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Eruption of Cordón Caulle volcano (Chile), June 2011

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Suggestive view of the huge umbrella-shaped cloud of ash and gas released during the initial phase of the Cordón Caulle eruption, on the late afternoon of 4 June 2011 (local time = GMT-4), seen from Puerto Varas, on the shore of Lake Llanquihue. The site of the eruption is about 110 km to the northeast of the photographer. Photo taken by Niccolo Cantarutti and published with kind permission of the author. (Source: Niccolo Cantarutti on Flickr)

Following an intense seismic crisis initiated on 2 June 2011, a fissure eruption started on the late afternoon of 4 June 2011 on the northwestern flank of Puyehue volcano, in southern Chile. This fissure system is known as Cordón Caulle, and is notable for the peculiar composition of its magmas, and for its pervious eruption, which started less than 48 hours after the strongest instrumentally recorded (magnitude 9.5) earthquake, which occurred on 22 May 1960. The current eruption has been preceded, by more than 14 months, by another large earthquake, the magnitude 8.8 earthquake of 27 February 2010.

A long period of premonitory seismic activity has heralded the eruption, going as far back as 1994. During the last few weeks of April 2011, a notable increase in the seismic activity was noted. During the 24 hours starting at 20 h on 2 June, about 1450 earthquakes were recorded, at an average frequency of about 60 events/hour. On 4 June, this frequency increased to about 230 events/hour, including 50 with magnitudes above 3, and 12 events stronger than magnitude 4.

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Ash plume produced by the initial, intensely explosive phase of the eruption recorded by the MODIS sensor on NASA's Aqua Satellite, on the late afternoon of 4 June 2011. In this phase, the height of the eruption column was 12-14 km. (Source: Nasa Earth Observatory)

The first explosion generated a spectacular eruption column, which rapidly rose to a height of 12-14 km, expanding into a typical umbrella cloud, and spreading eastward into neighboring Argentina, where heavy ash fallout was observed. During the first night of the eruption, intense electrical phenomena (lightning) was seen in the eruptive cloud, indicating a high amount of water vapor being emitted. Meteorological conditions during the following days prohibited direct observation of the eruption, but volcanic ash carried across a vast area in Argentina, Brazil and Paraguay led to the cancellation of numerous flights in those countries. One week after the start of the eruption, ash emission continued, even though at lower levels than during the first few days, causing further nuisance and disruption of air traffic. The volcanic plume circled the globe eastward, reaching the air space of Australia and New Zealand, where dozens of domestic and international flights had to be cancelled.

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Spectacular image of the intense lightning display in the eruption plume of Cordón Caulle during the night of 4-5 June 2011. Photograph taken by Claudio Santana, AFP/Getty Images (Source: Boston.com, photo #32)

Reconnaissance flights carried out over the volcano revealed the presence of extensive pyroclastic flow deposits that had been produced during the first phase of the eruption; some of these deposits had invaded the drainage system of the volcano, leading to the formation of lahars. Nine days from the start of the eruption, explosive activity is continuing at moderate levels, with ash falls to the northeast and east, mainly into Argentina. Thus far, no lava emission has been observed, a phenomenon which has typically followed the initial explosive phases of the previous eruptions in 1960 and 1921-1922.

Internet sources:

Servicio Nacional de Geología y Minería (SERNAGEOMIN)

Daily reports published by the Observatorio Volcanológico de los Andes del Sur (OVDAS)

The Global Volcanism Program (Smithsonian Institution) entry for the system Puyehue-Cordón Caulle

Eruptions blog and Volcanism blog with countless links to scientific and news articles, photographic sites and much more

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