Quiet returns after explosions on 10 and 13 June 2019

After a large, deadly explosive and effusive eruption during 1963-64, Indonesia's Mount Agung on Bali remained quiet until a new eruption began in November 2017 (BGVN 43:01). Activity continued throughout 2018 with explosions that produced ash plumes rising multiple kilometers above the summit, and the slow effusion of the lava within the summit crater. Increasingly frequent and intense explosions with ash emissions and incandescent ejecta characterized activity during February through May 2019 (BGVN 44:06). Two more explosions in June 2019 produced significant ash plumes; no further explosive activity occurred through October 2019. Information about Agung comes from Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG), also known as the Indonesian Center for Volcanology and Geological Hazard Mitigation (CVGHM), the Darwin Volcanic Ash Advisory Center (VAAC), and multiple sources of satellite data. This report covers the end of the eruption in June and observations through October 2019.

After a large explosion on 31 May 2019, a smaller event occurred on 10 June. Another large explosion with an ash plume that rose to 9.1 km altitude was recorded on 13 June (local time). It drifted hundreds of kilometers before dissipating. No further explosive activity was reported through October 2019, only diffuse white steam plumes rising at most a few hundred meters above the summit. The Alert Level remained at III (of four levels) throughout the period. The record of thermal activity showed an increase during the explosive events of late May and June, but then decreased significantly (figure 57). There was no obvious thermal signature in satellite images that explained the small increase in thermal energy recorded by the MIROVA data at the end of August 2019.

Figure 57. The thermal energy at Agung increased significantly during the explosive events of late May and early June 2019, and then decreased substantially as seen in this MIROVA graph from 23 January through October 2019. There was no obvious satellite thermal signature to explain the brief increase in thermal energy in late August. Courtesy of MIROVA.

On 31 May 2019 a large explosion produced an ash plume that rose more than 2 km above the summit (BGVN 44:06, figure 56). The Darwin VAAC reported that it split into two plumes, one drifted E at 8.2 km and the other ESE at 6.1 km altitude, dissipating after about 20 hours early on 1 June. A small eruption with an ash plume that rose to 3.9 km altitude was reported the next day by the Darwin VAAC. It was detected in the webcam and pilot reports confirmed that it drifted E for a few hours before dissipating. PVMBG reported gray emissions to 300 m above the peak on 1 June and 100 m above the summit on 2 June. By 6 June the emissions were white, rising only 50 m above the summit. For several subsequent days, the summit was covered in fog with no observations of emissions.

On 10 June 2019 an explosion lasting 90 seconds was reported at 1212 local time; PVMBG noted a gray ash plume 1,000 m above the summit (figure 58). The Darwin VAAC confirmed the emission in satellite imagery and by pilot report; it was moving SW at 4.3 km altitude and then drifted S before dissipating by the end of the day. Early on 13 June local time (12 June UTC) a new explosion that was clearly visible in the webcam produced a large ash plume that drifted W and SW (figure 59). The explosion was recorded on the seismogram for almost four minutes and sent incandescent ejecta in all directions up to 700 m from the summit. The first satellite imagery of the plume reported by the Darwin VAAC suggested the altitude to be 9.1 km. A secondary plume was drifting W from the summit at 5.5 km altitude a few hours later. By six hours after the eruption, the 9.1 km altitude plume was about 90 km SSW of the Denpassar airport and the 5.5 km altitude plume was about 110 km W of the airport. By the time the higher altitude plume dissipated after about 14 hours, it had reached 300 km S of the airport. For the remainder of June, only diffuse white steam plumes were reported, rising generally 30-50 m above the summit, with brief pulses to 150-200 m during 27-29 June.

Figure 58. An ash plume rose 1,000 m above the summit of Agung on 10 June 2019. Top image courtesy of Rita Bauer (Volcano Verse), bottom image courtesy of PVMBG (Information on G. Agung Eruption, 10 June 2019).

Figure 59. A large eruption at Agung at 0138 local time on 13 June 2019 sent an ash plume to 9.1 km altitude and incandescent ejecta 700 m in all directions. Courtesy of Jaime S. Sincioco, screenshot from volcano YT webcam.

Although no further surface activity was reported at Agung during July through October 2019, PVMBG kept the Alert Level at III throughout the period. Only steam plumes were reported from the summit usually rising 50 m before dissipating. Steam emissions rose to 150 m a few times each month. Plumes were reported at 300 m above the summit on 6 July and 15 August. No thermal anomalies were visible in Sentinel 2 satellite images during the period.

Information Contacts: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as Indonesian Center for Volcanology and Geological Hazard Mitigation, CVGHM), Jalan Diponegoro 57, Bandung 40122, Indonesia (URL: http://www.vsi.esdm.go.id/); 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/); Rita Bauer, Volcano Verse (Twitter @wischweg, URL: https://twitter.com/wischweg/status/1137956367258570752); Jamie S. Sincioco, Philippines (Twitter @jaimessincioco, URL: https://twitter.com/jaimessincioco/status/1139109685796020224).

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

July 1989 (SEAN 14:07) Cite this Report

Fumarolic activity

Fumarolic and solfataric activity (restricted to the crater) emitted a thin white plume periodically seen from the observatory. In late July, 69 tectonic, three volcanic A-type, and six volcanic B-type events were recorded.

Information Contacts: VSI.

November 1989 (SEAN 14:11) Cite this Report

Occasional seismicity but solfatara field quiet

Observations from both Rendang (S) and Budakeling (N) Observatories revealed neither white plumes from the solfatara field nor collapses of loose material from the inner crater wall. No explosion sounds from the crater have been heard. An earthquake was felt (MM I) on 9 June; 59 tectonic and two volcanic shocks [were] recorded in November.

Information Contacts: VSI.

March 2003 (BGVN 28:03) Cite this Report

Hot-spots located outside the summit crater are most likely due to fires

Thermal anomalies were detected by MODIS throughout 2001 and 2002 in zones proximal to the summit of Agung. The first alert occurred on 23 September 2001 when two alert-pixels were detected with a maximum alert ratio of -0.789. Larger anomalies were detected on 12 August 2002 (two alert-pixels with maximum alert ratio of -0.429) and 5 October 2002 (one alert-pixel with alert ratio of -0.536). All the alerts seem to occur outside the summit crater, with the possible exception of 5 October 2002, and are more likely to represent fires than volcanic activity.

No volcanic activity has been reported recently by the Volcanological Survey of Indonesia.

Information Contacts: Diego Coppola and David A. Rothery, Department of Earth Sciences, The Open University, Milton Keynes, MK7 6AA, UK. Thermal alerts courtesy of the HIGP MODIS Thermal Alerts Team (URL: http://modis.higp.hawaii.edu/).

January 2018 (BGVN 43:01) Cite this Report

New eruption after 54 years; extensive pre-eruption seismicity precedes ash emission on 21 November 2017

A large explosive and effusive eruption lasting about 11 months during 1963-64 at Indonesia's Mount Agung on Bali produced voluminous ashfall, devastating pyroclastic flows that caused extensive damage, and over 1,000 fatalities. The volcano remained largely quiet until renewed seismicity began in August 2017, the prelude to a new eruptive episode, which started in late November 2017 and is ongoing. Self and Rampino (2012) and Fontijn et al. (2015) published detailed summaries of historical activity at Agung prior to this new episode; a brief summary of their work is provided.

Information about the new eruptive episode comes from Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG), also known as the Indonesian Center for Volcanology and Geological Hazard Mitigation (CVGHM), Badan Nasional Penanggulangan Bencana (BNPB) which is the National Board for Disaster Management, the Darwin Volcanic Ash Advisory Center (VAAC), and various sources of satellite data. The first two months of this new episode, through December 2017, are discussed in this report.

Summary of 1963-64 eruption. The February 1963 to January 1964 eruption, Indonesia's largest and most devastating eruption of the twentieth century, was a multi-phase explosive and effusive event that produced both basaltic andesite tephra and andesite lava (Self and Rampino, 2012). After a few days of felt earthquakes on 16 and 17 February 1963, explosive activity began at the summit on 18 February. This was followed the next day by the effusion of about 0.1 km³ of andesite lava which was extruded until 17 March 1963, when a large explosive eruption generated pyroclastic density currents (PDCs) and lahars that devastated wide areas N, SW, and SE of the volcano (figure 1) (Fontijn et al, 2015).

Figure 1. Map of Gunung Agung and vicinity, eastern Bali, showing the extent of the 1963 lava flow (cross-hatched), pyroclastic flow deposits (stippled), and lahar deposits (dark shading) of the 1963–1964 eruption (after unpublished map courtesy of Indonesian Volcanological Survey). Sg is Siligading village, where many fatalities occurred. Reproduced from Self and Rampino (2012, figure 3).

