Grand Canyon age controversy

Visitors to the Grand Canyon always want to know: How old is it?

Park rangers are instructed to tell them that the canyon has been carved by the Colorado River for the past 5 or 6 million years. The park's Web site, under Frequently Asked Questions, notes that the rocks exposed by the canyon are up to 2 billion years old, and then adds: "The Canyon itself -- an erosional feature -- has formed only in the past five or six million years. Geologically speaking, Grand Canyon is very young."

That might need revision. The canyon is more like 17 million years old, according to a study published today in the journal Science.

Not so fast, said Joel Pederson, a geomorphologist at Utah State University who has spent his career studying the Grand Canyon. He said the estimated age of 5 million to 6 million years is based on abundant evidence amassed by scientists over many decades. Seventeen million is impossible, he said, because there is no evidence of a large quantity of sediment flowing out of a canyon before 6 million years ago.

- Washington Post (link here)

Always love a good science controversy.