Everyone knows that Yellowstone is home to a super-volcano—but it turns out that the magma reservoir it sits atop is at least 2.5 times larger than we previously thought.
Most of the magma which fuels Yellowstone's geysers and hot springs sits a few kilometers beneath the Earth's surface. Now, researchers at the University of Utah, have mapped the pool of molten rock more accurately than ever, by analyzing data taken from over 4,500 earthquakes.
By looking at the way seismic waves—the energy that travels through the planet following a volcanic eruption or earthquake—propagated through the Earth's structure, they were able to identify exactly where the reservoir was beneath the surface, and how much magma it contained. That's possible because the waves travel more slowly through molten rock than through solid, and the team has data with enough detail to pinpoint exactly where those changes in speed occur.
The results suggest that Yellowstone's reservoir is about 80 kilometers long and 20 kilometers across—a "4,000-cubic-kilometer underground sponge," as Nature refers to it—which is around 6–8 percent filled with magma. That means that there's at least 2.5 times more molten rock sat beneath the National Park than previous estimates suggested.
The work, which was presented on 27 October at the annual meeting of the Geological Society of America in Denver, Colorado, perhaps goes some way to explaining why volcanic events at Yellowstone are so severe. Let's just hope it's a while until the next one. [Nature]