Explosive activity continued intermittently until a second explosive phase of similar intensity occurred two months later, beginning on 16 May 1963 with reported ash plumes reaching 10 km above the 3-km-high summit (figure 2). This phase produced the greatest proportion of the pyroclastic flow material from the eruption and led to additional death and destruction in villages at the foot of the volcano (Self and Rampino, 2012). Explosive outbursts continued intermittently until 17 January 1964. The total death toll of the eruption was estimated between 1,100 and 1,900 (see references in Fontijn et al., 2015). A total estimated volume of erupted magma was ca 0.4 km³ (Self and Rampino, 2012).

Figure 2. Photograph reported to be of the 16 May 1963 eruption column at Agung; the view is from the SW, perhaps near Rendang (shown on figure 1). Photo courtesy of the family of Denis Mathews, reproduced from Self and Rampino (2012, figure 2b).

Activity between 1964 and 2017. Almost no activity was reported from Agung during 1964-2017. Weak solfataric activity from within the summit crater was reported in 1989 (SEAN 14:07). MODVOLC thermal alerts were reported intermittently on one or two days during a few years (2001, 2002, 2004, 2006, 2008, 2012, 2013), but all of the alerts were located on the middle or lower flanks, suggesting their source was agriculture or forest fires, unrelated to volcanic activity. Chaussard et al. (2013) reported inflation centered on the summit at a rate of 7.8 cm/year between mid-2007 and early 2009, followed by slow deflation at a rate of 1.9 cm/year until mid-2011 (the last acquired data).

Summary of September-December 2017 Activity. Increases in seismic activity were first noted at Agung during mid-August 2017. Exponential increases in the rate of events during the middle of September led PVMBG to incrementally raise the Alert Level from I to IV (lowest to highest) between 14 and 22 September. Steam-and-gas emissions were intermittently observed 50-500 m above the summit crater from the end of September through October, with occasional bursts as high as 1,500 m. Seismicity dropped off almost as quickly as it rose, beginning on 20 October, and then continued a more gradual decrease through the end of the month and into November. The number and intensity of hot spots observed within the summit crater increased during September, then leveled off during October.

Ash emissions first appeared on 21 November, rising to 700 m above the summit. Ash density and heights of plumes increased several times during the rest of November to about 3,000 m. Ashfall as deep as 5 mm affected neighboring communities, and was reported several hundred kilometers from the summit; the international airport about 60 km SW was forced to close for a few days at the end of the month. Thermal data indicated effusion of lava into the summit crater at the end of November. After 30 November, emissions continued, primarily comprised of steam and gas, with intermittent plumes of dense ash, rising up to 2.5 km above the summit throughout December.

Activity during August-September 2017. In their monthly report of volcanic activity for August 2017, PVMBG noted that 49 volcanoes, including Agung, were listed at Alert Level 1, meaning "Normal", with no apparent increases in visual or seismic activity. The first signs of renewed unrest at Agung appeared as an increase in the rate of deep volcanic earthquakes (VA or Vulkanik Dalam) beginning on 10 August 2017. Shallow volcanic earthquakes (VB or Vulkanik Dangkal) began to increase two weeks later on 24 August, followed by an increase in the number of local tectonic earthquakes on 26 August (figure 3). Based on this increased seismicity, and an observation on 13 September of new solfataric activity at the bottom of the summit crater, PVMBG raised the Alert Level the following day from Level I (Normal) to Level II (Beware); the Aviation Color Code was raised to Yellow on a four-color scale (Green, Yellow, Orange, Red). The deeper earthquakes (VA) had a seismic amplitude range from 3-10 mm. The shallow earthquakes (VB) had an amplitude range of 2-7 mm. Otherwise, there was no surface expression of activity during September.

Figure 3. Seismic activity at Agung between 1 July and 13 September 2017. The Y-axis is the number of daily earthquakes. The increase in deep volcanic seismicity (VA, or Vulkanik Dalam) that began on 10 August 2017 was followed two weeks later by an increase in shallow volcanic seismicity (Vulkanik Dangkal or VB). Courtesy of PVMBG (Peningkatan Tingkat Aktivitas Gunung Agung, 14 September 2017).

The Agung Volcano Observatory (AVO) is located in Rendang village about 8 km SW. Webcams are located in Rendang and in Bukit Asah, about 8 km W. On 15 September 2017 a steam emission was observed rising 50 m above the crater rim. The AVO issued a VONA on 18 September noting a rapid increase in volcanic earthquake activity with a small hot spot detected in satellite data. This contributed to them raising the Alert Level again to Level III (Standby), resulting in a 6-km-radius exclusion zone activated around the summit, extending to 7.5 km on the N, SE, and SSW flanks where the pyroclastic flows of 1963 had caused the most damage. Many of the 50,000 village residents within the 6 km exclusion zone began voluntary evacuations. The communities affected included Jungutan (7 km S) and Buana Giri (12 km SE) villages in the Bebandem District, Sebudi Village (6 km SW) in the Selat Subdistrict, Besakih Village (12 km SW) in the Rendang Subdistrict, and Dukuh (4 km NE) and Ban (7.5 km NW) villages in the Kubu Subdistrict. About 9,500 people had voluntarily evacuated from the villages by 22 September 2017.

The observatory issued another VONA on 19 September 2017, reporting an 'ash cloud' at 0255 UTC (1055 Central Indonesia Time, or WITA). It was described as a dense, white plume moving to the W. Around the same time (0240 UTC) MODVOLC recorded ten thermal alerts on the N and E flanks. Bali's Regional Disaster Management Agency (BPBD) reported in Antara News on 19 September that the source of the smoke and ash were forest fires caused by excessively dry conditions.

A VONA issued by AVO in the morning of 22 September stated that a steam emission about 50 m above the summit drifted NW. During the evening of 22 September, PVMBG raised the Alert Level to Level IV (Caution), the highest of the four-level scale, based primarily on continuing increases in seismicity. They expanded the exclusion zone to 9 km around the summit, and to 12 km in the areas S, SE, and NNE. The number of evacuees had risen to nearly 35,000 people by 24 September. Steam-and-gas plumes were intermittently observed rising to 200 m above the crater rim during the rest of September. By 26 September, PVMBG reported increasing seismic activity with 579 deep volcanic (VA) quakes, 373 shallow quakes (VB), and 50 local tectonic events that day. Seismicity continued to escalate through the end of the month. By the end of September, the government was assisting with the logistics of evacuating tens of thousands of livestock, primarily cattle, as well as over 90,000 people from within and around the 9 km exclusion zone. MAGMA Indonesia reported that new steaming and thermal areas within the summit crater expanded during the last week of the month.

Activity during October 2017. Narrow steam plumes rose 50-200 m above the summit crater during the first half of October. The rate of earthquakes during the last week of September and the first week of October continued to fluctuate at high levels, averaging 1-3 per minute, and more than 600 per day. By the first week of October, shallow earthquakes alone had increased to more than 200 per day, suggesting the possibility of magmatic activity at shallow depth. Satellite data showed increasing steam emissions along the NE edge of the crater rim. Tiltmeter data showed sudden deflation on 1 October, followed by continued inflation through 5 October. AVO released a VONA on 7 October noting a steam plume rising 1,500 m above the summit crater at 1245 UTC and drifting E (figure 4).

Figure 4. A steam plume rose 1,500 m above the summit of Agung on 7 October 2017. Courtesy of PVMBG (Penurunan Status Gunungapi Agung, Bali Dari Level IV (awas) Ke Level III (siaga) Tanggal 29 Oktober 2017 Pukul 16.00 WITA).

During the second half of the month, steam plumes were denser and rose more frequently to 200-500 m above the summit crater. BNPB flew drones over the summit on 20 and 29 October 2017 and captured 400 aerial photographs (figures 5 and 6). The images revealed a widening of the fracture zone on the E side of the summit crater, and a new fracture on the SE side.

Figure 5. A view into the summit crater of Agung on 20 October 2017, taken by a BNPB drone. Steam fumaroles rose from the NNE flank. N is to the left. Courtesy of PVMBG (Penurunan Status Gunungapi Agung, Bali Dari Level IV (awas) Ke Level III (siaga) Tanggal 29 Oktober 2017 Pukul 16.00 WITA).

Figure 6. A view into the summit crater of Agung on 29 October 2017, taken by a BNPB drone. The steam plumes rose from the NE corner of the summit crater. The NE rim of the crater slopes away to the upper left. Courtesy of PVMBG (Penurunan Status Gunungapi Agung, Bali Dari Level IV (awas) Ke Level III (siaga) Tanggal 29 Oktober 2017 Pukul 16.00 WITA).

