URL: http://www.abqjournal.com/travel/heritage_whitesands.htm

February 7, 1999
Sea of Sand
By James Abarr Of the Journal     For many miles, the glistening snow-white dunes spread out across the arid, high-desert basin in a panorama that challenges the imagination and delights the senses.
    Extending across the upper edge of the Chihuahuan Desert, 15 miles southwest of Alamogordo in south-central New Mexico, this shimmering sea of dunes blankets 275 square miles between two mountain ranges in the stark and lonely Tularosa Basin. It's a region that ranks among the nation's geologic treasures, because the great dunes here are unique. They are fashioned of rare gypsum sand so fine-grained that it feels silky to the touch.
    Sands in almost all of the Earth's deserts are composed of quartz, a hard silica mineral, but at White Sands, the building block is gypsum, a hydrous form of sulfur and calcium. Geologists estimate there are 8 billion tons of it in this white desert, enough to supply the nation with plaster and wallboard for 1,000 years, which makes White Sands the largest dune field of its kind in the world.
    While gypsum is the main ingredient in the White Sands formula, the building forces of the graceful dunes are gravity and the near-ceaseless wind, blowing mostly from the southwest. As a result, the dunes are ever changing and advancing. Fine gypsum grains are pushed upward to form crests as high as 60 feet on the upwind side, then, under pressure of gravity, the sand slides down steep slipfaces, giving the dunes movement.
    Relentlessly, they are driven northeastward, covering almost everything in their path. Each year, the field advances more than 30 feet.
    Although it's a harsh and dry environment, plants and animals have adapted to survive. Even so, only a few species of plants such as the robust soaptree yucca, sumac and some flowering bushes grow fast enough to escape being buried by the ever-marching dunes.
    Plants have developed elongated stems to keep their tops above the sand, and some yuccas have been found with roots 40 feet long.
    Small creatures such as lizards, mice and insects have adapted a whitish coloring, which makes them virtually invisible. In the surrounding quartz-based Chihuahuan Desert outside the dune field, these same forms of life wear colors of more traditional brown and black.
    Put all the parts together and the result is a bizarre world different from any other — a desert within a desert. Origin of the dunes

    Geologists have spent more than a century unraveling the White Sands phenomenon. How was this exotic landscape created?
    It began many millions of years ago in the primordial time when a shallow inland sea covered southern New Mexico. When the sea eventually retreated and evaporated, it left behind gypsum-bearing marine deposits hundreds of feet thick. These were eventually turned to stone and then uplifted into a giant dome during the period of earth-building that formed the Rocky Mountains about 70 million years ago.
    Then, beginning about 10 million years ago, the center of the dome began to collapse, eventually plunging downward more than 7,000 feet to form the vast Tularosa Basin — 150 miles long and 60 miles wide. On the flanks of the basin, the sides of the original dome now form the Sacramento Mountains to the east and the San Andres Range on the west.
    When the dome collapsed, it exposed the extensive layer of gypsum left behind by the ancient sea, principally in an area high on the eastern flank of the San Andres. Here, in what geologists call the Yeso (Spanish for gypsum) Formation, is a bed nearly 1,600 feet thick.
    For millions of years, rain and melting snow washed great quantities of gypsum-laden sediment down into the lowest point of the basin, which is landlocked with no outlet to the sea. As a result, by the end of the last Ice Age, roughly 12,000 years ago, a vast lake had formed in this low area at the foot of the San Andres. Great quantities of sediment were deposited in the ancient body of water, known as Lake Otero.
    Geologists believe that in that long-ago age, New Mexico's climate was a great deal wetter than it is today. Slowly that changed. In the drier climate that followed, and under the hot desert sun — summer temperatures in the Tularosa Basin can easily exceed 100 degrees — the waters of Lake Otero eventually sank into the ground or evaporated, leaving behind crystals of pure gypsum.
    Today, a large playa called Lake Lucero occupies what was the southern reaches of Lake Otero. Extending northward, along the base of the San Andres is an extensive alkali flat, the exposed northern bed of the ancient lake.
    Most of the time, the present Lake Lucero is dry, its surface strewn with patches of mud, but when strong summer storms lash the region, gypsum-laden runoff from the mountains collects. Usually, this ponded water is never more than a few inches deep.
    As the water evaporates, the dissolved gypsum is left behind in a crystalline form called selenite. Along the shore of the lake and across the alkali flat are great beds of sparkling selenite crystals, some as long as 4 feet. Subsequent freezing and thawing, wetting and drying eventually break down the crystals, leaving behind particles of gypsum sand.
    Then, the sculpturing power of the wind comes into play.
    Under conditions that range from mild breezes to winds clocked at more than 50 miles an hour that can send towering clouds of sand into the air, the fine crystals are plucked aloft and hurled northeastward.
    In this endless process, the dunes are born. Dominating factor

    Beginning in about 1890, geologists intensified their studies of White Sands. In 1915, O.E. Meinzer and R.F. Hare published their seminal description of the Tularosa Basin and the dune-building power of the wind. Since then, almost every scientific paper has focused on the wind as the dominating factor.
    Geologist Edwin KcKee, who did extensive studies at White Sands in the 1960s and 1970s, identified four types of dunes, each in different areas of the field, but all shaped by gravity and the relentless wind:
    Dome dunes: These are the first dunes to form downwind from Lake Lucero. They are low and rounded and form close to the gypsum source along the edge of the lake. Because they are low and streamlined, they can move as much as 30 feet a year.
    Barchan dunes: These form in a U-shaped crescent with the open end pointing upwind and the horns extending downwind around a central slipface. The name derives from the Arabic word for ram's horns. Barchans are created in areas of strong winds. They can reach a height of 60 feet and move about 12 feet a year.
    Transverse dunes: Like barchans, these dunes have a rising windward slope, but they have a steeper slipface. Transverse dunes have no arms. They extend in long, continuous ridges of sand perpendicular to the prevailing wind. They advance at about 12 feet a year.
    Parabolic dunes: These dunes, like barchans, have extended arms, but they point upwind rather than down. Parabolics are found largely on the edges of the dune field where their arms are anchored by vegetation. This slows their movement to about 2 to 8 feet a year.
    One geologist offered this salute to the role of the wind in building these diverse dunes:
    "The Tularosa Basin, lacking vegetation of any significant height, offers minimal resistance to the wind. The wind here is more than just the movement of air, more than something measured merely in miles an hour. The dunes are the wind made visible." A new monument

    In the 1920s, a number of studies were conducted to examine the feasibility of commercially mining the White Sands gypsum field.
    However, concerned citizens launched a campaign to defeat any such prospect. They recognized the geologic treasure represented by the area and called for a protected park safe from exploitation. Their campaign was successful, and in early 1933, President Herbert Hoover, in one of his last official acts in office, declared White Sands a national monument.
    On April 29, 1934, dedication ceremonies opening the monument's 143,000 acres drew more than 4,000 people. In 1938, a number of projects and improvements were completed, including the Visitor Center, a graceful adobe structure with rustic roof beams in classic Pueblo Revival architecture. The center is now listed on the National Register of Historic Places.
    Each year, more than 600,000 visitors come to White Sands to drive or walk through the great dunes set against the stark backdrop of the San Andres Mountains. They take the ranger-guided tours to the lonely shores of ancient Lake Otero and the stark alkali flat, birthplace of the dunes. They visit the Nature Center to learn about plant and animal life in this matchless world of silky white sand.

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