Report on Soufriere Hills (United Kingdom) — 14 February-20 February 2001
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 14 February-20 February 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, 14 February-20 February 2001. Smithsonian Institution and US Geological Survey.
16.72°N, 62.18°W; summit elev. 915 m
All times are local (unless otherwise noted)
The MVO reported that during 9 to 16 February activity at the Soufrière Hills volcano fluctuated markedly, as lava dome growth continued. The level of seismic activity varied considerably, with a pronounced peak in activity during 10 and 11 February, which was followed by a gradual decrease in rockfall activity. Observations revealed that the two large spines that were visible on the volcano's summit the previous week had collapsed, and a large lobe had formed on the eastern face of the dome above Tar River. New pyroclastic-flow deposits were observed down the Tar River extending to the old coastline. Small-volume deposits were observed down White River to the S and in Tuitt's Ghaut to the NE. The Washington VAAC reported that throughout the week low-level ash clouds (up to ~2.1 km a.s.l.), presumably produced by rockfalls, were visible on GOES-8 imagery.
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.