Volcanic activity at Soufriere Hills remained at a high level, similar to the previous week. Elevated activity on 2 December produced pyroclastic flows in the Tar River Valley that reached the sea. The flows originated in several places along the E face of the new lava dome. Two small pyroclastic flows also occurred in the upper reaches of White River, originating from the old dome material closest to Chances Peak. Short periods of pyroclastic-flow activity occurred in both valleys on 4 and 6 December. On 8 December a low-level plume of ash (~1.8 km a.s.l.) was visible extending ~140 km to the W of the volcano.

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: Montserrat Volcano Observatory (MVO), Washington Volcanic Ash Advisory Center (VAAC)