LOS ANGELES — The awe-inspiring Grand Canyon was probably carved about 70 million years ago, much earlier than thought, a provocative new study suggests — so early that dinosaurs might have roamed near this natural wonder.
Using a new dating tool, a team of scientists came up with a different age for the gorge's western section, challenging conventional wisdom that much of the canyon was scoured by the mighty Colorado River in the last 5 million to 6 million years.
Not everyone is convinced with the latest viewpoint published online Thursday in the journal Science. Critics contend the study ignores a mountain of evidence pointing to a geologically young landscape and they have doubts about the technique used to date it.
The notion that the Grand Canyon existed during the dinosaur era is "ludicrous," said geologist Karl Karlstrom of the University of New Mexico in Albuquerque.
Though its exposed rocks are ancient, most scientists think the Grand Canyon itself was forged in the recent geologic past, created when tectonic forces uplifted the land that the Colorado River later carved through.
The new work by researchers at the University of Colorado Boulder and California Institute of Technology argued that canyon-cutting occurred long before.
The team studied rocks from the canyon bottom and concluded that the western canyon is 70 million years old and likely shaped by a river running in the opposite direction.