Joanna Carver, reporter
(Image: John Burcham/NGS)
Picture the scene. It's late in the Cretaceous period, 70 million years ago. A group of dinosaurs have gathered at the rim of what will become known as the Grand Canyon. They're gawping over the edge, just as humans will in millennia to come.
That might not be complete fantasy. It had been thought that the canyon formed 6 million years ago. But now two geologists have evidence it is actually closer to 70 million years old.
Rebecca Flowers at the University of Colorado, Boulder, and Ken Farley at the California Institute of Technology calculated the canyon's age by examining helium levels in the mineral apatite in the rocks under the western part of the canyon's floor. Apatite contains uranium and thorium, which decay into helium over time. At high temperatures, like those found deep underground, helium can dissipate. But if surface erosion brings these rocks closer to the surface, as happened at the Grand Canyon, then the cooler temperatures they are exposed to can cause the mineral to hold on to its helium.
Based on higher than expected helium levels, Flowers and Farley concluded that the erosion that shaped the canyon began 70 million years ago. That will be debated among geologists, but if there is one thing that could add to the wonder of the canyon - up to 29 kilometres wide, 446 kilometres long, 1800 metres deep and very, very old - it is the thought of it filled with dinosaurs.
Journal reference: Science, doi.org/jvq
Dinosaurs might have once gazed into the Grand Canyon
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Dinosaurs might have once gazed into the Grand Canyon
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Dinosaurs might have once gazed into the Grand Canyon
