To stand on the South Rim and gaze into the Grand Canyon is to behold an awesome immensity of time. The serpentine Colorado River has relentlessly incised a 450-km-long chasm that in some places stretches 28 km wide and more than 1½ km deep. Visitors to Grand Canyon National Park will encounter an exhibit titled the "Trail of Time," and learn that scientists believe the canyon is about 6 million years old — relatively young by geological standards.
Now a few contrarian scientists want to call time out. The canyon is not 6 million years old, they say, but more like 70 million years old. If this order-of-magnitude challenge to the orthodoxy holds up, it will mean the Grand Canyon has been around since the days of T. rex.
"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."