PHREATIC ERUPTION AT KARTHALA VOLCANO (GR AND-COMORO) IN JULY 1991

The July 11th 1991 phreatic eruption of Karthala volcano was the first seismo-volcanic event since the establishment of a survey network. Th is purely phreatic eruptive phase was heralded by an increase in seism icity from April to June 1991, followed by a sharp seismic crisis asso ciated with inflation of the caldera between June 30th and the day of the explosion. Tephra from the explosion covered a large part oi the c aldera floor; the resultant explosion crater was filled by a lake. Dat a collected during this eruption lead to a better understanding of phr eatic activity on basaltic shield volcanoes.