Washington state contains five active volcanoes—Mounts Baker, Rainier, St. Helens, and Adams, plus Glacier Peak—and more than 35 scientists study them at Vancouver’s Cascades Volcano Observatory. What do they know about future flare-ups?

Glacier Peak: The Stealth Candidate

Tucked deep into the northern Cascades, Glacier Peak is the second-most explosive volcano in the range after St. Helens. Eruptions caused lahars and pyroclastic flows (aka explosions) around 920 CE, the height of the Byzantine Empire and the Dark Ages, and as recently as during the early 1700s. 

Reporting for Duty

Seismometers on Mount St. Helens: 20
Seismometers on Glacier Peak: 1

The USGS website notes every tiny earthquake recorded at Mount St. Helens. 


Technical name of the permanent gas monitor inside the Mount St. Helens crater. Increased sulfur dioxide means magma’s coming. 

Mount St. Helens Eruptions: 1980 vs. 2004­–8

Back in the day, volcanologists had to improvise instrumentation, measuring temperatures with Coke bottles and heat-sensitive paint. But when the mountain acted up in the 21st century, helicopter-mounted thermal infrared cameras scanned the volcano as often as twice a day. 


A mudslide off a volcano. Mount Rainier is particularly susceptible, given its clay content, massive snow, and glacier levels.

Lahar Early Warning System 

A network of seismic and infrasound instruments to automatically send an alarm along the Puyallup River drainage in the event of a lahar, currently under development at the Cascade Volcano Observatory.

“Mount St. Helens will erupt again in our lifetimes.”

—USGS Volcanologist Alexa Van Eaton. The likeliest type is a dome-forming event akin to 2004–8, not a “powerful and voluminous” blow like 1980.


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