Should it ever erupt, a supervolcano beneath Yellowstone National Park could blanket North America in an ash cloud, wipe out communications, and alter the climate. Given that eruptions of supervolcanoes buried on our planet—and there are several—are thought to occur every 100,000 years or so, however, the likelihood of such an event during your lifetime is small, reports the New York Times. As comforting as that may be, new research out of Arizona State University is far less so. Whereas researchers previously thought such an eruption would be centuries or millennia in the making, an analysis of fossilized ash left over from Yellowstone's last supereruption 630,000 years ago reveals the process could take only decades.
Tiny crystals left over from underground magma at Yellowstone show the first sign of the last supereruption was a spike in temperature that coincided with the movement of new magma into the reservoir beneath the supervolcano. The crystals also reveal a supereruption followed much quicker than scientists previously thought—perhaps within decades, or what Popular Mechanics calls "a geologic snap of the finger." This is the first indication that "the conditions that lead to supereruptions might emerge within a human lifetime," which one researcher describes as "shocking," per the Times. For now, though, you can rest easy. The lead scientist at the Yellowstone Volcano Observatory tells National Geographic there's no sign of any "magmatic event" at this time. (You might outrun a supervolcano's lava anyway.)