New research has pinpointed where theYellowstone supervolcano will likely erupt. It won’t blow today, but future eruptions will likely center on the northeastern side of the national park, the new study finds.
Not that Yellowstone is likely to still be a national park by the time it erupts. Any such eruption is expected to take place hundreds of thousands of years from now, study co-author Ninfa Bennington, a volcano seismologist at the Hawaiian Volcano Observatory, told Live Science.
The research, published Jan. 1 in the journal Nature, found that rather than being stored in one big blob under Yellowstone, melted magma lurks in four separate reservoirs within the crust of the caldera.
To the west, these reservoirs do not touch the deep mantle rocks that would otherwise heat them from below, keeping them liquid and eruptable. But to the northeast, near a landmark called Sour Creek Dome, deep rocks are heating the magma trapped in the crust. That means that while magma under the western side of Yellowstone will likely start to cool and solidify, the northeast will stay hot.
Previous studies of Yellowstone had used the passage of earthquake waves through the caldera to try to gauge where liquid magma versus solid rock sat beneath the park. But waves can change their behavior based not just on whether they’re traveling through a solid or a liquid, but also on temperature. That means hot, solid rock is hard to differentiate from similarly hot liquid magma.
The new study used a method called magnetotellurics to get a better look. Earth’s rotating core creates a magnetic field that surrounds the planet. Because magma contains magnetic minerals, pockets of subterranean liquid magma create their own mini-magnetic fields detectable at the surface, too. Using instruments deployed around Yellowstone, researchers mapped these mini-fields to find hidden pockets of magma.
They found four pockets together contain more liquid magma than was present during large, caldera-forming eruptions at Yellowstone in the past (one 2.8 million years ago, one 1.3 million years ago and one 640,000 years ago). This magma rests as deep as about 6 or 7 miles (9.6 to 11.2 kilometers) below the surface, Bennington told Live Science. But only in the northeastern region of the caldera is the magma in touch with hot basalt rock from the mantle that will keep the magma liquid in the long term.
Despite the large volume of magma pooling below Yellowstone, the caldera isn’t likely to erupt anytime soon. That’s because the magma sits in pore spaces in solid rock within the caldera, much like water in a sponge. Only when more than 40% of these pore spaces are filled can the magma in the pores link up, get mobile and start erupting, Bennington said. She and her colleagues estimated that the fraction of filled pores was 20% or less, similar to estimates in other studies.
“We have a much lower concentration of magma in these pore spaces, so a lot fewer of the pore spaces are filled with magma,” she said. “What that means is you can’t interconnect these magmas to mobilize and erupt.”
But as hot rock warms the northeastern magma pools over tens of thousands of years, that could eventually change. Exactly how long that will take, or if it will happen before the mantle rocks in the northeastern region of Yellowstone lose contact with its magma reservoir, remains unknown.
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