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

That’s according to a new study that looked at ancient river sediments that have long been hidden away inside the canyon’s caves, which now lie high above today’s Snake River. This new work ...

Hells Canyon ... new study that looked at ancient river sediments that have long been hidden away inside the canyon's caves, which now lie high above today's Snake River. This new work is ...