Report on Soufriere Hills (United Kingdom) — 8 October-14 October 2008
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 8 October-14 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, 8 October-14 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 3-10 October, the activity level at the Soufrière Hills lava dome was slightly higher than the previous week and consisted mainly of rockfalls and mudflows. As a result of slow and continuous erosion of the lower part of the dome, rockfalls occurred on both the W side in the gully over Gages Wall and on the E side in the Tar River Valley. The rate of lava extrusion had declined significantly. Thermal imagery captured during an overflight on 8 October revealed that a major E-W oriented fracture in the dome, aligned with the Gages Valley and extending vertically over a few tens of meters, was associated with very elevated temperatures. Several other very hot areas were also detected. These areas were visible using binoculars from MVO later that night. 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.