PVMBG noted a decline in seismicity beginning on 20 October 2017 which continued through the end of the month (figure 7), leading them to lower the Alert Level from IV to III on 29 October, and reduce the exclusion zone to a 6 km radius, plus a 7.5 km area in the NNE, SE and SSW sectors. In their late October report, they observed that remote sensing thermal infrared data had detected an increase in the thermal energy beginning on 10 July 2017, in the form of an increased number of hot spots within the summit crater. During August and September, the number of hot spots had increased significantly and correlated with the increases in seismicity (figure 8). The intensity of the thermal anomalies then decreased during October. Inflation resumed in mid-August and peaked in mid-September. After that, the GPS data indicated deflation at lower levels, but uplift of 6 cm occurred near the summit. The deformation rate slowed after 20 October.

Figure 7. Daily seismic activity at Agung from 27 July-29 October 2017. Seismicity decreased noticeably on 20 October 2017, leading PVMBG to lower the Alert Level from IV to III on 29 October. Note that the vertical axis counting the number of daily seismic events ranges from 0 to 1,200, while in figure 3 the same axis ranges from 0 to 14. Courtesy of MAGMA Indonesia (Penurunan Status Gunungapi Agung, Bali dari Level IV (AWAS) ke Level III (SIAGA) Tanggal 29 Oktober 2017 pukul 16.00 WITA).

Figure 8. Satellite thermal imagery from Citra-Sentinel 2 revealed an increase in the number and intensity of hotspots within the summit caldera of Agung during September 2017, followed by a decrease in early October. Courtesy of PVMBG (Penurunan Status Gunungapi Agung, Bali Dari Level IV (awas) Ke Level III (siaga) Tanggal 29 Oktober 2017 Pukul 16.00 WITA).

Activity during November 2017. For the first three weeks of November, dense white steam plumes rose 50-500 m above the summit crater. A VONA issued late on 11 November reported a 500-m-high steam plume. Seismicity continued at a much lower rate than during late September-October, with tens of daily events as opposed to hundreds.

The first ash emission of the current eruption occurred on 21 November at 1705 local time; the plume rose to 700 m and drifted ESE (figure 9). Trace amounts of ashfall were reported in the Pidpid-Nawehkerti area about 9 km SE. At the time of the first ash emission, BNPB reported the number of evacuees living in temporary housing at about 25,000. The emission was preceded by a low-frequency tremor. Multiple volcanic ash advisories were issued by the Darwin VAAC on 21 November, although the ash was not visible in satellite imagery due to weather clouds. Continuous tremor with 2-5 mm amplitude was recorded the following three days, and ash-and-steam emissions rose 300-800 m above the summit crater.

Figure 9. The first reported ash emission from Agung in 53 years rose 700 m and drifted SE on 21 November 2017. Courtesy of PVMBG (Letusan Gunung Agung Selasa, 21 November 2017 Pukul 17.05 WITA).

A larger emission on 25 November sent black-gray ash plumes 2,000 m above the crater rim (figure 10) which then drifted W. The Darwin VAAC reported an ash plume visible in satellite imagery at 7.6 km altitude drifting WSW. Emissions continued later in the day, rising 4.6-6.7 km altitude and extending SE. Bright incandescence at the summit crater was observed that night. Ashfall was reported to the WSW in the villages of Menanga and Rendang (12 km SW) at the AVO Post, and also in Besakih Village, located in the upper part of Pempatan (8 km W). A number of international flights were cancelled from the I Gusti Ngurah Rai International Airport in Denpasar (60 km SW), affecting about 2,000 passengers, although the airport remained open.

Figure 10. An ash emission rose at least 1,500 m above the summit of Agung on 25 November 2017 and drifted W. Courtesy of PVMBG (Letusan Gunung Agung 25 November 2017 Pukul 17:30 Wita).

Around 0545 local time the following day (26 November), the intensity of the ash emissions increased; the top of the plume reached 3,300 m above the summit at 1100 local time, and was drifting SE and E (figure 11). Ashfall was reported in many areas downwind including North Duda (9 km S), Duda Timur (12 km S), Pempetan, Besakih, Sideman (15 km SSW), Tirta Abang, Sebudi (6 km SW), Amerta Bhuana (10 km SSW), and some villages in Gianyar (20 km WSW) (figure 12). The largest amount, deposits 5 mm thick, was reported in Sibetan (11 km SSE). Trace amounts of ash were also reported much farther away, in Nusa Penida (an island 40 km S), Lombok (100 km ESE), and Sumbawa, 250 km E on the island of West Nusa Tenggara. Explosions from the crater were audible 12.5 km away that evening. Incandescence at the summit was observed from Bukit Asah and Batulompeh. The Darwin VAAC reported continuous ash emissions to 7.9 km altitude drifting SE throughout most the day, increasing to 9.1 km later in the day; ashfall was also reported at the international airport.

Figure 11. A dense plume of ash rose 3,000 m above the summit of Agung and drifted ESE on 26 November 2017. Courtesy of PVMBG (Peningkatan Status Gunungapi Agung, Bali Dari Level III (siaga) Ke Level IV (awas), 27 November 2017).

Figure 12. Ash from an eruption of Agung on 26 November 2017 covered garden plants in Jungutan Village, 7 km SE. Courtesy of Reuters.

The airport in Denpasar was forced to close during 27-29 November 2017. On those days ash drifted in multiple directions at different altitudes; it was observed drifting E at 9.1 km altitude, SW at 7.6 km altitude, and was moving S below 6.1 km. This increase in emissions led PVMBG to raise the Alert Level from III to IV on 27 November. Pictures and video showed a white steam plume adjacent to a gray ash plume rising from the crater, suggesting two distinct sources (figure 13).

Figure 13. A white steam plume and dense gray ash both rose from the summit of Agung on 27 November 2017. Photo by K. Parwata, courtesy of Sutopo Purwo Nugroho, Twitter.

A single MODVOLC thermal alert appeared at the summit that day, along with a strong thermal anomaly in the MIROVA system data (figure 14) consistent with the appearance of new lava in the summit crater. The tiltmeter installed at the Yehkori station 4 km S of the summit showed continued inflation of up to 6 microradians between 22 and 27 November (figure 15). PVMBG also increased the exclusion zone to a radius of 8 km from the summit crater plus areas 10 km from the summit to the NNE, SE, S, and SW.

Figure 14. A MIROVA plot of satellite infrared data for the year ending 23 February 2018 showed the first thermal anomaly from Agung in late November 2017, consistent with the emergence of lava in the summit crater. Courtesy of MIROVA.

Figure 15. A steady inflation was measured by the tiltmeter located at the Yehkori station 4 km S of the summit of Agung between 22 November and 27 November. Courtesy of PVMBG (Peningkatan Status Gunungapi Agung, Bali Dari Level III (siaga) Ke Level IV (awas), 27 November 2017).

MAGMA Indonesia reported that beginning with the ash eruption on 21 November, lahars appeared in the Tukad Yehsa, Tukad Sabuh, and Tukad Beliaung drainages on the S flank, as well as Tukad Bara on the N flank. As of the end of November 2017, these lahars had impacted houses, roads, and agricultural areas. Although ash emissions increased, and lava was confirmed within the summit crater during the last week of November, the number of seismic events remained well below the values recorded during September and October (figure 16).

Figure 16. Seismicity at Agung decreased significantly beginning on 20 October 2017 and remained well below 200 daily events throughout November, even though ash emissions began on 21 November. Courtesy of PVMBG (Peningkatan Status Gunungapi Agung, Bali Dari Level III (siaga) Ke Level IV (awas), 27 November 2017).

Ash emissions were reported by PVMBG rising to 3,000 m above the summit and drifting S on 27 November (figure 17). Continuing ash emission during 28-29 November rose to 2,000-4,000 m above the summit and drifted WSW (figure 18). Continuous seismic tremors were recorded during 28 November-1 December.

Figure 17. Ash plumes from Agung rose to altitudes of around 6,000 m (3,000 m above the summit crater) and drifted S on 27 November 2017. Image courtesy of MAGMA Indonesia (Peningkatan Status Gunungapi Agung, Bali Dari Level Ill (SIAGA) ke Level IV (AWAS), 27 November 2017 10:07 WIB, Ir. Kasbani, M.Sc.).

Figure 18. A dense plume of steam and ash rose from Agung and drifted away from this villager and his livestock on 28 November 2017. Courtesy of CNN.

With the increase in ash emissions during the last days of November 2017, satellite instruments also recorded significant releases of SO₂ (figure 19). MAGMA Indonesia reported on 1 December that satellite data also recorded high temperatures consistent with new lava within the crater on 27, 28, and 29 November 2017. They estimated the volume of lava in the crater to be about 20 million cubic meters, equivalent to about a third of the total crater volume. The base of the ash-and-steam plumes was often reddish during 29 November-5 December reflecting incandescence from the lava in the crater (figure 20).

