Beneath Dormant Volcanoes In The Pacific Northwest Are Hidden Magma Reserves
Beneath dormant volcanoes in the Cascades region of the Pacific Northwest, scientists found large reservoirs of magma.
The discovery challenges the belief that active volcanoes have large magma bodies that are released during eruptions and then gradually disappear as the volcanoes enter a dormant state.
In a new study, researchers used seismic waves to identify magma chambers beneath six volcanoes within the Cascade Range.
The volcanoes varied in size and dormancy. The team found that all of the volcanoes, including the dormant ones, have large bodies of magma that still persist.
The results were surprising because some of the volcanoes, such as the Crater Lake volcano in Oregon, have not been active for thousands of years.
“Regardless of eruption frequency, we see large magma bodies beneath many volcanoes,” said Guanning Pang, the first author of the study and a postdoctoral researcher in Earth sciences at Cornell University. “It appears that these magma bodies exist beneath volcanoes over their whole lifetime, not just during an active state.”
The recently discovered magma chambers are only partially melted, but they do not contain enough liquid to trigger an eruption.
The fact that more volcanoes have bodies of magma beneath their surfaces is important for monitoring and predicting future volcanic activity.
Thanks to the U.S. Geological Survey upgrading its volcanic monitoring networks in the Cascade Range, the research team has been able to track the waves of distant earthquakes as they traveled beneath the volcanoes to identify signals of impending eruptions.
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Under the volcanic summits, there was a consistent slowing of earthquake wave velocity. The slowdown indicated that large reservoirs of magma are located about three to nine miles below the surface.
The reservoirs were detected below Mount Rainier, Mount Hood, Mount St. Helen, Newberry Volcano, Lassen Peak, and Crater Lake.
Mount Shasta and Three Sisters did not display similar patterns, but that may have been due to a lack of seismic measurements.
Magma reservoirs are made of porous rock that liquid magma moves through. When the portion of liquid magma goes over 35 percent, the reservoir has the potential to erupt.
It is unclear exactly how much the magma beneath these mountains has melted, but the researchers estimate that it could range from three percent to 32 percent. Even if the melt rate was as high as 32 percent, it does not mean an eruption will occur.
Overall, the Cascades are monitored pretty closely, but scientists don’t know as much about the rest of the volcanoes in the world.
Similar tracking techniques involving seismic stations could help provide more information on those volcanoes.
“If we had a better general understanding of where magma was, we could do a much better job of targeting and optimizing monitoring,” said Geoffrey Abers, a senior author of the study and an Earth scientist at Cornell University.
The study was published in Nature Geoscience.
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