It’s no secret that a super volcano lies miles beneath the surface of Yellowstone National Park, but all this time researchers knew little beyond that — until now.

A team of researchers recently made a breakthrough discovery that sheds light on the forces shaping the volcanic system and what might keep it from erupting in our lifetime, experts said in a Rice University news release April 16.

The team, consisting of researchers from Rice, the University of New Mexico, the University of Utah and the University of Texas at Dallas, “discovered a sharp, volatile-rich cap” made of magma about 2.5 miles under Yellowstone’s surface that “acts like a lid,” trapping pressure and heat that it releases gradually, preventing the system from erupting.

The team’s findings were recently published in the scientific journal Nature.

Yellowstone hasn’t had a significant eruption for about 70,000 years, when lava flows formed the Pitchstone Plateau in the southwestern portion of the park, according to the U.S. Geological Survey.

“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 Brandon Schmandt, professor of Earth, environmental and planetary sciences at Rice and one of the lead researchers on the project. “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.”

Previous studies suggested the top of the system could be anywhere from 2 to 5 miles under the earth’s surface, but the uncertainty kept scientists in the dark about how the “mighty” magma system might act in the future, experts said. The team’s research sheds light on the system’s past and now future behavior.

The team “conducted a high-resolution seismic survey in the northeastern part of the caldera” using a “53,000-pound vibroseis truck — typically used for oil and gas exploration” to generate tiny earthquakes that sent seismic waves into the ground, the release said. The waves reflected “off subsurface layers,” revealing the cap 2.5 miles down.

“Seeing such a strong reflector at that depth was a surprise,” Schmandt said in the release. “It tells us that something physically distinct is happening there — likely a buildup of partially molten rock interspersed with gas bubbles.”

The team measured the bubble and melt contents and determined they were lower than levels usually associated with an imminent eruption, he 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,” he said, likening the system to “‘steady breathing’ with bubbles rising and releasing through the porous rock — a natural pressure-release valve that lowers eruption risk.”

Still, eruptions can and do happen.

Last summer, a geyser in Yellowstone erupted in a hydrothermal explosion right next to tourists on a boardwalk, McClatchy News reported. The boardwalk was destroyed, but no injuries were reported.

Before that, in January 2024, a long-dormant geyser erupted for the first time in decades, McClatchy News reported.

“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.”

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