episode 1 | Eruption

0061 BCE - Unknown

Evidence from Unknown

The CAVW listed a 61 BCE eruption, and Tanguy (1981) gave date of circa 60 BCE for an uncertain eruption. Stothers and Rampino (1983) stated that ancient sources do not support a 61 BCE eruption.

List of 1 Events for Episode 1

	Start Date	End Date	Event Type	Event Remarks
	- - - -	- - - -	Explosion

0122 BCE Confirmed Eruption VEI: 5

Episode 1 | Eruption

S flank, summit (Cratere del Piano caldera)

0122 BCE - Unknown

Evidence from Observations: Reported

List of 11 Events for Episode 1 at S flank, summit (Cratere del Piano caldera)

Start Date	End Date	Event Type	Event Remarks
- - - -	- - - -	Explosion
- - - -	- - - -	Phreatomagmatic
- - - -	- - - -	Pyroclastic flow
- - - -	- - - -	Lava flow
- - - -	- - - -	Lava flow	Entered water.
- - - -	- - - -	Ash
- - - -	- - - -	Lapilli
- - - -	- - - -	Scoria
- - - -	- - - -	Caldera	Explosion
- - - -	- - - -	Property Damage
0122 BCE	- - - -	VEI (Explosivity Index)

0126 Jun BCE (in or before) Confirmed Eruption

Episode 1 | Eruption

0126 Jun BCE (in or before) - Unknown

Evidence from Observations: Reported

List of 4 Events for Episode 1

Start Date	End Date	Event Type	Event Remarks
- - - -	- - - -	Explosion
- - - -	- - - -	Lava flow
- - - -	- - - -	Lava flow	Entered water. Uncertain
- - - -	- - - -	Earthquakes (undefined)

0135 BCE Confirmed Eruption

Episode 1 | Eruption

0135 BCE - Unknown

Evidence from Observations: Reported

List of 4 Events for Episode 1

Start Date	End Date	Event Type
- - - -	- - - -	Explosion
- - - -	- - - -	Lava flow
- - - -	- - - -	Ash
- - - -	- - - -	Property Damage

0141 Dec 31 BCE ± 365 days Confirmed Eruption

Episode 1 | Eruption

0141 Dec 31 BCE ± 365 days - Unknown

Evidence from Observations: Reported

List of 2 Events for Episode 1

	Start Date	End Date	Event Type	Event Remarks
	- - - -	- - - -	Explosion
	- - - -	- - - -	Lava flow

[ 0350 BCE (?) ] Discredited Eruption

Tanguy et al. (2007) did not list a circa 350 BCE eruption that was included in an earlier compilation.

0396 Apr 15 BCE (?) ± 45 days Confirmed Eruption

Episode 1 | Eruption

SE flank (700 m, Monte Gorna)

0396 Apr 15 BCE (?) ± 45 days - Unknown

Evidence from Observations: Reported

List of 4 Events for Episode 1 at SE flank (700 m, Monte Gorna)

Start Date	End Date	Event Type	Event Remarks
- - - -	- - - -	Explosion
- - - -	- - - -	Lava flow
- - - -	- - - -	Lava flow	Entered water.
- - - -	- - - -	Property Damage

0425 Mar 15 BCE ± 15 days - 0424 BCE (?) Confirmed Eruption

Episode 1 | Eruption

South flank (Monte Arso)

0425 Mar 15 BCE ± 15 days - 0424 BCE (?)

Evidence from Observations: Reported

List of 5 Events for Episode 1 at South flank (Monte Arso)

Start Date	End Date	Event Type	Event Remarks
- - - -	- - - -	Explosion	Uncertain
- - - -	- - - -	Lava flow	Entered water.
- - - -	- - - -	Lava flow
- - - -	- - - -	Earthquakes (undefined)
- - - -	- - - -	Property Damage

0479 Aug BCE (?) - 0475 BCE (?) Confirmed Eruption

Episode 1 | Eruption

South flank ?

0479 Aug BCE (?) - 0475 BCE (?)

Evidence from Observations: Reported

List of 4 Events for Episode 1 at South flank ?

Start Date	End Date	Event Type	Event Remarks
- - - -	- - - -	Explosion
- - - -	- - - -	Lava flow
- - - -	- - - -	Lava flow	Entered water.
- - - -	- - - -	Property Damage

[ 0565 BCE ] Uncertain Eruption

Episode 1 \| Eruption
0565 BCE - Unknown				Evidence from Unknown

0695 BCE ± 2 years Confirmed Eruption

Episode 1 | Eruption

South ?, Mt. Mompilieri ?

0695 BCE ± 2 years - Unknown

Evidence from Observations: Reported

List of 3 Events for Episode 1 at South ?, Mt. Mompilieri ?

Start Date	End Date	Event Type
- - - -	- - - -	Explosion
- - - -	- - - -	Lava flow
- - - -	- - - -	Property Damage

[ 0735 BCE ] Uncertain Eruption

Episode 1 \| Eruption
0735 BCE - Unknown				Evidence from Unknown

1050 BCE ± 75 years Confirmed Eruption

Episode 1 | Eruption

South flank (Monte Salto del Cane)

1050 BCE ± 75 years - Unknown

Evidence from Isotopic: 14C (uncalibrated)

List of 2 Events for Episode 1 at South flank (Monte Salto del Cane)

	Start Date	End Date	Event Type	Event Remarks
	- - - -	- - - -	Explosion
	- - - -	- - - -	Lava flow

1420 BCE ± 75 years Confirmed Eruption

Episode 1 | Eruption

FL tephra layer

1420 BCE ± 75 years - Unknown

Evidence from Isotopic: 14C (calibrated)

List of 5 Events for Episode 1 at FL tephra layer

Start Date	End Date	Event Type
- - - -	- - - -	Explosion
- - - -	- - - -	Pyroclastic flow
- - - -	- - - -	Ash
- - - -	- - - -	Blocks
- - - -	- - - -	Scoria

[ 1470 BCE ] Discredited Eruption

CAVW lists a 1470 BCE eruption, but this is confused with the ca. 1500 BCE eruption (Tanguy, pers. comm. 1982).

