Report on Soufriere Hills (United Kingdom) — 10 March-16 March 2010
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 10 March-16 March 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 March-16 March 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 heavy rains during 5-12 March caused vigorous steaming from hot deposits emplaced after part of the Soufrière Hills lava dome collapsed on 11 February. Geysers were visible at Trants near the old Bramble airport, about 5 km NE, along with ash and steam ejections. Lahars descended multiple drainages around the volcano. Cooled lava shed from the dome on 8 and 9 March due to the heavy rains caused a series of pyroclastic flows to travel W down Gages Valley on 9 March, as far as 2 km. Ashfall from the pyroclastic flows was noted in NE Montserrat. There was no evidence of fresh lava extrusion. The Hazard Level remained at 3.
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.