Mount St. Helens in Washington state is the most active volcano in the Cascade Range and it is the most likely of the contiguous U.S. volcanoes to erupt in the future. On the morning of May 18, 1980, a magnitude 5.1 earthquake struck, followed by the largest debris avalanche recorded in history. It resulted in the eruption of Mount St. Helens, leaving the surrounding areas devastated. The Toutle River in Mount St. Helen’s Monument, April 22, 2005, 25 years after the eruption. <br><br>An aerial view of Mount St. Helens erupting, May 18, 1980.
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After several weeks of activity, Mount St. Helens erupted, sending a plume of ash 650 feet into the air, May 18, 1980.
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Mount St. Helens erupting in Washington, May 18, 1980.
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During the first few minutes of the Mount St. Helens eruption, the flowing hot rocks and gas quickly eroded and melted some of the snow and ice capping the volcano, causing a volcanic mudflow, referred to as lahars, which uprooted countless trees and destroyed roads and bridges. <br><br>A forest flattened by the eruption of Mount St. Helens, June 30, 1980, in Washington.
During the first few minutes of Mount St. Helens eruption, the flowing hot rocks and gas quickly eroded and melted some of the snow and ice capping the volcano, causing a volcanic mudflow, referred to as lahars, which uprooted countless of trees and destroyed various roads and bridges.
A forest flattened by the eruption of Mount St. Helens, June 30, 1980, in Washington.
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A woman in a merchandising T-shirt with the publication "Mount St. Helens Holocaust, a diary of destruction," 1980.
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Washington State Police vehicles equipped with homemade air breathing devices to prevent volcanic ash from entering the engines, May 24, 1980. The vent tubes ran from the engine to the interior of the auto where the air is at least 60 percent cleaner than it is outside in an effort to cause as little damage to the engines as possible.
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Winds blew 250 million tons of ash eastward across the U.S., causing complete darkness in Spokane, Washington, 250 miles from the volcano. The ash cloud eventually spread across the U.S. in three days and completely circled the Earth in 15 days. <br><br>Heavy orange ash clouds hang over the buildings in Missoula, Montana following the eruption of Mount St. Helens ten days prior.
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Spirit Lake is littered with thousands of dead trees, Oct. 7, 2004, decades after they were blasted by the 1980 eruption of Mount St. Helens.
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Greenery makes a slow recovery on the site of Mount St. Helens, May 29, 2000, 20 years after the great eruption of 1980.
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A geologist stands in an 18-inch-deep trench cut into the ash left by the Mount St. Helens eruption in Coldwater Ridge, Washington, in 1980.
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A view from Johnston Ridge on Mount St. Helens in 1997 shows the landscape recovering.
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