White Sands National Monument is located on the floor of the Tularosa Basin in southern New Mexico The white dunes have enveloped 275 square miles of desert and are constantly moving northeast. As they move, new dunes are formed.
The sand at White Sands is made of crushed gypsum and is. well, white. The mountains that ring the valley contain gypsum. When it rains, some of the gypsum disolves and is carried into the valley. At the southern end of the dune fields is Lake Lucero, this lake has no outlet to the sea. During the summer, as water evaporates the disolved gypsum crystalizes out of the water. This form of gypsum is called selenite. These crystals can grow up to three feet long and early settlers somtimes used flakes of selenite as windows because it is translucent. As the crystals age, they break down due to natural forces (freezing/thawing, wetting/drying) into sand sized particles that the wind moves into the dune fields.
The shifting sands and dry weather make it hard for plants and animals to survive in this environment. Some have adapted, such as the soaptree yecca, and rosemary mint. Plants don't grow on the dunes, they are rooted in the soil that can be as much as twinty-five feet or more below the sand, and have long stems that grow to the top of the dune. They were living on the desert floor before the dune came, and with a little luck, will survive after the dune moves on. As the dunes advance, they smother most plants. For a plant to live in this harsh environment, it must grow faster than the sand rises or be buried. Yuccas can grow up to a foot a year and can usually out grow the sand. The yucca in the picture to the right has been almost completely buried.
As the dunes move on, plants face the reverse problem. They risk having no sand to support their long stem. Yucca's solve this problem by letting the stem break off as it looses support, then growing a new crown.
Rosmary mints take a different approach. The way its branches and roots are, it retards the movement of sand from around it's base. As the dune moves on, Whats left is a pedestal of sand with a plant growing on the top of it.
In between dunes are the inter-dunal flats. Several species of flowering plants live in the crusty, alkali soil. small animals burrow into the ground to escape the daytime heat This picture of the yucca shows an inter-dunal flat to its left.
Even in this environment, many animals live here. Kit foxes, rodents, porcupines and lizards make there home in the dunes. A few species (a pocket mouse two lizards, and several insects) have evoled a white coloration to protect them. Stink bugs in particular don't mind this climate. They climb up the dunes, leaving patterns in the sand.
White Sands National Monument lies 15 miles southwest of Alamogordo NM on U.S. 70/82 (505) 479-6124. there are several campgrounds within a half hour drive of the monument, and within the monument a primitive backcountry campsite is available on a first come first served basis. There are picnic areas with tables, charcoal grills and restrooms at the end of the senic drive. Don't tunnel into the sand dunes because they collapse easily. Injuries can occur when sand surfing so be careful. (Latitue 32deg 46min North; Longitude 106deg 20min West)
The dunes are beautiful at sunset and every evening there is a
ranger-guided tour through the dune field, where you can learn more
about the dunes and the plants and animals that live there. The following
two pictures were taken at the end of a tour.
(caution: the first picture is 71k)
Most information is from the White Sands Official Map and Guide, a publication of the National Park Service and available at the visitors center. Additional information was gathered from GPO 1969-392-709/21 from rangers at the monument, and from personal observation. All photos are copyright 1995 by G. Edward Johnson. More information about visiting the monument is available at the GORP White Sands page, on Wikipedia, and you can look at White Sands from Space.