Hidden magma discovered beneath dormant Cascade Range volcanoes

Researchers from Cornell University’s Department of Earth and Atmospheric Sciences have discovered that dormant volcanoes in the Cascade Range contain substantial magma reservoirs. The findings challenge the long-standing belief that magma bodies dissipate over time after eruptions.

Their study utilized seismic wave analysis to examine 6 volcanoes of varying sizes and activity levels.

“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,” Guanning Pang, the study’s lead researcher, stated.

The presence of these sustained magma bodies is an important factor for improving volcanic monitoring and hazard assessment.

Magma storage beneath dormant volcanoes

The research team focused on 6 Cascade Range volcanoes, a region that includes half of the U.S. Geological Survey’s (USGS) “very high threat” volcanoes.

Using seismic imaging techniques, they identified magma reservoirs at depths ranging from 5 to 15 km (3 to 9 miles). The reservoirs vary in size, depth, and complexity but exist across all surveyed volcanoes including long-dormant ones such as the Crater Lake volcano in Oregon.

Previous assumptions linked large magma bodies to increased eruption likelihood but this study suggests otherwise.

“We used to think that if we found a large amount of magma, that meant increased likelihood of eruption,” Pang said.

“But now we are shifting perception that this is the baseline situation.”

Volcanic monitoring and impacts

The USGS has been upgrading its monitoring systems in the Cascade Range as part of the National Volcano Early Warning System. The new understanding of magma persistence could enhance efforts to detect signs of impending eruptions by refining monitoring targets.

“If we had a better general understanding of where magma was, we could do a much better job of targeting and optimizing monitoring,” Geoffrey Abers, co-author of the study and professor in geological sciences, focused on the need for a more comprehensive monitoring approach.

Many volcanoes remain sparsely monitored and insights from this research could contribute to more effective hazard assessments.

Persistent magma and eruption cycles

The study also found that volcanic eruptions do not completely drain magma chambers. Instead, eruptions relieve excess pressure allowing the chamber to gradually expand and refill as the crust melts. This challenges previous models suggesting that magma reservoirs are ephemeral and diminish once a volcano becomes dormant.

Seismic imaging provided compelling evidence of low-seismic-velocity zones indicative of partially molten magma beneath these volcanoes. The findings suggest that large volumes of magma can persist at shallow depths throughout an eruption cycle regardless of a volcano’s dormancy period.

Advanced seismic imaging techniques

A key aspect of the research was its methodology.

Unlike traditional imaging methods that require deploying hundreds of seismometers, the team used small networks of seismic stations and applied a technique that analyzes scattered wavefields from distant earthquakes. This allowed them to generate high-resolution subsurface images with minimal equipment.

“Previously, imaging methods required deploying tens to hundreds of seismometers around a volcano, making for a challenging undertaking,” Abers explained the advantage of this approach.

The streamlined methodology offers a portable and efficient means of studying volcanic systems worldwide.

Future applications and expanding research

Plans are already in place to extend the research to other volcanic regions including Alaska, to determine whether similar conditions exist elsewhere.

The ability to map magma reservoirs with limited seismic stations could revolutionize volcanic hazard assessment by providing a standardized framework for monitoring systems globally.

“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,” Abers noted.

References:

¹ Magma found beneath dormant Cascade volcanoes – CORNELL CHRONICLE – January 28, 2025

² Long-lived partial melt beneath Cascade Range volcanoes – Guanning Pang, Geoffrey A. Abers, Seth C. Moran, & Weston A. Thelen – Nature – January 23, 2025 – https://doi.org/10.1038/s41561-024-01630-y

Rishika Yadav

Rishika holds a Master’s in International Studies from Stella Maris College, Chennai, India, where she earned a gold medal, and an MCA from the University of Mysore, Karnataka, India. Previously, she served as a Research Assistant at the National Institute of Advanced Studies, Indian Institute of Science, Bengaluru, India. During her tenure, she contributed as a Junior Writer for Europe Monitor on the Global Politics website and as an Assistant Editor for The World This Week. Her work has also been published in The Hindu newspaper, showing her expertise in global affairs. Rishika is also a recipient of the Women Empowerment Award at the district level in Haryana, India, in 2022.

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