The fourth paroxysmal eruptive episode in just 4 days started at Etna's Southeast Crater on the evening of February 20, 2021, and continued into February 21. This was the strongest of the four episodes since February 16.
The average magnitude of the volcanic tremor started increasing around 17:26 UTC on February 21, together with increasing infrasonic signals mainly located at the Southeast Crater.
Strombolian activity was progressively increasing to about 19:30 UTC when volcanic tremors showed a sudden increase to top levels. Lava overflow began shortly after 21:30 UTC toward the Valle del Bove, eventually reaching a length of about 1 km (0.62 miles), with a front at about 2 800 m (1.7 miles).
The activity at the eastern mouth of SE Crater gradually switched to pulsating lava fountains by 22:00 UTC and further intensified by 23:24 UTC.
Another surge in intensity was detected at 00:28 UTC on February 21, with lava fountains exceeding 1 000 m (3 300 feet) above the crater.
An incredibily powerful episode of lava fountaining (paroxysm) at Etna this night, 20-21 February 2021. Lava fountains exceeding 1000 m in height.— Boris Behncke (@etnaboris) February 21, 2021
This is the most beautiful volcano on Earth. pic.twitter.com/4kG6AhtSpi
The eruptive column was estimated to rise up to 6 km (20 000 feet) above sea level.
The Aviation Color Code was raised to Red at 20:53 UTC at lowered back to Orange at 01:59 UTC on February 21.
Etna on February 21, 2021. Credit: Copernicus EU/Sentinel-2, ADAM Platform, Antonio Vecoli
Eruptive activity quickly decreased from 01:00 and 01:15 UTC and completely ceased around 01:20 UTC.
Lava flows were still seen slowly advancing, with the longest through Valle del Bove about 3.5 to 4 km (2.2 - 2.5 miles) away from the top of the crater and at an altitude between 1 700 and 1 800 m (5 560 - 5 900 feet).
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 (5.1 x 6.2 miles) horseshoe-shaped caldera open to the east.
Two styles of eruptive activity typically occur at Etna. Persistent explosive eruptions, sometimes with minor lava emissions, take place from one or more of the three prominent summit craters, the Central Crater, NE Crater, and SE Crater (the latter formed in 1978).
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. (GVP)
Featured image credit: Boris Behncke/INGV