Report on Soufriere Hills (United Kingdom) — 30 December-5 January 2010
Smithsonian Institution / US Geological Survey
Weekly Volcanic Activity Report, 30 December-5 January 2010
Managing Editor: Sally Sennert.
Please cite this report as:
Global Volcanism Program, 2009. Report on Soufriere Hills (United Kingdom) (Sennert, S, ed.). Weekly Volcanic Activity Report, 30 December-5 January 2010. 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 during 24-31 December activity from the Soufrière Hills lava dome continued at a high level. Cycles of increased activity associated with vigorous ash venting and pyroclastic flows occurred every six to eight hours. Audible rockfalls, roaring, and occasional thunder were noted during the most intense events. Frequent pyroclastic flows traveled N down Whites Ghaut, Farrells plain, and Tyers Ghaut. Pyroclastic flows also traveled W down Gages Valley into Spring Ghaut, and occasionally to the S in Gingoes Ghaut. On 29 December several pyroclastic flows traveled 2.5 km, reaching Dyers village. A comparison of photographs from 30 December and 2 January revealed that the lava dome morphology had changed rapidly, with a significant addition of lava on the N side. The additional area of growth was approximately 60 m high and 100 m wide. The Hazard Level remained at 4.
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.