Recent studies have determined where the Yellowstone supervolcano is likely to erupt. It won’t erupt today, but future explosions will most probably focus on the northeastern part of the national park, according to the recent research.
It’s important to note that Yellowstone may not be a national park by the time it erupts. Such an event is predicted to occur hundreds of thousands of years from now, stated study co-author Ninfa Bennington, a volcanic seismologist at the Hawaiian Volcano Observatory, in an interview with Live Science.
The study, published on January 1 in the journal Nature, indicated that instead of being contained in one large mass beneath Yellowstone, molten magma exists in four distinct reservoirs within the crust of the caldera.
To the west, these reservoirs remain disconnected from the deep mantle rocks that could otherwise provide heat from below, maintaining them in a liquid state and ready for eruption. However, towards the northeast, near a landmark called Sour Creek Dome, deep rocks are warming the magma trapped within the crust. This means that, while magma under the western side of Yellowstone is likely to begin cooling and solidifying, the northeastern area will remain heated.
Previous research on Yellowstone utilized the travel of earthquake waves through the caldera to assess the presence of liquid magma versus solid rock beneath the park. However, wave behavior can vary not only based on whether they are moving through a solid or a liquid but also due to temperature differences. Consequently, it is challenging to distinguish hot solid rock from similarly hot liquid magma.
The latest research employed a technique known as magnetotellurics for a clearer analysis. The Earth’s rotating core generates a magnetic field that envelops the planet. Because magma contains magnetic minerals, areas of liquid magma beneath the surface form their own mini-magnetic fields which can also be detected from above. By utilizing instruments set up around Yellowstone, researchers were able to map these mini-fields to uncover concealed magma pockets.
The findings revealed that these four reservoirs collectively hold more liquid magma than what was present during significant caldera-forming eruptions in Yellowstone’s history (one 2.8 million years ago, another 1.3 million years ago, and one 640,000 years ago). This magma is located roughly 6 to 7 miles (9.6 to 11.2 kilometers) deep, according to Bennington. However, only in the northeastern section of the caldera does the magma make contact with hot basalt rock from the mantle, which will ensure the magma remains liquid in the longer term.
Despite the substantial quantity of magma accumulating beneath Yellowstone, the caldera is not expected to erupt in the near future. This is because the magma resides in pore spaces within solid rock in the caldera, akin to water in a sponge. Eruptions can only occur when over 40% of these pore spaces are filled, allowing the magma to interconnect and become mobile, explained Bennington. She and her colleagues approximated that the filled pore space fraction is 20% or lower, similar to findings in other research.
“We have a significantly lower concentration of magma in these pore spaces, which means many fewer of them are occupied by magma,” she stated. “This indicates that you can’t connect these magmas to mobilize and produce an eruption.”
However, as hot rock gradually warms the northeastern magma reservoirs over tens of thousands of years, this situation may eventually evolve. Exactly how long this process will take, or if it will occur before the mantle rocks in the northeastern part of Yellowstone detach from the magma reservoir, remains uncertain.