Too Hot to Handle

ByABC News
August 28, 2006, 5:17 PM

Aug. 29, 2006— -- What could cover the globe in ash, plunge Earth into an ice age and end life as we know it?

The answer is found in what lies beneath: supervolcanoes. Supervolcanoes are very rare. There is no need to run out and buy duct tape and plastic sheeting for this one. The last known supervolcano was about 74,000 years ago. But they are real, and one potential supervolcano lies right here in the United States, in one of America's most profound areas of natural beauty.

Just 20 miles beneath the earth's surface lies a pressurized ocean of molten rock looking for a way out. And a massive release of that molten rock would create a supervolcano -- arguably the largest natural disaster humanity would ever face.

Unlike regular volcanoes, which are shaped like mammoth cones, supervolcanoes spring from massive canyons -- calderas -- that measure hundreds of miles across. Underneath their surface is a vast lake of lava. When the underground liquid rock -- magma -- bursts forth to the surface, a series of violent, massive explosions could occur in a wide-ranging eruption that could last several days. It would incinerate anyone within a hundred miles, and layers of ash would blanket much of the earth.

"These eruptions are so big that you couldn't really see them, because you couldn't be close enough to the volcano, watching it and survive. You could watch it from a satellite and you could see the volcano erupt and see the ash cloud begin to spread," said Michael Rampino, geologist and professor of earth sciences at New York University.