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NOVA | The Grand Canyon's Oldest Rocks

“This rock is more than 4000 feet below the rim of the canyon, and it’s one of the oldest rocks of them all. “ By measuring the radioactive elements in this Granodiorite—the rock here at the bottom—geologists have figured out it formed 1.7 billion years ago.

Premiere Date: October 21, 2015 | Runtime: 00:00:19

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