[SKAMANIA COUNTY, Wash.] – Wednesday, May 18, 2016, marks the 36th anniversary of the eruption of Mount St. Helens, one of the most significant volcanic events in the continental United States.

The eruption, which was triggered by a series of earthquakes, decimated hundreds of square miles of land, killed 57 people and caused nearly $1 billion in damage. Here is a look at the 1980 Mount St. Helens eruption:

For two months, a series of small earthquakes under Mount St. Helens in southwestern Washington first scientists their first indication that the volcano no longer was dormant. Seismologists and volcanologists with the United States Geological Survey (USGS) were on-site measuring the small earthquake swarms that eventually triggered volcanic movement.

At approximately 8:32 a.m. PDT, a magnitude 5.1 earthquake struck. Within seconds, the north face of the mountain fell away, leaving its now-signature crater, and burying the valley below in avalanche debris, covering 23 square miles.

According to the USGS, Mount St. Helens’ blast sent pyroclastic flow, a current of hot gas and rock, across the mountainside, reaching speeds of at least 300 mph. The north face saw most of the damage, with 230 square miles of land destroyed. Scientists estimate 4 billion board feet of timber was lost in the eruption – enough to build 300,000 two-bedroom homes.

Mount St. Helens sent a giant mushroom cloud of ash into the air, growing to 80,000 feet within 10 minutes. The giant ash cloud spread across the continental United States within three days and circled the Earth in 15 days. USGS scientists estimate detectable amounts of ash from the eruption covered approximately 22,000 square miles.

It is believed 57 people died directly as a result of the eruption, although that number is widely debated. Due to the eruption’s wide-ranging devastation, many people were listed as possible victims simply for being near the area. Paul Hiatt and Doug Thayer are two of the alleged deceased that stir the most controversy. Little is known about the two men, and still today presumptive death certificates have not been issued for Hiatt and Thayer.

The eruption caused widespread devastation to the surrounding region, including loss of property, loss of income and clean-up. The Washington State Department of Commerce and Economic Development put the price tag for the total cost of damages at $969.8 million.

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