Due to increased seismic activity at Soufrière Hills during approximately 24-29 June, the Alert Level was raised to 4 (on a scale of 0-5). On 30 June around 1300, the lava dome partially collapsed and produced pyroclastic flows to the E. According to the Washington VAAC, a pilot reported that an ash plume reached an altitude of 3 km (10,000 ft) a.s.l. and drifted NW. The VAAC also reported that the Montserrat Volcano Observatory indicated a second dome collapse occurred at 1830 on 30 June that also generated ash plumes to altitudes of 3 km (10,000 ft) a.s.l.

Geological Summary. The complex, dominantly andesitic Soufrière Hills volcano occupies the southern half of the island of Montserrat. The summit area consists primarily of a series of lava domes emplaced along an ESE-trending zone. The volcano is flanked by Pleistocene complexes to the north and south. English's Crater, a 1-km-wide crater breached widely to the east by edifice collapse, was formed about 2000 years ago as a result of the youngest of several collapse events producing submarine debris-avalanche deposits. Block-and-ash flow and surge deposits associated with dome growth predominate in flank deposits, including those from an eruption that likely preceded the 1632 CE settlement of the island, allowing cultivation on recently devegetated land to near the summit. Non-eruptive seismic swarms occurred at 30-year intervals in the 20th century, but no historical eruptions were recorded until 1995. Long-term small-to-moderate ash eruptions beginning in that year were later accompanied by lava-dome growth and pyroclastic flows that forced evacuation of the southern half of the island and ultimately destroyed the capital city of Plymouth, causing major social and economic disruption.

Sources: Washington Volcanic Ash Advisory Center (VAAC), Associated Press, Montserrat Volcano Observatory (MVO), Antigua Sun [Original URL no longer exists 1/2017], Radio Jamaica