1500 BCE ± 50 years Confirmed Eruption VEI: 5 (?)

Episode 1 | Eruption

1500 BCE ± 50 years - Unknown

Evidence from Observations: Reported

List of 5 Events for Episode 1

Start Date	End Date	Event Type	Event Remarks
- - - -	- - - -	Explosion
- - - -	- - - -	Lava flow
- - - -	- - - -	Lahar or Mudflow	Uncertain
- - - -	- - - -	Property Damage
1500 BCE ± 50 years	- - - -	VEI (Explosivity Index)

1980 BCE ± 50 years Confirmed Eruption

Episode 1 | Eruption

FS tephra

1980 BCE ± 50 years - Unknown

Evidence from Isotopic: 14C (uncalibrated)

List of 2 Events for Episode 1 at FS tephra

	Start Date	End Date	Event Type	Event Remarks
	- - - -	- - - -	Explosion
	- - - -	- - - -	Scoria

2330 BCE ± 100 years Confirmed Eruption

Episode 1 | Eruption

2330 BCE ± 100 years - Unknown

Evidence from Isotopic: 14C (uncalibrated)

List of 2 Events for Episode 1

	Start Date	End Date	Event Type	Event Remarks
	- - - -	- - - -	Explosion
	- - - -	- - - -	Pumice

3050 BCE ± 150 years Confirmed Eruption

Episode 1 | Eruption

3050 BCE ± 150 years - Unknown

Evidence from Isotopic: 14C (uncalibrated)

List of 2 Events for Episode 1

	Start Date	End Date	Event Type	Event Remarks
	- - - -	- - - -	Explosion
	- - - -	- - - -	Pumice

3390 BCE ± 50 years Confirmed Eruption

Episode 1 | Eruption

Tufo varicolori tephra

3390 BCE ± 50 years - Unknown

Evidence from Isotopic: 14C (uncalibrated)

List of 2 Events for Episode 1 at Tufo varicolori tephra

	Start Date	End Date	Event Type	Event Remarks
	- - - -	- - - -	Explosion
	- - - -	- - - -	Ash

3510 BCE ± 150 years Confirmed Eruption

Episode 1 | Eruption

3510 BCE ± 150 years - Unknown

Evidence from Isotopic: 14C (uncalibrated)

List of 4 Events for Episode 1

Start Date	End Date	Event Type
- - - -	- - - -	Explosion
- - - -	- - - -	Phreatic activity
- - - -	- - - -	Pumice
- - - -	- - - -	Lahar or Mudflow

4150 BCE ± 150 years Confirmed Eruption

Episode 1 | Eruption

4150 BCE ± 150 years - Unknown

Evidence from Isotopic: 14C (uncalibrated)

List of 2 Events for Episode 1

	Start Date	End Date	Event Type	Event Remarks
	- - - -	- - - -	Explosion
	- - - -	- - - -	Pumice

5150 BCE ± 150 years Confirmed Eruption

Episode 1 | Eruption

5150 BCE ± 150 years - Unknown

Evidence from Isotopic: 14C (uncalibrated)

List of 2 Events for Episode 1

	Start Date	End Date	Event Type	Event Remarks
	- - - -	- - - -	Explosion
	- - - -	- - - -	Pumice

6190 BCE ± 200 years Confirmed Eruption

Episode 1 | Eruption

6190 BCE ± 200 years - Unknown

Evidence from Isotopic: 14C (uncalibrated)

List of 2 Events for Episode 1

	Start Date	End Date	Event Type	Event Remarks
	- - - -	- - - -	Explosion
	- - - -	- - - -	Pumice

Deformation History

There is data available for 2 deformation periods. Expand each entry for additional details.

Deformation during 2001 - 2005 [Subsidence; Observed by InSAR]

Start Date: 2001

Stop Date: 2005

Direction: Subsidence

Method: InSAR

Magnitude: 13.000 cm

Spatial Extent: Unknown

Latitude: Unknown

Longitude: Unknown

Remarks: Subsidence of Mt. Etna between 2001 and 2003 was coincident with high eruptive rates.

Observed SAR interferograms. (a) Descending track (222) interferogram 2000/11/15?2001/10/31. (b) Ascending track (129) interferogram 2001/07/11 ? 2001/08/ 15. The white arrows show the pointing azimuth of the radar (incidence angle ??23? at ERS scene mid-swath). Black box outlines the areas used for the surface deformation models. North-south dimension of box is 18 km.

From: Lundgren and Rosen 2003a.

Reference List: Neri et al. 2009; Massonnet et al. 1995; Borgia et al. 2000; Froger et al. 2001; Lundgren et al. 2003b; Lundgren and Rosen 2003a; Neri et al. 2007; Lundgren et al. 2004; Palano et al. 2008.

Full References:

Borgia, A., Lanari, R., Sansosti, E., Tesauro, M., Berardino, P., Fornaro, G., Neri, M. and Murray, J.B.,, 2000. Actively growing anticlines beneath Catania from the distal motion of Mount Etna's decollement measured by SAR interferometry and GPS. Geophysical Research Letters, 27, pp.3409-3412.

Froger, J. L., Merle, O., & Briole, P., 2001. Active spreading and regional extension at Mount Etna imaged by SAR interferometry. Earth and Planetary Science Letters, 187(3), 245-258.

Lundgren, P., Casu, F., Manzo, M., Pepe, A., Berardino, P., Sansosti, E., & Lanari, R., 2004. Gravity and magma induced spreading of Mount Etna volcano revealed by satellite radar interferometry. Geophysical Research Letters, 31, L04602. https://doi.org/10.1029/2003GL018736

Lundgren, P., P. Berardino, M. Coltelli, G. Fornaro, R. Lanari, G. Puglisi, E. Sansosti, and M. Tesauro,, 2003. Coupled magma chamber inflation and sector collapse slip observed with synthetic aperture radar interferometry on Mt. Etna volcano. J. Geophys. Res., 108(B5), 2247. https://doi.org/10.1029/2001JB000657

Massonnet, D., P. Briole, and A. Arnaud, 1995. Deflation of Mount Etna monitored by spaceborne radar interferometry. Nature, 375, 567-570.

Neri, M., Casu, F., Acocella, V., Solaro, G., Pepe, S., Berardino, P., Sansosti, E., Caltabiano, T., Lundgren, P. and Lanari, R.,, 2009. Deformation and eruptions at Mt. Etna (Italy): a lesson from 15 years of observations. Geophysical Research Letters, 36, L02309. https://doi.org/10.1029/2008GL036151

Neri, M., F. Guglielmino, and D. Rust, 2007. Flank instability on Mount Etna: Radon, radar interferometry, and geodetic data from the southwestern boundary of the unstable sector. J. Geophys. Res., 112, B04410. https://doi.org/10.1029/2006JB004756

Palano, M., Puglisi, G., & Gresta, S., 2008. Ground deformation patterns at Mt. Etna from 1993 to 2000 from joint use of InSAR and GPS techniques. J. Volcanol. Geotherm. Res., 169(3), 99-120.

