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Report on Soufriere Hills (United Kingdom) — 14 February-20 February 2007

Soufriere Hills

Smithsonian Institution / US Geological Survey
Weekly Volcanic Activity Report, 14 February-20 February 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, 14 February-20 February 2007. Smithsonian Institution and US Geological Survey.

Weekly Report (14 February-20 February 2007)

Soufriere Hills

United Kingdom

16.72°N, 62.18°W; summit elev. 915 m

All times are local (unless otherwise noted)

During 9-16 February, seismic activity at Soufrière Hills was slightly elevated as compared to previous weeks. The lava-dome volume was estimated at 200 million cubic meters based on recent measurements from LIDAR data. Previous measurements over-estimated the lava-dome volume due to the perceived location of the dome and the lack of data from inside the crater. The height of the dome was about 1060 m a.s.l. During 17-18 February, rockfalls and small pyroclastic flows traveled W down Gages Valley and E down Tar River Valley. Incandescence was seen from the E and N sides of the dome. Rockfalls continued on 19 and 20 February.

Based on satellite data and information from the MVO, the Washington VAAC reported continuous emissions during 14-20 February. Resultant plumes rose to altitudes of km (5,000-8,000 ft) a.s.l. and drifted mainly NW, W, and S. A thermal anomaly in the crater was detected on satellite imagery.

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