White Sands National Monument

White Sands National Monument encompasses 275 square miles, yet it includes only about half of the largest field of gypsum dunes in the world.  Having no outlet to the sea, runoff from the San Andres and Sacramento Mountains, which contain a strata of gypsum, into the Tularosa Basin accumulates in Lake Lucero where it either evaporates or sinks into the ground leaving behind deposits of gypsum in its crystalline form of selenite.  For 20,000 years, southwest winds have blown particles of selenite off the lake, breaking them into finer and finer pieces which have created the dunes.  The dunes continue to grow and advance at a rate of up to 30 feet per year.

The drive to the "Heart of the Dunes" is 8 miles from the visitor center.  Along the drive is the Big Dune Trail, a one-mile nature trail which includes a climb up onto the dunes.  The trail guide for the nineteen stations along the trail discusses the formation and movement of the dunes and the flora and fauna living on the dunes.  The advancing dunes bury some plants and trees, but others can grow fast enough to keep ahead of the sand--at least for a while.  This cottonwood tree is probably much taller than is apparent.

Once a month, park rangers arrange with the White Sands Missile Range to have MP's escort a caravan of cars through part of the range to Lake Lucero, which is part of the National Monument but not accessible from the dune road.  The tour takes all afternoon and is well worth the effort of having to make advance reservations.  From what the ranger said, I gather that there was an unusually large amount of water in the lake last weekend.

The picture to the right is of the selenite as it exposed by the wind.  It is amber in color and transparent.

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