Yellowstone Supervolcano Has a Hidden Magma Cap—How Close Are We to an Eruption? – The Debrief
2025-04-22T12:20:45Z
Yellowstone Caldera, the volcanic complex underneath Yellowstone National Park, is held at bay from eruption by a cap 3.8 meters underground.
A new study reveals that a volatile-rich cap of magma located just 3.8 kilometers beneath Yellowstone National Park plays a critical role in preventing a major eruption of the park’s massive volcanic system.
Scientists from Rice University, the University of New Mexico, the University of Utah, and the University of Texas at Dallas collaborated on the research, which identified a distinct layer of magma that retains heat and pressure while allowing gases to escape—an important stabilizing mechanism for the caldera.
Magma Mysteries
The project was led by Chenlong Duan and Brandon Schmandt of Rice University, who investigated the movement of magma, fluids, and volatiles in the Earth’s crust under a grant from the National Science Foundation. Their research utilized controlled-source seismic imaging and advanced computer modeling.
Previous studies left considerable uncertainty about the depth and structure of Yellowstone’s magma reservoir, with estimates ranging from 3 to 8 kilometers below the surface. Scientists also debated how the current magma system compares to past states.
“For decades, we’ve known there’s magma beneath Yellowstone, but the exact depth and structure of its upper boundary has been a big question,” said Schmandt, professor of Earth, environmental and planetary sciences. “What we’ve found is that this reservoir hasn’t shut down — it’s been sitting there for a couple million years, but it’s still dynamic.”
Seismic Imaging in Yellowstone
The team began their work using a seismic vibrator—a 53,000-pound truck outfitted with a device designed to send low-frequency vibrations into the ground. These vibrations reflected off subsurface layers, enabling the researchers to use reflection seismology to map geological structures. The resulting data revealed the presence of a distinct magma layer at a depth of 3.8 kilometers.
“Seeing such a strong reflector at that depth was a surprise,” Schmandt said. “It tells us that something physically distinct is happening there — likely a buildup of partially molten rock interspersed with gas bubbles.”
Modeling the Magma Cap
To better understand the nature of the cap, Duan and Schmandt turned to computer simulations, testing various combinations of rock, melt, and volatile content. The best match came from a model of porous rock containing silicate melt and supercritical water bubbles. This configuration produced a volatile-rich cap with about 14% porosity—half of which was occupied by fluid bubbles.
Rising and decompressing magma often forms bubbles of water and carbon dioxide gas, which can increase buoyancy and potentially trigger eruptions. However, the researchers found that Yellowstone’s system functions differently. The porous rock acts like a release valve, allowing gases to escape gradually, similar to a system “breathing” under pressure.
“Although we detected a volatile-rich layer, its bubble and melt contents are below the levels typically associated with imminent eruption,” Schmandt said. “Instead, it looks like the system is efficiently venting gas through cracks and channels between mineral crystals, which makes sense to me given Yellowstone’s abundant hydrothermal features emitting magmatic gases.”
Overcoming Challenges in the Field
The research team faced multiple obstacles, including the logistical challenges of conducting fieldwork during the COVID-19 pandemic, operating heavy equipment in a national park, and dealing with highly complex geological noise in their seismic data.
“The challenge was that the raw data made it almost impossible to visualize any reflection signals,” Duan said. “We used the STA/LTA function to enhance coherent seismic reflections, and this was the first time we had innovatively applied STA/LTA data within the wave-equation imaging algorithm.”
“When you see noisy, challenging data, don’t give up,” Duan advised future researchers. “After we realized the standard processing was not going to work, that’s when we got creative and adapted our approach.”
Looking Ahead
This research marks a significant advancement in understanding Yellowstone’s volcanic activity. By establishing a baseline of how the caldera currently functions, future studies may be able to detect early signs of changes in melt or gas content that could signal potential instability. Additionally, the seismic imaging techniques developed here could be applied to other geologic settings, including for geothermal energy exploration and carbon dioxide storage.
“Being able to image what’s happening underground is important for everything from geothermal energy to storing carbon dioxide,” Schmandt said. “This work shows that with creativity and perseverance, we can see through complicated data and reveal what’s happening beneath our feet.”
The paper “A Sharp Volatile-rich Cap to the Yellowstone Magmatic System” appeared on April 16, 2025 in Nature.
Ryan Whalen covers science and technology for The Debrief. He holds an MA in History and a Master of Library and Information Science with a certificate in Data Science. He can be contacted at ryan@thedebrief.org, and follow him on Twitter @mdntwvlf.
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