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White Sands National Monument

Southcentral New Mexico is home to the San Andreas Mountains and the most immense white sands desert on the planet. At White Sands National Monument the dunes play tricks with your mind – distances deceive and the bareness is totally surreal. The white sands are located in North America’s largest desert called the Chihuahaun Desert. It is the least known of the big four deserts because more than 80 percent of it occurs in Mexico.

Summers are searing with daytime temperatures exceeding 38 degrees Celsius and winters are cold with freezing temperatures some nights. The lion’s share of the precipitation occurs in July, August and September from monsoonal thunderstorms generated by the Gulf of Mexico.

The dunes of White Sands Monument are unique, in fact they make-up the largest gypsum sand dunes on the planet. Most of he world’s sand is made up of quartz – a hard silicon material. Gypsum is made up of calcium and sulfur atoms.

Between 24,000 and 12,000 years ago rain and snow melt from the peaks of the San Andreas Mountains dissolved gypsum (calcium sulfate), salt (sodium chloride) and Epsom salt (magnesium sulfate) and carried it into the valley bottom where it formed a 772 square mile (2,000 square kilometer) lake called Lake Otero. Millions of tons of dissolved gypsum, silt and clay were washed from the mountains into the lake which dried up 4,000 years ago. Once Lake Otero completely evaporated the lake bed left behind was salty or alkaline. Beneath the clay and silt gypsum was locked into a crystal form, called selenite, waiting for the wind. Strong southwesterly winds picked up clay and silt particles carrying them high into the atmosphere and out of the area.

The freezing, thawing and sand blasting by the winds broke selenite crystals into white sands particles. As more crystals were disintegrated more gypsum sand began to accumulate and the white sands of this exquisite monument were created.

Forty percent of 185 square miles (480 square kilometers) of the dunes are actually in the national monument, while the rest of the dunes are located in White Sands Missile Range.

The winds are always at least light here out of the south, east or west. In the springtime this desert is raked by extremely strong southwesterlies with average wind speeds in March and April of 47 miles per hour (75 kilometers per hour).

There are at least three kinds of dunes. Barchan or crescent dunes look like a ram’s horn and can reach a height of 66 feet (20 meters). They accumulate in areas with limited sand. Transverse dunes occur where there’s lots of sand and resemble a wave on a lake. Both types of dunes can move four meters a year.

Parabolic dunes have arms like Barchan’s but occur upwind rather than down wind so the direction of their arms is reversed. The move only a meter or two a year and occur on the eastern edge of the monument.

Far from being void of plants and animals White Sands is brimming with life.

Soaptree yuccas cope with shifting dunes by growing higher or outgrowing the encroaching sea of gypsum. They are also able to grow new shoots from their existing root system.

Yucca flowers have a special mutualistic relationship with the Pronuba moth, which visit at night, gather pollen and assist with cross-pollinating the yucca plants. In return, the moth lays her eggs in the developing ovary of the yucca flower. She deposits one egg in a seed but is careful not to disturb every yucca seed because she needs the plants to perpetuate; they are the moth’s only food source.

There are 76 animal species and over 100 families of insects here. Some of them rely on camouflage, or more specifically white coloration, in order to live here.

The Cowles prairie lizard is normally black but it would stick out like a sore thumb in a white desert, so it adapted and it’s white. Cowles spadefoot toads and camel crickets have also specially adapted with white coloration.

This unique White Sands desert and many other treasures of New Mexico in the land of enchantment are worthy of exploration this summer.

Visit White Sands National Monument with Earth Dr Reese Halter

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Earth Dr Reese Halter is an award-winning broadcaster and distinguished biologist. His latest books are The Insatiable Bark Beetle and The Incomparable Honeybee

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Text © by Dr Reese Halter 2012. All rights reserved.


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