Figure 19. The concentrations of SO2 emitting from Agung increased to levels that were easily detected by the Ozone Mapper Profiler Suite (OMPS) on the Suomi National Polar-orbiting Partnership (Suomi-NPP) satellite on 27 (top) and 28 (bottom) November 2017. The concentration of SO2 is measured in Dobson Units, a measure of the molecular density of the SO2 in the atmosphere. These NASA Earth Observatory images were created by Joshua Stevens, using OMPS data from the Goddard Earth Sciences Data and Information Services Center (GES DISC).

Figure 20. Incandescence appeared at the base of the ash-and-steam plume at Agung on 29 November 2017, consistent with lava effusion in the summit crater. Courtesy of MAGMA Indonesia (Perkembangan Terkini Aktivitas Gunung Agung (1 Desember 2017 21:00 WITA), 2 December 2017 07:55 WIB, Ir. Kasbani, M.Sc.).

By 29 November, continuous ash emissions were rising to 6.4 km altitude and drifting from the SW towards the S, becoming diffuse over the Denpasar region (figure 21). The plume was observed moving E at the same elevation on 30 November, lowering to 5.5 km later in the day. Although emissions were primarily steam and gas beginning on 30 November, pilot reports on 1 December indicated ash was still visible SE of Agung, and steam-and-ash emissions were continuing. Steam-only emissions were reported on 2 December rising less than 1,000 m above the summit.

Figure 21. Gas-and-ash emissions from Agung on 29 November 2017 were drifting both W and S in this false-color image generated by the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA's Terra satellite. The image uses a combination of shortwave infrared light and natural color, making it easier to differentiate between ash, clouds, and forest. The plumes appear to rise from two vents in the volcano's summit crater. Courtesy of NASA Earth Observatory.

Activity during December 2017. Steam, gas, and ash emissions continued throughout December 2017. During the first two weeks, emissions were primarily steam and gas, rising up to 2,000 m (figure 22), and incandescence was often observed at the summit. Dense gray ash emissions were observed, however, during 1-2 December. BNPB noted on 5 December that 63,885 evacuees were distributed in 225 evacuation shelters. On 8 December at 0759 a brief event generated a dense ash plume that rose 2.1 km above the crater rim and drifted W (figure 23). Minor amounts of ash were deposited on the flanks, and lapilli were reported in Temakung. A second ash plume rose 3 km at 1457 later that day.

Figure 22. A burst of dense steam rose as high as 1,500 m from the crater of Agung on 5 December 2017 at 0848 local time (WITA) and drifted E, after which only a narrow diffuse plume remained. View is from the S. Courtesy of Sutopo Purwo Nugroho, Twitter.

Figure 23. An eruption at Agung on 8 December 2017 at 0759 WITA sent a dense gray ash plume 2,100 m above peak to the W. View is from the S. Courtesy of Sutopo Purwo Nugroho, Twitter.

The Darwin VAAC reported multiple daily explosions during 8-15 December, creating ash plumes that drifted NW, W, and WSW at altitudes between 4.3 and 5.5 km. The explosions were visible in the webcams and from ground-based observers, and occasionally in satellite imagery when not blocked by weather clouds. VONA's were issued for events on 8 and 12 December. Multiple events during 11-12 December sent plumes rising up to 2.5 km above the crater rim and drifting NW and W (figure 24).

Figure 24. A small ash emission rose from the crater of Agung during the early morning of 11 December 2017. Courtesy of Sutopo Purwo Nugroho, Twitter.

The Darwin VAAC reported larger ash emissions to 7.6 km altitude on 15 and 16 December interspersed with lower altitude (5.5-6.1 km) plumes. Continuing, regular discrete emissions during 16-17 December rose to 6.1 km and drifted WNW. An overhead image of the summit crater of 16 December revealed that, since a similar photo was taken on 20 October, new lava had filled about 1/3 of the crater with an estimated 30 million cubic meters of material (figure 25).

Figure 25. Repeated overhead images of the Agung summit crater taken on 20 October and 16 December 2017 showed new lava filling about 1/3 of the crater with an estimated 30 million cubic meters of material. Posted on Twitter by Sutopo Purwo Nugroho for BNBP.

Discrete emissions to 5.5 km moving N and NNE were common during 18-21 December. Ash and steam drifted both E and W from the summit on 22 December. An ash emission on 23 December rose to 5.8 km and drifted NE, after which repeated emissions continued, rising to 4.6 km (figure 26). Ash fell on the flanks and in Tulamben, Kubu (9 km NE). In the morning of 24 December, a much larger plume drifting W at 10.7 km altitude was visible in satellite imagery. It dissipated after a few hours, and a separate plume was observed drifting NE at 5.5-5.8 km (figure 27); emissions continued throughout the day and into the next. PVMBG reported that the ash deposits from the NE-drifting plume were up to 3 mm thick (figure 28).

Figure 26. An event at Agung on 23 December 2017 sent a dense, gray plume to 2,500 m above the crater rim at 1157 WITA. View is from a village on the W flank, likely about 7 km from the summit. Courtesy of Sutopo Purwo Nugroho, Twitter.

Figure 27. Agung erupted steam and ash with a plume height of 2,000-2,500 m on 24 December 2017 at 1005 WITA. Courtesy of Sutopo Purwo Nugroho, Twitter.

Figure 28. Map showing distribution and thickness of volcanic ash and lapilli from the ash emissions at Agung that began on 24 December 2017 at 1005 WITA. A thin layer of ash was deposited in a narrow NE trending band on the NE side of Agung. Courtesy of Sutopo Purwo Nugroho, Twitter.

As of 25 December, BNPB reported just over 70,000 evacuees spread out in 239 shelters. Discrete ash emissions continued through the end of the month rising as high as 2 km above the crater rim and drifting in several different directions. The last VAAC report of 2017 indicated an ash plume drifting W at 4.3 km altitude on 31 December.

References: Chaussard E, Amelung F, Aoki Y, 2013, Characterization of open and closed volcanic systems in Indonesia and Mexico using InSAR time series. J Geophys Res Solid Earth, 118:3957–3969. DOI: 10.1002/jgrb.50288.

Fontijn K, Costa F, Sutawidjaja I, Newhall C G, Herrin J S, 2015, A 5000-year record of multiple highly explosive mafic eruptions from Gunung Agung (Bali, Indonesia): implications for eruption frequency and volcanic hazards. Bull Volcanol, 77: 59. DOI: 10.1007/s00445-015-0943-x.

Self S, Rampino M, 2012, The 1963–1964 eruption of Agung volcano (Bali, Indonesia). Bull Volcanol 74:1521–1536. DOI: 10.1007/s00445-012-0615-z.

Information Contacts: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as Indonesian Center for Volcanology and Geological Hazard Mitigation, CVGHM), Jalan Diponegoro 57, Bandung 40122, Indonesia (URL: http://www.vsi.esdm.go.id/); Badan Nasional Penanggulangan Bencana (BNPB), National Disaster Management Agency, Graha BNPB - Jl. Scout Kav.38, East Jakarta 13120, Indonesia (URL: http://www.bnpb.go.id/); MAGMA Indonesia, Kementerian Energi dan Sumber Daya Mineral (URL: https://magma.vsi.esdm.go.id/); 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/); 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/); Antara News (URL: https://bali.antaranews.com); Sutopo Purwo Nugroho, Head of Information Data and Public Relations Center of BNPB via Twitter (URL: https://twitter.com/Sutopo_PN); Cable News Network (CNN), Turner Broadcasting System, Inc. (URL: http://www.cnn.com/); Reuters (URL: http://www.reuters.com/).

August 2018 (BGVN 43:08) Cite this Report

Ash explosions and lava dome effusion continue during January-July 2018

After a large, deadly explosive and effusive eruption during 1963-64, Indonesia's Mount Agung was quiet until a new eruption began in November 2017 (BGVN 43:01). A lava dome emerged into the summit crater at the end of November and intermittent plumes of ash rose as high as 3 km above the summit through the end of the year. Activity continued into 2018 with explosions that produced ash plumes rising multiple kilometers above the summit, and the growth of the lava dome within the summit crater. Information about the ongoing eruptive episode comes from Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG), also known as the Indonesian Center for Volcanology and Geological Hazard Mitigation (CVGHM), the Darwin Volcanic Ash Advisory Center (VAAC), and multiple sources of satellite data. This report covers the ongoing eruption from January through July 2018.

