Report on Soufriere Hills (United Kingdom) — 22 February-28 February 2006
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 22 February-28 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, 22 February-28 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)
Photographs of Soufrière Hills taken during 17-24 February confirmed ongoing lava-dome growth. The newest lobe, which appeared on the dome's NW side on 10 February, continued to grow on all sides. It appeared to have filled in the gap between the lava dome and the N and W crater walls. It also grew significantly to the E, overtopping the older lobe by the end of the report period. After 22 February, incandescent rockfalls were visible at night, coursing down the N,E, and SW sides of the dome and into the Tar River Valley. The sulfur-dioxide flux was low, with an average of 286 metric tons per day.
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.