Friday, 4 January 2013

Eruption on Mount Pacaya.

Mount Pacaya is one of Central America's most active volcanoes, having erupted at least 23 times in the last 500 years. It is located 30 km southwest of Guatemala City on the rim of the ancient Amatitlán Caldera, a 14 by 16 km structure that was last active in the Pliocene, between 5.3 and 2.5 million years ago. The volcano forms a massif on the rim of the older caldera, comprising the Cerro Grande Lava Dome, the eruptive MacKenney Cone, and the Cerro Chino Crater, which was last active in the nineteenth century. Pacaya is visible from Guatemala City, and its frequent small Stombolian Eruptions (ejections of lava bombs and incandescent ash) make it a popular tourist attraction.

MacKenney Cone, Pacaya Volcano, Guatemala. Steve McKenna.

On 28 December 2012 the Instituto Nacional de Sismologia, Vulcanologia, Meteorologia, e Hidrologia reported three explosions on the volcano, resulting in an ash plume that rose 500 m into the air and drifted to the southwest. This persisted till 1 January 2013.

The volcanoes of Guatemala, and Central America in general, are fed by the subduction of the Cocos Plate beneath the Caribbean Plate along the Middle American Trench, which runs roughly parallel to the southwest coast of the isthmus. As the Cocos Plate sinks into the Earth, it passes under Central America, which lies on the western margin of the Caribbean Plate. As this happens it is heated by the friction and the heat of the planet's interior, causing the sinking plate to partially melt. Some of the melted material then rises through the overlying Caribbean Plate as magma, fueling the volcanoes of Central America.

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1 comment:

  1. This is a great blog, and you post some very interesting articles, so please don't take this the wrong way, but I would just like to put the records straight about how subduction related volcanism works. It is a popular misconception that frictional heat causes the down going slab to partially melt thus creating volcanoes. You will get some melt contributed from slab melting, but the biggest proportion of the melt is contributed from another source.

    The down going slab is dehydrated as it descends into the mantle and the fluids driven into the mantle wedge above. These fluids lower the melting point of the overlying mantle wedge and it starts to melt. It is this that produces the magma that feeds the sub aerial volcanoes.

    Subduction related volcanism is also often highly explosive, another consequence of the hydrous melting of the mantle wedge above the down going slab.