Nevada Supervolcano's Flesh Exposed

That's one reason the Caetano caldera is so special -- Nevada's faulted, blocky crust there has slid and tilted so the insides are visible on the surface, like books on a shelf without a bookend.

"You can actually put your hands on the rocks," said geologist David John, also of the USGS. John is also the author of a paper about the Caetano caldera in the February edition of the journal Geosphere.

This close encounter with the long-dead supervolcano's guts is a good way to learn what makes active places like Yellowstone tick.

Among the surprises John and his colleagues discovered, for instance, is that the collapse of Caetano caldera was a whopping three miles deep -- far deeper than expected in such an eruption.

When the Caetano caldera formed, much of Nevada and Utah was a high continental divide -- perhaps 13,000 feet above sea level, according to some estimates. The region was riddled with supervolcanoes, said Lipman, of which Caetano was just one. An analogous region today would be the Altiplano of South America -- the widest part of the Andes -- which contains many intact calderas.

Related Links:

Larry O'Hanlon's blog: Earth Impacts

Supervolcano

How Stuff Works: Volcanoes