In the visualization of Yellowstone Lake above, the black arrows show the movement of thermal liquid, and the maroon arrows show thermal fluid moving along the brown fault lines. “What we can see is how some of these faults actually bring water to the surface,” Finn says.
You can think of this complex hydrothermal plumbing as being like a city’s infrastructure, with all the pipes carrying the water across the landscape. And it’s important to understand how it works because there’s a lot of geological activity underneath Yellowstone. “There’s not that much concern right now that we’re going to see a volcanic eruption from Yellowstone in our lifetimes—it’s just not a system that’s on that sort of edge,” says Michael Poland, scientist-in-charge at the Yellowstone Volcano Observatory and a geophysicist at the US Geological Survey, who wasn’t involved in the research. “But the thing that a lot of people don’t fully appreciate is that hydrothermal explosions—basically steam explosions—are also an important hazard.”
These happen about once a year, when steam builds up underground until the land above pops like a pimple, flinging rock far and wide. Some 13,000 years ago, one of these explosions left a bay on the north side of Yellowstone Lake that’s over a mile wide. “It’s the largest such explosion crater on the planet that we know of,” says Poland. “There can be some huge steam explosions in Yellowstone. So understanding more about these hot water circulation patterns is really important for understanding more about that kind of hazard.”
The map is also useful when considering geothermal energy, or using Earth’s natural warmth to generate electricity or heat homes. Extracting such energy is illegal within Yellowstone itself, but if it was tapped nearby in, say, Idaho, that might influence hydrothermal activity in the park. “There are examples all over the world of geysers that have gone silent when geothermal energy has been tapped nearby,” says Poland. “But we don’t know how the hydrothermal system [in Idaho] is connected to Yellowstone. So this sort of thing starts to give us some clues as to how the system works, how the system is interconnected.”
The geothermal industry already has a good idea of which active areas to exploit for energy; they use a method similar to the one from this study, only with instruments on the ground that image what’s immediately below them. But for scientists trying to study swaths of geothermically active terrain, a helicopter gives a nice broad view. “It’s given a spectacularly comprehensive view of hydrothermal systems of this very famous volcanic region, and I hope that it motivates further studies in other systems that will probably be just as revealing,” says University of Utah geophysicist Philip Wannamaker, who wasn’t involved in the research. “They’re groundbreaking on that front.”
Understanding how Yellowstone’s subterranean water mixes has also been a critical missing piece in the study of the many microbes that live in the park’s 10,000 hot springs. Each spring has a unique chemistry based on the particular water bubbling into it, which has created some of the most biodiverse ecosystems on Earth. The hot springs are packed with species living not on photosynthesis from the sun above, but the chemical energy from below, similar to how bacteria live off sulfur on deep-sea hydrothermal vents.