Report on Soufriere Hills (United Kingdom) — 30 June-6 July 2010
Smithsonian / US Geological Survey Weekly Volcanic Activity Report,
30 June-6 July 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, 30 June-6 July 2010. Smithsonian Institution and US Geological Survey.
16.72°N, 62.18°W; summit elev. 915 m
All times are local (unless otherwise noted)
On 28 June, MVO reported that for the first time since February 2010 ash venting from the Soufrière Hills lava dome was observed and caused light ashfall in several areas across Montserrat. Ash venting began on 25 June and was coincident with small swarms of volcano-tectonic earthquakes on 23 and 25 June, although with no other discernable associated seismicity. Observations initially from MVO staff and during a later overflight indicated that the ash venting occurred from inside the collapse scar (near the N rim of English's crater) and from the S part of the summit crater that had formed on 11 February. On the nights of 25 and 26 June audible roaring was heard from several locations on the island. Ash venting diminished on 28 June. The Hazard Level remained at 3.
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.