America's Supervolcano

Yellowstone has erupted catastrophically three times in the last 2.1 million years. The most recent, about 640,000 years ago, buried much of the continent in ash.

The park's famous geysers, hot springs, and bubbling mud pots are not separate wonders. They are all signs of one thing: a vast pocket of superheated magma still sitting a few kilometers below the trail.

The Restless Ground

Yellowstone is not asleep so much as breathing. As magma and hot fluids shift below, the whole landscape slowly rises and falls — by several centimeters a year.

This is normal for a living volcanic system, not a countdown to disaster. The same swelling and sinking has gone on for thousands of years without an eruption. It is the surface quietly reporting on the furnace beneath it.