Report on Etna (Italy) — 15 September-21 September 2021
Smithsonian / US Geological Survey Weekly Volcanic Activity Report,
15 September-21 September 2021
Managing Editor: Sally Kuhn Sennert
Please cite this report as:
Global Volcanism Program, 2021. Report on Etna (Italy). In: Sennert, S K (ed.), Weekly Volcanic Activity Report, 15 September-21 September 2021. Smithsonian Institution and US Geological Survey.
37.748°N, 14.999°E; summit elev. 3320 m
All times are local (unless otherwise noted)
INGV reported that tremor amplitude at Etna began gradually increasing at 0420 on 21 September and then suddenly increased at 0440. Ash emissions rose from the Southeast Crater (SEC) at 0815 and by 0855 Strombolian activity was visible. An eruption plume rose 4.5 km above the summit and drifted ENE. Within an hour lava fountaining began and the plume rose 9 km and drifted ENE. Lava overflowed the crater and traveled SW. Lava fountaining had ceased by 1130, though Strombolian activity within the crater continued. Tremor amplitude decreased at 1250 and explosive activity ceased.
Geological Summary. 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.