Yellowstone National Park sits above a massive, active volcano. Using a new way to track heat flow under the park, researchers now estimate its magma chamber could be recharging from deep within the Earth twice as fast as previously thought.
Can we expect rivers of lava in Eastern Idaho, mimicking images from Kilauea in Hawai’i? Is there a catastrophic eruption right around the corner? Not likely.
“Imminent to a geologist is very different than imminent to most people,” says Jerry Fairley, professor of geological sciences at the University of Idaho and one of the lead researchers on the study. For geologists, “imminent” could be any time in the next 200,000 years. What has changed is not the park itself, but scientists' understanding of it.
Impending doom, however, is far from the only reason to study Yellowstone. It is this volcanic powerhouse that provides the energy needed to produce all the most famous attractions, from Old Faithful and the Grand Prismatic Spring in the center of the park, to the Mammoth Hot Springs in the north.
Understanding its nuances can help develop Idaho’s significant geothermal resources, some of the best in the United States.
Studying the ecosystem built upon Yellowstone’s heat also can yield tremendous scientific dividends. DNA fingerprinting is heavily used in criminal investigations and has been popularized by television shows such as Law and Order and CSI. This technology became commercially viable only after the discovery of a bacterium in the 1960s in the park’s hot springs, one that can withstand tremendous heat.
“When you go to Yellowstone, it’s not just about the geysers and hot springs. There’s a whole ecosystem based on this heat, from the bison and elk that winter in the warm areas of the park all the way down to the microbial level,” says Fairley.
PLUMBING YELLOWSTONE'S DEPTHS
The key to understanding the Yellowstone super-volcano is understanding what powers it in the first place. Fairley, along with Peter Larson, a professor in the Washington State University School of the Environment, have found a better way to do just that.
No one really knows how fast the magma chamber below Yellowstone is recharging, says Fairley. “It’s kind of a puzzle, you know?”
Imagine boiling a pot of water on your stove. Turning on the burner supplies heat. In Yellowstone, this happens as magma seeps up from the mantle, a vast semi-solid region below the Earth’s crust. The heat from this magma then melts rocks in the crust, much like how the heat from the burner boils the water. If you place a lid on top of that pot, the rattling and steaming is like the things we see on the surface in Yellowstone.
Fairley and his colleagues are trying to understand the burner by observing the pot. To achieve this goal, they came up with a novel way to measure the heat flowing out of Yellowstone’s hot springs.
Most of the water flow in a hot spring occurs under the surface rather than being expelled in an eruption. Typically, a chemical tracer would be added to the water, like a salt or dye, to track the flow. You can't do that in Yellowstone; salts could adversely affect the ecosystem in the springs and dyes can discolor them. To avoid this, they used a substance called deuterium.
Deuterium is a naturally occurring, stable isotope of the element hydrogen. With it, you can make heavy water, D2O, instead of the familiar H2O. In any 8-ounce glass of water from your faucet, about half a drop is heavy water. Fairley and his team added heavy water to several of Yellowstone’s hot springs and tracked the rate at which its amount decreased over time. This allowed them to more accurately track the heat flow out of the springs.
"Using heavy hydrogen as a tracer is a promising way of investigating how water moves through the subsurface," said Nicholas Pollock, a volcanologist and Ph.D. candidate in the Department of Geosciences at BSU, who was not involved in the study. "Anything that allows us to gain insight into the hydrothermal processes occurring at Yellowstone will increase our knowledge of how these systems work."
Since all of the heat must come from the underlying magma chamber, just as all of the heat boiling the water must come from the burner, researchers can work out the rate at which the magma is recharging. Measuring the hot springs alone, however, is not enough.
Back to the example of the pot on the stove: Heat is lost from the walls of the pot as well. In Yellowstone, the underlying system of hot water heats the ground, something that is not accounted for when just water flow is measured.
Fairley and his team had previously measured ground temperatures in 2016. When combined with the data from this new study, they estimate that as much as 50 percent of the heat is carried away by the ground. That helped them reach the conclusion that the magma beneath Yellowstone is recharging as much as twice as fast as was previously thought.
IDAHO'S GEOTHERMAL POTENTIAL
This heavy water tracer also could be used to explore something more immediately applicable to Idaho: geothermal power.
More than three-fourths of in-state electricity generation comes from renewable sources, mainly hydroelectric power. But the rich volcanic landscape gives Idaho some of the best geothermal potential in the United States. It's used to heat Boise government buildings and the nearby university campus.
According to Pollock, geothermal remains an underutilized resource in many parts of the country. "Any regions that have high . . . heat fluxes provide the potential for geothermal resources, and large volcanoes certainly have high heat fluxes."
The key to tapping into this potential is to quickly and cheaply assess the usefulness of a given site for geothermal power. Drilling is the primary way to survey a site, at an appreciable cost. Having a fast, non-invasive method such as heavy water tracing would be a great economic boon.
Yellowstone offers a pristine location to hone this technique, free from man-made influences. This is important, says Fairley, because once you sink a well, you change the dynamics of the system in ways that are difficult to understand.
Making sense of the complexities of Yellowstone promises to improve life in many more ways than just avoiding disaster. “There’s a really intimate connection between geology and our daily lives," said Fairley. "It’s not something we think about very much”
Kevin Davenport is an experimental physicist at the University of Utah and a 2018 AAAS Mass Media Science and Engineering Fellow with the Idaho Statesman: 208-377-6411, @tropnevaDniveK.