Here we introduce Mount St. Helens, the most active volcano in Washington state’s Cascade Mountains.
Mount St. Helens is located in Washington state, approximately 85 miles northeast of Portland, Oregon, and 155 miles south of Seattle.
It is managed by the National Forest Service, not the National Park Service.
Over the past 500 years, Mount St. Helens has experienced at least four major explosive eruptions and numerous smaller eruptions.
Mount St. Helens was named by Commander George Vancouver after British diplomat Alleyne Fitzherbert, who held the title Baron St. Helens.
1792-1794 – The mountain was named by Commander Vancouver while surveying the northern Pacific coast.
1835 – First recognized as a volcano.
1857-1980 – Inactive.
May 18, 1980 – Eruption.
57 people died. Damage from the explosion was estimated at $1.1 billion.
Hot ash causes forest fires. Floods occur when snow from the tops of mountains melts.
Volcanic ash spreads to the northwest. More than 900,000 tons of ash have been removed from the Washington area.
1980-1986 – Many small eruptions occurred.
September 2004 – Several days of unusual seismic activity lead seismologists to believe that an explosion due to water vapor buildup is likely.
October 2004 – Several small steam and ash explosions occurred.
March 8, 2005 – A column of smoke and ash is emitted approximately 9 miles high, and the plume is visible for more than 80 miles.
January 2008 – Continuous eruptions since October 2004 cease.
July 2014 – Final preparations begin for what geophysicists call “the equivalent of a combined ultrasound and CAT scan” inside the volcano. A joint project by scientists from Rice University, the University of Washington, the University of Texas at El Paso and others will install 3,500 seismic sensors around the volcano. The project will take four years and aims to improve volcano monitoring and advance warning systems.
November 3, 2015 – Scientists investigating the volcano’s interior present their first results at a Geological Society of America convention, saying that not only is there a magma chamber directly beneath Mount St. Helens, but there is also another chamber on the mountain’s east side that appears to be connected, with magma flowing between them.
Spring 2016 – Over an eight-week period, more than 130 small earthquakes occurred beneath the surface of Mount St. Helens.
October 2018 – Ranked #2 in the U.S. Geological Survey’s report on America’s most dangerous volcanoes. The volcano is considered a “very high threat” based on the danger it poses to people and infrastructure.
September 16, 2025 – Strong easterly winds swept across the crater, kicking up old volcanic ash deposits from the historic 1980 eruption, often referred to as the “Great Eruption,” and sending them thousands of feet into the air, according to the U.S. Geological Survey (USGS). The agency stressed that this is “not a sign that volcanic activity has resumed.” Both the volcano alert level and aviation color code remain at their lowest setting, green, and activity “remains at normal background levels.”
