SOUFRIÈRE HILLS VOLCANO
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 2011), and the southern part of Montserrat has been off-limits to residents. Many former Plymouth residents have emigrated to Britain.
Montserrat - the Soufrière Hills Volcano is under the cloud cover in the southern part of the island. The grayish-colored areas are recent ash deposits.
(Satellite photos provided by TerraMetrics/Google Earth/DigitalGlobe)
Soufrière Hills Volcano andesitic lapilli & ash (field of view ~5.1 cm across) from a 1997 pyroclastic flow (maybe the 3 August 1997 flow?) that engulfed Plymouth, due west of the volcano. This was collected from just inside a doorway of a destroyed building in Plymouth. Collected & generously donated by David Lea.
Soufrière Hills andesite lava (above & below; 9.6 cm across at its widest) - this lava sample consists two lithologies, sharply demarcated (see boundary line drawn below) 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, 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 & generously donated by Attila Kilinc.
Soufrière Hills Volcano andesite (field of view ~5.8 cm across) - close-up of sample shown above. Light gray semi-vesicular andesite is to the left. Very light gray pumiceous porphyritic andesite is to the right.
Soufrière Hills Volcano andesite (field of view ~3.6 cm across) - close-up of sample shown above. This is very light gray pumiceous porphyritic andesite showing large disrupted amphibole phenocrysts (black).
Soufrière Hills Volcano andesite ash (field of view ~5.1 cm across) - loose, very fine-grained ash from a February 2006 eruption of the Soufrière Hills Volcano. It was collected from the top of St. Georges Hill, just west-northwest of the volcano (see satellite photos above). Collected & generously donated by David Lea.