Mount Etna volcano, Sicily
Panoramic view of the southeastern flank of Mount Etna in the winter, seen from the village of Trecastagni, in autumn 2007. Photo by Boris Behncke Catalogue Number: 0101-06= (Smithsonian Institution, Global Volcanism Program) |
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Etna is the largest and tallest volcano of Europe, and one of the most active volcanoes on the Earth. Its eruptions occur both at the summit, where currently there are four crateres, and from its flanks, down to a few hundred meters above the sea-level. Summit activity can go on virtually continuously for many years or even decades (e.g., 1955-1971; 1995-2001), but it also often occurs during the intervals between flank eruptions. Such intervals can last from few months to more than 20 years, although in the past 40 years the average interval between flank eruptions has been only about 2 years. The duration of a flank eruption can be as short as a few hours, but in some cases exceed one year (1991-1993: 472 days; 2008-2009: 419 days). The four summit craters are: the Voragine and the Bocca Nuova, formed in 1945 and 1968, respectively, within the Central Crater; the Northeast Crater that exists since 1911 and is currently the highest point on Etna (3330 m); and the Southeast Crater, born in 1971, which has recently been the most active of the four craters. This configuration contrasts strongly with that of one century ago, when at the summit of Etna there was only the Central Crater. Until recently, Etna has been considered a prevalently effisuve volcano, that is, characterized mostly by the emission of lava flows. These can cause material damage but do not represent a direct threat to the lives of the about 900,000 people living in the area potentially threatened by eruptions of Etna. New studies, however, have revealed that this volcano is capable of producing violently explosive activity, like the Plinian eruption of 122 B.C. (B.C.E.). In recent years, especially since the late 1970s, there has been a significant increase in the frequency of explosive eruptive episodes, foremost at the summit craters. In particular, the summit eruptions of 1995-2001 included about 150 episodes of lava or fire fountaining (such episodes are often referred to as paroxysms), many of which generated tall columns of ash and gas. The flank eruptions of 2001 and 2002-2003 have demonstrated that significant amounts of pyroclastic material (ash, lapilli, bombs, and blocks) can be also generated by flank eruptions. Differently from the usually short-lived summit paroxysms, pyroclastic fallout during flank eruptions can go on for weeks or even months, and impact life in the populated areas, besides representing a serious threat for traffic both on the ground and in the air. The latest phase of activity at Etna to date (October 2012) was a series of 25 episodes of lava fountaining (paroxysms) from a new vent on the east flank of the Southeast Crater cone, between January 2011 and April 2012, followed by a period of mild Strombolian activity and lava emission within the Bocca Nuova in July-August 2012. The geological history of Etna Eruptions of Etna: impact on the territory The explosive eruptions of Etna Weekly reports and other updates
Eruption column about 3 km tall above the summit of Etna during the episode of lava fountaining on 8 September 2011, seen from the village of Fleri, on the southeastern flank of Etna. Photo by Boris Behncke |
Aerial view of the summit craters of Etna, 28 May 2008. In the uper center is the Central Crater, which contains the Voragine and the Bocca Nuova, which have nearly coalesced into one single large depression. At right is the Northeast Crater showing strong degassing, and at left the Southeast Crater, with promiment sulfur deposits on its rim. The fracture at lower right is the upper portion of the eruptive fissure that opened on 13 May 2008. Photo by Stefano Branca
A few of the more than 300 flank cones of Etna, on the western flank of the volcano just after sunrise on 5 November 2006. In the foreground are the two cones (Monti De Fiore) formed during the January-March 1974 flank eruption; in the center is the regular cone of Monte Nuovo (formed in 1763), and in the background Monte Lepre, probably of prehistoric age. Photo by Boris Behncke
Incandescent vent at the eastern base of the Southeast Crater cone, seen from Trecastagni (on the southeast flank) on the evening of 9 January 2010. This vent has since grown significantly in diameter and no further shows any incandescence. Photo by Boris Behncke |
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Flank eruption of 2008-2009. Lava flow on the western slope of the Valle del Bove, and ash emission from the eruptive vents located at about 2800 m elevation on the east flank of Etna. Behind the ash plume rises the Southeast Crater cone, in the right background are the Pizzi Deneri. View from Monte Zoccolaro (on the south rim of the Valle del Bove), 19 July 2008. Photo by Boris Behncke |
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