It’s been a hell of a year for volcanophobes, who grew anxious as the Montana earthquake shook the Yellowstone supervolcano in July and watched their worst fears play out as Bali’s Mount Agung erupted in November. But 2017 isn’t done toying with them yet. On Wednesday, a team of UK scientists reported in a new study that the time between super-eruptions is much shorter than previous estimates, suggesting that Yellowstone’s supervolcano might spew disaster a lot sooner than we thought.

If that happens, the fallout will be catastrophic. Yellowstone’s volcano is most remarkable because it’s huge, with a rim that measures 30 miles long by 45 miles wide. Technically, it’s not a volcano but a caldera — a cauldron of magma in the earth that looks somewhat like an inverse volcano and has a much greater potential for intense damage.

When a caldera blows, its magma doesn’t just flow out of a single opening, the way it does in classic volcanos; rather, it bursts out of multiple exit points, causing them to collapse into floods of lava and ash.

Upper terraces of Mammoth Hot Springs, Yellowstone National Park, Wyoming. Hot water is the creative force of the terraces. Even though Mammoth Hot Springs lie north of the caldera ring-fracture system, a fault trending north from Norris Geyser Basin, 21 miles (34 km) away, may connect Mammoth Hot Springs to the hot water of that system. A system of small fissures carries water upward to create approximately 50 hot springs in the Mammoth Hot Springs area. Another necessary ingredient for terrace growth is the mineral calcium carbonate. Thick layers of sedimentary limestone, deposited millions of years ago by vast seas, lie beneath the Mammoth area. As ground water seeps slowly downward and laterally, it comes in contact with hot gases charged with carbon dioxide rising from the magma chamber. Some carbon dioxide is readily dissolved in the hot water to form a weak carbonic acid solution. This hot, acidic solution dissolves great quantities of limestone as it works up through the rock layers to the surface hot springs. Once exposed to the open air, some of the carbon dioxide escapes from solution. As this happens, limestone can no longer remain in solution. A solid mineral reforms and is deposited as the travertine that forms the terraces. Photo credit: Brocken Inaglory via Wikimedia Commons commons.wikimedia.org/wiki/File:Upper_Terraces_of_Mammoth...
Hot springs in Yellowstone lie north of the caldera system.

While spillage from regular volcanos is usually sequestered in the valley immediately surrounding them, caldera explosions generally leave a much bigger mess. Previously, Inverse described Yellowstone’s last few explosions:

Lava last gushed out of the Yellowstone supervolcano around 70,000 years ago, and in the last two million years, scientists believe that three “major” volcanic eruptions occurred. One of these, the Island Park super-eruption, left a telltale blanket of volcanic rock in the area about two million years ago, and scientists estimate that this event produced 2,500 times more ash than the 1980 Mount St. Helens eruption.

A recent re-analysis of the geological record left by Yellowstone’s last big explosions, which occurred 630,000 years ago, showed that the ash that spewed skyward was so thick that it caused a “volcanic winter.” In the study, the scientists from the University of California, Santa Barbara showed that the earth cooled by several degrees after the ash obscured the sun’s rays, preventing them from warming the planet.

Fortunately, the UK scientists behind the latest study on supervolcano eruptions don’t think we have anything to worry about. “My view … is that we should not be worried about super-eruptions,” Jonathan Rougier, Ph.D., a statistician and the study’s first author, told Inverse in a previous interview. By his team’s estimates, super-eruptions happen every 5,200 to 48,000 years — their “best guess” is that they happen every 17,000 — which he said is “comfortably longer than our civilization.” The United States Geological Survey, for their part, puts the odds that the Yellowstone volcano will blow at about one in 730,000.