November 30, 2012

Grand Canyon carved out much earlier, study says

The Associated Press

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 viewpoint published online Thursday in the journal Science.

Critics contend the study ignores 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.

How the Grand Canyon became grand has been debated since John Wesley Powell navigated the whitewater rapids and scouted the sheer walls during his famous 1869 expedition.

Some 5 million tourists flock to Arizona each year to marvel at the 277-mile-long chasm, which plunges a mile deep in some places. It's a geologic layer cake with the most recent rock formations near the rim stacked on top of older rocks that date back 2 billion years.

Most scientists believe 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.

 

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