At the northern end of the Chihuahuan Desert lies a mountain-ringer valley, the Tularosa Basin. Rising from the heart of this basin are the glistening white sands of New Mexico. Great wave-like dunes of gypsum sand have engulfed 275 square miles of deser and created the largest gypsum dune field in the world.
The gypsum that forms the white sand was deposited at the bottom of a shallow sea covering the area 250 million years ago. Eventually turned into stone, these deposits were uplifted into a giant dome when the Rocky Mountains formed. Ten million years ago, the center of this dome started to collapse, creating the Tularosa Basin.
Gypsum is rarely found as sand because it is soluble in water. Rain and snow in the mountains dissolve gypsum from the rocks and carry it into the Tularosa Basin. Rivers would usually carry dissolved gypsum to the sea, but no river drains the Tularosa Basin. The water, with the gypsum, is trapped in the basin.
Strong winds blowing across the playa (a dry lake bed) pick up gypsum particles and then carry them downwind. As sand grains accumulate as a dune, the bounce up and gentle windward slope and ripple its surface. At a dune's steep leading edge, sand builds up until gravity pulls it down the slip face, moving the dune forward.
White Sands Missile Range surrounds the park. It was first used as a military proving grounds after WW II for testing rockets captured from German armed forces. The Trinity Site is the location of the first atomic bomb detonation. (That is on my list of places to visit next year.)
These dunes are fabulous for sledding or just climbing. They are truly one of the most beautiful and wonderous sites on earth.