Geologist Richard Young of the State University of New York at Geneseo said his own work suggests there was a cliff in the place of the ancient Grand Canyon.
Flowers "wants to have a canyon there. I want to have a cliff there. Obviously, one of us can't be right," he said.
Whatever the age, there may be a middle ground, said Utah State University geologist Joel Pederson.
Researchers have long known about older canyons in the region cut by rivers that flow in a different direction than the Colorado River. It's possible that a good portion of the Grand Canyon was chiseled long ago by these smaller rivers and then the Colorado came along and finished the job, he said.
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