Nevada Supervolcano's Flesh Exposed

Feb. 7, 2008 -- The fault-riddled landscape of northern Nevada has sliced and diced the remains of one of the world's largest volcanoes, providing a rare chance to inspect the innards of the so-called "supervolcano."

The Caetano caldera was a 12-mile-wide crater after it erupted 33.8 million years ago and sent a catastrophic ejection of more than 270 cubic miles of molten, lathered rock into the air.

"This is an eruption very much on the scale as the Yellowstone eruption," said caldera volcano expert Peter Lipman of the U.S. Geological Survey (USGS). The hot springs and geysers at Yellowstone National Park are remnants of the last catastrophic eruption there about 600,000 years ago.

The Caetano caldera is not related to the Yellowstone eruption, but both were caused by a gigantic plume of hot rock moving up through the crust. Calderas like these are so large that they can't erupt through a single opening, like most volcanoes. Instead, a caldera ejects molten material and gas in a ringed fracture zone.

The land in the center of the ring, which acts like a lid on the huge pool of magma, collapses. The collapsing lid provides even more oomph to the explosion of hot, foaming magma out of the ring of fractures.

Caldera eruptions, the most powerful volcanic eruptions on Earth, have never occurred during recorded history, Lipman told Discovery News. That makes them all the more difficult to study.