Report on Soufriere Hills (United Kingdom) — 29 October-4 November 2008
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 29 October-4 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, 29 October-4 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 24-31 October the activity level at the Soufrière Hills lava dome was low. There was no evidence of lava extrusion. On 26 October, observers aboard a fixed-wing aircraft confirmed that a few small pyroclastic flows traveled about 1.5 km down the Tar River Valley. Erosion down several V-shaped chutes continued at the E and SE bases of the dome further deepened the moat in the talus around the dome. Ongoing erosion of the talus pile on the W flank resulted in a well-incised network of gullies leading into the White River. On 27 October, a small pyroclastic flow seen from MVO traveled about 1 km down the Tar River Valley and generated a small ash plume that drifted over unpopulated areas to the W and SW, towards Plymouth. 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.