What makes Old Faithful blow?
That is a question scientists are trying to answer as they launch an effort to map the subterranean systems of hot water and rock that constitute the plumbing for Yellowstone’s famous geysers. Starting this week, researchers with the U.S. Geological Survey, the University of Wyoming and Aarhus University in Denmark will survey the national park’s hydrothermal features using a giant, hoop-like electromagnetic monitor suspended from helicopters flying 200 feet above the ground.
“This is really kind of a last frontier if you will, in Yellowstone, of being able to look at a large part that’s underground that people have not looked at,” Carol Finn, one of the scientists on the surveying team, told Wyoming Public Media. “This survey can visualize the geology and the water down to about 500 meters, so 1,500 feet.”
The monitor senses and records tiny pulses of electricity related to the interactions between hot water and rock underground.
The electromagnetic survey will help Finn and her colleagues understand the causes of geysers and much bigger hydrothermal explosions. More than 13,000 years ago, one of these explosions created the 1.5 mile crater that forms the bottom of Yellowstone Lake. It is thought to be the largest crater of its kind on the planet.
A study published in spring 2015 found a massive reservoir of molten rock lurking beneath the park. A calderic eruption, in which that magma came rushing to the surface, would eject 1,000 times more material than the 1980 eruption of Mount St. Helens and could create a caldera dozens of miles wide. The last time this happened, 640,000 years ago, Homo sapiens didn’t even exist yet. No one is certain what causes such an eruption, or when the Yellowstone supervolcano might erupt again.