Friday, January 24, 2014

Dormant Peruvian Volcano El Misti Waking Up?

One of Peru's most well known volcanoes, El Misti, may be gearing up for some action. The Smithsonian GVP reports that El Misti has had some rather alarming seismic activity that could indicate magma intrusion at the volcano. El Misti does not have many historical eruptions under it's belt. The only confirmed one on record would be in the 15th century when it forced villagers to flee pyroclastic clouds.

The current seismic crisis is described by the GVP:

"Instituto Geofísico del Perú (IGP) reported that seismicity at El Misti increased during January, and a seismic swarm consisting of 119 volcano-tectonic events was detected during 14-15 January. Despite the increase, activity remained at a low level."

It is unclear exactly what they mean by 'activity remained at a low level', as all indications I can come across don't show any 'unusual' activity. The summit crater has nestled within it a fumerolic lava dome that displays heavy sulfur concentrations.

Image from Panoramio user 'dockx thierry' of summit lava dome and associated fumerolic activity.

An eruption of El Misti would likely include explosive eruption of the current lava dome, with associated pyroclastic flows descending its flanks (depending on which way the wind is blowing, it could descend any direction of the symmetrical volcano). There are several cities and towns in the shadow of the large stratovolcano, which could conceivably be at risk of ash fall and lava flow advancement, should the volcano enter into a more active phase.

As with all long-dormant volcanoes, only time will tell if the current seismicity will eventually result in an eruption. The majority of magma dike intrusions into volcanic systems do not immediately result in an eruption, and magma chambers can remain molten and pressurized for an indefinite amount of time. A good example of a fully primed, yet inactive volcano would be Mount Fuji (a very similar stratovolcano) in Japan. Scientists recently mentioned that Fuji's magma chamber is pressurized far higher than it was when it last erupted, leading some to suggest that only a minor earthquake along a bisecting fault line, could result in the triggering of an explosive eruption. 

Like Fuji, El Misti is a volcano on the Pacific Ring of Fire, a chain of volcanoes that spans the outline of the Pacific tectonic plate. It, like Fuji, also lies on a subduction zone, which causes eruptions to be far more explosive, rather than effusive like a hotspot volcano (Hawaii, Piton de la Fournaise, etc), possibly due to the immense amount of water and gases that accumulate on subduction generated magma.

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