“Our data detects a major canyon sitting there about 70 million years ago,” said Rebecca Flowers, 36, a geologist at the University of Colorado and the lead author of a paper published online Thursday by the journal Science. “We know it’s going to be controversial.”
About that she is quite correct. Her research, which reconstructs the ancient landscape using a technique called thermochronology, is being met with a cool reception from veteran geologists who study the Colorado Plateau.
“It is simply ludicrous,” said Karl Karlstrom, 61, a professor of geology at the University of New Mexico who has made more than 50 river trips through the canyon — one with Flowers, when she chipped her samples off the canyon walls — and helped create the Trail of Time exhibit for the National Park Service.
“We can’t put a canyon where they want to put it at the time they want to put it,” said Richard Young, a geologist at SUNY Geneseo who has been studying the Grand Canyon for four decades.
Wondrous though it is, Grand Canyon doesn’t seem terribly mysterious at first glance. It’s a gash in the landscape with a river at the bottom. The causality seems obvious. But Flowers and her fellow Old Canyon theorists say that what we see today in northern Arizona was originally carved, in large degree, by two rivers — neither of which was the Colorado River.
The western part of the canyon, they say, was largely incised about 70 million years ago by what has been dubbed the California River, which drained a mountain range to the west and flowed to the east, in the opposite direction from today’s Colorado River. The eastern part of the canyon, they say, was created later, around 55 million years ago, by a different river.
Under the Old Canyon scenario, the Colorado River, which originates in the Rocky Mountains, is a bit of an opportunist, and about 6 million years ago took advantage of the pre-existing canyons and linked them in a fashion that creates the sinuous canyon of today.
The debate to some extent hinges on the semantic question of whether “an Ancient Grand Canyon” (as the Science paper calls it) is the same thing as the Grand Canyon of today. The Flowers paper says the depth of the ancient canyon was within a “few hundred” meters — roughly a thousand feet — of today’s canyon.