the "Laramide revolution" lifted the Rocky Mountains and their southwestern spine, exposing the gypsum-rich rock. Over the course of many centuries, the forces of wind and rain eroded the San Andres Mountains to the west, and the Sacramento Mountains to the east, causing the accretion of gypsum on the basin floor.[1]
Often a visitor to the dunes in his long career with the service, Dodge spoke highly of their unique ecological character in a region noted for its breathtaking environmental phenomena. White Sands was "a striking example of geology in action," said the naturalist, "unnoticed by most people yet … a fundamental process of nature." Contributing to their singular character were the extremes of heat and cold, moisture and aridity, and the surprisingly complex and populous flora and fauna of the region. Annual rainfall rarely exceeded ten inches, yet the water table lay only three to four feet below the surface of the dunes. Temperatures ranged from zero degrees Fahrenheit in January to 110 degrees-plus in the summer. The whiteness of the sands, a function of their purity (over 99 percent gypsum), reflected rather than absorbed the heat of the desert, creating temperate conditions in the midst of summer or the depths of winter.[2]
The naturalist Dodge also catalogued in the "harsh" dune ecosystem no less than 144 species of birds, 23 small mammals, 371 species of insects, and several types of reptiles. Dodge marvelled at the adaptability of the insects and rodents, including the fur color of the "Apache pocket mouse," which was lighter in tone and shade than its cousins amid the Valley of Fires, a lava flow north of the monument.[3]
Much like the plant and animal life of the Tularosa basin, human beings faced identical choices of adaptation for survival. The earliest people identified in the dunes area belonged to the "Folsom" culture; hunters who used spear points like those discovered in far northeastern New Mexico in the early 1900s near the town of Folsom. Archeologists speculated that their preference for "big-game" hunting, especially the bison of 10,000 years ago, kept them away from the dunes proper because of their sparse vegetation. In like manner, later cave dwellers called the "Hueco" culture (from the Spanish word for "tank") appeared along the west face of the Sacramento Mountains by AD 500. Building upon the centuries of agricultural evolution in the region, the Hueco people lived in pit houses and cultivated crops by diverting water from nearby streams. Pottery remains found along the margins of the basin have been linked to the cliff-dwelling "Mogollon" culture of southwestern New Mexico, indicating the trade networks and leisure time available to these advanced peoples amid the harshness of the Tularosa basin.[4]
Drought conditions throughout the Southwest after AD 1100 struck the basin, depopulating the area in a fashion similar to that of the Chaco culture of northwestern
