MAGMA PRODUCTION AND GROWTH OF THE LAVA DOME OF THE SOUFRIERE HILLS VOLCANO, MONTSERRAT, WEST-INDIES - NOVEMBER 1995 TO DECEMBER 1997

From November 1995 to December 1997 a total volume of 246 x 10(6) (DRE ) m(3) of andesite magma erupted, partitioned into 93 x 10(6) m3 of th e dome, 125 x 10(6); m3 of pyroclastic flow deposits and 28 x 10(6) m( 3) of explosive ejecta. In the first 11 weeks magma discharge rate was low (0.5 m(3)/s). From February 1996 to May 1997 discharge rates have averaged 2.1 m(3)/s, but have fluctuated significantly and have incre ased with time: Three pulses lasting a few months can he recognised wi th discharge rates reaching 3 to 8 m(3)/s. Short term pulsations in gr owth lasting a few days reach discharge rates of over 10 and there are periods of days to a few weeks when dome growth is < 0.5 m(3)/s. Disc harge rate increased from May 1997 with an average rate of: 7.5 m(3)/s to Decemher 1997. The observations indicate an open magmatic system.