Report on Soufriere Hills (United Kingdom) — 31 May-6 June 2006
Smithsonian Institution / US Geological Survey
Weekly Volcanic Activity Report, 31 May-6 June 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, 31 May-6 June 2006. Smithsonian Institution and US Geological Survey.
16.72°N, 62.18°W; summit elev. 915 m
All times are local (unless otherwise noted)
During 26 May to 2 June, the Soufrière Hills lava dome continued to grow at a high rate of 10 cubic meters per second (average growth rate during January-April was 6 cubic meters per second). Numerous rockfalls and vigorous ash venting occurred from a vent to the W of the lava dome. A pilot reported that a small ash plume extended NW on 31 May. Ash plumes extending W and NW were visible on satellite imagery during 1-5 June and reached a maximum altitude of 2.7 km (9,000 ft) a.s.l. on 3 and 5 June. An ash plume on 4 June extended N of Puerto Rico.
According to the Washington VAAC, ash-plume emissions continued during 24-30 May. On 24 May, emission of small volumes of gas and thin ash plumes continued and drifted W and SW. A pilot near St. Croix (NW) reported that the ash/haze layer reached an altitude of 1.5 km (5,000 ft) a.s.l. Ashfall was reported at San Juan (NW) airport. During 25-30 May, ash plumes reached an altitude of 4.6 km (15,000 ft) a.s.l. and drifted W and NW. On 24-26 May, a hot spot was visible on infrared satellite imagery.
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.