Report on Soufriere Hills (United Kingdom) — 18 December-24 December 2002
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 18 December-24 December 2002
Managing Editor: Gari Mayberry
Please cite this report as:
Global Volcanism Program, 2002. Report on Soufriere Hills (United Kingdom). In: Mayberry, G (ed.), Weekly Volcanic Activity Report, 18 December-24 December 2002. Smithsonian Institution and US Geological Survey.
16.72°N, 62.18°W; summit elev. 915 m
All times are local (unless otherwise noted)
Volcanic activity at Soufrière Hills increased to a high level during 13-20 December. Activity generally remained at moderate levels during the first half of the report period, but increased to a high level over the last 3 days. Spectacular incandescence of the dome was observed on most nights. The active extruded lobe on the dome's N side continued to grow, producing numerous rockfalls and small-to-moderate pyroclastic flows. Most of the activity was concentrated on the NNE and N flanks, producing numerous pyroclastic flows in White's Ghaut, the Tar River Valley and Tuitt's Ghaut. Pyroclastic flows and rockfalls also traveled down the W and NW flanks. On 19 December mudflows occurred in White River, Tar River Valley and Fort Ghaut.
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.