Small steam explosion in the lake ultra acid of the active crater.
Yesterday, June 5, 2016, occurred between 9 am and 10 am a small steam explosion (phreatic eruption or hydrothermal explosion) in the ultra-acidic lake of Poas volcano. The explosion formed a column of water, sediment and vapor in the lake, which reached about 20 to 30 meters high. The shape of the column was “cipressoidale” (in the form of cypress).
Since May 28, 2016, the OVSICORI-A has noticed an increase in the strength of underwater fumaroles that are below the lake as well as a change in the color of the lake, from a milky green to gray milky with many floating molten sulfur to the surface.
Recent changes in the lake from the end of May 2016 and the small explosion of steam yesterday morning indicate processes in the magmatic-hydrothermal system promoting greater interaction water-gas – hot rock (or water -Gas-magma) and a flow of hot fluid to the deepest levels of the active crater.
The broad, well-vegetated edifice of Poás, one of the most active volcanoes of Costa Rica, contains three craters along a N-S line. The frequently visited multi-hued summit crater lakes of the basaltic-to-dacitic volcano, which is one of Costa Rica’s most prominent natural landmarks, are easily accessible by vehicle from the nearby capital city of San José.
A North-South-trending fissure cutting the 2708-m-high complex stratovolcano extends to the lower northern flank, where it has produced the Congo stratovolcano and several lake-filled maars. The southernmost of the two summit crater lakes, Botos, is cold and clear and last erupted about 7500 years ago. The more prominent geothermally heated northern lake, Laguna Caliente, is one of the world’s most acidic natural lakes, with a pH of near zero.
It has been the site of frequent phreatic and phreatomagmatic eruptions since the first historical eruption was reported in 1828. Eruptions often include geyser-like ejections of crater-lake water.
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June 06 , 2016.Poas , Costa Rica :
Source : Ovsicori , GVP
Photos : Archives landsinlove.com.