Why did Mount St. Helens erupt?

When did Mount St. Helens last erupt?

• Answer:

  Mount St. Helens is an active stratovolcano in the Cascade range in the state of Washington, approximately 53 miles (85 km) NE of Portland, OR. On May 18, 1980, an earthquake marked the collapse of the north face of the mountain at 8:32 AM PDT. A violent pyroclastic explosion of magma occurred, hurling huge quantities of rock, ash and dust to the north and east. The eruption continued for more than nine hours before lessening around 5:30 PM PDT. 57 persons were directly killed, forests were flattened, and torrents of ash, mud, and debris choked the nearby rivers, destroying bridges and industry. Much of eastern Washington state was affected by the ash and dust plume. (for other eruptions, see related link) An earthquake at 8:32:17 a.m. on Sunday, May 18, 1980 caused the eruption on Mt St. Helens Mt. St. Helens last major eruption was on may 18 1980. But this volcano remains active and often spurts ash and other debris. The last minor eruption of Mount St. Helens was in July of 2008.