Study: Grand Canyon much older than thought

LOS ANGELES -- The 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 nearby.

Using a new dating tool, 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 Colorado River in the past 5 million to 6 million years.

Not everyone is convinced about the latest viewpoint, published online yesterday in the journal Science by researchers at the University of Colorado, Boulder, and California Institute of Technology.

Critics contend that the study ignores evidence pointing to a geologically young landscape, and they have doubts about the technique used to date it.

The researchers crushed rocks from the canyon bottom to analyze a mineral called apatite. It contains radioactive elements used to calculate the time since the canyon eroded. -- AP