Report on Etna (Italy) — 4 January-10 January 2012
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 4 January-10 January 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, 4 January-10 January 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 night of 4 January the New SE Crater (New SEC) of Etna entered another paroxysmal eruption episode after about 50 days of quiescence. Several hours of Strombolian activity were observed on the SE and NE slopes starting at 2230 on 4 January. This activity continued into the early morning of 5 January when (around 0200) a small lava flow spread out into several branches at the SE base of the cone. Strombolian activity increased around 0400, generating lava fountains, from several vents within the crater that rose 100-150 m above the crater.
Significant ashfall and pyroclastic material fell onto the flanks at 0450 on 5 January. Around 0515 lava fountains generated a continuous eruption of ash-and-gas plumes that rose to an altitude of 2.1-2.4 km (7,000-8,000 ft) a.s.l. Small pyroclastic flows went a few hundred meters and lahars traveled down the NE, E, and S flanks of the cone. Around 0600 active vents along the N edge of the New SEC produced intermittent lava fountains. The most intense phase of the eruption occurred around 0620 when a strong explosion opened a vent on the top side of the SE cone, removed a portion of the SE crater rim, and generated ash plumes. The N slope of New SEC showed gravitational movement due to the amount of deposited pyroclastic material. Around 0630 activity started to diminish and ceased abruptly at 0730, but was followed by passive ash emissions that lasted until 0830.
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.