White Sands National Monument

At the northern end of the Chihuahuan Desert lies a mountain-ringed valley, the Tularosa Basin. Rising from the heart of this basin is one of the world’s great natural wonders – the glistening White Sands New Mexico. Here, great wavelike sand dunes of gypsum sand have engulfed 275 square miles of desert and have created the world’s largest gypsum dunes field. The brilliant white sand dunes are ever changing: growing, cresting, then slumping, but always advancing. Slowly but relentlessly the sand, driven by strong southwest winds, covers everything in its path. Within the extremely harsh environment of the dune field, even plants and animals adapted to desert conditions struggle to survive. Only a few species of plants grow rapidly enough to survive burial by moving dunes, but several types of small animals have adapted a white coloration that camouflages them in the gypsum sand. White Sands National Monument preserves a major portion of this gypsum dune field along with the plants and animals that have successfully adapted to this constantly changing environment.

Exploring White Sand Dunes

How the Dunes Formed

The Tularosa Basin

The gypsum that forms the white sands was deposited at the bottom of a shallow sea that covered this area 250 million years ago. Eventually turned into stone, these gypsum-bearing marine deposits were uplifted into a giant dome 70 million years ago when the Rocky Mountains were formed. Beginning 10 million years ago, the center of this dome began to collapse and create the Tularosa Basin. The remaining sides of the original dome formation now form the San Andres and Sacramento mountain ranges that ring the basin.

Gypsum Sand: A Rare Form of Sand

The common mineral gypsum (CaSO_4$ H²O),a hydrous form of calcium sulfate, is rarely found in the form of sand because it is soluble in water. Rain and snow that fall in the surrounding mountains dissolve gypsum from the rocks and carry it into the Tularosa Basin. Normally, dissolved gypsum would be carried by rivers to the sea. But no river drains the Tularosa Basin. The water, along with the gypsum and other sediments it contains, is trapped within the basin.

Lake Lucero

With no outlet to the sea, water flowing into the Tularosa Basin either sinks into the ground or pools up in low spots. One of the lowest points in the basin is a large playa called Lake Lucero. Occasionally, this dry lake bed fills with water. As the water evaporates, the dissolved gypsum is deposited on the surface. Even more gypsum deposition occurred during the last Ice Age when a larger lake, Lake Otero, covered much of the basin. The Alkali Flat area is the exposed bed of this Ice Age lake.

Crystal beds

In wet periods, water evaporating slowly on the playa floor causes gypsum to be deposited in a crystalline form called selenite. Along Lake Lucero’s shore and in the Alkali Flat, beds of selenite crystals – some three feet long – cover the ground. The forces of nature – freezing and thawing, wetting and drying – eventually break down the crystals into sand-size particles light enough to be moved by the wind.

Four Types of Dunes at White Sands

Dome Dunes. The first dunes to form downwind of Lake Lucero are low mounds of sand that move up to 30 feet per year.

Barchan Dunes. Crescent-shaped dunes form in areas with strong winds but a limited supply of sand.

Transverse Dunes. In areas with ample sand, barchan dunes join together into long ridges of sand.

Parabolic Dunes. On the dune field edges, plants anchor the arms of barchans and invert their shape.

Visitor Activities

The Dunes Drive leads from the visitor center eight miles into the heart of the dunes. Wayside exhibits along the Dunes Drive interpret the geology and natural history of the white sands. Four marked trails, including the wheelchair-accessible Interdune Boardwalk, allow you to park and leave your car for exploring the dunes on foot.

Ranger-led activities offered during the summer include orientation talks, nature walks, evening slide programs, and star talks. Auto caravans to Lake Lucero are offered monthly (advance reservations required). Motorcoach tours and other organized groups can arrange special programs in advance.

Wildlife in the park, as in other desert areas, mostly remains underground in burrows during the heat of the day and emerges at night. Tracks of rodents, rabbits, foxes, coyotes, porcupines, and other nocturnal animals can be seen in the sand the following morning. Lizards, beetles, and birds area active during the day and can be observed in vegetated areas. A few species of animals – a pocket mouse, two lizards, and several insects – have evolved a white coloration to blend with the sands. The oryx, an African antelope, was introduced by the State of New Mexico onto the White Sands Missile Range. Oryx have successfully adapted to the area, multiplied, and spread into the park. The National Park Service considers this exotic animal to be a threat to the park’s native plants and animals.

Even desert plants and animals have difficulty surviving among shifting dunes. A small number of plants have made remarkable adaptations to avoid burial by moving sand. The soaptree yucca can elongate its stem to keep its leaves above the sand, growing as much as a foot per year. Other plants can anchor part of a dune with their roots and continue to grow on a pedestal of sand after the dune moves on.

Photography is best in morning and evening when low light produces colors. Photographing dunes can be difficult. White dunes usually come out gray if exposed as indicated by your camera’s internal meter. For manual cameras, if the picture includes mostly dunes, overexpose the shot by one or two stops to bring out the sand’s whiteness. If the subject is a person or plant, meter off the subject for a proper reading. A polarizing filter will enhance contrast.