mount st. helens

Thirty years ago today, sometime not long after 8:30 a.m. Pacific time, Mount St. Helens explosively erupted. The shock wave from the eruption washed over Oregon and Washington, shaking the ground up to 400 kilometers away. Two earthquakes followed, at 8:32 and 8:34 a.m. Shortly thereafter, with a tremendous burst, the upper north flank gave way as gas, steam and ash vented outward and sent out an immense landslide of hot rock, mud, water, ash and debris.

SAN FRANCISCO — After more than three and a half years of continuous eruption, Mount St. Helens in Washington quieted earlier this year. Following intense monitoring efforts, the volcano is officially “asleep,” researchers reported Thursday at the annual meeting of the American Geophysical Union.