The Soufriere Hills volcano, Montserrat, West Indies, has undergone a series of dome growth and collapse events since the eruption began in 1995. Over 90% of the pyroclastic material produced has been deposited into the ocean. Sampling of these submarine deposits reveals that the pyroclastic flows mix rapidly and violently with the water as they enter the sea. The coarse components (pebbles to boulders) are deposited proximally from dense basal slurries to form steep-sided, near-linear ridges that intercalate to form a submarine fan. The finer ash-grade components are mixed into the overlying water column to form turbidity currents that flow over distances > 30 km from the source. The total volume of pyroclastic material off the east coast of Montserrat exceeds 280 X 106 m(3), with 65% deposited in proximal lobes and 35% deposited as distal turbidites.
Univ Bristol, Dept Earth Sci, Bristol BS8 1RJ, Avon, England; CNRS, F-75252 Paris 05, France; Inst Phys Globe, F-75252 Paris 05, France; Univ W Indies, Seism Res Unit, St Augustine, Trinid & Tobago; Univ Plymouth, Sch Earth Ocean & Environm Sci, Plymouth PL4 8AA, Devon, England; British Antarctic Survey, NERC, Cambridge CB3 0ET, England; British Geol Survey, Nat Environm Res Council, Kingsley Dunham Ctr, Nottingham NG12 5GG, EnglandArticleEnglish