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Report on Soufriere Hills (United Kingdom) — 8 November-14 November 2006

Soufriere Hills

Smithsonian Institution / US Geological Survey
Weekly Volcanic Activity Report, 8 November-14 November 2006
Managing Editor: Sally Sennert.

Please cite this report as:

Global Volcanism Program, 2006. Report on Soufriere Hills (United Kingdom) (Sennert, S, ed.). Weekly Volcanic Activity Report, 8 November-14 November 2006. Smithsonian Institution and US Geological Survey.

Weekly Report (8 November-14 November 2006)

Soufriere Hills

United Kingdom

16.72°N, 62.18°W; summit elev. 915 m

All times are local (unless otherwise noted)

During 3-10 November, lava-dome growth at Soufrière Hills continued and was concentrated on the E part of the edifice. Rockfalls and small pyroclastic flows originating from a large active lobe on the NE sector of the dome traveled down the SW and NE flanks. High-temperature rockfalls from the NNE sector were deposited on a ridge between Tuitt's and White's Ghauts. Sulfur dioxide measurements were higher than previous weeks, but still within the long-term average range.

Based on information from the MVO, satellite imagery, and pilot reports, the Washington VAAC reported continuous ash-and-gas emissions during 8-14 November. Resulting plumes drifted mainly W and S. A hotspot was detected on satellite imagery during 9-13 November.

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)