Remnants of a Frozen Sahara

Navajo sandstone, the pale rock capping the top of the Vermilion Cliffs for more than 80 miles and forming the high canyon walls at Zion National Park, came from an enormous Sahara-like desert of wind-blown sand dunes that stretched from present-day Wyoming to southern California. Geologists theorize that when a vast inland sea covered that desert, it solidified in place, and minerals such as calcium and iron cemented the ancient dunes together.

Kaibab, Arizona · United States