Mount St. Helens, a volcano in the state of Washington that had lain dormant for 123 years, began to experience seismic activity in March 1980. A series of earthquakes and small eruptions ensued as a large bulge grew in the North face of the mountain. On 18 May another earthquake caused the north face to collapse, triggering an eruption that blew off the top and side of the volcano. 57 tourists, local residents and scientists perished.