Petrified sand dunes eroding out of sandstone

Much of the 4-Corners area is underlain by a geologic formation known as the Navajo Sandstone. It can be several hundred feet thick, and was not formed (as usual) from water-deposited sand, but rather from overlapping, coalescing sand dunes. In many places, such as here at Canyon de Chelly, as the sandstone erodes it reveals the original sand dunes. Canyon de Chelly National Monument, Arizona.

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