The Observatorio Vulcanologico y Sismologico de Costa Rica-Universidad Nacional in Costa Rica reported a large phreatic eruption on Mount Poás, a volcano in the central part of the country, slightly after noon local time (slightly after 6.00 pm GMT) on Tuesday 25 February 2014. Phreatic eruptions occur when magma or other very hot material is produced by a volcano in direct contact with water, in this case beneath the surface of a crater lake, causing a large volume of the water to convert immediately to vapor, resulting in an explosion. On this occasion the eruption resulted in a blast which through material over 300 m into the air.
Phreatic eruption on Mount Poás on Tuesday 25 February 2014. Observatorio Vulcanologico y Sismologico de Costa Rica-Universidad Nacional.
Mount Poás rises to 2708 m above sea level, but has gently sloping, forested flanks making the summit easily accessible. The summit consists of two craters, each with a lake. To the south is the cool, clear, Lake Botos, which has not seen an eruption for 7500 years, and to the north is Laguna Caliente, which is thermally heated, extremely acidic (about pH 0), and prone to frequent eruptions. The volcano and its surrounding area form the Poás Volcano National Park.
Costa Rica, along with the rest of Central America, likes on the southwest margin of the Caribbean Plate. To the south the Cocos Plate is being subducted along the Middle American Trench, passing under Central America as it sinks into the Earth. As this happens it is heated by the friction and the warmth of the planet's interior, causing it to partially melt. Some of the melted material then rises through the overlying Caribbean Plate, fuelling the volcanoes of Central America.
See also Magnitude 6.0 Earthquake off the coast of northwest Costa Rica, Eruption on Mount Turrialba, Costa Rica,
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