Mount St. Helens eruption

The eruption of Mount St. Helens in 1980 is the momentous volcanic eruption to occur in the lower 48 U.S. states which has recorded a history, leading a vicious power and volume of material released by the 1915 eruption which took place in California's Lassen Peak. The eruption was preceded by a two-month-long series of earthquakes and steam-venting episodes, caused by an injection of magma at shallow depth below the mountain which created a huge bulge and a fracture system on Mount St. Helens' North Slope. The entire weakened north face to slide away suddenly exposes the partly molten, gas- and steam-rich rock in the volcano to lower pressure due to the earthquake which caused at 8:32 AM on May 18, 1980.