Report on Etna (Italy) — 12 January-18 January 2011
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 12 January-18 January 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, 12 January-18 January 2011. Smithsonian Institution and US Geological Survey.
37.748°N, 14.999°E; summit elev. 3295 m
All times are local (unless otherwise noted)
On the evening of 12 January Strombolian activity from a pit crater located on the lower E flank of Etna's Southeast Crater cone intensified and volcanic tremor amplitude increased. Just after 2100 lava breached the crater's E rim and formed a lava flow that traveled towards the W wall of the Valle del Bove. During the night of 12-13 January, the pit crater produced lava fountains, voluminous lava flows that descended to about 1,630 m elevation (about 4.2 km from the vent), and an ash plume that rose several kilometers. The ash plume drifted S and caused ashfall on Etna's S flank and in population centers such as Nicolosi. Scoria several centimeters in diameter fell in Rifugio Sapienza, at 1,910 m elevation. The lava fountains were sustained initially and rose 300-500 m high, then pulsated and became less vigorous, and eventually formed one single jet that rose less than 100 m. Fountaining ceased at 0055 on 13 January. Emissions of ash during 13 January were generated in part by collapses within the crater and also by sporadic explosions within the conduit. On 14 January small landslides within the pit crater produced grayish-brown plumes.
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.