Etna showing signs of renewed unrest, Italy

Etna showed signs of increased unrest on November 15, 2022, forcing the Etna Volcano Observatory to raise the Aviation Color Code for the volcano from Green to Yellow. It was lowered back to Green at 10:20 UTC on November 16 after geophysical parameters returned to background levels.

The average amplitude of volcanic tremor at Etna showed an increase starting at 16:55 UTC on November 15, 2022, reaching a maximum value at 17:30 UTC.

The magnitude of the tremor at 18:22 UTC on November 15 — the time of INGV’s update report for the volcano — showed fluctuation with medium-high values.¹

The location was in the area of the Bocca Nuova crater at an altitude of 3 km (1.8 miles) above sea level. Low level infrasonic activity was detected at the Bocca Nuova crater.

The clinometric monitoring stations in the summit area detected significant changes between 00:00 and 04:00 UTC. A first variation was observed between 00:00 and about 00:30, and a second variation between 02:50 and about 03:30 UTC, cumulating an inclination not exceeding 1 micro radian, and indicating an uplift centered approximately in the summits area. No significant changes were recorded at clinometric stations since 04:00 UTC.

During the same time period, the dilatometric station in Monte Ruvolo (DRUV) also recorded significant changes.

The GNSS monitoring network did not record significant changes and the surveillance cameras did not catch any eruptive activity.

Geophysical parameters returned to background levels by 10:20 UTC on November 16 when the Aviation Color Code was lowered back to Green.²

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.³

References:

¹ PRIMO COMUNICATO (VALUTAZIONE MULTIDISCIPLINARE) – ETNA – INGV – November 15, 2022

² LA FINE DELL’ATTIVITà VULCANICA – ETNA – INGV – November 16, 2022

³ Etna – Geological summary – GVP