Report on Soufriere Hills (United Kingdom) — 15 October-21 October 2008
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 15 October-21 October 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, 15 October-21 October 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 10-17 October, the activity level at the Soufrière Hills lava dome was low and consisted mainly of mudflows. Mudflows were particularly numerous during 15-16 October due to the passage of hurricane Omar to the N. Erosion of the talus slope on the E side of the lava dome also significantly increased and as a result, a large gap in the talus was created that exposed the core of the dome. During an overflight on 17 October, the lava dome was seen vigorous steaming and thermal imagery revealed that the hottest temperatures were associated with the new Gages vent formed in August. The Hazard Level remained at 3.
Based on analysis of satellite imagery and information from MVO, the Washington VAAC reported that on 20 October a pyroclastic flow or a rockfall generated a plume that drifted about 45 km W and was detaching from the island.
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.