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Report on Soufriere Hills (United Kingdom) — 7 March-13 March 2007

Soufriere Hills

Smithsonian Institution / US Geological Survey
Weekly Volcanic Activity Report, 7 March-13 March 2007
Managing Editor: Sally Sennert.

Please cite this report as:

Global Volcanism Program, 2007. Report on Soufriere Hills (United Kingdom) (Sennert, S, ed.). Weekly Volcanic Activity Report, 7 March-13 March 2007. Smithsonian Institution and US Geological Survey.

Weekly Report (7 March-13 March 2007)

Soufriere Hills

United Kingdom

16.72°N, 62.18°W; summit elev. 915 m

All times are local (unless otherwise noted)

During 2-9 March, lava-dome growth at Soufrière Hills continued and was concentrated on an E-facing lobe topped with blocky, spine-like protrusions. Rockfalls affected the E and NE flanks. Pyroclastic flows traveled 2 km and were confined E in the Tar River Valley. Heightened pyroclastic activity on 7 March resulted in an ash plume that rose to an estimated 2.4 km (8,000 ft) a.s.l. and drifted W. On 11 March, a pyroclastic flow traveled down the NE flank into White's Ghaut. On 12 March, a large, blocky spine leaned steeply towards the NE.

Based on satellite imagery, San Juan Weather Forecast Agency (WFO), and pilot reports, the Washington VAAC reported light ash and haze over several Caribbean islands during 7-10 March. Based on news articles, the presence of ash and dust from the Sahara Desert prompted some airlines in Puerto Rico to delay and cancel flights on 10 March.

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), Associated Press, Washington Volcanic Ash Advisory Center (VAAC)