Report on Etna (Italy) — 15 June-21 June 2011
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 15 June-21 June 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, 15 June-21 June 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 on 13 June mountain guides heard loud hissing sounds coming from the interior of Etna's Bocca Nuova crater. After nearly six months of quiescence, ash emissions rose from Bocca Nuova the next morning. The emissions were composed of small ash clouds that seemingly originated from the central part of the crater and rose about 200-250 m above the crater rim, then drifted E. Thermal monitoring cameras showed no signs of incandescence in the emissions, which were observed for a few hours before meteorological clouds moved in and prevented further observations. During limited periods of good visibility from 15 to 17 June, sporadic small reddish-to-grayish-brown ash plumes were observed to occur every 5-15 minutes. Usual rhythmic emissions of gas and vapor from the Northeast Crater continued.
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.