image courtesy USGS/Cascades Volcano Observatory; Photograph by Austin Post
MSH80_eruption_mount_st_helens_05-18-80.jpg

May 18, 1980 - Mount St. Helens erupts

8:32 Sunday morning.

5.1 magnitude earthquake.

The north flank of the mountain collapses, resulting in a debris avalanche that covers
nearly 24 square miles (in comparison, the city of Davis is 11 sq mi).

Pyroclastic flows from the crater reach speeds of 50-80 mph and cover 6 sq mi.

520 million tons of ash blow eastward across the US,
causing complete darkness in Spokane, WA (250 miles from the volcano).

Approximately 230 square miles of surrounding forest is destroyed
(an area the size of Chicago).

The eruption lasts 9 hours.