Magma reservoirs beneath volcanoes along the Cascade Range arc vary in depth, size and complexity, but upper-crustal magma bodies are widespread, according to a team of geoscientists from Cornell University and Cascades Volcano Observatory.
Mount Rainier. Image credit: Walter Siegmund / CC BY-SA 3.0.
While visible lava at the surface is an obvious indicator of activity, the long-standing belief is that active volcanoes have large magma bodies that are expelled during eruptions and then dissipate over time as the volcanoes become dormant.
However, a new study published in the journal Nature Geoscience challenges this assumption.
The study authors used seismic waves to identify magma chambers beneath the surface of six volcanoes of various sizes and dormancy within the Cascade Range.
They found that all of the volcanoes, including dormant ones, have persistent and large magma bodies.
Their results are surprising given that some of these volcanoes, such as the Crater Lake volcano in Oregon, have not been active in millennia.
“Regardless of eruption frequency, we see large magma bodies beneath many volcanoes,” said lead author Dr. Guanning Pang, a researcher at Cornell University.
“It appears that these magma bodies exist beneath volcanoes over their whole lifetime, not just during an active state.”
The fact that more volcanoes have sustained magma bodies is an important consideration for how researchers may monitor and predict future volcanic activity.
“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,” Dr. Pang said.
The results suggest that an eruption does not completely drain a magma chamber, instead, it lets off some of the excess volume and pressure.
The chamber can be slowly expanded and refilled over time due to gradual melting of the crust.
“If we had a better general understanding of where magma was, we could do a much better job of targeting and optimizing monitoring,” said Cornell University’s Professor Geoffrey Abers.
“There are many volcanoes that are sparsely monitored or have not been subject to intensive study.”
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G. Pang et al. Long-lived partial melt beneath Cascade Range volcanoes. Nat. Geosci, published online January 23, 2025; doi: 10.1038/s41561-024-01630-y
Source : Breaking Science News