Report on Etna (Italy) — 20 July-26 July 2011
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 20 July-26 July 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, 20 July-26 July 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 seventh eruption of Etna in 2011 occurred from the active crater on the E flank of the SE Crater cone. On 24 July vigorous Strombolian activity started within the crater, gradually increased through the night, and culminated on 25 July. Strombolian activity gradually turned into a pulsating lava fountain, accompanied by increasingly voluminous ash emissions. The fountain fluctuated between 250 and 300 m above the crater with a few jets rising 350 m. Lava flowed through a breach on the E crater rim and divided into multiple parallel flows that reached the base of the steep W slope of the Valle del Bove near Monte Centenari. Plumes drifted E causing ashfall between the villages of Fornazzo and Milo on the flank (10 km E), and the Ionian coast near Riposto (18 km E). The final phase of the eruption was characterized by a series of violent explosions that produced loud detonations heard in the E and SE sectors of 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.