Andesite (1997 lava from Soufriere Hills Volcano, Montserrat, Lesser Antilles Volcanic Arc, eastern Caribbean Sea) 1

Autor:

James St. John

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Shortlink:

https://czwiki.cz/b/b4158

Zdroj:

Wikimedia Commons

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2383 x 1918 Pixel (2322264 Bytes)

Popis:

Soufrière Hills andesite lava (9.6 cm across at its widest) - this lava sample consists two lithologies, sharply demarcated and defined by a slight color change, a phenocryst abundance/size change, and a vesiculation difference. The left portion of the sample is light gray, semi-vesicular porphyritic andesite. The right portion of the sample is a very light gray, semi-pumiceous porphyritic andesite. Available petrologic information indicates that 1997 Soufrière Hills andesite is a quartz-bearing, two-pyroxene, porphyritic hornblende andesite. Dominant phenocrysts include hornblende amphibole, hypersthene pyroxene, and plagioclase feldspar. Minor phenocrysts include titanomagnetite, quartz, and augite pyroxene microphenocrysts. The groundmass material is a mix of finely-crystalline plagioclase feldspar, orthopyroxene, augite clinopyroxene, pigeonite, titanomagnetite, and quartz, plus rhyolitic glass.

Locality: summit of Soufrière Hills Volcano, southern Montserrat, northern West Indies, eastern Caribbean Sea.

Collected in June 1998.

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A significant series of volcanic eruptions decimated the southern half of Montserrat during the 1990s. Montserrat is an island in the northern Lesser Antilles Volcanic Arc (eastern Caribbean Sea). The islands of the Lesser Antilles have a volcanic origin, the result of the North American Plate subducting westward & downward beneath the Caribbean Plate.

The Soufrière Hills Volcano occupies much of the southern half of Montserrat. It is a 31,000+ year old, andesitic, subduction zone stratovolcano. Its current phase of activity began in 1995 and 1996, prompting the evacuation of most of the island’s southern half. A significant ash eruption in summer 1997 destroyed the capital city of Plymouth along the southwestern shore of the island. The eruption was apparently triggered by the injection of basaltic magma into one of the volcano's two magma chambers. Soufrière Hills has been erupting intermittently to the present day (including activity in the 2010s), and the southern part of Montserrat has been off-limits to residents. Many former Plymouth residents have emigrated to Britain.

Licence:

CC BY 2.0

Credit:

https://www.flickr.com/photos/47445767@N05/14839780968/

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