Intermittent explosions with ash plumes were reported at Agung several times during January 2018, including Strombolian activity on 19 January. Activity decreased significantly by the end of the month; only one explosion with ash was reported during February. Two ash plumes were reported in March and three were reported each month during April and May. A more substantial explosion in mid-June produced an ash plume that rose to 7 km altitude. A series of deep-seated earthquakes during the third week of June was followed by large explosions and new effusions of lava inside the summit crater beginning on 28 June. A strong thermal signal also appeared on 28 June that gradually diminished during July. Intermittent plumes of steam and ash recurred daily until 19 July; plume heights rose up to 3 km above the summit on several occasions. Strombolian explosions on 2 and 8 July sent ejecta as far as 2 km from the summit. Explosive activity became more intermittent during the last two weeks of the month; the last reported explosion was on 27 July.

Activity during January-May 2018. During most days of January 2018 when fog was not obscuring the summit, PVMGB reported plumes of steam and minor ash rising about 500 m above the summit. In addition, intermittent explosions produced higher, denser ash plumes that rose 1,000-2,500 m above the summit several times. Ash plumes on 1 and 2 January rose to 1,000 and 1,500 m above the summit; incandescence was observed at the summit on both nights, and trace ashfall was reported at the Rendang Post on 2 January. The Darwin VAAC reported the ash plume on 1 January at 6.1 km altitude moving SW. A single MODVOLC thermal alert was recorded on 4 January. On 5 January PVMGB lowered the evacuation radius from 10 to 6 km, permitting the return of thousands of displaced people to their homes. Approximately 17,000 people in seven villages within 6 km of Agung were still under evacuation orders from the events of late 2017.

The Agung Volcano Observatory issued VONA's (Volcano Observatory Notice for Aviation) on 4, 8, 9, 11, 15, 17, 19, 23, 24, and 30 January relating to the larger explosions and ash plumes. On 11 January, an ash plume rose to 2,500 m above the summit and drifted N and NE (figure 29). Another 2,500-m-high ash plume on 19 January was accompanied by Strombolian activity at the summit for several hours, and incandescent ejecta that traveled 1,000 m from the crater. Ashfall was later reported in Tulamben village in the Kubu district (9 km NE) and in Purwekerti village in the Abang district (14 km ENE). Visual monitoring using drones carried out on 22 January showed that the volume of the lava dome was relatively unchanged at around 20 million m³. The summit was obscured by fog for the last week of the month.

Figure 29. An eruption at Agung on 11 January 2018 sent an ash plume to 2,500 m above the summit. Courtesy of MAGMA Indonesia and PVMBG (Erupsi Gunung Agung 11 Januari 2018 17:54 WITA).

Activity decreased noticeably in late January and February. Steam and minor ash plumes rose only 50-800 m above the summit for most of the month. As a result of the decrease in activity, PVMBG lowered the Alert Level from Level IV to Level III (on a four-level scale) on 10 February 2018. The radius of evacuation was also lowered from 6 to 4 km. A single explosion on 14 February sent an ash plume to 1,500 m above the summit.

For most of March 2018, steam plumes rose less than 400 m above the summit. VONA's were issued by the Agung Volcano Observatory for ash plumes twice, on 12 March (local time) when a plume rose 800 m above the summit and drifted E, and on 26 March when the ash plume rose to 500 m and drifted NW. During much of April 2018, steam plumes rose less than 300 m above the summit; weather obscured views of the summit for most of the last week of the month. AVO issued VONA's for ash plumes on 6, 11 and 30 April; the plumes on 6 and 11 April rose 500 m and drifted W and SW respectively. The Darwin VAAC reported a series of four short-lived explosions with ash plumes on 11 April; they each dissipated within a few hours. PVMBG reported another explosion on 15 April that produced an ash plume that also rose 500 m. The plume on 30 April rose 1,500 m and drifted SW.

Similar activity persisted throughout May 2018. Steam plumes generally rose 50-100 m above the summit crater each day. In addition, explosions were reported on 9, 19, and 29 May. PVMBG reported that no ash plume was observed on 9 May, due to fog obscuring the summit, but the ash plume on 19 May rose to 1,000 m above the summit and drifted SE, and the ash plume on 29 May rose 500 m and drifted SW.

Activity during June and July 2018. The volcano was covered in fog for much of the first two weeks of June. A short-lived explosion on 10 June 2018 was reported by PVMBG, but meteoric clouds obscured the summit. The Darwin VAAC noted the plume in a satellite image drifting W at about 4.6 km altitude. An explosion on 13 June produced an ash plume that rose 2,000 m above the summit and drifted WSW (figure 30). Another explosion was recorded on 15 June, but the summit was obscured, and no ash cloud was visible to ground observers. However, the Darwin VAAC reported the plume visible in satellite imagery at 7 km altitude (about 4 km above the summit) drifting SW and S for most of the day before dissipating. Ashfall was reported about 7 km W in the village of Puregai. PVMBG reported white and gray emissions on 17 June that rose 500 m.

Figure 30. An ash plume at Agung on 13 June 2018 rose about 2,000 m above the summit and drifted WSW. View is looking N. Courtesy of PVMBG (Information on G. Agung Eruption, 13 June 2018).

An explosion during the evening (local time) of 27 June 2018 produced an ash plume that rose 2,000 m from the summit and drifted W. Another explosion the following morning produced a sustained ash cloud that lasted for several hours and again caused ashfall around the village of Puregai. It rose to about 2,000 m above the summit and drifted W and SW (figure 31).

Figure 31. A sustained ash eruption began early on 28 June 2018 at Agung (top) and lasted well into the afternoon (bottom). Photo from a PBVBG webcam, posted on Twitter by Sutopo Purwo Nugroho‏ (BNPB).

PVMBG noted in late June that inflation of 5 mm had occurred since 13 May 2018. They reported that the ash plumes on 28 June caused some airlines to cancel flights to Bali, and ashfall was reported in several villages in Bangli and areas to the W and SW the following day (figure 32). The International Gusti Ngurah Rai (IGNR) airport (60 km SW) in Denpasar, the Blimbing Sari Airport (128 km W) in Banyuwangi, and the Noto Hadinegoro Airport (200 km W) in Jember closed for portions of the day on 29 June (ANTARA News).

Figure 32. Settlement and plantation areas were coated with ash from Mount Agung in Pemuteran Village (10 km W) on 29 June 2018. Courtesy of Tempo.com and ANTARA/Nyoman Budhiana.

Incandescence overnight on 28-29 June indicated fresh effusions of lava at the summit; they were accompanied by ash emissions that rose 1,500-2,500 m. Thermal satellite images recorded on 29 June indicated significant hotspots within the crater with thermal energy reaching 819 Megawatts; this was the largest amount of thermal energy recorded during the 2017-2018 activity, significantly higher than the maximum recorded of 97 Megawatts reached at the end of November 2017. The MIROVA data clearly reflected the sudden surge of thermal energy into the summit crater at the end of June (figure 33).

Figure 33. A large spike in thermal energy beginning on 28 June 2018 signaled a new surge of lava into the summit crater at Agung. This MIROVA plot of Log Radiative Power showed pulses of activity in early January, May, and early June, followed by the much larger surge of heat in late June that tapered off throughout July. Inset shows the nighttime incandescence on 28 June 2018 that resulted from the new effusion of lava. Photo taken at the PGMBG Webcam in Batu Lompeh (15 km N). Graph courtesy of MIROVA, photo courtesy of PVMBG (Press Release of Mount Agung's Latest Activities, June 29 to 3:00 p.m.)

The Darwin VAAC reported continuous emissions of ash beginning on 28 June that drifted to the W for over 24 hours. The height was initially reported by ground observers at 3.7 km altitude but was raised to 7 km altitude a few hours later, based on satellite imagery and pilot reports. By late that day, an upper plume (at 7 km) drifted SW and a second plume drifted W at 5.5 km altitude. By late on 29 June the continuous ash plume was drifting NW at 4.9 km altitude; it finally dissipated early on 30 June. In addition to large ash plumes and a major thermal anomaly, a substantial SO₂ plume also emerged from Agung on 28-29 June 2018. The plume drifted W over Java and then dispersed to the NW over the next 24 hours (figure 34). A lingering, smaller plume was still visible two days later.

Figure 34. A substantial SO2 plume was released from Agung during 28-29 June 2018 and captured by both the OMPS instrument on the Suomi satellite (upper images) and the OMI instrument on the Aura satellite (lower images). The plume first appeared on 28 June (top left) and was much larger the next day (top right). By 30 June it was dissipating over Java to the W and N (bottom left). A smaller plume drifted SW two days later (bottom right). Courtesy of NASA Goddard Space Flight Center.

