Large magma bodies found beneath dormant volcanoes, surprising scientists

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Research led by Cornell University challenges the long-held assumption that active volcanoes have large magma reservoirs that are ejected during eruptions and then gradually disappear as the volcanoes fall dormant.

Scientists used seismic waves to locate magma chambers beneath six volcanoes in various states and levels of activity within the Cascade Range, which is home to half of the U.S. volcanoes labeled by the U.S. Geological Survey as "very high threat." The researchers discovered that all of the volcanoes, including those that are no longer actively erupting, have large and persistent magma bodies beneath the surface.

Co-authored by Geoffrey Abers, professor of geological sciences.

Their results are surprising, given that some of these volcanoes, like the one at Crater Lake in Oregon, have been dormant for thousands of years.

We notice big bodies of molten rock beneath many volcanoes, regardless of how often they erupt," Pang said. "It seems that these bodies exist beneath volcanoes throughout their entire lifespan, not just when they're active.

The fact that more volcanoes have extensive reservoirs of molten rock is an important factor for researchers to consider when monitoring and predicting future volcanic activity. The United States Geological Survey has been expanding and upgrading its volcanic observation networks in the Cascade Range and other areas as part of the National Volcano Early Warning System, with the goal of spotting signs of an impending eruption as soon as possible.

We used to think that finding a lot of magma meant an eruption was more likely, but now we're starting to view that as normal.

Several studies indicate that a volcanic eruption does not fully empty a magma chamber, but rather releases some of the extra volume and pressure that have built up. The chamber continues to grow and refills gradually over time as the Earth's crust melts and provides new material.

We would be able to better pinpoint and track magma if we had a broader understanding of its locations. This could help us improve our monitoring efforts, particularly for the significant number of volcanoes that currently receive limited attention or have not been thoroughly studied.

Preparations are underway to expand the magma monitoring system in order to determine if the findings in the Cascade are applicable to other areas, including Alaska.

DOI: 10.1038/s41561-024-01630-y

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