There's a time bomb ticking under the Rockies. A 2,400-cubic-mile chamber of magma simmers beneath Yellowstone's geysers, and University of Wisconsin geochemist Ilya Bindeman says this geologic hot spot is due to blow. His warning comes from an analysis of the volcanic rocks in the chamber and around Yellowstone. When magma flows and hardens above ground, it carries with it uranium-bearing zircon crystals. The uranium decays into lead at a predictable rate, making it possible to date past eruptions. Bindeman found that massive outbursts occurred with startling regularity 2, 1.3, and 0.6 million years ago. "It's likely this periodicity will continue, meaning the next eruption will happen sometime in the next 100,000 years," he says. Maybe tomorrow.
Past blasts hint that Yellowstone's magma chamber could erupt with 1,000 times the force of the 1980 Mount St. Helens explosion, spewing enough ash to cover half the United States, block out the sun, and plunge Earth into years of unending winter. "The effects of this kind of eruption would be comparable to a small asteroid impact, and it's far more probable," Bindeman says.