Report on Etna (Italy) — 11 July-17 July 2012
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 11 July-17 July 2012
Managing Editor: Sally Kuhn Sennert
Please cite this report as:
Global Volcanism Program, 2012. Report on Etna (Italy). In: Sennert, S K (ed.), Weekly Volcanic Activity Report, 11 July-17 July 2012. 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 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.
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.