The summit of Soufrière Hills volcano towers above the streets of Plymouth, the capital city of Montserrat Island. Plymouth is located only 4 km west of the volcano, on relatively flat pyroclastic-flow deposits from previous eruptions. This photo was taken in August 1995, shortly after the start of a long-term eruption that severely impacted the island. A lava dome that grew above the height of the crater rim produced pyroclastic flows that by August 1997 swept into the sea through the center of the evacuated city of Plymouth. Photo by Cynthia Gardner, 1995 (U.S. Geological Survey).

Geologic Summary from Smithsonian’s Global Volcanism Program. Soufriere Hills is a volcanic complex, chiefly of andesitic compositions, which occupies the southern part of Montserrat Island. The summit area consists of a series of lava domes emplaced along an ESE-trending zone. English's Crater, a 1-km-wide crater breached widely to the E, was formed during an eruption about 4,000 years ago in which the summit collapsed, producing a large submarine debris avalanche. Block-and-ash flow and surge deposits associated with dome growth predominate in flank deposits at Soufriere Hills. Non-eruptive seismic swarms occurred at 30-year intervals in the 20th century, but with the exception of a 17th-century eruption that produced the Castle Peak lava dome, no historical eruptions were recorded on Montserrat until 1995. Long-term small-to-moderate ash eruptions beginning in that year were later accompanied by lava-dome growth and subsequent collapse that produced, pyroclastic flows, inducing authority to a forced evacuation of the southern part of the island before the destruction of the capital city of Plymouth.