Mount St. Helens

Mount St. Helens on May 18, 1980Forty years ago on the morning of May 18, 1980, a magnitude 5.1 earthquake triggered the collapse of the summit and north flank of Mount St. Helens and formed the largest landslide in recorded history.

Gas rich magma and super-heated groundwater trapped inside the volcano were suddenly released in a powerful lateral blast. In less than three minutes, 230 square miles of forest lay flattened. The hot gas and magma melted the snow and ice that covered the volcano. The resulting floodwater mixed with the rock and debris to create concrete-like mudflows that scoured river valleys surrounding the mountain.

A MSH Coldwaterplume of volcanic ash and pumice billowed out of the volcano reaching a height of 15 miles and transformed day into night across Eastern Washington. Avalanches of super-heated gas and pumice, called pyroclastic flows, swept down the flanks of the volcano. While the landslide and lateral blast were over within minutes, the eruption column, mudflows and pyroclastic flows continued throughout the day and following night.

By the following morning major eruptive activity had ceased and the landscape appeared to be a gray wasteland. In 1982, Congress created the 110,000-acre National Volcanic Monument for research, recreation, and education. From this wasteland, new life soon emerged and thrived. The following decades have offered insight into the recovery of ravaged landscapes. 

Follow us on Twitter @MtStHelensNVM 

View Mount St Helens recreation information to plan a trip.

Visit Mount St Helens Institute for educational opportunities.

Multimedia:

Historic Mt. Saint Helens photos on Flickr.

Mt St Helens A Story of Change by Thomas Iraci

Biological Legacies on Mount St. Helens

Mount St. Helens: the Lateral Blast by Ranger Anna Coburn

Mount St. Helens transformed the landscape of Spirit Lake and the North Fork Toutle River

USGS scientists recount their experiences before, during and after the May 18, 1980 eruption of Mount St. Helens: 

This place in time: The Mount St. Helens story:

Mount St. Helens Road to Recovery:

View the Mt St Helens Video Gallery via US Geological Survey

Resources





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