Report on Soufriere Hills (United Kingdom) — 18 January-24 January 2006
Smithsonian / US Geological Survey Weekly Volcanic Activity Report,
18 January-24 January 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, 18 January-24 January 2006. Smithsonian Institution and US Geological Survey.
16.72°N, 62.18°W; summit elev. 915 m
All times are local (unless otherwise noted)
Activity at Soufrière Hills remained elevated during 13-20 January 2006. The seismic network recorded 61 rockfall signals, 17 long-period earthquakes, and 15 long-period rockfall signals. Measured sulfur dioxide fluxes ranged between 350 and 1,160 metric tons/day (t/d); the weekly average was 767 t/d. Images taken by the remote camera on Perches Mountain show that the dome continued to grow over a broad sector extending from the SW around to the NE. A central spine was first observed on 17 January when cloud cleared briefly from the. Continuing small rockfalls from the S, E, and NE flanks of the dome are visible at, and are adding to the talus in the upper reaches of the Tar River valley.
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.