Further evidence that the Yellowstone megavolcano could blow without warning

Yellowstone National Park sits on top of a giant volcanic caldera, or an earthen cap that covers a huge reservoir of superhot liquid rock and poison gasses. Large parts of the park were formed in previous eruptions, the most recent of which happened about 70,000 years ago. Now, the floor of the caldera is rising, and… » 9/03/12 11:37am 9/03/12 11:37am