Desert Dunes, Namibia
Photograph by Frans Lanting, National Geographic
Over thousands of years winds have sculpted sand in the Namib Desert into some of the world's tallest dunes, colored red by iron oxide. The sand contains just enough moisture to sustain a few hardy plants. Not far from this dune, one called Big Daddy looms 1,200 feet above the desert floor.
Photo Tip: Patterns are especially revealing from the air, whether they are the rectangles of agricultural fields or the symmetry of sand dunes.
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