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Etna and Stromboli update, 10 January 2013


These frames extracted from video recorded on the morning of 10 January 2013 by the high-sensitivity visible (EMOH) and thermal (EMOT) surveillance cameras of the INGV-Osservatorio Etneo (Catania) on the Montagnola, show jets of incandescent lava rising tens of meters above the rim of the Bocca Nuova, generating small thermal anomalies like the one shown in the second frame.

Etna: renewed Strombolian activity at the Bocca Nuova. Three months after the latest episode of intracrater Strombolian and effusive activity of Etna's Bocca Nuova, vigorous Strombolian activity started during the night of 9-10 January 2013. Starting around 23:00 GMT (=local time -1) on 9 January, the INGV-Osservatorio Etneo seismic surveillance network showed a rapid rise in the volcanic tremor amplitude, in particular at the "ECPN" (Etna Cratere del Piano) station, which among the currently functioning stations station is the one closest to Bocca Nuova. At 23:10 GMT, the high-sensitivity visual surveillance camera on the Montagnola (EMOH) recorded a first brief, and weak burst of incandescence coming from the eastern part of the crater. This was followed by others, which progressively became stronger and more frequent. From 02:50 GMT on, jets of incandescent lava fragments began to rise significantly higher than the crater rim, producing also small anomalies in images recorded by the thermal surveillance camera on the Montagnola (EMOT). The images at left show some of these jets, which between 04:00 and 05:30 GMT reached heights of 50-80 m above the crater rim. With daylight, the phenomenon was no longer visible via the surveillance cameras; however, throughout the morning the volcanic tremor amplitude remained elevated but started to show a diminution around noon.

The Bocca Nuova, the largest of Etna's four summit craters, showed first signs of coming back to life after a long quiescence at the end of August 2010 with a series of ash emissions, which were repeated more decisively in mid-June 2011. Finally, the first magmatic activity for 10 years occurred between 11 and 17 July 2011, with an episode of Strombolian and effusive activity on the crater floor., after which the Bocca Nuova reentered a state of quiescence for nearly one year. On 2 July 2012, vigorous Strombolian activity resumed, and after a few days was accompanied by the emission of small lava flows onto the crater floor. After going on continuously for two weeks, from 26 July 2012 on the activity took on an episodic character, with five episodes of which the latest, in the night of 10-11 August, was the most intense. A further episode, similar to those of July-August, occurred on 2-7 October 2012.

The resumption of Strombolian activity at the Bocca Nuova was preceded, in the past three months, by rather low levels in the eruptive activity of Etna. However, the New Southeast Crater (NSEC) showed some signs of life between 22 November and early December 2012, with weak glows coming from the interior of the crater.

These glows were due to the emission of high-temperature gas; visits carried out by INGV-OE staff and Etnean mountain guides disclosed the absence of Strombolian activity. The glows were most intense during the night of 1-2 December (see image below), and then rapidly diminished to reappear again on 24 December 2012. During the interval 25-27 December, the NSEC produced sporadic and weak emissions of ash, accompanied by a notable increase in gas emissions. Finally, on the evening of 3 January a strong glow was briefly observed at the NSEC, but due to cloud cover the phenomenon was not recorded by the surveillance cameras of the INGV-OE.

Night view of Etna taken shortly after midnight on 2 December 2012 from Trecastagni. The glow at the New Southeast Crater is well visible. Photo taken by Boris Behncke (INGV-OE)

Stromboli: lava overflows from the crater terrace. Since the morning of 23 December 2012, there have been repeated lava overflows from the crater terrace of Stromboli, generating small lava flows down the northern and northwestern sectors of the Sciara del Fuoco (see images below). Furthermore, the rapid accumulation of fluid spatter during intense explosive activity often generated small flows; these phenomena were accompanied by numerous landslides. The major lava flows occurred on the evening of 23 December (toward north), on 25-27 December 2012 (toward northwest), and on the morning of 7 January 2012 (toward northwest). Lava emission occurred from vents lying just below the rim of the northernmost explosive vent on the crater terrace. During the intervals between the main effusive episodes, lava was extruded at extremely low rates from the effusive vents, resulting in the descent of numerous incandescent blocks down the Sciara. At times, small lava flows advanced for a few tens of meters before disintegrating into blocks, such as on the morning of 10 January 2013 (see the last photo in the sequence below). In all cases, the effusion of lava was preceded, and often accompanied, by intense explosive activity on the crater terrace.

Frames extracted from video recorded by the visible surveillance camera at 400 m elevation on Stromboli (SQV) during the effusive episodes between 23 December 2012 and 10 January 2013. The first frame shows the sliding of material caused by the emplacement of a lava flow onto unstable material on the slope of the Sciara del Fuoco.