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MARGARET WARNER (Newshour): ...... Just how old is the Grand Canyon?
The conventional wisdom holds that this natural wonder of the world was shaped by the Colorado River about five or six million years ago. But there's been a long-running debate over whether it's much older. And, yesterday, researchers published a study in the journal "Science," arguing these majestic formations were formed by two much older rivers cutting through the landscape some 70 million years ago. That was during the age of the dinosaurs.
We have NewsHour science correspondent Miles O'Brien here to tell us what the debate is all about.
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