The Sezione di Catania - Osservatorio Etneo (INGV) reported that eruptive activity at Etna’s summit craters significantly intensified on 24 December. Activity within NE Crater (Northeast Crater), which had been occurring for several weeks, significantly intensified on 24 December. Though weather clouds partially obscured views of the summit, a webcam view showed incandescent material being ejected above the crater rim at around 1910. A dense steam plume drifted ENE. Eruptive events detected in infrasonic data were frequent, with increasing amplitudes, and originated both from NE Crater and to a lesser extent from Bocca Nuova Crater (BN). Tremor detected in infrasonic data began at around 2250. Strombolian activity at the BN-2 vent in BN Crater became more frequent and intense overnight during 25-26 December and ejected incandescent material 100 m above the crater rim. Incandescence within NE Crater intensified and during the morning Strombolian activity ejected material that occasionally fell onto the flanks. A gas, steam, and ash plume drifted NE, causing minor ashfall in Piano Provenzana (6 km NE) and Taormina (28 ENE). Weather conditions worsened through the day on 26 December and by sunset and through the night only intense reddish glow through the clouds was observed. Activity again intensified and continuous roars were heard at locations along the flanks.

Visibility gradually improved during the early hours of 27 December. Ash-and-steam plumes rose from a vent on the E flank of the Voragine Crater at 0700 based on webcam views. The vent produced a lava flow that descended towards the Valle del Bove. The activity rapidly intensified at NE Crater at around 1000; lava fountains rose 150-200 m and ash emissions were continuous. Activity at NE Crater decreased by 1050 and ash emissions became sporadic. Plumes mostly consisting of white steam rose several kilometers high from the summit area. After a few hours of lower-level activity lava fountaining began at NE Crater at around 1515. Fountains rose 300-400 m and a plume containing tephra rose several kilometers and drifted W. By 1545 lava fountaining transitioned to strong explosions and bursting lava bubbles, ejecting coarse pyroclastic material that landed around the base of the cone and beyond. Ash emissions were intermittent. Around the same time moderate explosive activity continued from the vent on the E flank of Voragine, producing continuous ash plumes that rose a few hundred meters high.

Visibility improved later that evening, and the entire summit was visible. Beginning at 1948 a series of strong explosions at NE Crater ejected coarse pyroclastic material across the entire cone and well beyond its base. Activity at Voragine Crater’s flank vent intensified and by 2046 was producing a constant lava fountain that rose several dozen meters high. The lava flow had traveled almost 2 km. Overnight during 27-28 December activity at the vent continued with frequent ash emissions drifting W and jets of pyroclastic material rising up to 100 m above the vent. The NE Crater produced sporadic explosions overnight and some ash puffs early on 28 December. The lava flow was flowing at dawn but appeared to have stopped by 2122 on 28 December, with only a few incandescent areas visible.

Geological Summary. Mount Etna, towering above Catania on the island of Sicily, has one of the world's longest documented records of 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 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.

Source: Sezione di Catania - Osservatorio Etneo (INGV)