Thursday, 15 October 2015

Eruptions on Cotopaxi

The Instituto Geofísico-Escuela Politécnica Nacional reported a series of eruptions on Cotopaxi, an active volcano in the Andes of central Ecuador, about 50 km south of Quito, between Wednesday 7 and Tuesday 13 October 2015, with ash columns rising up to 2.5 km above the summit of the mountain and ash falls reported in communities almost 60 km away. The volcano began to show signs of activity in June this year, with a series of small Earthquakes and a sudden rise in sulphur dioxide, emissions, and has been growing steadily in activity ever since, with small eruptions beginning around the middle of August. 

An ash cloud emerging from the caldera of Cotopaxi on 9 October 2015. Jose Luis Espinosa-Naranjo/Earth of Fire.

Cotopaxi is the second highest mountain in Ecuador, and has a reputation for being the world's highest active volcano, though this is inaccurate. It is a symmetrical cone-shaped volcano (stratovolcano) rising 3800 m above the highland plains on which it sits, for a total height of 5897 m. Cotopaxi last erupted in 1942, though between 1738 and 1942 their were frequent eruptions, and the volcano is still considered a hazard to local populations. There have been occasional bouts of seismic activity (earth tremors) and fumarole (gas) emissions within the last decade. Cotapaxi has been popular with climbers since the nineteenth century.

The approximate location of Cotopaxi. Google Maps.

Like all South American volcanoes Cotopaxi 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 the South American Plate. Marot et al. (2012).

See also...

Concern is rising in Colombia and Ecuador following a rise in seismic activity beneath Cerro Negro de Mayasquer, a volcano in the Andes straddling...

Mount Tungurahua, 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, erupted suddenly at about 6.10 pm local time...

The United States Geological Survey recorded a Magnitude 4.5 Earthquake at a depth of 8.7 km in southern Carchi Province in northern Ecuador...

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