Report on Soufriere Hills (United Kingdom) — 24 April-30 April 2002
Smithsonian / US Geological Survey Weekly Volcanic Activity Report,
24 April-30 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, 24 April-30 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)
Volcanic activity at Soufrière Hills was at high levels during 19-26 April. The direction of lava-dome growth switched during the earlier part of the week, becoming focussed on the southeastern part of the dome complex. Rockfalls traveled down the SE flank of the dome almost continuously. The lobe on the SE portion of the dome reached 1,041 m a.s.l. and the NE lobe, which had been highly active the previous two weeks, stagnated at a height of 1,020 m a.s.l. Fluctuations in SO2 emission rates appeared to reflect variations in the intensity of rockfall activity.
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)