Deformation during 1993 - 2000 [Uplift; Observed by InSAR]

Start Date: 1993

Stop Date: 2000

Direction: Uplift

Method: InSAR

Magnitude: Unknown

Spatial Extent: Unknown

Latitude: Unknown

Longitude: Unknown

Remarks: Between 1993 and 1998, Etna uplifted at a rate of 1 cm/yr, and between 1998 and 2000 the rate decreased, possibly due to the increase in eruptive activity.

Differential synthetic aperture radar (SAR) interferograms spanning approximately 6 year time intervals from different starting and ending dates since 1993 using European Space Agency ERS-1 and ERS-2 SAR data. Interferograms on the left (a, c) are from ascending satellite passes (radar looks to ENE), while those on the left (b, d) are from descending satellite passes (radar looks to the WNW). (a) Interferogram from 30 May 1993 to 11 Aug. 1999. (b) From 06 June 1993 to 01 Dec. 1999. (c) From 17 Oct. 1993 to 19 Oct. 1999. (d) From 19 Sep. 1993 to 21 Sep. 1999. Solid lines indicate faults and rift zones shown in Figure 1. Observed anticline growth is indicated in (c).

From: Lundgren et al. 2004.

Full References:

Froger, J. L., Merle, O., & Briole, P., 2001. Active spreading and regional extension at Mount Etna imaged by SAR interferometry. Earth and Planetary Science Letters, 187(3), 245-258.

Massonnet, D., P. Briole, and A. Arnaud, 1995. Deflation of Mount Etna monitored by spaceborne radar interferometry. Nature, 375, 567-570.

Palano, M., Puglisi, G., & Gresta, S., 2008. Ground deformation patterns at Mt. Etna from 1993 to 2000 from joint use of InSAR and GPS techniques. J. Volcanol. Geotherm. Res., 169(3), 99-120.

Emission History

There is data available for 27 emission periods. Expand each entry for additional details.

Emissions during 2015 Dec 03 - 2015 Dec 03 [25 kt SO₂ at 13 km altitude]

Start Date: 2015 Dec 03	Stop Date: 2015 Dec 03	Method: Satellite (Aura OMI)
SO₂ Altitude Min: 13 km	SO₂ Altitude Max: 13 km	Total SO₂ Mass: 25 kt

Data Details

Date Start	Date End	Assumed SO₂ Altitude	SO₂ Algorithm	SO₂ Mass
20151203		13.0		25.000

Emissions during 2013 Oct 26 - 2013 Oct 26 [10 kt SO₂ at 8 km altitude]

Start Date: 2013 Oct 26	Stop Date: 2013 Oct 26	Method: Satellite (Aura OMI)
SO₂ Altitude Min: 8 km	SO₂ Altitude Max: 8 km	Total SO₂ Mass: 10 kt

Data Details

Date Start	Date End	Assumed SO₂ Altitude	SO₂ Algorithm	SO₂ Mass
20131026		8.0		10.000

Emissions during 2013 Nov 17 - 2013 Dec 30 [40 kt SO₂ at 4 km altitude]

Start Date: 2013 Nov 17	Stop Date: 2013 Dec 30	Method: Satellite (Aura OMI)
SO₂ Altitude Min: 4 km	SO₂ Altitude Max: 8 km	Total SO₂ Mass: 40 kt

Data Details

Date Start	Date End	Assumed SO₂ Altitude	SO₂ Algorithm	SO₂ Mass
20131230		4.0		10.000
20131214		4.0		5.000
20131202		4.0		10.000
20131123		8.0		5.000
20131117		4.0		10.000

Emissions during 2013 Feb 28 - 2013 Feb 28 [5 kt SO₂ at 4 km altitude]

Start Date: 2013 Feb 28	Stop Date: 2013 Feb 28	Method: Satellite (Aura OMI)
SO₂ Altitude Min: 4 km	SO₂ Altitude Max: 4 km	Total SO₂ Mass: 5 kt

Data Details

Date Start	Date End	Assumed SO₂ Altitude	SO₂ Algorithm	SO₂ Mass
20130228		4.0		5.000

Emissions during 2013 Apr 27 - 2013 Apr 27 [7 kt SO₂ at 4 km altitude]

Start Date: 2013 Apr 27	Stop Date: 2013 Apr 27	Method: Satellite (Aura OMI)
SO₂ Altitude Min: 4 km	SO₂ Altitude Max: 4 km	Total SO₂ Mass: 7 kt

Data Details

Date Start	Date End	Assumed SO₂ Altitude	SO₂ Algorithm	SO₂ Mass
20130427		4.0		7.000

Emissions during 2012 Mar 04 - 2012 Apr 24 [31 kt SO₂ at 6 km altitude]

Start Date: 2012 Mar 04	Stop Date: 2012 Apr 24	Method: Satellite (Aura OMI)
SO₂ Altitude Min: 6 km	SO₂ Altitude Max: 11 km	Total SO₂ Mass: 31 kt

Data Details

Date Start	Date End	Assumed SO₂ Altitude	SO₂ Algorithm	SO₂ Mass
20120424		6.0		9.100
20120412		6.0		2.700
20120401		11.0		7.400
20120318		8.0		6.800
20120304		8.0		5.000

Emissions during 2012 Jan 05 - 2012 Jan 05 [7 kt SO₂ at 9 km altitude]

Start Date: 2012 Jan 05	Stop Date: 2012 Jan 05	Method: Satellite (Aura OMI)
SO₂ Altitude Min: 9 km	SO₂ Altitude Max: 9 km	Total SO₂ Mass: 7 kt

Data Details

Date Start	Date End	Assumed SO₂ Altitude	SO₂ Algorithm	SO₂ Mass
20120105		9.0		6.500

Emissions during 2012 Feb 09 - 2012 Feb 09 [1 kt SO₂ at 9 km altitude]

Start Date: 2012 Feb 09	Stop Date: 2012 Feb 09	Method: Satellite (Aura OMI)
SO₂ Altitude Min: 9 km	SO₂ Altitude Max: 9 km	Total SO₂ Mass: 1 kt

