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Earth of fire

Actualité volcanique, Article de fond sur étude de volcan, tectonique, récits et photos de voyage

Publié le par Bernard Duyck
Publié dans : #Actualités volcaniques
 Cotopaxi, September 12, 2015 - photo-Espinosa Jose Luis Naranjo.

Cotopaxi, September 12, 2015 - photo-Espinosa Jose Luis Naranjo.

Although a decrease in surface activity was detected at Cotopaxi in the last two weeks characterized by gases and ash less intense emissions, there was an increase in the number of volcano tectonic earthquakes in connection with the internal fracturing of rocks and a tangential deformation rising.

The combination of these factors indicates a possible replenishment of magma reservoir between 3 and 7 km beneath the crater and an increase in internal pressure.

Cotopaxi - deformation and seismicity between 01.08. and 09.15.2015 - Doc. IGEPN

Cotopaxi - deformation and seismicity between 01.08. and 09.15.2015 - Doc. IGEPN

Cotopaxi - location of earthquakes - those of September 15 are surrounded in green - doc.IGEPN

Cotopaxi - location of earthquakes - those of September 15 are surrounded in green - doc.IGEPN

Microscopic examination of the issued ashes shows an evolution of the ash since August 28, with a reduction of the contribution of hydrothermal system and a possible increase in the supply of fresh magma, characterized by free crystals and glassy particles a little bit vesiculated and with a high content of microliths.

Emissions of sulfur dioxide, which is kept around 2,000 tons / day, passed from continuous to pulsatile, with lower values ​​on September 13. According to IGEPN, this corresponds to either a depletion of magma in SO2, or a decrease in the permeability of the pipe, preventing the evacuation of gas continuously.

Cotopaxi - new areas of  fumaroles with the thermal camera and her photo location - image and photo S. Vallejo / P. Ramón, IGEPN

Cotopaxi - new areas of fumaroles with the thermal camera and her photo location - image and photo S. Vallejo / P. Ramón, IGEPN

An overview of the volcano on September 15 let observed the presence of new fields of fumaroles inside the crater and in the southeast sector, where the temperature reaches up to 43.1 ° C.

Cotopaxi - on 09/15/2015 - photo Alejandra Romero via El Comercio

Cotopaxi - on 09/15/2015 - photo Alejandra Romero via El Comercio

The most likely scenarios of evolution
 
are :
- More likely an intensification of the eruptive activity in various episodes spread over months, with small pyroclastic flows, as in Tungurahua, with small secondary lahars following the rains or glacial melt,

- A paroxysmal eruption, accompanied by important pyroclastic flows, generating a partial glacial melt, and major lahars.

 

Sources : IGEPN -Actualización de la Actividad Eruptiva--Volcán Cotopaxi N°16 - 17.09.2015

 

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