Report on Soufriere Hills (United Kingdom) — 3 September-9 September 2008
Smithsonian / US Geological Survey Weekly Volcanic Activity Report,
3 September-9 September 2008
Managing Editor: Sally Kuhn Sennert
Please cite this report as:
Global Volcanism Program, 2008. Report on Soufriere Hills (United Kingdom). In: Sennert, S K (ed.), Weekly Volcanic Activity Report, 3 September-9 September 2008. 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 29 August-5 September, data suggested that the W side of the Soufrière Hills lava dome continued to grow. Lahars and rockfalls dominated the activity. Lahars likely descended the Tar River valley on 29 and 31 August. On 1 September, a lahar descended the Belham River valley to the NW; the event lasted approximately 50 minutes. A new vent on the NW part of the lava dome, a little further N of the previous Gages vent, was observed during an overflight on 4 September. The smell of volcanic gases was occasionally noticed when the wind blew N and NE. The Hazard Level remained at 3.
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.