What happened during the big eruption of 1980?
On the morning of May 18, 1980, after weeks of small tremors, a magnitude 5.1 earthquake shook beneath Mount St. Helens and triggered an enormous eruption. The eruption involved a complex series of events that unfolded over the next 12 hours, with many events going on simultaneously. These volcanic events buried some areas in debris avalanches and mudflows, scoured other areas with hot gases, blew down or scorched forests on slopes several miles away, and dusted forests farther away with volcanic ash.
