Report on Soufriere Hills (United Kingdom) — 16 January-22 January 2002
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 16 January-22 January 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, 16 January-22 January 2002. Smithsonian Institution and US Geological Survey.
16.72°N, 62.18°W; summit elev. 915 m
All times are local (unless otherwise noted)
During 11-18 January volcanic activity was slightly lower at Soufrière Hills compared to the previous week. Growth appeared to be concentrated on the lava dome's E flank, where intense rockfall activity and small pyroclastic flows continued. On 12 January a long-period earthquake was accompanied by an ash plume that rose to ~2.5 km above the dome. This event was followed by a series of pyroclastic flows that traveled down the Tar River Valley to the sea. A large steam plume was generated when the pyroclastic flows entered the sea. The steam plume and a dense ash cloud drifted W over the Plymouth, Richmond Hill, and Fox's Bay area. Minor mudflows occurred in the Belham Valley on the morning of 18 January.
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.