During 13-20 May, the seismic network at Soufrière Hills recorded 18 volcano-tectonic earthquakes (most occurred on 17 May) and 3 hybrid earthquakes. Steam venting that began on the NW side of the crater on 15 April continued. The daily recorded sulfur-dioxide flux varied from a low of 222 metric tons per day (t/d) on 16 May to a maximum of 363 t/d on 14 May, with an average of 286 t/d. This was below the eruption's long-term average of 500 t/d.

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)