Report on Soufriere Hills (United Kingdom) — 3 February-9 February 2010
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 3 February-9 February 2010
Managing Editor: Sally Kuhn Sennert
Please cite this report as:
Global Volcanism Program, 2010. Report on Soufriere Hills (United Kingdom). In: Sennert, S K (ed.), Weekly Volcanic Activity Report, 3 February-9 February 2010. Smithsonian Institution and US Geological Survey.
16.72°N, 62.18°W; summit elev. 915 m
All times are local (unless otherwise noted)
MVO reported that during 29 January-5 February activity from the Soufrière Hills lava dome was variable as the lava dome continued to grow. Cycles of vigorous ash venting, rockfalls, and pyroclastic flows occurred every seven to twelve hours. Pyroclastic flows traveled mostly W down Gages into Spring Ghaut, as far as 3 km, but also occurred in Whites Ghaut to the NE. Rockfall activity was abundant on the N flank. On 4 February, ash fell across NW Montserrat. Observations the next day revealed that the central W part of the lava dome had grown and was 1,070 m a.s.l.
Pyroclastic flows following a Vulcanian explosion on 5 February traveled W, reaching Plymouth and spreading 500 m across the sea. Pyroclastic flows also traveled as far as 2 km NW down Tyers Ghaut and NE down Whites Ghaut. An ash plume rose to an altitude of 6.4 km (21,000 ft) a.s.l. A small Vulcanian explosion on 8 February generated pyroclastic flows that mostly traveled W down Gages Valley. Small pyroclastic surges observed using a thermal camera descended the N flanks. An ash plume rose to an altitude of 4.6 km (15,000 ft) a.s.l. and drifted E and ENE. Ashfall was reported in NW Montserrat and in SW Antigua, 50 km NW. The Hazard Level remained at 4.
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.