Photos: On this day – May 18, 1980 – Mount St. Helens erupts
An earthquake at 8:32:17 a.m. on Sunday, May 18, 1980, caused the entire weakened north face to slide away, suddenly exposing the partly molten, gas and steam-rich rock in the volcano to lower pressure. The rock responded by exploding a hot mix of lava and pulverized older rock. An eruption column rose 80,000 feet (24,400 m) into the atmosphere and deposited ash in 11 U.S. states.At the same time, snow, ice and several entire glaciers on the volcano melted, forming a series of large lahars (volcanic mudslides) that reached as far as the Columbia River, nearly fifty miles (eighty kilometers) to the southwest.
The eruption was preceded by a two-month series of earthquakes and steam-venting episodes, caused by an injection of magma at shallow depth below the volcano that created a huge bulge and a fracture system on Mount St. Helens’ north slope.Fifty-seven people (including innkeeper Harry R. Truman, photographer Reid Blackburn and geologist David A. Johnston) and thousands of animals were killed. Hundreds of square miles were reduced to wasteland, causing over a billion U.S. dollars in damage ($2.74 billion in 2011 dollars).(Wikipedia)
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