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Report on Soufriere Hills (United Kingdom) — 21 February-27 February 2001

Soufriere Hills

Smithsonian / US Geological Survey Weekly Volcanic Activity Report,
21 February-27 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, 21 February-27 February 2001. Smithsonian Institution and US Geological Survey.

Weekly Report (21 February-27 February 2001)

Soufriere Hills

United Kingdom

16.72°N, 62.18°W; summit elev. 915 m

All times are local (unless otherwise noted)

The MVO reported that during 16 to 23 February activity at the Soufrière Hills volcano was similar to the previous week, as lava dome growth continued. The level of seismic activity was also comparable to last week. A large stubby spine was visible in the S part of the summit area on 22 February. The top of the spine was measured as 1,068 m a.s.l. and the main summit area was about 1,030 m a.s.l. New pyroclastic-flow deposits were emplaced towards the E, down Tar River as far as the old coastline, and to the S in the White River Valley as far as 50 m short of the coast on the new pyroclastic delta. Many rockfalls descended the NE flank of the dome into the upper reaches of Tuitt's Ghaut. The Washington VAAC reported that throughout the week low-level ash clouds (up to ~3.4 km a.s.l.), presumably produced by rockfalls, and periodic hot-spot activity were visible on GOES-8 imagery.

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.

Sources: Montserrat Volcano Observatory (MVO), Washington Volcanic Ash Advisory Center (VAAC)