A series of discrete eruptions lasting from late on 30 June through 2 July 2018 produced ash plumes that rose from 3.7 to 5.5 km altitude and drifted NW and W, according to the Darwin VAAC. Effusive activity continued to increase during the first week of July 2018 with the continued growth of the lava dome in the summit crater. PVMBG reported an additional volume of lava of 4 million m³ erupted from 28 June through the middle of July bringing the size of the dome to about 27 million m³. The frequency of explosions peaked on 2 July when Strombolian activity sent incandescent ejecta 2 km from the summit in all directions (figure 35).

Figure 35. The eruption of Mount Agung on 2 July 2017 produced Strombolian activity and incandescent ejecta that traveled 2 km from the summit crater in all directions. Courtesy of ANTARA News/HO/BMKG.

Several VONA's issued during 2-3 July reported multiple explosions that sent ash plumes 700-2,000 m above the summit. Eighteen explosions were reported by PVMBG between 1 and 8 July. The Darwin VAAC noted a substantial explosion early on 2 July that produced a plume that rose to 7.6 km altitude and drifted W. The remains of the ash plume were discernable in satellite imagery about 250 km W of Agung by the end of the day. The ash plume on 4 July rose 2,500 m above the summit (figure 36).

Figure 36. An explosion at Agung on 4 July 2018 produced an ash plume that rose 2,500 m above the summit, according to PVMBG. Courtesy of PVMBG (Information on G. Agung Eruption, July 4, 2018).

Strombolian activity was reported again on 8 July 2018 (figure 37). The Darwin VAAC reported intermittent explosions every day from 3-19 July, with ash plumes rising to altitudes from 3.7 to 6.7 km. Additional explosions were reported on 21, 24, 25, and 27 July (figure 38); ash plumes rose 700-2,000 m and drifted W or SE. MODVOLC thermal alerts resumed on 27 June, and multiple daily alerts persisted on most days through the end of July.

Figure 37. Strombolian activity at Agung recurred for the third time in 2018 on 8 July 2018. Courtesy of PVMBG (Agung Strombolian Eruption Today July 8, 2018).

Figure 38. A dense ash plume rose about 2,000 m above Mount Agung on 27 July 2018 at 1406 local time. Courtesy of PVMBG (Information on G. Agung Eruption, 27 July 2018).

Information Contacts: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as Indonesian Center for Volcanology and Geological Hazard Mitigation, CVGHM), Jalan Diponegoro 57, Bandung 40122, Indonesia (URL: http://www.vsi.esdm.go.id/); MAGMA Indonesia, Kementerian Energi dan Sumber Daya Mineral (URL: https://magma.vsi.esdm.go.id/); Darwin Volcanic Ash Advisory Centre (VAAC), Bureau of Meteorology, Northern Territory Regional Office, PO Box 40050, Casuarina, NT 0811, Australia (URL: http://www.bom.gov.au/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/); 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 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/); Sutopo Purwo Nugroho?, BNPB, Twitter (URL: https://twitter.com/Sutopo_PN); TEMPO.CO, Tempo Building, Jl. Palmerah Barat No. 8, South Jakarta 12210, Indonesia (URL: https://nasional.tempo.co/read/1102118/pvmbg-energi-thermal-erupsi-gunung-agung-kali-ini-paling-besar); ANTARANEWS.com, ANTARA guesthouse lt 19, Jalan Merdeka Selatan No. 17, Jakarta Pusat, Indonesia, (URL: https://en.antaranews.com).

February 2019 (BGVN 44:02) Cite this Report

Ongoing intermittent ash plumes and frequent gas-and-steam plumes during August 2018-January 2019

Agung is an active volcano in Bali, Indonesia, that began its current eruptive episode in September 2017. During this time activity has included ash plumes, gas-and-steam plumes, explosions ejecting ballistic blocks onto the flanks, and lava extrusion within the crater.

This report summarizes activity from August 2018 through January 2019 based on information from Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG), also known as the Indonesian Center for Volcanology and Geological Hazard Mitigation (CVGHM), MAGMA Indonesia, the National Board for Disaster Management - Badan Nasional Penanggulangan Bencana (BNPB), the Darwin Volcanic Ash Advisory Center (VAAC), and satellite data.

During August 2018 through January 2019 observed activity was largely gas-and steam plumes up to 700 m above the crater (figures 39 and 40). In late December and January there were several explosions that produced ash plumes up to 5.5 km altitude, and ejected ballistic blocks.

Figure 39. Graph showing the observed white gas-and-steam plumes and gray ash plumes at Agung during August 2018 through January 2019. The dates showing no data points coincided with cloudy days where the summit was not visible. Data courtesy of PVMBG.

Figure 40. A white gas-and-steam plume at Agung on 21 December 2018. Courtesy of MAGMA Indonesia.

The Darwin VAAC reported an ash plume on 8-9 August based on satellite data, webcam footage, and ground report information. The ash plume rose to 4.3 km and drifted to the W. They also reported a diffuse ash plume to 3.3 km altitude on 16-17 August based on satellite and webcam data. During September through November there were no ash plumes observed at Agung; activity consisted of white gas-and-steam plumes ranging from 10-500 m above the crater.

Throughout December, when observations could be made, activity mostly consisted of white gas-and-steam plumes up to 400 m above the crater. An explosion occurred at 0409 on 30 December that lasted 3 minutes 8 seconds produced an ash plume rose to an altitude of 5.5 km and moved to the SE and associated incandescence was observed at the crater. Light Ashfall was reported in the Karangasem regency to the NE, including Amlapura City and several villages such as in Seraya Barat Village, Seraya Tengah Village, and Tenggalinggah Village (figure 41).

Figure 41. A webcam image of an explosion at Agung that began at 0409 on 30 December 2018. Light Ashfall was reported in the Karangasem regency. Courtesy of PVMBG.

White gas-and-steam plumes continued through January 2019 rising as much as 600 m above the crater. Several Volcano Observatory Notices for Aviation (VONAs) were issued during 18-22 January. An explosion was recorded at 0245 on 19 January that produced an ash plume to 700 m above the crater and ejected incandescent blocks out to 1 km from the crater. On 21 January another ash plume rose to an estimated plume altitude of 5.1 km. The next morning, at 0342 on the 22nd, an ash plume to an altitude of 2 km that dispersed to the E and SE.

Satellite data shows continued low-level thermal activity in the crater throughout this period. MIROVA thermal data showed activity declining after a peak in July, and a further decline in energy in September (figure 42). Low-level thermal activity continued through December. Sentinel-2 thermal data showed elevated temperatures within the ponded lava in the crater (figure 43).

Figure 42. Log radiative power MIROVA plot of MODIS infrared data for May 2018 through January 2019 showing thermal anomalies at Agung. The black data lines indicate anomalies more than 10 km from the crater, which are likely due to fires. Courtesy of MIROVA.

Figure 43. Sentinel-2 thermal satellite images showing areas of elevated temperatures within the lava ponded in the Agung crater during August 2018 through January 2019. Courtesy of Sentinel Hub Playground.

Information Contacts: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as Indonesian Center for Volcanology and Geological Hazard Mitigation, CVGHM), Jalan Diponegoro 57, Bandung 40122, Indonesia (URL: http://www.vsi.esdm.go.id/); Badan Nasional Penanggulangan Bencana (BNPB), National Disaster Management Agency, Graha BNPB - Jl. Scout Kav.38, East Jakarta 13120, Indonesia (URL: http://www.bnpb.go.id/); MAGMA Indonesia, Kementerian Energi dan Sumber Daya Mineral (URL: https://magma.vsi.esdm.go.id/); Darwin Volcanic Ash Advisory Centre (VAAC), Bureau of Meteorology, Northern Territory Regional Office, PO Box 40050, Casuarina, NT 0811, Australia (URL: http://www.bom.gov.au/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/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground).

June 2019 (BGVN 44:06) Cite this Report

Continued explosions with ash plumes and incandescent ejecta, February-May 2019

After a large, deadly explosive and effusive eruption during 1963-64, Indonesia's Mount Agung on Bali remained quiet until a new eruption began in November 2017 (BGVN 43:01). Lava emerged into the summit crater at the end of November and intermittent ash plumes rose as high as 3 km above the summit through the end of the year. Activity continued throughout 2018 with explosions that produced ash plumes rising multiple kilometers above the summit, and the slow effusion of the lava within the summit crater (BGVN 43:08, 44:02). Information about the ongoing eruptive episode comes from Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG), also known as the Indonesian Center for Volcanology and Geological Hazard Mitigation (CVGHM), the Darwin Volcanic Ash Advisory Center (VAAC), and multiple sources of satellite data. This report covers the ongoing eruption from February through May 2019.

