Washington State: The main explosion happened at 8:32 a.m. PDT. 57 people died, 210 square miles of wilderness were destroyed.

Volcanic activity had first been recorded on March 20, 1980, and on the 27th March steam and ash were emitted through St Helen's crater and vents.

The explosion was triggered by an earthquake of about 5.0 on the Richter Scale.

The north side of the summit began to slide down the mountain and the explosion levelled everything for about 12 miles in all directions, 10 million trees were felled.