5 Things You Didn't Know About Mount St. Helens

On May 18, 1980, Mount St. Helens, a volcanic peak in southwestern Washington, suffered a massive eruption, killing 57 people and devastating some 210 square miles of wilderness. Here are 5 things you probably didn’t know about the eruption of Mount St. Helens...


Scientists Had Advance Warning Several months before the devastating eruption of Mount St. Helens, small earthquakes began occurring, so a new seismograph system was installed by the University of Washington, particularly near the volcano. On March 20, there was a 4.2-magnitude earthquake and tremors grew steadily. The U.S. Forest Service and U.S. Geological Survey held conferences and deployed teams, which went out and placed research posts, along with taking readings and photos. It was determined that the north side of Mount St. Helens had developed a bulge that was increasing six feet each day, and it was just a matter of time before an eruption occurred.

The Blast Radius Was Enormous The material that was ejected by the eruption was so much that one million Olympic-sized pools could have been filled and caused the mountain to depressurize. This caused an explosion out the side of the mountain, shooting out material and hot, poisonous gasses at more than 300 mph, which was hundreds of times stronger than the atomic bomb dropped on Hiroshima. All the structures and trees were destroyed for 19 miles or more to the east and 12 miles to the north, and it happened within moments.


The Explosion Was Heard a Long Distance Away The blast of the volcanic explosion at Mount St. Helens was so strong that people in California, Idaho, Montana and British Columbia heard it. However, those living in closer cities such as Portland, Oregon, which is 50 miles away, heard nothing because they were inside the quiet zone. This is related to the complexity of sound waves, depending on air motion, temperature, topography and atmosphere.

The Eruption Killed 57 People Even though the area around Mount St. Helens was lightly populated, it destroyed hundreds of houses, and killed thousands of animals. Fifty-seven people died from breathing in the ash or were buried alive. One local resident, Harry Randall Truman, was adamant about staying in his home and is assumed to have died because of the eruption, but his body was never found. Robert Landsburg was a photographer who died as a result of the explosion because he didn’t have enough time to get to safety but had protected his camera, which showed the approaching ash cloud as it overtook him.

Mount St. Helen’s Is an Active Volcano Mount St. Helens experienced a smaller eruption in 2004, sending steam and ash 10,000 feet into the air and continued to experience periodic eruptions into 2008. Since then, although there has been some earthquake activity, it has not erupted. Because of the danger to nearby Seattle and other towns, the volcano is closely monitored.