Report on Soufriere Hills (United Kingdom) — 10 February-16 February 2010
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 10 February-16 February 2010
Managing Editor: Sally Kuhn Sennert
Please cite this report as:
Global Volcanism Program, 2010. Report on Soufriere Hills (United Kingdom). In: Sennert, S K (ed.), Weekly Volcanic Activity Report, 10 February-16 February 2010. Smithsonian Institution and US Geological Survey.
16.72°N, 62.18°W; summit elev. 915 m
All times are local (unless otherwise noted)
MVO reported that during 5-12 February activity from the Soufrière Hills lava dome increased significantly. Activity was concentrated on the W side of the lava dome during the first part of the week then shifted to the N side on 9 February.
On 11 February part of the lava dome collapsed leaving a large collapse scar on the NE flank. Pyroclastic flows traveled NE and then, along with pyroclastic surges, across the sea at several places on the E side of Montserrat. Pyroclastic flow deposits covered several hundred meters of the coastline near the old Bramble airport, about 5 km NE. Pyroclastic flows also traveled NW into Tyers Ghaut and down the Belham valley as far a Cork Hill, 4 km NW. An ash plume rose to an altitude of 15.2 km (50,000 ft) a.s.l. and drifted E and then SE. Ashfall occurred in NE Montserrat, SW Antigua (50 km NW), Guadeloupe (65 km SE), and Dominica (145 km SE). According to news articles, flights in and out of the region were temporarily suspended due to the ash plumes.
Geologic Background. 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.