Report on Soufriere Hills (United Kingdom) — 11 October-17 October 2006
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 11 October-17 October 2006
Managing Editor: Sally Kuhn Sennert
Please cite this report as:
Global Volcanism Program, 2006. Report on Soufriere Hills (United Kingdom). In: Sennert, S K (ed.), Weekly Volcanic Activity Report, 11 October-17 October 2006. Smithsonian Institution and US Geological Survey.
16.72°N, 62.18°W; summit elev. 915 m
All times are local (unless otherwise noted)
During 6-13 October, lava-dome growth at Soufrière Hills continued and was concentrated on the NE part of the edifice. The vents just inside Gage's wall and on the summit of the dome periodically produced both ash and gas. Heavy rainfall on 9 and 11-12 October resulted in mudflow activity in all drainage systems. Ash fell in the N part of the island.
Based on information from the MVO, pilot reports, and the Piarco MWO, the Washington VAAC reported that continuous ash and gas emissions during 10-17 October produced plumes that drifted NW, N, and NE. Plumes reached altitudes of 2.1-4.6 km (7,000-15,000 ft) a.s.l. A minor pyroclastic flow on 16 October produced an ash plume that drifted NNE. A hotspot was detected on satellite imagery from 12 to 17 October.
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.