White Sands National Monument is home to the largest gypsum dunefield in the world, nestled in the heart of the Tularosa Basin. The basin, and therefore this island of glistening white dunes, is located in the northern end of the Chihuahuan Desert, rising approximately 4000 feet above sea level. There are approximately 275 total square miles of dunes here, with 115 square miles (about 40%) located within White Sands National Monument. The remainder lies on military land and not accessible to the public. Many who see the dunefield for the first time think it's a barren place but in reality, it's home to a wide variety of natural features and ecosystems.
Geologically speaking, the dunefield is very young, incredibly dynamic, and ever changing.The most active dunes move northeast at a rate of up to 30 feet per year, while the more stable areas of sand move very little. The 98% pure gypsum (calcium sulfate dihydrate) sand originates in the western portion of the monument from an ephemeral lake or playa known as Lake Lucero. As water from rainfall and snowmelt runs down the surrounding mountains, it dissolves gypsum deposits in the rock and carries it into Lake Lucero, the lowest point in the basin. It then evaporates in the hot sun, leaving behind deposits of crystalized gypsum in the form of selenite. Thanks to wind and erosion, it is eventually broken down into sand grains and blown into the dunefield, amassing into dunes that can reach up to 60 feet in height.
Several species of animals have developed very specialized means of surviving in this harsh environment, enabling them to thrive in a place with very little surface water and highly mineralized ground water. In fact, the monument is home to more than 800 different animal species, many of them nocturnal. Included in this number are species from all groups of the animal kingdom: mammals, reptiles, amphibians, birds, fish, and insects. Plants, too, have adapted to flourish here, including many that have long been used by Native Americans for food, clothing and medicines.