Geologists, who have been fighting about the Grand Canyon’s age, now have evidence that suggests the bottom of one of the world’s most famous gorges is about 65 million years older than thought.
Scientists from the California Institute of Technology and the University of Colorado at Boulder found data that may point to the formation being carved to near its modern depth 70 million years ago. That would date the canyon to the Late Cretaceous period when Tyrannosaurus Rex still roamed the earth before their demise about 5 million years later, according to a study published in the journal Science.
The scientists measured rocks from the Grand Canyon’s floor using a technique based on the decay of uranium and thorium atoms into helium in grains of a mineral called apatite. The history of how the buried rock cooled over time as the river cut downward can be read by looking at how much helium is in the apatite, as well as how the helium is distributed.
“There has been a resurgence of work on this problem over the past few years because we now have some new techniques that allow us to date rocks that we couldn’t date before,” Rebecca Flowers, one of the authors of the paper and an assistant professor at the University of Colorado, said in a statement.
Previously, scientists thought the canyon was carved more recently, 5 million to 6 million years ago, or around the time humans diverged from other apes.
The western canyon would have been carved around the same time as the dinosaur’s existence, according to today’s study. A previous study, from 2008, suggested parts of the eastern canyon were developed about 55 million years ago, a period that’s the dividing line between the Paleocene and the Eocene, when the first modern mammals emerged.
The Grand Canyon, on the Colorado Plateau in northern Arizona, is 277 river miles long, up to 18 miles wide, and 1 mile deep. The Colorado River runs through it.