Report on Soufriere Hills (United Kingdom) — 2 May-8 May 2001
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 2 May-8 May 2001
Managing Editor: Gari Mayberry
Please cite this report as:
Global Volcanism Program, 2001. Report on Soufriere Hills (United Kingdom). In: Mayberry, G (ed.), Weekly Volcanic Activity Report, 2 May-8 May 2001. 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 27 April- 4 May volcanic activity at Soufrière Hills remained low, although there was a slight increase during 28 and 29 April. An increase in rockfall activity occurred from 28 April to 1 May; there were 16 rockfalls on 29 April, 34 on 30 April, and 15 on 1 May. For the previous six weeks there had usually been less than 10 rockfalls per day. The increase in activity may have been due to heavy rain on 29 and 30 April. A very small amount of growth occurred on the S side of the lava dome, which was accompanied by occasional ash venting. Sulfur dioxide flux remained low. MVO warned that although activity is low, dangerous conditions can develop quickly and in the event of heavy rain the Belham Valley to the NE of the volcano should be avoided due to the possibility of mudflows.
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.