In December 2015, Mt. Etna underwent a new eruptive phase that was surprisingly peculiar, as it involved all the volcano summit craters – Voragine (VOR), New South-East crater (NSEC), North-east crater (NEC) - except for the Bocca Nuova (BN), which role is still not clear (FIG. 1).
The eruptive phase can be considered the climax of the moderate and sporadic explosive activity displayed in the previous months, through of which continuous inflation and seismicity spread over all the flanks of the volcano were observed. Overall in three days, from 3 to 5 December, VOR fed four episodes of lava fountaining among the most powerful of the last two decades (Fig. 2). Lava fountains reached heights up to about 11 km above the volcano, thus causing copious tephra fallout that severely impacted on air traffic and population living on the eastern sector of the volcano edifice.
On 6 December, the NSEC activated producing intense strombolian activity and lava flows (Fig. 3) ; the eruptive activity at this crater gradually decreased and ceased after two days. On 13 December, a weak explosive activity with ash emission was observed.
Finally, between 7 and 9 December, also NEC fed ash emissions and weak strombolian activity that formed a volcanic plume expanding eastwards. Ash emissions have discontinuously continued until present.
Air observations carried out on 12 December showed that the summit area of Mt. Etna was significantly modified by VOR lava fountaining. In particular, it was not possible to discriminate between the VOR and BN crater that morphologically appeared as a unique depression filled by the accumulation of the lava fountain products.
Contact : Letizia Spampinato and Giuseppe Puglisi (INGV Catania)
See INGV-Catania portal for details : http://www.ct.ingv.it/en/
More eruption pictures here.