Intermittent but increasingly frequent and intense explosions with ash emissions and incandescent ejecta characterized activity at Agung during February through May 2019. During February, explosions were reported three times; events on seven days in March were documented with ash plumes and ashfall in surrounding villages. Five significant events occurred during April; two involved incandescent ejecta that traveled several kilometers from the summit, and ashfall tens of kilometers from the volcano. Most of the five significant events reported in May involved incandescent ejecta and ashfall in adjacent villages; air traffic was disrupted during the 24 May event. Ash plumes in May reached altitudes over 7 km multiple times. Thermal activity increased steadily during the period, according to both the MIROVA project (figure 44) and MODVOLC thermal alert data. MAGMA Indonesia reported at the end of May 2019 that the volume of lava within the summit crater remained at about 25 million m³; satellite information indicated continued thermal activity within the crater. Alert Level III (of four levels) remained in effect throughout the period with a 4 km exclusion radius around the volcano.

Figure 44. Thermal activity at Agung from 4 September 2018 through May 2019 was variable. The increasing frequency and intensity of thermal events was apparent from February-May. Courtesy of MIROVA.

Steam plumes rose 30-300 m high daily during February 2019. The Agung Volcano Observatory (AVO) and PVMBG issued a VONA on 7 February (UTC) reporting an ash plume, although it was not visible due to meteoric cloud cover. Incandescence, however, was observed at the summit from webcams in both Rendang and Karangasem City (16 km SE). The seismic event associated with the explosion lasted for 97 seconds. A similar event on 13 February was also obscured by clouds but produced a seismic event that lasted for 3 minutes and 40 seconds, and ashfall was reported in the village of Bugbug, about 20 km SE. On 22 February a gray ash plume rose 700 m from the summit during a seismic event that lasted for 6 minutes and 20 seconds (figure 45). The Darwin VAAC reported the plume visible in satellite imagery moving W at 4.3 km altitude. It dissipated after a few hours, but a hotspot remained visible about 10 hours later.

Figure 45. An ash plume rose from the summit of Agung on 22 February 2019, viewed from the Besakih temple, 7 km SW of the summit. Courtesy of PunapiBali.

Persistent steam plumes rose 50-500 m from the summit during March 2019. An explosion on 4 March was recorded for just under three minutes and produced ashfall in Besakih (7 km SW); no ash plume was observed due to fog. A short-lived ash plume rose to 3.7 km altitude and drifted SE on 8 March (UTC) 2019. The seismic event lasted for just under 4 minutes. Ash emissions were reported on 15 and 17 March to 4.3 and 3.7 km altitude, respectively, drifting W (figure 46). Ashfall from the 15 March event spread NNW and was reported in the villages of Kubu (6 km N), Tianyar (14 km NNW), Ban, Kadundung, and Sukadana. MAGMA Indonesia noted that two explosions on the morning of 17 March (local time) produced gray plumes; the first sent a plume to 500 m above the summit drifting E and lasted for about 40 seconds, while the second plume a few hours later rose 600 m above the crater and lasted for 1 minute and 16 seconds. On 18 March an ash plume rose 1 km and drifted W and NW. An event on 20 March was measured only seismically by PVMBG because fog prevented observations. An eruption on 28 March produced an ash plume 2 km high that drifted W and NW. The seismic signal for this event lasted for about two and a half minutes. The Darwin VAAC reported the ash plume at 5.5 km altitude, dissipating quickly to the NW. No ash was visible four hours later, but a thermal anomaly remained at the summit (figure 47). Ashfall was reported in nearby villages.

Figure 46. Ash plumes from Agung on 15 (left) and 17 (right) March 2019 resulted in ashfall in communities 10-20 km from the volcano. Courtesy of PVMBG and MAGMA Indonesia (Information on G. Agung Eruption, 15 March 2019 and Gunung Agung Eruption Press Release March 17, 2019).

Figure 47. A thermal anomaly was visible through thick cloud cover at the summit of Agung on 29 March 2019 less than 24 hours after a gray ash plume was reported 2,000 m above the summit. "Atmospheric Penetration" rendering (bands 12, 11, and 8A) courtesy of Sentinel Hub Playground.

The first explosion of April 2019 occurred on the 3rd (UTC); PVMBG reported the dense gray ash plume 2 km above the summit drifting W. A few hours later the Darwin VAAC raised the altitude to 6.1 km based on infrared temperatures in satellite imagery. The seismic signal lasted for three and a half minutes and the explosion was heard at the PGA Post in Rendang (12 km SW). Incandescent material fell within a radius of 2-3 km, mainly on the S flank (figure 48). Ashfall was reported in the villages of Telungbuana, Badeg, Besakih, Pempatan, Teges, and Puregai on the W and S flanks (figure 49). An explosion on 11 April also produced a dense gray ash plume that rose 2 km above the summit and drifted W. A hotspot remained about six hours later after the ash dissipated.

Figure 48. Incandescent ejecta appeared on the flanks of Agung after an eruption on 4 April 2019 (local time) as viewed from the observation post in Rendang (8 km SW). Courtesy of Jamie Sincioco.

Figure 49. Ashfall in a nearby town dusted mustard plants on 4 April 2019 from an explosion at Agung the previous day. Courtesy of Pantau.com (Photo: Antara / Nyoman Hendra).

PVMBG reported an eruption visible in the webcam early on 21 April (local time) that rose to 5.5 km altitude and drifted SW. The ash spread W and S and ash fell around Besakih (7 km SW), Rendang (8 km SW), Klungkung (25 km S), Gianyar (20 km WSW), Bangli (17 km WNW), Tabanan (50 km WSW), and at the Ngurah Rai-Denpasar Airport (60 km SW). About 15 hours later a new explosion produced a dense gray ash plume that rose to 3 km above the summit and produced incandescent ejecta in all directions as far as 3 km away (figure 50). The ash spread to the S and ashfall was reported in Besakih, Rendang, Sebudi (6 km SW), and Selat (12 km SSW). Both of the explosions were heard in Rendang and Batulompeh. The incandescent ejecta from the explosions remained within the 4-km exclusion zone. A satellite image on 23 April showed multiple thermal anomalies within the summit crater (figure 51). A dense gray plume drifted E from Agung on 29 April (30 April local time) at 4.6 km altitude. It was initially reported by ground observers, but was also visible in multispectral satellite imagery for about six hours before dissipating.

Figure 50. An explosion at Agung on 21 April 2019 sent incandescent eject 3,000 m from the summit. Courtesy of MAGMA Indonesia (Gunung Agung Eruption Press Release April 21, 2019).

Figure 51. Multiple thermal anomalies were still present within the summit crater of Agung on 23 April 2019 after two substantial explosions produced ash and incandescent ejecta around the summit two days earlier. "Atmospheric Penetration" rendering (bands 12, 11, and 8A) courtesy of Sentinel Hub Playground.

PVMBG reported an eruption on 3 May 2019 that was recorded on a seismogram with a signal that lasted for about a minute. Satellite imagery reported by the Darwin VAAC showed a growing hotspot and possible ash near the summit at 4.3 km altitude moving NE. A few days later, on 6 May, a gray ash plume rose to 5.2 km altitude and drifted slowly W before dissipating; it was accompanied by a seismic signal that lasted for about two minutes. Explosions on 12 and 18 May produced significant amounts of incandescent ejecta (figure 52). The seismic signal for the 12 May event lasted for about two minutes; no plume was observed due to fog, but incandescent ejecta was visible on the flanks and the explosion was heard at Rendang. The Darwin VAAC reported an ash plume from the explosion on 17 May (18 May local time) at 6.1 km altitude in satellite imagery moving E. They revised the altitude a short while later to 7.6 km based on IR temperature and movement; the plume drifted N, NE, and E in light and variable winds. A few hours after that it was moving NE at 7.6 km altitude and SE at 5.5 km altitude; this lasted for about 12 hours until it dissipated. Ashfall was reported in villages downwind including Cutcut, Tongtongan, Bonyoh (20 km WNW), and Temakung.

Figure 52. Explosions on 12 (left) and 18 (right) May (local time) 2019 produced substantial ejecta on the flanks of Agung visible from a distance of 10 km or more in PVMBG webcams. The ash plume from the 18 May event resulted in ashfall in numerous communities downwind. Courtesy of PVMBG (Information Eruption G. Agung, May 13, 2019, Information Eruption G. Agung, May 18, 2019).

The initial explosion on 18 May was captured by a webcam at a nearby resort and sent incandescent ejecta hundreds of meters down the NE flank within 20 seconds (figure 53). Satellite imagery on 3, 8, 13, and 18 May indicated multiple thermal anomalies growing stronger at the summit. All of the images were captured within 24 hours of an explosive event reported by PVMBG (figure 54).

