Report on Etna (Italy) — 8 February-14 February 2012
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 8 February-14 February 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, 8 February-14 February 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 8 February the New SE Crater (New SEC) of Etna entered another paroxysmal eruption episode after about 12 days of Strombolian activity. During the afternoon of 8 February, the Strombolian activity increased in both frequency and intensity of explosions from the vent on the W portion of the crater floor, and occasionally from a vent to the E. After about 1900, lava began to spill into the deep breach on the SE crater rim and then descended to the base of the cone. The lava flow expanded around 2100 and the Strombolian activity slowly increased, turning into a discontinuous lava fountain around 2330.
On 9 February the pulsating lava fountain rose 100-500 m above the crater before a continuous jet rising 300-400 m above the crater. A cloud with a small amount of tephra rose 6 km above the summit and then drifted W, producing some pyroclastic fallout that was on the upper portion of the volcano. Around 0200 and 0400, lava fountains from the two vents within the crater rose as high as 500 m above the crater. The fountain from the E vent caused abundant fallout on the crater rim and E flank. A third vent, located in the breach cutting the SE crater rim, produced sporadic violent explosions that ejected bombs many meters in diameter all over the E portion of the cone.
The lava flow reached the W rim around 0130, descended the flank, and branched into three different flows that reached a distance of 3 km from the New SEC. Lava fountaining started to diminish around 0530, and then around 0545 sporadic jets rose as high as 300 m above the crater. At the same time, the vent in the SE crater breach produced strong explosions that again ejected bombs many meters in diameter. These explosions generated loud bangs that were heard all over Etna and small ash emissions that were reported on the W portion of Bocca Nuova. Around 0900 activity started to diminish and ceased abruptly at 1000.
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.