Grand Canyon May Be Older (And Younger) Than You Think | WAMU 88.5 - American University Radio
Filed Under:

Grand Canyon May Be Older (And Younger) Than You Think

Play associated audio

In recent years geologists have hotly debated the age of the Grand Canyon. Some think it's young (just 6 million years old), while others argue that it dates back 70 million years — to the days of dinosaurs.

Now one group says the Grand Canyon is neither young nor old. Instead, these geologists say, it's both.

In the journal Nature Geoscience, Karl Karlstrom, of the University of New Mexico, and some colleagues describe a new creation story for the Grand Canyon. They think that about 6 million years ago, a river zigzagging a path across the Colorado plateau found part of its way through canyons that already existed.

So, although the Grand Canyon as a whole is relatively young, they say, a couple of sections are ancient.

"We're making a major leap from thinking of a canyon that has a simple history ... to a more sophisticated understanding of how landscapes actually evolve through time," Karlstrom says.

It wasn't too long ago that scientists generally agreed on a simpler history. Karlstrom was part of the team that developed a walking path called the Trail of Time along the south rim of the Grand Canyon. Signs there tell visitors that the Colorado River carved the Grand Canyon in the past 6 million years.

"The Trail of Time exhibit has what we considered at the time, in 2010, to be the scientific consensus," says Karlstrom, who hiked the canyon as a kid and has studied it professionally for 30 years.

Figuring out when a canyon was cut is not easy, he says, because rivers do their sculpting through erosion.

"Erosion takes away material, and so geologists are left without the rock record," he explains, "without the physical evidence of the carving. What you are left with is a landscape, a land form."

Scientists have started using sophisticated new techniques that can reconstruct the history of erosion by analyzing the chemistry of one of the minerals in canyon rocks. And in 2012, a research team used those techniques to make the controversial claim that the Grand Canyon was actually cut about 70 million years ago — in the Late Cretaceous. Experts like Karlstrom were startled.

"That whole episode — Is it old? Is it young? — caused my group to rethink what we meant by 'old' and 'young,' " he says. "And what is the evidence?"

Not everyone thinks the latest findings will be the last word. Brian Wernicke, a geologist at the California Institute of Technology, is in the camp that leans toward a more ancient Grand Canyon, and doesn't buy all of the arguments of Karlstrom and his colleagues.

But to him, the important thing is that this report shows a real shift in thinking. The monolithic view of a young canyon no longer dominates, Wernicke says. "That's not the discussion right now. We've all learned that it's a lot more complicated than that."

Wernicke says he expects that over the next year, there will be more data and more debate.

And all of this is exciting for a scientist, Karlstrom says. "It's spectacular. If you're willing to change your mind based on evidence, it's great fun."

Now when he takes river trips through the canyon, he says, he sees everything with new eyes.

Copyright 2014 NPR. To see more, visit http://www.npr.org/.

NPR

For The Autumnal Equinox, A Poem As Chilling As The Fall Weather

Tuesday is the first day of fall. This time of year reminds critic Abigail Deutsch of Stephen Dobyns' "How to Like It" — a poem about a man who ponders his lost summers and fleeting dreams.
NPR

Keeping Heirloom Apples Alive Is 'Like A Chain Letter' Over Many Centuries

Scott Farm in Vermont grows 100 apple varieties, some of them dating back to the 1700s. These apples may not look as pretty as the Red Delicious, but what they lack in looks they make up for in taste.
WAMU 88.5

New Anthony Brown Video Accuses Opponent Of 'Hiding' And 'Lying"

Democrat Anthony Brown unveiled a new web video today alleging that Republican Larry Hogan is "hiding" his positions on contentious issues like abortion and gun control.
NPR

Retailers' Customers Cautioned As Cyber Attacks Continue

Home Depot says some 56 million card holders were possibly compromised in a cyber attack. It says there's no evidence that debit PIN numbers were comprised or that the breach affected online shoppers.

Leave a Comment

Help keep the conversation civil. Please refer to our Terms of Use and Code of Conduct before posting your comments.