Report on Etna (Italy) — 20 October-26 October 2021
Smithsonian / US Geological Survey Weekly Volcanic Activity Report,
20 October-26 October 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, 20 October-26 October 2021. Smithsonian Institution and US Geological Survey.
37.748°N, 14.999°E; summit elev. 3320 m
All times are local (unless otherwise noted)
Strombolian activity resumed at Etna’s Southeast Crater (SEC) beginning at 0447 on 20 October. Small ash-and-gas puffs drifted SW. Activity gradually increased and by 1920 on 21 October explosions were ejecting incandescent material out of the crater. Activity intensified during the evening of 22 October, and crater incandescence was visible in between weather clouds at night during 22-23 October. Ash plumes drifted NE.
Explosive Strombolian activity increased at 1000 on 23 October, producing ash plumes that then abruptly stopped at 1035. A series of strong explosions began a few minutes later, producing visible pressure waves and ash emissions. Lava fountaining began sometime before 1043 and dense ash-and-gas plumes rose several kilometers high and drifted ENE. A fracture opened on the SE side of the SEC cone and at 1048 a pyroclastic flow traveled 1.5 km SE toward the Valle del Bove. A second pyroclastic flow observed at 1100 also traveled 1.5 km SE. Several smaller pyroclastic flows were visible on the E flank of the cone. At 1158 a pyroclastic flow bifurcated and traveled a few hundred meters S and SE. Lava fountains rose as high as 800 m during the most intense period and a lava flow originating from the E side of the crater descended SE. The ash plumes rose more than 10 km (32,800 ft) a.s.l. and caused ash and lapilli to fall in many areas downwind, including Linguaglossa, Vena, Presa, Piedimonte Etneo, Taormina, and Mascali. Explosive activity began to decrease around 1200 and then ceased at 1220. Ash emissions continued to rise from the SEC and by 1932, the lava flows on the SE flank had stopped advancing.
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.