About 2,000 feet deeper than the Grand Canyon, Hells Canyon was rapidly carved when a lake spilled over about 2.1 million years ago, new research estimates.

The caverns sit atop the Grand Canyon Inn between Peach Springs and Seligman and are a worldwide tourist attraction.

Hells Canyon, the deepest river gorge in the United States, was carved just about 2.1 million years ago — making it much younger than the Grand Canyon.