Saturday 3 December 2011

New eruptions on Mount Tungurahua, Ecuador. November 2011.

Mount Tungurahua is a stratovolcano (a 'conventional' cone-shaped volcano, the sort you see in Hollywood movies) located in the Sangay National Park in Ecuador, overlooking the town of Baños de Agua Santa. The town's major industry is tourism, attracting visitors to visit the volcano, the hot springs associated with the volcano, and the Amazon Rainforest.

Tungurahua has been intermittently active since 1999 (prior to which it had been inactive for about 75 years), with major eruptions in August 2006, February 2008, May 2010, December 2010 and April 2011. The 2006 eruption killed seven people; two volcanologists and a local family.

The August 2006 eruption on Mount Tungurahua.

On 27 November 2011 a number of earthquakes were felt in the area, followed by pyroclastic flows (flows of heavy superheated gas containing large amounts of hot ash, rocks and debris) were observed on the northern and northwestern flanks of the volcano. Later in the afternoon a series of explosions were heard near the summit of the volcano, and pyroclastic flows were observed on the southern and southwestern flanks. The following day there were further explosions, and pyroclastic flows on the south flank. A plume of ash and hot gas rose 3 km above the volcano, several local towns reported ash-falls, and nearby villages were evacuated with the help of the National Secretariat for Risk Management.

By the beginning of December the Geophysical Institute of Ecuador reported that the amount of gas being produced by the volcano had dropped dramatically, with no further pyroclastic flows. The volcano is still undergoing frequent earthquakes, but these do not necessarily imply an eruption is immanent. The situation is being monitored by the Tungurahua Volcanological Observatory in Guadelupe, 14 km to the north.

The current Tungurahua volcano is the third on the site, referred to by volcanologists as Tungurahua III. The first volcano on the site, Tungurahua I, built up and then collapsed some time in the Mid-Pleistocene. This was followed by Tungurahua II, which started to grow about 14 000 years ago, then collapsed about 3000 years ago. The current volcano has been growning since this time, and lies within the caldera of Tungurahua II.

Like all South American volcanoes Tungurahua owes its existence to the subduction of the Nazca Plate (which underlies the southeast Pacific) beneath South America. The Nazca Plate is being pushed from the east and forced down into the Earth's interior beneath South America. As it sinks rocks in the crust melt, and the lighter portions of it rise up through the overlying South American Plate to form volcanoes at the surface. These are dotted throughout the Andes Mountains; a range of mountains that is formed by a mixture of volcanism and crumpling of the South American Plate where is is forced against the Nazca Plate.

The subduction of the Nazca Plate beneath South America creates the Andes Mountains.

The Open University run a course in Volcanoes, earthquakes and tsunamis by distance learning. This can be counted towards a degree, but does not need to be taken as part of a degree course. The course costs £170 for UK residents and £405 for overseas residents, though financial support may be available for UK and European residents.