Data Details

Date Start	Date End	Assumed SO₂ Altitude	SO₂ Algorithm	SO₂ Mass
20120209		9.0		1.100

Emissions during 2011 Nov 15 - 2011 Nov 15 [5 kt SO₂ at 11 km altitude]

Start Date: 2011 Nov 15	Stop Date: 2011 Nov 15	Method: Satellite (Aura OMI)
SO₂ Altitude Min: 11 km	SO₂ Altitude Max: 11 km	Total SO₂ Mass: 5 kt

Data Details

Date Start	Date End	Assumed SO₂ Altitude	SO₂ Algorithm	SO₂ Mass
20111115		11.0		4.800

Emissions during 2011 May 12 - 2011 May 12 [6 kt SO₂ at 6 km altitude]

Start Date: 2011 May 12	Stop Date: 2011 May 12	Method: Satellite (Aura OMI)
SO₂ Altitude Min: 6 km	SO₂ Altitude Max: 6 km	Total SO₂ Mass: 6 kt

Data Details

Date Start	Date End	Assumed SO₂ Altitude	SO₂ Algorithm	SO₂ Mass
20110512		6.0		6.000

Emissions during 2011 Jul 09 - 2011 Oct 23 [53 kt SO₂ at 4 km altitude]

Start Date: 2011 Jul 09	Stop Date: 2011 Oct 23	Method: Satellite (Aura OMI)
SO₂ Altitude Min: 4 km	SO₂ Altitude Max: 13 km	Total SO₂ Mass: 53 kt

Data Details

Date Start	Date End	Assumed SO₂ Altitude	SO₂ Algorithm	SO₂ Mass
20111023		6.0		2.300
20111008		13.4		5.000
20110928		11.0		3.100
20110919		8.0		1.300
20110908		10.0		9.000
20110829		10.0		3.200
20110820		9.0		3.600
20110812		4.0		3.200
20110805		11.0		6.400
20110730		6.0		5.000
20110725		7.0		2.900
20110719		5.0		5.000
20110709		7.0		2.700

Emissions during 2011 Jan 12 - 2011 Jan 12 [7 kt SO₂ at 7 km altitude]

Start Date: 2011 Jan 12	Stop Date: 2011 Jan 12	Method: Satellite (Aura OMI)
SO₂ Altitude Min: 7 km	SO₂ Altitude Max: 7 km	Total SO₂ Mass: 7 kt

Data Details

Date Start	Date End	Assumed SO₂ Altitude	SO₂ Algorithm	SO₂ Mass
20110112		7.0		7.000

Emissions during 2011 Feb 18 - 2011 Feb 18 [8 kt SO₂ at 8 km altitude]

Start Date: 2011 Feb 18	Stop Date: 2011 Feb 18	Method: Satellite (Aura OMI)
SO₂ Altitude Min: 8 km	SO₂ Altitude Max: 8 km	Total SO₂ Mass: 8 kt

Data Details

Date Start	Date End	Assumed SO₂ Altitude	SO₂ Algorithm	SO₂ Mass
20110218		8.0		8.000

Emissions during 2011 Apr 10 - 2011 Apr 10 [5 kt SO₂ at 5 km altitude]

Start Date: 2011 Apr 10	Stop Date: 2011 Apr 10	Method: Satellite (Aura OMI)
SO₂ Altitude Min: 5 km	SO₂ Altitude Max: 5 km	Total SO₂ Mass: 5 kt

Data Details

Date Start	Date End	Assumed SO₂ Altitude	SO₂ Algorithm	SO₂ Mass
20110410		5.0		5.000

Emissions during 2008 May 10 - 2008 May 13 [47 kt SO₂ at 5 km altitude]

Start Date: 2008 May 10	Stop Date: 2008 May 13	Method: Satellite (Aura OMI)
SO₂ Altitude Min: 5 km	SO₂ Altitude Max: 6 km	Total SO₂ Mass: 47 kt

Data Details

Date Start	Date End	Assumed SO₂ Altitude	SO₂ Algorithm	SO₂ Mass
20080513		5.0		26.500
20080510		6.0		20.000

Emissions during 2007 Sep 04 - 2007 Sep 04 [12 kt SO₂ at 5 km altitude]

Start Date: 2007 Sep 04	Stop Date: 2007 Sep 04	Method: Satellite (Aura OMI)
SO₂ Altitude Min: 5 km	SO₂ Altitude Max: 5 km	Total SO₂ Mass: 12 kt

Data Details

Date Start	Date End	Assumed SO₂ Altitude	SO₂ Algorithm	SO₂ Mass
20070904		5.0		12.000

Emissions during 2007 Nov 24 - 2007 Nov 24 [10 kt SO₂ at 7 km altitude]

Start Date: 2007 Nov 24	Stop Date: 2007 Nov 24	Method: Satellite (Aura OMI)
SO₂ Altitude Min: 7 km	SO₂ Altitude Max: 7 km	Total SO₂ Mass: 10 kt

Data Details

Date Start	Date End	Assumed SO₂ Altitude	SO₂ Algorithm	SO₂ Mass
20071124		7.0		10.000

Emissions during 2007 Mar 29 - 2007 Apr 11 [11 kt SO₂ at 5 km altitude]

Start Date: 2007 Mar 29	Stop Date: 2007 Apr 11	Method: Satellite (Aura OMI)
SO₂ Altitude Min: 5 km	SO₂ Altitude Max: 8 km	Total SO₂ Mass: 11 kt

Data Details

Date Start	Date End	Assumed SO₂ Altitude	SO₂ Algorithm	SO₂ Mass
20070411		5.0		5.500
20070329		8.4		5.000

Emissions during 2007 Apr 29 - 2007 May 07 [6 kt SO₂ at 6 km altitude]

Start Date: 2007 Apr 29	Stop Date: 2007 May 07	Method: Satellite (Aura OMI)
SO₂ Altitude Min: 6 km	SO₂ Altitude Max: 8 km	Total SO₂ Mass: 6 kt

Data Details

Date Start	Date End	Assumed SO₂ Altitude	SO₂ Algorithm	SO₂ Mass
20070507		8.4		2.000
20070429		6.0		4.000

Emissions during 2006 Nov 16 - 2006 Nov 21 [9 kt SO₂ at 4 km altitude]

