After the effusive eruption of August-November 2014, Stromboli's activity remained at very modest levels for more than two years, and only in the last few months has the volcano reappeared in its characteristic form, with frequent explosions from various vents placed inside its crater terrace. This activity, in recent months, has been interrupted by 4 major explosions (26 July, 23 October, 1 November and 1 December 2017). After the last of these, the explosive activity remained at a high level, so as to motivate the authorities to declare a ban on access to the summit areas of the volcano.
Late yesterday morning, December 15th, a change in the activity of the eruptive vents was observed: one of them, located in the northern crater area, began producing small, almost continuous jets of fluid lava. This activity, known as spattering, is often accompanied by the formation of small lava flows. Around 2:00 PM local time, a team of researchers and technicians from the Etna Observatory, the Catania Section of theIstituto Nazionale di Geofisica e Vulcanologia (INGV), observed how small lava flows formed from two of the vents, which began to fill the crater depression, within which the three active vents are located. Around 2:30 PM, lava filled the depression and began to overflow its northern rim, generating a lava overflow that spilled onto the upper northern slope of the Sciara del Fuoco. A few hours later, spattering activity rapidly decreased, and by late afternoon, the lava flow had stopped.
Lava overflows from the Stromboli crater terrace are not an unusual phenomenon. In the interval between January 2010 and August 2014, there were several episodes of lava overflows, some confined within the crater terrace, while others produced small lava flows on the upper parts of the Sciara del Fuoco; more rarely (e.g. January 2013) the lava flows expanded to the lower part of the Sciara and, in one case (on 7 August 2014), a lava flow reached the sea. As in the current case, all these episodes ended after a few hours.
The phenomenon is constantly monitored by the Etna Observatory, the Vesuvius Observatory and the Palermo Section of INGV.
Figure: Early phases of the lava overflow of Stromboli on 15 December 2017, observed by the thermal cameras of Pizzo sopra la Fossa (left) and from Quota 400 (right)