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.

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.

Source: Sezione di Catania - Osservatorio Etneo (INGV)