MVO reported that during 4-18 April the lava dome at Soufrière Hills changed very little, based on measurable parameters. Overflights on 9 and 16 April revealed that the E side of the lava dome continued to erode and exposed more resistant solid material below. A small pyroclastic flow traveled 500 m down the E flank on 10 April and generated a small ash plume that quickly dissipated to the W. Two more pyroclastic flows were observed on 16 April. The larger flow traveled 1 km down the E flank and was followed by relatively strong degassing. The Alert Level remained elevated at 4 (on a scale of 0-5).

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)