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Scientists map the 'mystery sandwich' of Yellowstone's thermal water features

5 tourists photograph the Old Faithful geyser erupting in Yellowstone National Park, Wyo.
Julie Jacobson
Tourists photograph Old Faithful geyser erupting in 2011 in Yellowstone National Park, Wyo.

Tourists flock to Yellowstone National Park each year to see Old Faithful and the thousands of other thermal features. Scientists understand the top layer pretty well, and the magma layer about a mile down which heats the water. But what’s in between?

Geology professor Steve Holbrook affectionately calls it a 'mystery sandwich'.

“There's this gap in the upper kilometer or so of the Earth's crust that's been very difficult to study,” Holbrook said.

He currently leads the geosciences department at Virginia Tech, but about six years ago, Holbrook worked at the University of Wyoming.

He helped establish research using electromagnetic imaging to get a picture of that middle layer to figure out how the water was moving around. Holbrook and his team would hike to an area and measure seismic activity, electrical and magnetic resistance.

“The results we were getting back were showing such wonderful signals from the electrical and electromagnetic methods, wonderful signals from the deep hydrothermal pathways,” he said. While he was confident in the methods they were using, he knew they needed to scale up, and he found out a group of U.S. Geological Survey scientists led by geologist Carol Finn was conducting similar experiments.

The electromagnetic field reacts differently to different substances, allowing researchers to create a 3D image of what is below the surface.

The groups teamed up and using a helicopter flying a Danish-made coil and magnet, they were able to map a huge subterranean area of the park. The group published initial findings in the Journal Nature this month.

“The quality of the data and the level of detail and structure in the images really exceeded my wildest expectations,” Holbrook said.

The images validate decades of hypotheses about how water travels underneath Yellowstone’s thermal features. Holbrook says the data could improve our understanding about the biodiversity of the entire system.

“We were able not just to look deep beneath the hydrothermal features, but also to see how adjacent features might be connected in the subsurface across great distances. That’s never been possible before,” he said.

The initial publication is just the tip of the proverbial iceberg, Holbrook said. He expects the enormous amount of subterranean data collected at Yellowstone will "keep giving" for quite a while.

Funding for the project came from the USGS, The University of Wyoming and The National Science Foundation.