New day, old ash (Etna, 23 June 2011)

In these days of summer, Etna is providing a spectacular show even without erupting incandescent, red-hot lava.

 

On 14 June 2011, the Bocca Nuova started emitting reddish-brown ash from two small vents in its center, and has continued ever since, though with fluctuations in the frequency and size of the ash emissions. Weather conditions in the past few days have been the best we've seen in Sicily for a long time, and so the phenomenon is well visible and attracting a lot of public attention. In any case, the ash from the Bocca Nuova is nothing more than pulverized, altered, old rock (that is, the rock debris that is blocking the conduit and has been turned into a sort of clayey mud by the passage of hot, sulfurous gases in the past ten years). Much of it is pink to pale orange in color, and much of the summit area is now covered with a thin layer of this ash, although this is less apparent when seen from a distance.

 

While the Bocca Nuova is, as it seems, clearing its throat, the common, rhythmic gas emissions are continuing from the Northeast Crater, accompanied by deep-seated explosive activity (probably at least 1000 m down within its conduit). At nearly windstill conditions, this is forming a conspicuous plume (seen in as a somewhat more dilute cloud in the center of this image). Finally, there's also a bit going on at the crater that lies on the east side of the Southeast Crater cone, and which has been the site of four spectacular paroxysms this year (most recently on 11-12 May). This crater, often still called "pit crater", although volcanologically speaking, it is no longer a pit crater (a simple hole formed by collapse), has started emitting bluish and whitish gas a few days ago. These emissions have grown denser and more continuous on 21-22 June, and on the latter day were also accompanied by a few bursts of gray ash. Such phenomena have been observed previously in the days preceding the paroxysms of this year, so chances are that within the next few days we will again see The Greatest Show On Earth. It will be interesting to see what sort of relationship there is between Bocca Nuova and Southeast Crater - the dynamics of Etna's summit craters is certainly a bit more complex than it has been for a long, long time.

 

To better understand the configuration of Etna's summit craters, see this aerial view that I took 3 years ago from a helicopter.

 

This particular ash emission occurred at 06:51 h (local time = GMT+2) on 23 June 2011 and was photographed from my home in Trecastagni, about 15 km southeast of Etna's summit.

 

The Etna monitoring cameras of the INGV-Catania (located in Catania, Milo, Nicolosi, and on the Montagnola)

 

The Etna monitoring camera of the INGV-Catania on the Schiena dell'Asino (southeast flank of Etna)

 

Seismic signals recorded by the Monte Scavo seismic station of the INGV-Catania (northwest flank of Etna)

 

Volcanic tremor recorded by the "Belvedere (EBEL)" and "Cratere del Piano (ECPN)" stations of the INGV-Catania, located immediately southeast and southwest of the summit craters, respectively

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Taken on October 23, 2011