Start Date: 2006 Nov 16	Stop Date: 2006 Nov 21	Method: Satellite (Aura OMI)
SO₂ Altitude Min: 4 km	SO₂ Altitude Max: 5 km	Total SO₂ Mass: 9 kt

Data Details

Date Start	Date End	Assumed SO₂ Altitude	SO₂ Algorithm	SO₂ Mass
20061121		5.0		7.800
20061116		4.0		1.500

Emissions during 2002 Oct 27 - 2002 Oct 27 [80 kt SO₂ at 13 km altitude]

Start Date: 2002 Oct 27	Stop Date: 2002 Oct 27	Method: Satellite (Earth Probe TOMS)
SO₂ Altitude Min: 13 km	SO₂ Altitude Max: 13 km	Total SO₂ Mass: 80 kt

Data Details

Date Start	Date End	Assumed SO₂ Altitude	SO₂ Algorithm	SO₂ Mass
20021027		13.4		80.000

Emissions during 2001 Jul 25 - 2001 Jul 25 [10 kt SO₂ at 8 km altitude]

Start Date: 2001 Jul 25	Stop Date: 2001 Jul 25	Method: Satellite (Earth Probe TOMS)
SO₂ Altitude Min: 8 km	SO₂ Altitude Max: 8 km	Total SO₂ Mass: 10 kt

Data Details

Date Start	Date End	Assumed SO₂ Altitude	SO₂ Algorithm	SO₂ Mass
20010725		8.4		10.000

Emissions during 1990 Jan 15 - 1990 Jan 15 [10 kt SO₂ at 8 km altitude]

Start Date: 1990 Jan 15	Stop Date: 1990 Jan 15	Method: Satellite (Nimbus-7 TOMS)
SO₂ Altitude Min: 8 km	SO₂ Altitude Max: 8 km	Total SO₂ Mass: 10 kt

Data Details

Date Start	Date End	Assumed SO₂ Altitude	SO₂ Algorithm	SO₂ Mass
19900115		8.4		10.000

Emissions during 1989 Sep 19 - 1989 Sep 19 [37 kt SO₂ at 8 km altitude]

Start Date: 1989 Sep 19	Stop Date: 1989 Sep 19	Method: Satellite (Nimbus-7 TOMS)
SO₂ Altitude Min: 8 km	SO₂ Altitude Max: 8 km	Total SO₂ Mass: 37 kt

Data Details

Date Start	Date End	Assumed SO₂ Altitude	SO₂ Algorithm	SO₂ Mass
19890919		8.4		37.000

Emissions during 1986 Nov 30 - 1986 Nov 30 [10 kt SO₂ at 8 km altitude]

Start Date: 1986 Nov 30	Stop Date: 1986 Nov 30	Method: Satellite (Nimbus-7 TOMS)
SO₂ Altitude Min: 8 km	SO₂ Altitude Max: 8 km	Total SO₂ Mass: 10 kt

Data Details

Date Start	Date End	Assumed SO₂ Altitude	SO₂ Algorithm	SO₂ Mass
19861130		8.4		10.000

Emissions during 1980 Sep 02 - 1980 Sep 06 [70 kt SO₂ at 9 km altitude]

Start Date: 1980 Sep 02	Stop Date: 1980 Sep 06	Method: Satellite (Nimbus-7 TOMS)
SO₂ Altitude Min: 9 km	SO₂ Altitude Max: 13 km	Total SO₂ Mass: 70 kt

Data Details

Date Start	Date End	Assumed SO₂ Altitude	SO₂ Algorithm	SO₂ Mass
19800906		13.4		9.000
19800902		9.0		61.000

Emissions during 1979 Aug 04 - 1979 Aug 04 [10 kt SO₂ at 8 km altitude]

Start Date: 1979 Aug 04	Stop Date: 1979 Aug 04	Method: Satellite (Nimbus-7 TOMS)
SO₂ Altitude Min: 8 km	SO₂ Altitude Max: 8 km	Total SO₂ Mass: 10 kt

Data Details

Date Start	Date End	Assumed SO₂ Altitude	SO₂ Algorithm	SO₂ Mass
19790804		8.4		10.000

Photo Gallery

Snow-capped Mount Etna, seen here from the SE, rises more than 3 km above the coastline of Sicily. The massive basaltic stratovolcano is 60 km by 40 km in width. Its summit is truncated by several small calderas, and the Valle de Bove, a 5 x 10 km horseshoe-shaped depression created by incremental landsliding, extends to the eastern coast. Persistent summit eruptive activity is punctuated by intermittent eruptions from cones and fissures that dot its massive flanks.

Copyrighted photo by Katia and Maurice Krafft.

Three large craters cap the summit of Mount Etna, the NE Crater, the Central Crater, and the SE Crater. Long-term minor eruptions occur from the NE and Central craters, and to a lesser extent from the SE Crater, which formed in 1978. Pyroclastic ejecta mantles the upper flanks of the summit cones, and lava flows furrow the lower flanks.

Copyrighted photo by Katia and Maurice Krafft.

A painting depicts an eruption of Mount Etna on August 21, 1852. The eruption, which began the previous day, originated from a radial fissure in the Valle del Bove, the large horseshoe-shaped depression on the east flank. Explosive eruptions occurred along the fissure, which fed lava flows down the west flank that damaged inhabited areas.

From the collection of Maurice and Katia Krafft.

Lava flows spread over the snow-covered slopes of Etna on 17 March 1981 at the beginning of a NW-flank eruption. During the six-day eruption lava flows descended 8 km into populated areas and caused significant damage.

Photo by Romolo Romano, 1981 (IIV-CNR, Catania, Italy).

A major S-flank eruption of Etna beginning on 28 March 1983 produced lava flows that damaged tourist facilities. Extensive efforts at lava diversion, such as the gray embankment at the left of this photo, were made to divert the flows from populated areas. The flows eventually descended to 1,080 m altitude and stopped short of several villages.

Photo by Romolo Romano, 1983 (IIV-CNR, Catania, Italy).

A March 1981 lava flow from vents on the upper NW flank of Mount Etna in Sicily descended 8 km into populated areas and caused extensive damage to orchards and farm buildings. This photo shows the steaming lava flow front as it overran a railroad bed and highway.

Photo by Romolo Romano, 1981 (IIV-CNR, Catania, Italy).

