The eruption of Mount St. Helens on May 18, 1980, was the most destructive volcanic eruption in US history. What were scientists monitoring beginning in March of 1980 that alerted them that the volcano would soon erupt?
Scientists were monitoring a series of small earthquakes that began in March of 1980, indicating that magma was moving beneath the surface and building up pressure. These seismic events, along with visible changes in the shape of the volcano, led scientists to predict that an eruption was imminent.
