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Phreatic eruption at Poás, Costa Rica 21 September 2009

Posted by admin in activity reports, Costa Rica, Poás.
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Poás volcano produced a phreatic eruption on Friday morning, 18 September, reports Costa Rican newspaper La Nación. The eruption projected water and sediment to a height of 300 metres above the surface of the crater lake. It is the northern of the volcano’s two summmit crater lakes, Lago Caliente, which is the site of frequent phreatic eruptions; the most recent, a smaller event, was in January this year.

The report also mentions that scientists visiting the summit of Poás have found burning sulphur on the north wall of the crater lake, the first time this phenomenon has been seen since 1994. Recent high temperatures and low rainfall have reduced the water volume in the highly acidic lake, and degassing from the crater has intensified with the gas plume – ‘bright yellow’ in certain areas – reaching 400 metres in height when measured on 16 September. The sulphurous plume may present a hazard for visitors to the volcano, which is one of Costa Rica’s most popular tourist attractions.

Volcán Poás hizo erupción de agua y sedimentosLa Nación, 20 September 2009

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


1. christy garrett - 30 September 2009

how did it occur, i.e. with the plate boundaries and tectonic plates

2. Jackie B. - 1 October 2009

Christy, might I suggest a google search? Something like ‘costa rica geology’ would probably help you find the information you need.

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