Mount St. Helens

Mount St. Helens on May 18, 1980Forty one 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. 

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Multimedia:

Photos:

View historic Mount St. Helens photos on Flickr.

Mount St. Helens

 

Videos:

Biological Legacies on Mount St. Helens (May 1, 2020):

Mount St. Helens Remains A Mystery to Ecologists (May 15, 2020):

Mt St Helens A Story of Change by Thomas Iraci (May 17, 2020) :

Mount St. Helens and the Cascade Range Volcanoes: The 40th Anniversary (May 18, 2020):

40 Years of Watching Mount St. Helens (May 18, 2020):

A short film about Mount St. Helens eruption and the legacy of the Greatest Good (May 18, 2020):

Mount St. Helens: the Lateral Blast by Ranger Anna Coburn (May 18, 2020):

Mount St. Helens transformed the landscape of Spirit Lake and the North Fork Toutle River (Jun 24, 2020):

Mount St. Helens Road to Recovery (May 18, 2015) :

USGS scientists recount their experiences before, during and after the May 18, 1980 eruption of Mount St. Helens (May 11, 2010): 

This place in time: The Mount St. Helens story (May 7, 2010):

View the Mt St Helens Video Gallery via US Geological Survey

Resources