Report on Soufriere Hills (United Kingdom) — 21 August-27 August 2002
Smithsonian / US Geological Survey Weekly Volcanic Activity Report,
21 August-27 August 2002
Managing Editor: Gari Mayberry
Please cite this report as:
Global Volcanism Program, 2002. Report on Soufriere Hills (United Kingdom). In: Mayberry, G (ed.), Weekly Volcanic Activity Report, 21 August-27 August 2002. Smithsonian Institution and US Geological Survey.
16.72°N, 62.18°W; summit elev. 915 m
All times are local (unless otherwise noted)
Volcanic and seismic activity at Soufrière Hills were at moderate levels during 16-23 August. Lava-dome growth continued to be focused on the N side of the dome complex and rockfall talus continued to accumulate to the N in the upper reaches of Tuitt's Ghaut. In addition, there were overspills of talus from the northern side of the Tar River Valley into the two tributaries of White's Ghaut. Talus also slowly accumulated in the notch in the NW sector of the old dome that leads towards Tyre's Ghaut. During intense rainfall in the early hours of Wednesday morning, a small collapse occurred in the Tar River Valley. SO2 flux remained at moderate levels.
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.