Report on Etna (Italy) — 13 January-19 January 2021
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 13 January-19 January 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, 13 January-19 January 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 during 11-17 January activity at Etna was characterized by intra-crater Strombolian activity at Northeast Crater (NEC), occasional ash emissions from the Voragine (VOR) and Bocca Nuova (BN) craters, and Strombolian activity, lava effusion, and ash emissions at the Southeast Crater (SEC). In general, the activity was similar to the pervious week, though activity at SEC on 18 January was notable.
Lava effusion began around 0700 on 17 January but was confined to the SEC summit cone. At around 0740 the lava breached the crater and lava flowed down to the base of the cone. The effusion rate increased by 0819 and an ash emission was possibly visible; the lava flow lengthened and had reached an elevation of 3,000 m by 1000. Weather clouds moved in and prevented visual observations until 1830 on 18 January when the lava flow was visible again; it was no longer being fed and was cooling. Volcanic tremor amplitude increased and Strombolian activity intensified at 2000. A new lava flow emerged at 2015 and traveled towards the Valle del Bove, reaching an elevation of 2,900 m. Low lava fountains were visible at 2130 and an ash plume drifted ESE, causing ashfall on the downwind flank. Lava flows descended the SE, E, and NE flanks of the SEC. Explosive activity significantly decreased at 2200. Two distinct lava flows were visible, with one heading N and the other moving towards the Valle del Bove. Tremor and infrasound signals decreased to pre-episode levels by 2230. The the lava flows were stable and cooling on 19 January.
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.