Report on Soufriere Hills (United Kingdom) — 1 February-7 February 2006
Smithsonian / US Geological Survey Weekly Volcanic Activity Report,
1 February-7 February 2006
Managing Editor: Sally Kuhn Sennert
Please cite this report as:
Global Volcanism Program, 2006. Report on Soufriere Hills (United Kingdom). In: Sennert, S K (ed.), Weekly Volcanic Activity Report, 1 February-7 February 2006. 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 elevated levels during 27 January to 3 February. Images taken by a remote camera at the beginning of the report period indicated that the lava dome continued to grow over a broad sector extending from the SW around to the NE. A pair of spines was observed on the SE side of the dome on 29 January, although both these and the fin-like structures (relatively thin, vertical planar spines) on the SE flank of the dome collapsed during the report period. Numerous small rockfalls were observed emanating from the S,E, and NE flanks of the lava dome, adding to the talus in the upper reaches of the Tar River Valley. Continued lava-dome growth was observed, particularly at the southern end, which was higher than the northern end of the dome. The sulfur-dioxide flux averaged 594 metric tons per day.
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.