Magnificent sand seas of the West.
Early travelers saw dunes as desolate obstacles. In the late 1800s, surveyor George Wheeler described a traverse of Death Valley: "The route lay for miles over light, white, shifting sand. The stifling heat, radiation, and constant glare from the sand were almost overpowering."
Today, the image of dunes as barren, lifeless places has changed, and the growing appreciation of these sand-bound ecosystems is reflected in fervent efforts to protect them. Offroad vehicles have been banned from some preserves and restrictued from entering parts of others. One area, Eureka Dunes is a newly designated national natural landmark.
As the map at top right indicates, these big dunes--from nearly 4 to 40 square miles--are scattered over the West. We list 13 of the biggest and most accessible dune systms on the opposite page. Even if you visit just one of them (or stop by a smaller coastaul (dune) on a day or weekened outing, you might get hooked. Some aficionados can never get enough time hiking, sliding, and photographing these compelling formations.
Now through April is perhaps the most clement season to visit most these dunes. The inland ones are in arid, almost rain-free regions offering clear, crisp winter days. You can hike for miles without gasping for water or bracing yourself against gritty blasts. (Late spring often brings high winds; summer brings savage heat.) And several are on or near routes to popular getaways: Palm springs and Las Vegas. The two coastal dunes we list take winter rain straight in the face, but between storms they offr sparkling vistas. How nature stockpiles sand
Why is the West so dune-rich? Aridity is one major factor in the formation of our inalnd dunes. Another factor in many areas is the ample supply of building material: sand deposited in river-beds or eroded from cliffs. On our coast, ocean waves pound sandstone and granitic cliffs and deposits the lightest grains on wide beaches.
Certain conditions are required for dune building: an abundant souce of dry, fine- to medium-grain sand (.125 to .5 millimeters); wind that blows in a consistent direction and with sufficient strength (at least 10 mph) to move sand; and an opposing wind or land barrier to halt the sand.
Over sometimes hundreds of years, grains of sand are blown overland, bouncing along not far off the ground, before piling up against a barrier, perhaps a mounting. At coastal systems, such as the Oregon and Pismo dunes, ocean current and tides deposit sand on wide, flat beaches where it is banked and held by prevailing winds and vegetation against natural backstops. The four distinct dune shapes shown above testify to the varied work of the wind. Leeward sides (slipfaces) of dunes are never steeper than 32 [deg.] to 34 [deg.], called the angle of repose--the maximum angle at which loose sand remains stable.
Some dunes can speak. Called barking, squeaking, or whispering dunes, they make a low humming sound when great amounts of dry sand slide down a long slipface. A few inland dunes actually boom. At Great Sand Dunes National Monument, Chief Naturalist Robert Schultz quips, "I never met a dune I couldn't make boom." He believes that when any tall dune is quite dry and the air still, a person can set off a boom by pushing sand off the crest. Others claim it takes certain dry, highly polished rounded grains set in motion to cause a boom. Dune fun, and sense
Since prodding up a dune can be tiring, consider going in the morning, when sand is still hard-packed and a bit moister. Sand is usually firmer on the windward (stoss) slope than it is on the steeper slipface. If you can't start early, wait until late in the afternoon, since winds commonly pick up at midday as the temperature rises. It's wise to wear sunblock, a wide-brimmed hat, and sunglasses to protect against reflected sunshine, and a bandanna and long-sleeve shirt to shield you nfrom blowing sand. High-topped boots will help keep sand out. Always carry a supply of water. In desert dunes, watch for rattlesnakes and scorpions.
Photographers drool over the picture possibilities. Like chameleons, sand dunes change color as the day progresses: pale gold at dawn, glaring white at midday, rosy at sunset. Shooting at daybreak or sundown best captures the richest tones and the longest shadows. Carry camera gear in a tightly sealable bag to keep sand out.
Children know instinctively what to do: they run, jump, slide. In open, unvegetated areas, you can try sliding on a lightly inflated truck inner-tube, snow dish, or thin plastic mat. If you have a castoff pair of downhill skis, apply silicone spray to the bases and try dune skiing. Don't do this with good gear: It's about as abrasive as skiing on sandpaper. Tenacious flora, adaptive fauna
The harsh dune environment winnows out the weak. Plants must be tenacious enough to survive high winds (40 mph or more), abrasion, burial, drastic temperature ranges, incessant sun, and meager rain. Long taproots (40 feet deep on some species) and extensive root systems help plants cling and absorb scant moisture. Dunes actually retain subsurface water, and while the top layer may register an infernal 140 degrees on a summer day, just inches below it may be a cool, moist 60 degrees.
On inland dunes, open swaths of sand provide habitat for sunloving annual plants and low-growing desert wildflowers such as white evening primrose, pink sand verbena, and violet locoweed. In the troughs between the dunes (interdune areas), you'll find scurf-pea and "blowout" or bunchgrasses, and at dune edges, taller shrubby plants like creosote bush, four-winged saltbush, honey mesquite.
On coastal dunes, tough, salt-tolerant European dune grass stabilizes the foredunes 'those nearest the waves), and back dunes are scattered with bright yellow beach primrose, pink morning glory, Indian paintbrush, and California poppy.
Nocturnal creatures such as snakes, beetles, and mice abound in each dune system. These animals survive by burrowing below the surface or hiding under brush by day, then emerging at night to hunt or forage. Tiny crisscrossing tracks tell of journeys and chases in the night. In the morning, look around shrubs for tracks before the wind erases them.
Many animals have made special adaptations to their arid, sandy world. The kangaroo rat drinks no water but absorbs moisture solely through the seeds it eats. The sand treader camel cricket and fringe-toed lizard have feet that act like snowshoes.
You might want to bring a pocket magnifier for close-up inspections and a field guide to seashore or desert wildflowers, mammals, reptiles, and insects. Wheels on the sand: controversy and compromise
Off-road vehicles are barred from seven of the dune systems we list. In the other areas, such vehicles have limited access or are allowed to range the dunes. Self-propelled explorers may find this vehicular presence intrusive. While most dune drivers follow the rules and regulations, those who stray into vegetated areas can cause more than visual disturbance. Some ephemeral plants--short-lived annuals that grow, blossom, and set seed in a brief time span--die out if disturbed. Desert plants take decades to regenerate; when they're crushed or the soil mantle is broken by tires, the delicate balance of the dunes is upset. Even the natural contours of dunes can give way: as vehicles cut trails through vegetation, blowouts occur, and the sand fans out through the cut.
Vehicular access remains a controversial issue at the Panamint Dunes near Lone Pine, California: they were closed to vehicles in 1980, but 500 acres are being considered for reopening by permit after requests from recreation groups and Inyo County officials.
Dune studies continue: inventories of plant and animal species have only begun in some areas; botanists are looking at how plants stabilize sand and how dunes can protect coastal developments; geologists are monitoring sand movement. Such research can help us better understand the complex world of the dunes.
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|Date:||Jan 1, 1984|
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