Figure 53. The 18 May 2019 explosion at Agung produced an ash plume that rose to over 7 km altitude and large bombs of incandescent material that traveled hundreds of meters down the NE flank within the first 20 seconds of the explosion. Images taken from a private webcam located 12 km NE. Courtesy of Volcanoverse, used with permission.

Figure 54. Satellite images from 3, 8, 13, and 18 May 2019 at Agung showed persistent and increasing thermal anomalies within the summit crater. All images were captured within 24 hours of explosions reported by PVMBG. "Atmospheric Penetration" rendering (bands 12, 11, and 8A) courtesy of Sentinel Hub Playground.

PVMBG issued a VONA on 24 May 2019 reporting a new ash emission. They indicated that incandescent fragments were ejected 2.5-3 km in all directions from the summit, and the seismic signal lasted for four and a half minutes (figure 55). A dense gray ash plume was observed from Tulamben on the NE flank rising 2 km above the summit. Satellite imagery indicated that the plume drifted SW and ashfall was reported in the villages of Besakih, Pempatan, Menanga, Sebudi, Muncan, Amerta Bhuana, Nongan, Rendang, and at the Ngurah Rai Airport in Denpassar. Additionally, ashfall was reported in the districts of Tembuku, Bangli, and Susut (20 km SW). The Darwin VAAC reported an ash plume visible in satellite imagery at 4.6 km altitude along with a thermal anomaly and incandescent lava visible in webcam imagery. The remains of the ash plume were about 170 km S of the airport in Denpasar (60 km SW) and had nearly dissipated 18 hours after the event. According to a news article several flights to and from Australia were cancelled or diverted, though the International Gusti Ngurah Rai (IGNR) airport was not closed. On 31 May another large explosion produced the largest ash plume of the report period, rising more than 2 km above the summit (figure 56). The Darwin VAAC reported its altitude as 8.2 km drifting ESE visible in satellite data. It split into two plumes, one drifted E at 8.2 km and the other ESE at 6.1 km altitude, dissipating after about 20 hours.

Figure 55. A large explosion at Agung on 24 May 2019 produced incandescent ejecta that covered all the flanks and dispersed ash to many communities to the SW. Courtesy of PVMBG (Gunung Agung Eruption Press Release 24 May 2019 20:38 WIB, Kasbani, Ir., M.Sc.).

Figure 56. An explosion at Agung on 31 May 2019 sent an ash plume to 8.2 km altitude, the highest for the report period. Courtesy of Sutopo Purwo Nugroho, BNPB.

Information Contacts: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as Indonesian Center for Volcanology and Geological Hazard Mitigation, CVGHM), Jalan Diponegoro 57, Bandung 40122, Indonesia (URL: http://www.vsi.esdm.go.id/); MAGMA Indonesia, Kementerian Energi dan Sumber Daya Mineral (URL: https://magma.vsi.esdm.go.id/); 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/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground); The Jakarta Post, Mount Agung eruption disrupts Australian flights, (URL: https://www.thejakartapost.com/news/2019/05/25/mount-agung-eruption-disrupts-australian-flights.html); PunapiBali (URL: http://punapibali.com/, Twitter: https://twitter.com/punapibali, image at https://twitter.com/punapibali/status/1098869352588288000/photo/1); Jamie S. Sincioco, Phillipines (Twitter @jaimessincioco, Image at https://twitter.com/jaimessincioco/status/1113765842557104130/photo/1); Pantau.com (URL: https://www.pantau.com/berita/erupsi-gunung-agung-sebagian-wilayah-bali-terpapar-hujan-abu?utm_source=dlvr.it&utm_medium=twitter); Volcanoverse (URL: https://www.youtube.com/channel/UCi3T_esus8Sr9I-3W5teVQQ); Sutopo Purwo Nugroho, BNPB (Twitter: @Sutopo_PN, URL: https://twitter.com/Sutopo_PN ).

November 2019 (BGVN 44:11) Cite this Report

Quiet returns after explosions on 10 and 13 June 2019

After a large, deadly explosive and effusive eruption during 1963-64, Indonesia's Mount Agung on Bali remained quiet until a new eruption began in November 2017 (BGVN 43:01). Activity continued throughout 2018 with explosions that produced ash plumes rising multiple kilometers above the summit, and the slow effusion of the lava within the summit crater. Increasingly frequent and intense explosions with ash emissions and incandescent ejecta characterized activity during February through May 2019 (BGVN 44:06). Two more explosions in June 2019 produced significant ash plumes; no further explosive activity occurred through October 2019. Information about Agung comes from Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG), also known as the Indonesian Center for Volcanology and Geological Hazard Mitigation (CVGHM), the Darwin Volcanic Ash Advisory Center (VAAC), and multiple sources of satellite data. This report covers the end of the eruption in June and observations through October 2019.

After a large explosion on 31 May 2019, a smaller event occurred on 10 June. Another large explosion with an ash plume that rose to 9.1 km altitude was recorded on 13 June (local time). It drifted hundreds of kilometers before dissipating. No further explosive activity was reported through October 2019, only diffuse white steam plumes rising at most a few hundred meters above the summit. The Alert Level remained at III (of four levels) throughout the period. The record of thermal activity showed an increase during the explosive events of late May and June, but then decreased significantly (figure 57). There was no obvious thermal signature in satellite images that explained the small increase in thermal energy recorded by the MIROVA data at the end of August 2019.

Figure 57. The thermal energy at Agung increased significantly during the explosive events of late May and early June 2019, and then decreased substantially as seen in this MIROVA graph from 23 January through October 2019. There was no obvious satellite thermal signature to explain the brief increase in thermal energy in late August. Courtesy of MIROVA.

On 31 May 2019 a large explosion produced an ash plume that rose more than 2 km above the summit (BGVN 44:06, figure 56). The Darwin VAAC reported that it split into two plumes, one drifted E at 8.2 km and the other ESE at 6.1 km altitude, dissipating after about 20 hours early on 1 June. A small eruption with an ash plume that rose to 3.9 km altitude was reported the next day by the Darwin VAAC. It was detected in the webcam and pilot reports confirmed that it drifted E for a few hours before dissipating. PVMBG reported gray emissions to 300 m above the peak on 1 June and 100 m above the summit on 2 June. By 6 June the emissions were white, rising only 50 m above the summit. For several subsequent days, the summit was covered in fog with no observations of emissions.

On 10 June 2019 an explosion lasting 90 seconds was reported at 1212 local time; PVMBG noted a gray ash plume 1,000 m above the summit (figure 58). The Darwin VAAC confirmed the emission in satellite imagery and by pilot report; it was moving SW at 4.3 km altitude and then drifted S before dissipating by the end of the day. Early on 13 June local time (12 June UTC) a new explosion that was clearly visible in the webcam produced a large ash plume that drifted W and SW (figure 59). The explosion was recorded on the seismogram for almost four minutes and sent incandescent ejecta in all directions up to 700 m from the summit. The first satellite imagery of the plume reported by the Darwin VAAC suggested the altitude to be 9.1 km. A secondary plume was drifting W from the summit at 5.5 km altitude a few hours later. By six hours after the eruption, the 9.1 km altitude plume was about 90 km SSW of the Denpassar airport and the 5.5 km altitude plume was about 110 km W of the airport. By the time the higher altitude plume dissipated after about 14 hours, it had reached 300 km S of the airport. For the remainder of June, only diffuse white steam plumes were reported, rising generally 30-50 m above the summit, with brief pulses to 150-200 m during 27-29 June.

Figure 58. An ash plume rose 1,000 m above the summit of Agung on 10 June 2019. Top image courtesy of Rita Bauer (Volcano Verse), bottom image courtesy of PVMBG (Information on G. Agung Eruption, 10 June 2019).

Figure 59. A large eruption at Agung at 0138 local time on 13 June 2019 sent an ash plume to 9.1 km altitude and incandescent ejecta 700 m in all directions. Courtesy of Jaime S. Sincioco, screenshot from volcano YT webcam.

Although no further surface activity was reported at Agung during July through October 2019, PVMBG kept the Alert Level at III throughout the period. Only steam plumes were reported from the summit usually rising 50 m before dissipating. Steam emissions rose to 150 m a few times each month. Plumes were reported at 300 m above the summit on 6 July and 15 August. No thermal anomalies were visible in Sentinel 2 satellite images during the period.

Information Contacts: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as Indonesian Center for Volcanology and Geological Hazard Mitigation, CVGHM), Jalan Diponegoro 57, Bandung 40122, Indonesia (URL: http://www.vsi.esdm.go.id/); 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/); Rita Bauer, Volcano Verse (Twitter @wischweg, URL: https://twitter.com/wischweg/status/1137956367258570752); Jamie S. Sincioco, Philippines (Twitter @jaimessincioco, URL: https://twitter.com/jaimessincioco/status/1139109685796020224).