Report on Soufriere Hills (United Kingdom) — 13 August-19 August 2008
Smithsonian / US Geological Survey Weekly Volcanic Activity Report,
13 August-19 August 2008
Managing Editor: Sally Kuhn Sennert
Please cite this report as:
Global Volcanism Program, 2008. Report on Soufriere Hills (United Kingdom). In: Sennert, S K (ed.), Weekly Volcanic Activity Report, 13 August-19 August 2008. Smithsonian Institution and US Geological Survey.
16.72°N, 62.18°W; summit elev. 915 m
All times are local (unless otherwise noted)
MVO reported that new lava extrusion from Soufrière Hills started from the W side of the lava dome sometime between the 28 July lava-dome collapse event and 8 August, when a new channel of fresh rockfall material was seen below Gages Wall. Cloud cover often prevented visual observations. During 8-15 August, seismicity and the rate of lava extrusion were generally low and sulfur dioxide emissions were elevated. On 14 August the W side of the dome was visible and the explosion crater that was generated on 28 July was almost completely filled with new lava. Lava spilled over the lower and W side of the crater and generated rockfalls below Gages Wall that were observed and heard from St. George's Hill. During 14-15 August, the scent of volcanic gases was noticeable at times in inhabited areas of Montserrat. The Hazard Level was 3.
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.