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.

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.

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/).