Recent research reveals that some long-dormant volcanoes in the Cascades of the Pacific Northwest still hold substantial magma reservoirs beneath them. This new insight, published in the journal Nature Geoscience, enhances our understanding of volcano behavior and eruption prediction.
Scientists have long debated whether magma stays beneath volcanoes for extended periods or only arrives shortly before an eruption. The current study, however, shows that magma chambers can exist for thousands of years without leading to an eruption. Guanning Pang, a postdoctoral researcher in Earth sciences at Cornell University, explains that these magma bodies are present throughout a volcano’s life cycle, not just during eruptions.
Interestingly, the magma found in these chambers isn’t in a molten state ready to erupt. The researchers indicate that all the chambers identified are only partially melted, lacking sufficient liquid magma to trigger an eruption.
The findings emerged from upgraded seismic monitoring stations by the U.S. Geological Survey. These enhancements enabled the researchers to analyze seismic waves traveling beneath several key volcanoes, such as Mount St. Helens and Mount Rainier. They observed significant slowdowns in the velocity of these waves, suggesting the presence of large magma reservoirs located between 3 to 9 miles (5 to 15 kilometers) underground.
While Mount Rainier and similar volcanoes exhibited this pattern, Three Sisters and Mount Shasta did not, possibly due to limited seismic data. However, recent ground inflation near Three Sisters hints at magma movement in that area.
Magma reservoirs are quite different from bubbling lakes of lava. They consist of a porous rock structure that allows liquid magma to flow. For an eruption to occur, the liquid content must exceed 35%, and researchers estimate that the current melt percentage beneath these volcanoes ranges from 3% to 32%. Even with a melt percentage close to 32%, it doesn’t guarantee an imminent eruption; the magma could remain stable for years or even decrease depending on local geological conditions.
Despite the detailed monitoring of the Cascades, there’s still a lot we don’t know about magma dynamics beneath many volcanoes worldwide. The study’s senior author, Geoffrey Abers, emphasizes that improved understanding and monitoring of magma would enhance our ability to predict volcanic activity globally.
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