Mount St. Helens, located in Washington State, was sleeping peacefully on the morning of May 18, 1980. However, in just a while, the mountain blew out as lava and smoke poured out of the volcano. Long dormant, Mount St. Helens was erupting.
A 5.1 earthquake had occurred near or around Mount St. Helens. This actually caused the eruption.
As the mountain erupted, it blew out a whole side of itself, as if caused by a massive bomb.
Below is a photograph taken by the USGS.
Mount St. Helens released massive amounts of ash in the air and warped the Earth's climate for years to come. Below is a USGS image of the ash distribution.
Some people in Washington State awoke to 2-5 inches of ash covering their lawns and houses.
Following the eruption, over a course of 2 months, over 10,000 seismic events occurred in the Mount St. Helens area.
Mount St. Helens also shrunk to a much smaller degree.