An ash plume rises above Etna’s NE Crater on 24 September 1986. This marked the end of an eruption episode that began in July 1984. Intermittent explosive eruptions from the Northeast Crater took place for two years. In July 1986, Strombolian eruptions formed a scoria cone in the crater. On 14 September 1986 lava overtopped the west rim of Northeast Crater and flowed 1.5 km down its flank.

Photo by Romolo Romano, 1986 (IIV-CNR, Catania, Italy).

Incandescent lava flows in May 1983 descend the south flank of Mount Etna toward city lights. During the four-month-long eruption, lava descended to 1080 m altitude, stopping just short of inhabited areas. Extensive efforts were made to construct barriers to divert lavas away from populated areas.

Copyrighted photo by Katia and Maurice Krafft.

This 31 December 1991 view of Etna from the E shows lava flows descending the headwall of the Valle del Bove. This eruption began from the Southeast Crater and nearby fissures and lasted until 30 March 1993. The eruption was Etna's largest during the past 300 years, producing 0.3 km³ of lava that descended 7.5 km down the flank.

Photo by Jean-Claude Tanguy, 1991 (University of Paris).

Lava flows descending the Valle del Bove on Mount Etna on 16 March 1992, observed from Monte Pomiciaro Belvedere on the S rim. The eruption, which had begun in December 1991, lasted more than 16 months and was the most voluminous at Etna during the past 300 years.

Photo by Jean-Claude Tanguy, 1992 (University of Paris).

Etna is Europe's highest volcano, towering above the city of Taormina on its NE flank. One of the world's longest documented historical records continues, dating back to the 2nd millennium BCE. Historical lava flows cover much of the surface of this 40 x 60 km wide basaltic stratovolcano and extend to the sea. Eruptions occur both from persistently active summit craters and intermittently from flank fissures and cones.

Photo by Jean-Claude Tanguy, 1991 (University of Paris).

An active lava channel near the vent of the March 1981 NW flank eruption fed flows that traveled 7.5 km. The week-long eruption, one of few Etna eruptions originating on the NW or NNW flanks, entered populated areas and resulted in evacuations. Active vents progressively migrated downhill along eruptive fissures between 2,250 and 1,150 m altitude and produced vigorous lava fountains and lava flows.

Photo by Roberto Scandone (University of Rome).

Black lava flows descend the south flank of Etna a week after the eruption began on 28 March 1983 and went on to last for five months. Prominent levees are visible on the surface of the lava flows that crossed a highway and formed a complex lava field as much as 1 km wide. The flows originated from a NNE-SSW-trending fissure 4 km S of Etna's snow-capped Central Crater.

Photo by Romolo Romano, 1983 (IIV-CNR, Catania, Italy).

Fresh black lava flows overrun a highway and tourist facility buildings the day after the start of an eruption at Sicily's Mount Etna on 28 March 1983. The lava flows originated from a fissure 4 km S of the summit, and over a 5-month period formed a complex lava field as much as 1 km wide.

Photo by Romolo Romano, 1983 (IIV-CNR, Catania, Italy).

Weak Strombolian activity on 5 December 1985 from Bocca Nuova, one of two active vents in the Central Crater, is typical of persistent summit activity at Etna. Fresh black lava flows cover the floor of the crater. Both Bocca Nuova and the E vent, La Voragine, frequently eject scoria and molten lava bombs that commonly do not reach above the height of the roughly 100-m-high crater. Occasional periods of high lava fountaining and ash ejection also occur.

Photo by Romolo Romano, 1985 (IIV-CNR, Catania, Italy).

An aerial view looking SW across the Valle del Bove on 6 December 1986 shows a lava flow descending the floor of the broad depression on Etna's E flank. The eruption began on 30 October from a 2-km-long fissure that cut the upper Valle del Bove, and lasted until 27 February 1987. Lava flows traveled 5 km E to 1,325 m altitude.

Photo by Romolo Romano, 1986 (IIV-CNR, Catania, Italy).

Etna during the climax of the 2001 eruption, which took place on 21-23 July. The upper ash column rises from a vent on the far side of Montagnola. The lower, smaller series of plumes rise from vents and associated lava flow at 2,100 m elevation. The 2001 eruption began on 17 July and lasted until 9 August.

Photo by Jean-Claude Tanguy, 2001 (University of Paris).

Two vents and lava flows inside Etna’s Voragine crater within the Central Crater are seen in July 1998. Explosions on 17 June and 12 July 1994 were the first sign of explosive activity since the end of the 1991-93 eruption. Intermittent eruptions from the Central Crater, Northeast Crater, and Southeast Crater continued into 2001. Paroxysmal eruptions on 23 December 1995 produced lava fountains as high as 500-600 m, and an eruption column that rose 6.2 km above the summit.

Photo by Jean-Claude Tanguy, 1998 (University of Paris).

A major eruption took place from fissure vents on the N and S flanks of Italy's Etna volcano beginning on 26 October 2002. Lava flows cut across roads, and several hotels, restaurants, a ski school, ski lift pylons, and power lines were destroyed. This photo, taken on the 28th, looks towards the summit from the lower NE rift zone and shows lava fountaining and an ash plume from the two upper vents as well as small white plumes from the upper part of the eruptive fissure (far middle right).

Photo by Jean-Claude Tanguy, 2002 (University of Paris).

Two days after the onset of the eruption on the morning of 28 October 2002, the southern vents of Etna produce ash and gas plumes. The white plume on the right comes from the lava vent, and the plume in the left background is from the summit craters.

Photo by Jean-Claude Tanguy, 2002 (University of Paris).

The southern vents of Etna viewed from the SW in the early afternoon of 28 October 2002. From left to right the image shows the summit craters emitting white gas plumes, the cone of Mt. Frumento Supino, vents giving off a dark ash plume, the lower lava vent emitting a faint white plume, new lava flows (dark narrow band), the 2001 cone, and Montagnola cone. Explosive activity began on 26 October and lasted until 28 January 2003. Lava flows cut across roads on the volcano's flanks, causing substantial damage.

Photo by Jean-Claude Tanguy, 2002 (University of Paris).

An eruption at Etna on 30 October 2002 shows incandescent lava fountains and associated spatter. The photo was taken from Mt. Ponte di Ferro looking E. This was part of an eruption that began on 26 October. Lava fountaining began on 27 October from fissure vents on the N and S flanks.

Photo by Jean-Claude Tanguy, 2002 (University of Paris).

