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Magma still sits under Cascade volcanoes
The Cascade volcanoes that dot the Pacific Northwest are not extinct. They are mostly dormant, meaning they could erupt sometime in the future. Scientists had long thought an indicator of an active volcano was a large pool of magma beneath a volcano, and once the magma becomes depleted, the volcano goes dormant. But on January 28, 2025, researchers at Cornell University said their new study found large, persistent pools of magma in chambers beneath six volcanoes in the Cascade range.
The scientists were surprised by the finding, because some of the volcanoes they studied haven’t erupted in thousands of years. For example, Crater Lake in Oregon is the site of Mount Mazama, a volcano that blew itself apart in an enormous, explosive eruption 7,700 years ago. Lead author Guanning Pang of Cornell University said:
Regardless of eruption frequency, we see large magma bodies beneath many volcanoes. It appears that these magma bodies exist beneath volcanoes over their whole lifetime, not just during an active state. We used to think that if we found a large amount of magma, that meant increased likelihood of eruption, but now we are shifting perception that this is the baseline situation.
The researchers published their study in the peer-reviewed journal Nature Geoscience on January 23, 2025.

Locating the magma
The researchers used seismic data to find the magma chambers. The discovery of pools of magma below volcanoes that haven’t erupted in thousands of years leads the researchers to believe that an eruption does not empty the chamber. Instead, it likely just releases the pressure, letting off a little steam, as the saying goes. Plus, the magma in the chamber can refill over time, as more of Earth’s crust melts beneath the volcano.
This new insight can help improve the plan for a National Volcano Early Warning System. Co-author Geoffrey Abers of Cornell University in New York said:
If we had a better general understanding of where magma was, we could do a much better job of targeting and optimizing monitoring.
He added that there are:
… a great many volcanoes that are sparsely monitored or have not been subject to intensive study.
Using a limited number of seismometers
The researchers were especially encouraged because they could acquire the data using only a few seismometers placed around the base of the volcanoes. They looked at something called scattered wavefields caused by distant volcanoes in other parts of the world to get an image of what’s under the Cascade volcanoes. Abers said:
Previously, imaging methods required deploying tens to hundreds of seismometers around a volcano, making for a challenging undertaking.
In fact, the study went so well they are already planning to expand it to volcanoes outside the Cascade range. Volcanoes in Alaska are on the list. Abers said:
Our method is very portable and can be used at many if not most other volcanoes around the world, with just a small number of modern seismographic stations. We think it can help systemize volcano studies, and provide a key piece of global frameworks for volcanic hazard assessment.

Bottom line: Researchers have used seismometers to discover pools of lava sitting under dormant Cascade volcanoes in the Pacific Northwest.
Source: Long-lived partial melt beneath Cascade Range volcanoes