Landmark may be eons older than believed
The Grand Canyon may be much older than widely believed, according to a new study that challenges the view that the American landmark was born just 5 million or 6 million years ago.
Analyzing helium levels in rocks chipped from outcrops in the western portion of the canyon, geologist Rebecca Flower, of the University of Colorado at Boulder, and geochemist Kenneth Farley, of the Califor- nia Institute of Technology, concluded that the gorge was there — and within a few hundred meters of its modern depth — about 70 million years ago.
The findings, published online Thursday in the journal Science, add fuel to an ongoing debate between scientists who argue in favor of an “ancient Grand Canyon” and colleagues who maintain the miledeep formation must have been carved by the Colora- do River far more recently.
“It’s one of these classic conundrums,” said geologist Brian Wernicke, of Caltech, a supporter of the ancient canyon theory who has worked with the coauthors, but was not involved in this research. “You have two pieces of information that butt heads against each other. One of them isn’t going to be right.”
Determining a precise history of how and when the Grand Canyon came to be is difficult, Flowers said, because there are few direct ways to read how it was carved from the rock.
If an ancient date of origin turns out to be correct, it would have implications for scientists’ understanding of how the topography of the West came to be, Flowers said. But other researchers said they doubt that will be the case.