Report on Etna (Italy) — 3 August-9 August 2011
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 3 August-9 August 2011
Managing Editor: Sally Kuhn Sennert
Please cite this report as:
Global Volcanism Program, 2011. Report on Etna (Italy). In: Sennert, S K (ed.), Weekly Volcanic Activity Report, 3 August-9 August 2011. Smithsonian Institution and US Geological Survey.
37.748°N, 14.999°E; summit elev. 3295 m
All times are local (unless otherwise noted)
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.
Geologic Background. Mount Etna, towering above Catania, Sicily's second largest city, has one of the world's longest documented records of historical 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 horseshoe-shaped 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.