Report on Soufriere Hills (United Kingdom) — 13 January-19 January 2010
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 13 January-19 January 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, 13 January-19 January 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 8-15 January activity from the Soufrière Hills lava dome increased significantly. One explosion on 8 January and two on 10 January generated ash plumes that rose to altitudes of 5.5-7.6 km (18,000-25,000 ft) a.s.l. Ash fell in occupied areas to the NW, along with lapilli fall on 10 January. The explosions occurred from an area on the NE side of the volcano. Pyroclastic flows from column collapses moved rapidly NE (down Whites Bottom and Tuitts Ghaut), NW (down Tyers Ghaut and Belham Valley), W (down Gages Ghaut), and the SE (down the Tar River Valley). After the explosions activity decreased until 12 January, when cycles of increased numbers of rockfalls, pyroclastic flows, and ash venting were noted.
Observations during 8-15 January revealed that lava-dome growth resumed at the top, central part of the dome. On 18 January, a partial lava-dome collapse generated a pyroclastic flow that traveled W down Gages Valley, into Spring Ghaut, and then WSW down Aymers Ghaut, reaching the sea. Ash plumes rose to an altitude of 3 km (10,000 ft) a.s.l. and drifted W. Smoke from burning houses in Kinsale was visible after the event. 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.