During 18-25 January, volcanic activity remained high at Soufrière Hills. Continued growth on the E side of the lava dome produced numerous rockfalls and small pyroclastic flows down the volcano's E flank. On the 21st the dome was crowned by a large 40- to 50-m tall spine inclined steeply upwards towards the E. While the number of rockfalls gradually decreased over the previous 3 weeks, their size and duration significantly increased during the report period, exceeding total energy rates during the past few months.

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.

Source: Montserrat Volcano Observatory (MVO)