Is a volcano in the U.S. going to blow?
Yes. The only question is when. Some geologists are worried that it might be sooner rather than later, given the ominous rumblings recently detected in Yellowstone National Park in Wyoming. Filled with geysers, fumaroles, and other geological hot spots, much of Yellowstone sits atop a giant caldera—which is a collapsed volcano. Volcanoes are openings in the Earth’s crust through which molten rock, ash, and gas periodically escape. Frequently, magma—molten rock—moves beneath the surface, prior to spewing out, and such movement registers as seismic tremors. In 2008 and early this year, geologists recorded an unusually high number of tremors in Yellowstone: 813 in 11 days, the second most intense cluster since recordkeeping began, in 1973. Such heightened activity might signal that an eruption is brewing. When might that happen? It could happen next week—or possibly 50,000 years from now. If that sounds vague, such is the nature of geologic time. Yellowstone’s last major eruption was abou
