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Many geologists believe it took the Colorado River just 5 million years to carve the Grand Canyon. But a recent study argues the canyon is really 55 million years old, which means dinosaurs may have once stomped along the rim. The study based its conclusions on the decay of radioactive elements in rocks that cools near the surface just as the dinosaurs died out.

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Grand Canyon mystery

Geologists debate the age of the planet’s deepest canyon, with the answer to ancient riddles hanging in the balance

So I’m sitting on a river-smoothed swirl of Vishnu Schist in the bottom of the Grand Canyon trying to reset my imagination as the Colorado River roars past.


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