Strong strombolian activity and lava fountaining were observed at Etna's Southeast Crater on December 22, 2020, after dense cloud cover prevented initial clear observations of strong explosive activity that started on December 21.
At 01:30 UTC on December 22, the seismic network detected a sharp increase in the average amplitude of the volcanic tremor in the Southeast Crater, rising to high values.
Starting at 04:19 UTC, strombolian activity suddenly evolved into lava fountaining, feeding two distinct lava flows -- one heading toward the southwest, branching west and east of Mount Frumento Supino, and the second heading eastward, inside the Bove Valley.
Analysis of surveillance camera images at 04:20 UTC revealed a small ground explosion in the Bove Valley, caused by the interaction of the lava flow and the snow cover.
Lava fountaining gradually subsided until it ceased at around 05:00 UTC.
Lava flow in Bove Valley has reached an estimated altitude of about 2 400 m (7 870 feet) at the time. The second lava flow was also still powered and the front stood at an estimated altitude of about 2 500 m (8 200 feet) a.s.l.
Volcanic tremor sharply decreased around 04:00 UTC, reaching average values. Infrasonic activity remained sustained and located mainly in the area of the Southeast Crater. Soil deformations monitoring networks no longer showed significant deformations.
In an update released at 16:38 UTC, INGV said lava flows were no longer being powered and have begun to cool. "Volcanic tremor exhibited modest fluctuations in the last few hours and currently stands at an average value."
Regarding infrasonic activity, there is a slight decrease in the number of infrasonic events; the sources are located mainly in the area of the Northeast Crater and, to a lesser extent, in the area of the Southeast Crater.
Soil deformations monitoring networks show no more significant deformations on high and medium-altitude station signals.
Featured image credit: Boris Behncke/INGV