An ash plume rises about 1 km above the active vent on the eastern slope of Etna's Southeast Crater on the morning of 10 January 2008. The view is from Trecastagni, about 16 km SSE of the active vent. Summit vent eruptive activity began with a minor explosive eruption from Bocca Nuova on 19 March 2007. On 29 April activity began at Southeast Crater and flank vents produced lava flows. Intermittent explosive and effusive eruptions from Southeast Crater continued into 2008.

Photo courtesy of INGV-Catania, 2007.

This photomosaic was taken from a helicopter of the Italian Civil Defense Department on 15 May 2008. The eastern sector of Etna has an active eruptive fissure just below the summit craters to the right, and the extent of active lava flows in the Valle del Bove is seen in the center to the left. A major effusive eruption began on 13 May and within the first month lava flows had traveled about 5 km down the Valle del Bove. Effusive activity continued into 2009.

Photo courtesy of INGV-Catania, 2008.

GVP Map Holdings

Maps are not currently available due to technical issues.

Smithsonian Sample Collections Database

The following 124 samples associated with this volcano can be found in the Smithsonian's NMNH Department of Mineral Sciences collections, and may be availble for research (contact the Rock and Ore Collections Manager). Catalog number links will open a window with more information.

Catalog Number	Sample Description	Lava Source	Collection Date
NMNH 100021	Andesine Andesite	--	--
NMNH 100022	Andesine Andesite	--	--
NMNH 100023	Andesine Andesite	--	--
NMNH 100024	Andesine Andesite	--	--
NMNH 100025	Tuff	--	--
NMNH 100026	Andesite	--	--
NMNH 100027	Marl	--	--
NMNH 100028	Basalt	--	--
NMNH 100029	Andesite	--	--
NMNH 100030	Olivine Basalt	--	--
NMNH 100031	Oligoclase Andesite	--	--
NMNH 100032	Oligoclase Andesite	--	--
NMNH 100033	Oligoclase Andesite	--	--
NMNH 100034	Oligoclase Andesite	--	--
NMNH 100035	Oligoclase Andesite	--	--
NMNH 100036	Oligoclase Andesite	--	--
NMNH 100037-1	Andesite	--	--
NMNH 100037-2	Oligoclase Andesite	--	--
NMNH 100037-3	Andesine Andesite	--	--
NMNH 100038	Andesite	--	--
NMNH 100039	Andesite	--	--
NMNH 100040	Andesite	--	--
NMNH 100041	Andesite	--	--
NMNH 100042	Andesite	--	--
NMNH 100043	Andesite	--	--
NMNH 100044-1	Andesite	--	--
NMNH 100044-2	Oligoclase Andesite	--	--
NMNH 100045	Andesite	--	--
NMNH 100046	Andesite	--	--
NMNH 100047	Andesite	--	--
NMNH 100048	Andesite	--	--
NMNH 100049	Andesite	--	--
NMNH 100050	Andesite	--	--
NMNH 100051	Andesite	--	--
NMNH 100052	Andesite	--	--
NMNH 100053-1	Andesite	--	--
NMNH 100053-2	Andesine Andesite	--	--
NMNH 100054	Andesite	--	--
NMNH 100055	Basaltic Andesite	--	--
NMNH 100056	Andesine Basalt	--	--
NMNH 100057	Andesine Andesite	--	--
NMNH 100058	Andesine Andesite	--	--
NMNH 100059	Andesine Basalt	--	--
NMNH 100060	Andesine Andesite	--	--
NMNH 100061	Andesine Basalt	--	--
NMNH 100062	Andesine Basalt	--	--
NMNH 100063	Andesine Basalt	--	--
NMNH 100064	Andesine Basalt	--	--
NMNH 100065	Andesine Basalt	--	--
NMNH 100066	Andesine Basalt	--	--
NMNH 100067	Andesine Basalt	--	--
NMNH 100068	Andesine Basalt	--	--
NMNH 100069	Andesine Basalt	--	--
NMNH 100070	Andesine Basalt	--	--
NMNH 100071	Andesine Basalt	--	--
NMNH 100072	Andesine Basalt	--	--
NMNH 100073	Andesine Basalt	--	--
NMNH 100074	Andesite	--	--
NMNH 109075	Basalt	--	--
NMNH 109076	Scoria	--	--
NMNH 113109-1	Phonolitic Tephrite	--	--
NMNH 113109-10	Unidentified	--	--
NMNH 113109-2	Olivine Andesite	--	--
NMNH 113109-3	Olivine Andesite	--	--
NMNH 113109-4	Basalt	--	--
NMNH 113109-5	Hawaiite	--	--
NMNH 113109-6	Olivine Basalt	--	--
NMNH 113109-7	Alkalic Basalt	--	--
NMNH 113109-8	Basalt	--	--
NMNH 113109-9	Phonolitic Tephrite	--	--
NMNH 113559-2	Basalt	--	--
NMNH 113598-66	Marble	--	--
NMNH 115424-1	Olivine Tholeiite	--	--
NMNH 115424-10	Etnaite	--	--
NMNH 115424-11	Trachyandesite	--	--
NMNH 115424-2	Pigeonite Tholeiite	--	--
NMNH 115424-3	Pigeonite Tholeiite	--	--
NMNH 115424-4	Tholeiite	--	--
NMNH 115424-5	Olivine Basalt	--	--
NMNH 115424-6	Etnaite	--	--
NMNH 115424-7	Etnaite	--	--
NMNH 115424-8	Trachyte	--	--
NMNH 115424-9	Trachyte	--	--
NMNH 115482-1	Hawaiite	--	--
NMNH 115482-2	Hawaiite	--	--
NMNH 115482-3	Basic Mugearite	--	--
NMNH 115482-4	Mugearite	--	--
NMNH 115482-5	Benmoreite	--	--
NMNH 116259-1	Zeolites	--	--
NMNH 116259-10	Basalt	MONTI SILVESTRI	--
NMNH 116259-11	Basalt	MT RICCO	--
NMNH 116259-12	Basalt	MT RICCO	--
NMNH 116259-13	Lava	--	--
NMNH 116259-2	Basalt	--	--
NMNH 116259-3	Lava	--	--
NMNH 116259-4	Basalt	--	--
NMNH 116259-5	Lava	--	--
NMNH 116259-6	Lava	--	--
NMNH 116259-7	Basalt	--	--
NMNH 116259-8	Basalt	I PIZZI (?)	--
NMNH 116259-9	Basalt	--	--
NMNH 117254-106	Lava	Etna	1 Jan 1983
NMNH 117254-107	Lava	--	1 Jan 1983
NMNH 117254-108	Lava	--	1 Jan 1983
NMNH 117270-35	Volcanic Rock	--	1 Jan 1983
NMNH 117270-36	Volcanic Rock	--	1 Jan 1983
NMNH 117270-37	Volcanic Rock	--	1 Jan 1983
NMNH 117270-38	Volcanic Rock	--	1 Jan 1983
NMNH 117270-39	Volcanic Rock	--	1 Jan 1983
NMNH 117270-40	Volcanic Rock	--	1 Jan 1983
NMNH 117270-41	Volcanic Rock	--	1 Jan 1983
NMNH 117270-42	Volcanic Rock	--	1 Jan 1983
NMNH 117270-43	Volcanic Rock	--	1 Jan 1983
NMNH 165331-00	Gypsum	--	--
NMNH 168348-00	Hypersthene	--	--
NMNH 73157	Volcanic Ash	--	--
NMNH 73251	Basalt	--	--
NMNH 73742	Basalt	--	--
NMNH 77432	Volcanic Bomb	--	--
NMNH 86581	Augite	--	--
NMNH 87666	Volcanic Dust	--	--
NMNH B18230-00	Hypersthene	--	--
NMNH B7296-00	Hematite	--	--
NMNH R3241-00	Hornblende	--	--

