Hells Canyon is the deepest river canyon in the United States. Now scientists have solved the mystery of when it formed.

Hells Canyon, the deepest river gorge in the United States, likely got rapidly carved 2.1 million years ago when a shifting landscape in Idaho caused a giant lake to start overflowing. That's ...

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 ...