Yellowstone supervolcano has a lot more magma than previously thought: Scientists

The supervolcano at Yellowstone National Park has substantially more magma reservoir under the caldera than scientists previously thought, according to new research.

In addition, the newly found lava is flowing at shallow depths that fueled prior eruptions, according to a paper published Thursday in Science.

Researchers mapped the seismic wave speed below the Yellowstone volcano using a technique called seismic tomography. This 3D modeling of seismic waveforms measures the volume of the melt and makes assumptions of the distribution of how the melt is spread in the subsurface in Yellowstone's magma reservoir, Ross Maguire, an assistant professor at the University of Illinois Urbana-Champaign's department of geology and author of the study, told ABC News.

"We found that it's likely that Yellowstone's crustal magma reservoir holds more melt than previously was thought," Maguire said, adding that there is up to 20% melt at shallow depths.

Previous studies have suggested the partial melt fraction was between 5% and 15%, Maguire said.

The Yellowstone magma reservoir is not so much "a big tank of magma," with accumulation all in one body, Maguire said, but rather, more like a "snow cone," in which there is a solid component and a liquid component, Kari M. Cooper, professor and chair at the University of California Davis's department of earth and planetary sciences, told ABC News.

The findings show it's possible there are some relatively small to moderate-size bodies of magma that are below Yellowstone that could be mobilized and expelled, Cooper said. Yellowstone tends to garner a lot of attention because of the potential for "catastrophic, explosive eruptions," Maguire said, but that's not the most common type of eruption in the park.

"They would be of a similar size to what's happened in the very recent Yellowstone history that's produced a series of lava flows that filled the most recent caldera after the most recent really large eruption," she said.

Despite the new discovery, the research does not indicate that an eruption will happen any time soon, the scientists said. There are no signs of "increased volcanic unrest" at Yellowstone, Maguire said.

"This really does not change the hazard assessment at all, because we already knew that. We already knew this was the recent activity," Cooper said. "We already knew that was the most likely sort of activity to happen next."

However, a key issue for assessing the hazards of volcanic eruption is to ascertain how much magma is below the surface and where, and continued monitoring of the subsurface is important to provide a clear picture if the situation begins to dramatically change, the researchers said.

In addition, Yellowstone is thoroughly monitored by the U.S. Geological Survey and the Yellowstone Volcano Observatory, Cooper said.