Place : Chain Cascades , Washington.
Description : The 1980-03-27, after more than one century of rest, the St-Helen mount awoke. Following a strong seism, all the northern side of the volcano broke down and caused a remains avalanche of 2 km3.
Before its last eruption which took place the 18/05/1980, it was 9680 feet (2950 m) height. The eruption made lose 1310 feet (400 m) of altitude to the origin height (8360 feet - 2549 m) which dug a broad crater (or caldeira) as a horseshoe, deep of 1970 feet (600 m).