Magma production and growth of the lava dome of the Soufriere Hills Volcano, Montserrat, West Indies: November 1995 to December 1997

Abstract

From November 1995 to December 1997 a total volume of 246 × 106 (DRE) m3 of andesite magma erupted, partitioned into 93 × 106 m3 of the dome, 125 × 106 m3 of pyroclastic flow deposits and 28 × 106 m3 of explosive ejecta. In the first 11 weeks magma discharge rate was low (0.5 m3/s). From February 1996 to May 1997 discharge rates have averaged 2.1 m3/s, but have flucutated significantly and have increased with time. Three pulses lasting a few months can be recognised with discharge rates reaching 3 to 8 m3/s. Short term pulsations in growth lasting a few days reach discharge rates of over 10 m3/s and there are periods of days to a few weeks when dome growth is <0.5 m3/s. Discharge rate increased from May 1997 with an average rate of 7.5 m3/s to December 1997. The observations indicate an open magmatic system.