External Sites

Copernicus Browser

The Copernicus Browser replaced the Sentinel Hub Playground browser in 2023, to provide access to Earth observation archives from the Copernicus Data Space Ecosystem, the main distribution platform for data from the EU Copernicus missions.

MIROVA

Middle InfraRed Observation of Volcanic Activity (MIROVA) is a near real time volcanic hot-spot detection system based on the analysis of MODIS (Moderate Resolution Imaging Spectroradiometer) data. In particular, MIROVA uses the Middle InfraRed Radiation (MIR), measured over target volcanoes, in order to detect, locate and measure the heat radiation sourced from volcanic activity.

MODVOLC Thermal Alerts

Using infrared satellite Moderate Resolution Imaging Spectroradiometer (MODIS) data, scientists at the Hawai'i Institute of Geophysics and Planetology, University of Hawai'i, developed an automated system called MODVOLC to map thermal hot-spots in near real time. For each MODIS image, the algorithm automatically scans each 1 km pixel within it to check for high-temperature hot-spots. When one is found the date, time, location, and intensity are recorded. MODIS looks at every square km of the Earth every 48 hours, once during the day and once during the night, and the presence of two MODIS sensors in space allows at least four hot-spot observations every two days. Each day updated global maps are compiled to display the locations of all hot spots detected in the previous 24 hours. There is a drop-down list with volcano names which allow users to 'zoom-in' and examine the distribution of hot-spots at a variety of spatial scales.

WOVOdat
   Single Volcano View
   Temporal Evolution of Unrest
   Side by Side Volcanoes

WOVOdat is a database of volcanic unrest; instrumentally and visually recorded changes in seismicity, ground deformation, gas emission, and other parameters from their normal baselines. It is sponsored by the World Organization of Volcano Observatories (WOVO) and presently hosted at the Earth Observatory of Singapore.

GVMID Data on Volcano Monitoring Infrastructure The Global Volcano Monitoring Infrastructure Database GVMID, is aimed at documenting and improving capabilities of volcano monitoring from the ground and space. GVMID should provide a snapshot and baseline view of the techniques and instrumentation that are in place at various volcanoes, which can be use by volcano observatories as reference to setup new monitoring system or improving networks at a specific volcano. These data will allow identification of what monitoring gaps exist, which can be then targeted by remote sensing infrastructure and future instrument deployments.

Volcanic Hazard Maps

The IAVCEI Commission on Volcanic Hazards and Risk has a Volcanic Hazard Maps database designed to serve as a resource for hazard mappers (or other interested parties) to explore how common issues in hazard map development have been addressed at different volcanoes, in different countries, for different hazards, and for different intended audiences. In addition to the comprehensive, searchable Volcanic Hazard Maps Database, this website contains information about diversity of volcanic hazard maps, illustrated using examples from the database. This site is for educational purposes related to volcanic hazard maps. Hazard maps found on this website should not be used for emergency purposes. For the most recent, official hazard map for a particular volcano, please seek out the proper institutional authorities on the matter.

IRIS seismic stations/networks

Incorporated Research Institutions for Seismology (IRIS) Data Services map showing the location of seismic stations from all available networks (permanent or temporary) within a radius of 0.18° (about 20 km at mid-latitudes) from the given location of Etna. Users can customize a variety of filters and options in the left panel. Note that if there are no stations are known the map will default to show the entire world with a "No data matched request" error notice.

UNAVCO GPS/GNSS stations

Geodetic Data Services map from UNAVCO showing the location of GPS/GNSS stations from all available networks (permanent or temporary) within a radius of 20 km from the given location of Etna. Users can customize the data search based on station or network names, location, and time window. Requires Adobe Flash Player.

DECADE Data

The DECADE portal, still in the developmental stage, serves as an example of the proposed interoperability between The Smithsonian Institution's Global Volcanism Program, the Mapping Gas Emissions (MaGa) Database, and the EarthChem Geochemical Portal. The Deep Earth Carbon Degassing (DECADE) initiative seeks to use new and established technologies to determine accurate global fluxes of volcanic CO₂ to the atmosphere, but installing CO₂ monitoring networks on 20 of the world's 150 most actively degassing volcanoes. The group uses related laboratory-based studies (direct gas sampling and analysis, melt inclusions) to provide new data for direct degassing of deep earth carbon to the atmosphere.

Large Eruptions of Etna

Information about large Quaternary eruptions (VEI >= 4) is cataloged in the Large Magnitude Explosive Volcanic Eruptions (LaMEVE) database of the Volcano Global Risk Identification and Analysis Project (VOGRIPA).

EarthChem

EarthChem develops and maintains databases, software, and services that support the preservation, discovery, access and analysis of geochemical data, and facilitate their integration with the broad array of other available earth science parameters. EarthChem is operated by a joint team of disciplinary scientists, data scientists, data managers and information technology developers who are part of the NSF-funded data facility Integrated Earth Data Applications (IEDA). IEDA is a collaborative effort of EarthChem and the Marine Geoscience Data System (MGDS).