Intense explosive activity at Etna volcano, Aviation Color Code raised to Red, Italy


Explosive activity intensified at Etna's Southeast Crater (SEC) on Monday, February 15, 2021, and continued into Tuesday. The activity further intensified at 16:10 UTC on February 16 with lava fountaining and strong ash emissions reaching a height of about 10 km (33 000 feet) a.s.l. The Aviation Color Code was raised to Red.

Activity at the crater started intensifying in the early hours (UTC) of February 15, INGV reported. 

The average size of the volcanic tremor had already shown an increasing trend in the early hours and further intensified around 16:00 UTC, with the amplitude reaching high values. The tremors were located below the SE crater, at a depth of about 2.9 km (1.8 miles) above sea level.

The infrasonic activity was also high, but deformation data from GPS and clinometric networks showed no significant changes.

Starting at 16:10 UTC on February 16, explosive activity at the SE crater evolved into lava fountaining with the formation of a growing ash cloud, drifting southward.

From a seismic point of view, the average magnitude of volcanic tremor in the last few hours remained at high levels and then significantly increased from 16:00 UTC.

The tremors remained confined below the SE crater in the depth range between 2.9 and 3 km (1.8 miles) above sea level. The increasing tremor was accompanied by violent infrasonic activity with high amplitude signals.

According to data provided by Toulouse VAAC, the activity produced very strong ash emission with an estimated volcanic cloud height around 10 km (33 000 feet) above sea level.

The Aviation Color Code was raised to Red at 16:31 UTC.

Lava fountaining ended at around 17:00 UTC but lava emission along the Valle del Bove continued and the fallout of small ash and lapilli was reported up to Catania airport.

A sudden and obvious decrease of average volcanic tremor amplitude and infrasonic activity was observed starting at 16:50 UTC. 

The activity forced the temporary suspension of all operations at the Catania international airport.

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 (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: Eva

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