The Grand Canyon in Arizona, USA, is probably one of the most famous canyons in the world. It has been around for about 5 to 6 million years, yet it still holds lots of undiscovered secrets.
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On a winding trail through the red cliffs, one geologist discovered that one boulder had separated from a rock formation. When he examined it closely, he discovered something shocking. This discovery shed some light on the prehistoric life in Arizona.