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. Image: Matthew Morriss/ ...

Hells Canyon, which is on the border between Oregon and Idaho, is almost 8,000 feet deep. That makes it far deeper than the famous Grand Canyon of Arizona, which reaches a depth of about 6,000 feet ...