Report on Soufriere Hills (United Kingdom) — 27 March-2 April 2002
Smithsonian / US Geological Survey Weekly Volcanic Activity Report,
27 March-2 April 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, 27 March-2 April 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 23-29 March, the level of volcanism remained high at Soufrière Hills. Lava-dome growth continued to be focused to the E of the summit region, producing numerous rockfalls and small pyroclastic flows into the upper portions of the Tar River Valley. Minor amounts of rockfall debris from the NE flank of the dome spilled into the head of Tuit's Ghaut. During the first half of the report period, ash from venting, rockfalls, and pyroclastic flows drifted W over Plymouth and the Richmond Hill area. Later in the week, ash drifted to the NW and N and was deposited in populated areas. SO2 emission rates remained high (1,110-1,200 metric tons per day).
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.
Sources: Montserrat Volcano Observatory (MVO), Washington Volcanic Ash Advisory Center (VAAC)