Report on Etna (Italy) — 9 December-15 December 2020
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 9 December-15 December 2020
Managing Editor: Sally Kuhn Sennert
Please cite this report as:
Global Volcanism Program, 2020. Report on Etna (Italy). In: Sennert, S K (ed.), Weekly Volcanic Activity Report, 9 December-15 December 2020. 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 during 7-12 December activity at Etna was similar to the previous week, characterized by intra-crater Strombolian activity at Northeast Crater (NEC), and Strombolian activity, lava effusion, and pyroclastic flows at the Southeast Crater (SEC). Additionally, infrequent ash emissions at the Bocca Nuova (BN) craters and some explosions and minor ash emissions at the Voragine (VOR) were also recorded. Webcam views of activity was limited due to weather conditions; a field visit was made on 14 December.
Strombolian activity originated from the E and central vents at SEC ejected lava onto the inner crater walls. Occasional ash emissions dispersed quickly near the summit. Activity intensified at 2020 on 13 December and lava fountains formed around 2300. Collapses of the SW part of the SEC cone spurred a series of pyroclastic flows. At 2315 a small pyroclastic flow traveled down the SSW flank. A second pyroclastic flow began at 2316 and traveled 2 km down the SSW flank and covered Monte Frumento Supino cone (SSW). At 2330 a third and minor pyroclastic flow traveled SSW. Around the same time as the generation of the first two pyroclastic flows, two fissures opened on the SW flank of the SEC and produced lava flows to the S and SW until about 2350. A period of lava fountaining was visible during 0050-0110 and 0210-0223 on 14 December.
During a field inspection on 14 December scientists confirmed the partial cone collapses and noted that the two lava flows (S and SW) were cooling. The S lava flow had widened at the near the base of SEC and formed four lobes. One of the lobes continued on and stopped just NW of cones that had formed in 2002-2003. The SW flow traveled SSW, branched, curved around the W part of Monte Frumento Supino, and then stopped. Explosive activity from central SEC vent continued, with roaring and sporadic ash emissions. An explosion at 1352 formed an ash plume that rose about 4 km and drifted S. Strombolian explosions deposited material outside of the crater.
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.