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Small phreatic eruption at Poás, Costa Rica 16 January 2009

Posted by admin in activity reports, Costa Rica, eruptions, Poás.
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A magnitude 6.1 earthquake took place at 19:21 UTC (13:21 local time) on 8 January 2009 near La Cinchona, Costa Rica, some 6km east of Poás volcano. Poás is a highly active stratovolcano with a recent history of frequent phreatic and phreatomagmatic eruptions. The close proximity of the 8 January earthquake to the volcano has led to concerns that the quake, which produced rockfalls within the crater, could have disturbed the volcano, possibly provoking some kind of eruptive activity.

Ovsicori reports (see source below) that on 12 January 2009 there was a small phreatic eruption at Poás volcano:

The event can be described as a small phreatic eruption with dimensions of 50m diameter and 15m height which occurred in the centre of the lake in the active crater … This can be interpreted as a small eruption of a bubble of gas which was released suddenly from the fractured hydrothermal system.

The implication is that the hydrothermal system, described by Ovsicori as ‘already fractured and shallow’ was disrupted by the earthquake.

A report in Spanish on the 8 January 2009 earthquakes from the Observatorio Vulcanológico y Sismológico de Costa Rica (Ovsicori) is available in PDF at this link. The Ovsicori report on the Poás activity of 12 January 2009 quoted above can be found, also as a PDF, here.

News
Thirteen dead in Costa Rica quake – BBC News, 10 January 2009
Bodies found as quake toll rises – Press Association, 11 January 2009
Death toll in Costa Rica quake rises to 20 – Associated Press, 14 January 2009
Thousands on alert for aftershocks – Inside Costa Rica, 14 January 2009
Preocupados costarricenses por erupciones en el volcán Poás – Prensa Latina, 14 January 2009
Experts say Poás activity normal – Inside Costa Rica, 15 January 2009

Information
Global Volcanism Program: Poás – information about Poás (1405-04=)
Observatorio Vulcanológico y Sismológico de Costa Rica – Volcanological and Seismological observatory of Costa Rica (Ovsicori)
Volcán Poás – profile of Poás volcano from Ovsicori

The Volcanism Blog