During 8-15 March, the level of volcanic activity at Soufrière Hills was higher than during the previous week. Activity began to increase on the 8th, remaining at elevated levels for the remainder of the report period. Lava-dome growth continued to be concentrated towards the E, sending rockfalls and small pyroclastic flows to the upper portions of the Tar River Valley. The summit of the dome had a generally spiny appearance and minor episodes of ash venting occurred from it. Incandescence was visible at the summit during the night. SO2 emission rates were higher than average during the week (430 to 860 metric tons per day).

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), Montserrat Volcano Observatory (MVO)