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Report on Soufriere Hills (United Kingdom) — 10 March-16 March 2004

Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 10 March-16 March 2004
Managing Editor: Gari Mayberry

Please cite this report as:

Global Volcanism Program, 2004. Report on Soufriere Hills (United Kingdom). In: Mayberry, G (ed.), Weekly Volcanic Activity Report, 10 March-16 March 2004. Smithsonian Institution and US Geological Survey.

Volcano Profile |  Weekly Report (10 March-16 March 2004)

Soufriere Hills

United Kingdom

16.72°N, 62.18°W; summit elev. 915 m

All times are local (unless otherwise noted)

Following a lava-dome collapse at Soufrière Hills on 3 March, activity was relatively lower during 5-12 March. Around 0330 on 10 March a short period of elevated seismic activity lasting around 10-20 minutes occurred. Later that day fresh pyroclastic-flow deposits were observed toward the NE in the upper reaches of the Tar River Valley. Several short periods of ash-and-steam venting were observed during 9-12 March, with ash deposited as far N as St. Georges Hill. The sulfur-dioxide flux peaked at 1,250 metric tons on 9 March.

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.

Sources: Montserrat Volcano Observatory (MVO), Washington Volcanic Ash Advisory Center (VAAC)