12 of the world's most awe-inspiring canyons and craters

These geological formations will take your breath away.

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Grand Canyon Grand Canyon (Photo: prochasson frederic / Shutterstock)

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Grand Canyon

In Arizona, the Colorado River has worn away at the rocky Grand Canyon, making it a mile deep. The multicolored walls of this 277-mile-long wonder, showing billions of years of Earth's history, have beckoned geologists to study the layers since the 1850s, though the jury's still out on exactly why the river chose this path and created the wondrous phenomenon.

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