Mount Saint Helens erupted catastrophically on May 18, 1980, at 8:32 a.m. The eruption was preceded by a series of smaller eruptions and earthquakes starting from March 1980. The major May 18 eruption was triggered by a magnitude 5.1 earthquake that caused a massive landslide, followed by a lateral blast and a vertical eruption column that reached about 16 miles high. This eruption is considered the most economically destructive volcanic event in U.S. history. There were also earlier steam and minor explosive eruptions beginning on March 27, 1980, leading up to the main eruption in May.