Report on Soufriere Hills (United Kingdom) — 5 November-11 November 2008
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 5 November-11 November 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, 5 November-11 November 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 31 October-7 November the activity level at the Soufrière Hills lava dome was low and there was no evidence of lava extrusion. Photographs taken during an aerial inspection of the dome confirmed that the SE side was a very high (150-200 m) free-standing cliff not supported by talus. Erosion continued on the NE side and at the E and SE bases of the dome, further deepening the moat in the talus around the dome. The morphology of the top of the dome was complex and highly irregular with multiple steep lava protrusions separated by areas of lower elevation. Several spines and a bulbous shear lobe were visible. 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.