Report on Soufriere Hills (United Kingdom) — 4 April-10 April 2012
Smithsonian / US Geological Survey Weekly Volcanic Activity Report,
4 April-10 April 2012
Managing Editor: Sally Kuhn Sennert
Please cite this report as:
Global Volcanism Program, 2012. Report on Soufriere Hills (United Kingdom). In: Sennert, S K (ed.), Weekly Volcanic Activity Report, 4 April-10 April 2012. 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 30 March-6 April activity at the Soufrière Hills lava dome was generally at a low level and no ash-venting episodes had been detected since 23 March. The average sulfur dioxide emission rate measured during the week was 529 tonnes per day with a minimum of 200 and a maximum of 1,033. Scientists aboard a helicopter overflight on 4 April observed a new vent which had formed on 23 March; it was 30-50 m across and on the W side of the crater floor. The Hazard Level remained at 2.
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.