Report on Etna (Italy) — 25 May-31 May 2016
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 25 May-31 May 2016
Managing Editor: Sally Kuhn Sennert
Please cite this report as:
Global Volcanism Program, 2016. Report on Etna (Italy). In: Sennert, S K (ed.), Weekly Volcanic Activity Report, 25 May-31 May 2016. Smithsonian Institution and US Geological Survey.
37.748°N, 14.999°E; summit elev. 3295 m
All times are local (unless otherwise noted)
INGV reported that at around noon on 20 May Strombolian activity was visible at Etna's Voragine (VOR) crater and produced explosion noises audible across a large area on the S and E flanks. At night the activity intensified with explosions occurring at two or three vents, contemporaneous with renewed inflation of the summit area. Just after 0400 volcanic tremor amplitude rapidly increased and the Strombolian explosions turned into pulsating jets of lava, launching incandescent bombs 1 km S; an ash plume drifted SSE. A thermal camera also recorded activity from a vent in the S portion of Northeast Crater (NEC). Observers noted that a fracture had formed on the SE flank of the central cone. In addition, an effusive vent in the saddle between the cone and the old cone of the Southeast Crater produced a small lava flow that traveled towards the Valle del Leone. Activity decreased around 0500 and was over at about 0600.
On 22 May a vent on the upper E flank of New Southeast Crater cone produced a series of ash emissions which rose several hundred meters above the summit and dispersed. Some of the emissions had a thermal signature, indicating the presence of hot material. That evening Strombolian activity resumed at NEC; the rate and intensity of the activity fluctuated through the night. The strongest explosions ejected incandescent bombs up to a few hundred meters above the crater rim and onto the flanks. On 23 May sporadic ash emissions continued from the vent on the upper E flank of the New Southeast Crater cone.
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.