when did mount st helens erupt

Mount St. Helens erupted catastrophically on May 18, 1980, at 8:32 a.m. PDT. The eruption was triggered by a magnitude 5.1 earthquake that caused the north face of the mountain to collapse, resulting in the largest subaerial landslide in recorded history, followed by a massive lateral explosion and an ash column reaching 80,000 feet into the atmosphere. This eruption marked the first major explosive activity in the contiguous United States since 1915 and was one of the most disastrous volcanic events in U.S. history. Earlier in the year, small earthquakes and steam venting episodes began in March 1980, with the first minor explosive steam eruption occurring on March 27, 1980. The main eruption on May 18 caused significant devastation, including lahars (volcanic mudflows) that traveled miles down rivers, destruction of forest and property, and loss of life. The eruption lasted about nine hours, dramatically reshaping the volcano and the surrounding landscape.