A volcanologist's dream and nightmare a video by etnaboris on Flickr.
Pyroclastic flows entered into volcanological and collective conscience nearly 110 years ago, when an until then poorly known volcano wiped out the town of Saint-Pierre on the Caribbean island of Martinique, killing all but two of the roughly 28,000 people who were present in the town at the moment. The deadly agent was a strange cloud, which rather than rising up into the sky like a "normal" volcanic eruption cloud, rushed down from the volcano as a ground-hugging avalanche, and covered the distance of 8 km separating the unfortunate town from the volcano in about 2 minutes.
Since that tragedy, generations of volcanologists have been haunted and intrigued by pyroclastic flows, a quite elusive phenomenon whose generation and products seem to be the result of incredibly complex processes. A few volcanoes are notorious for producing pyroclastic flows during nearly all of their eruptions, like Merapi in Indonesia, where nearly 400 people were killed during a large eruption in October-November 2010, and Mayon in the Philippines, last active in December 2009. The Soufrière Hills on the Caribbean island of Montserrat produced countless pyroclastic flows between 1996 and 2010, causing death and devastation, but also allowing more detailed observation and documentation of these flows than has been ever obtained elsewhere.
Although not many volcanologists and volcano aficionados would have the Sicilian volcano Etna in their minds when thinking of pyroclastic flows, Etna is actually one of the busier producers of pyroclastic flows worldwide, and it has proved more "inventive" when it comes to how to generate these flows, and - luckily - they are rather small and confined to the immediate summit area and the upper flanks of the mountain. So the only people at risk are volcanologists, mountain guides, mountain rescue service staff, and occasional onlookers who enter the off-limits area. Since 1986, pyroclastic flows have occurred on at least 12-13 occasions, though others have probably passed unobserved. The most notable cases are the pyroclastic flows of the Bocca Nuova of 25 October 1999 (which I had the chance to see from only about 1 km distance), at the Southeast Crater on 16 November 2006 (again, I could witness numerous small pyroclastic flows at very close range but luckily had left the scene when a much bigger one occurred), and during a paroxysm at the New Southeast Crater on 10 April 2011 (on the steep slope of the Valle del Bove). In a surprising number of cases, people were present at close distance, but none of them have ever been hit by any of these pyroclastic flows.
One of the most exciting moments during the latest paroxysmal eruptive episode from Etna's New Southeast Crater early on 5 January 2012 was when a black cloud appeared on the slope of the erupting cone, which swept downward toward the snow-covered terrain at the base of the cone. When the cloud hit the snow, countless small puffs of steam rose. This video shows these scenes, and you can even see how the impact of the pyroclastic flow on the snow generates a small "lahar" - a volcanic mudflow, a phenomenon rarely observed at Etna. Next to pyroclastic flows, lahars are globally the second most deadly volcanic phenomenon, but luckily only one larger lahar is known to have occurred at Etna in historical time, in 1755.
The full, 8:39-min long video showing footage recorded by myself during the 5 January 2012 paroxysmal episode from the New Southeast Crater is now available at YouTube. YOU DEFINITELY HAVE TO WATCH THIS.
:)
super video Boris!!!!
:)
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