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Mini Tour
Geological marvels can also be one heckuva lot of fun. Colorado's Great Sand Dunes National Monument and Preserve is one of those rare attractions that's not only scientifically and geologically fascinating, but downright fun as well.Landscape photos and article by John Fielder Ripples of water running through your toes. Building sandcastles two feet high. Climbing a dune and jumping off the other side. Soaking up rays for an early season tan. Cabo, Cozumel, Puerto Vallarta? No way! It's Colorado's own Great Sand Dunes National Monument and Preserve. This ecological marvel is in our own backyard, and April, May and June are the best times to beat the crowds and the heat of summer. Embraced within what is now known as the Great Sand Dunes National Monument and Preserve, North America's tallest sand dunes create an unlikely scene just 35 miles northeast of Alamosa in the San Luis Valley, about a four-hour drive from Denver. Designated a national monument in 1932, this Colorado "beach" is a geologic marvel with 30 square miles of dunes up to 750 feet high, and an incredible backdrop of snowcapped mountain peaks. With the passage of the Great Sand Dunes National Park and Preserve Act of 2000, the boundaries were extended beyond the dunes. Now the area also encompasses six mountains topping 13,000 feet in elevation, alpine lakes and tundra, ancient forests of spruce and pine, stands of aspen and cottonwood trees, and grasslands and wetlands. Wind and water — a magical recipeWind plays a big part in the formation of the constantly changing sand dunes. Prevailing winds from the southwest carry sand from the San Luis Valley floor toward three low gaps in the Sangre de Cristo Range: Music, Medano, and Mosca Passes. Taking the path of least resistance, the wind funnels into these mountain notches. But this creates air turbulence which weakens the wind enough so it drops the sand at the foot of the peaks, creating the dunes. Helping to stabilize the sand are countering winds from the northeast.This complex "wind regime" creates two distinctive dune types: reversing and star dunes. Reversing winds have allowed our Colorado dunes to become the continent's highest, and the most fun to jump off! Star dunes, shaped like stars, can only occur where the wind blows from varied directions during the course of a year, as it does in the San Luis Valley. Water also plays a part in dune formation. In April, May and June, snowmelt from the adjacent Sangre de Cristo Range flows down Sand Creek north of the dunes, and down Medano Creek east and south of the dunes. The water carries sand that ultimately dries and becomes fodder for the aforementioned winds. Best of all, though, is the "magic" that Medano Creek creates in the spring. The mountain runoff turns into a two-inch flow of pure mountain water that spreads across 100 yards of sand. One minute the Creek can be bubbling around your feet, the next minute it can completely shift to your right or left. Countless children — and numerous adults! — have spent many an hour chasing the water back and forth. A fascinating bonus is that the two inches of water can also quickly become six inches when you witness the best example of "surge flows" in North America. At regular intervals, roughly every 15 seconds, a "pulse" in the form of a wave of water moves downstream. Waves have been known to reach 12 inches in height. No surfing, but almost! What creates these magical waves? Just as the wind forms dunes on dry land, water carries grains of sand and forms dunes underwater called "antidunes." When an antidune reaches a certain height, it collapses and sends a surge of water down to the next antidune. This chain reaction of collapsing antidunes creates a surge of water every 15 seconds. While playing in the creek can be fun, what's truly exhilarating is climbing around on the dunes. The temperature of both air and sand — the latter of which can reach a sweltering 140 degrees in summer — is moderate in the spring. April can be chilly, but the sun is almost always out in the San Luis Valley to warm you up. It can get hot in June. Many visitors climb 650 feet up the high dune just west of the main parking lot. There are no trails, so just zigzag up the dune ridgelines. From the top you can see the spectacular star dune to the southwest at 750 feet high. Make sure you take your camera, as star dunes are very photogenic. Speaking of cameras, here's a photography tip. Evening light in the San Luis Valley is sublime. Because the San Juan Mountains west of the valley are so far away, the setting sun gets quite low in the sky before it disappears. Thanks to the physics of light, on clear days the color of light turns deep red at sunset. Imagine not only beige dunes turned red, but the contrast created by intense light on one side of a dune and shadow on the other. Stand on top of a dune ridge that runs north to south, and compose the crest as a "lead-in line" to draw your eye from foreground to background. Nature's WaySince the designation of the dunes as a national monument more than 50 years ago, we've learned much about the science of ecology. The connectivity of ecosystems and life zones is critical to the long-term survival of the Great Sand Dunes. Different life zones exist at various elevations, overlapping each other. Each zone harbors a certain combination of animals, plants and processes. One example is mule deer: they graze at high elevations in summer and at low elevations in winter, thus helping to support — and be supported by — numerous and varied ecosystems.Another example is water: The mountains provide runoff that sustains all living things — plants, animals and people — across the San Luis Valley. It also creates the Medano and Sand Creeks, both of which actually disappear underground in the national monument! But this "groundwater," which becomes an underground aquifer, resurfaces near the dunes as ponds and wetlands that support abundant life. Rare shorebirds, mammals, amphibians and the endangered slender spiderflower all depend on these fragile wetlands. As agriculture has blossomed in the San Luis Valley, thousands of water wells have been drilled to tap into this precious resource. It's interesting to note that aerial photos from the 1930s reveal more than 80 natural ponds within the dunes. What's alarming, though, is that only five remain there today. We don't know if natural or manmade changes caused this loss, but a wise person would certainly err on the side of conservatism. There are those who would like to drill more wells in the vicinity of the dunes to export and sell the water to Front Range water consumers. Ecology-minded people, such as myself, feel it's important that this never happens. The good news is that the recent expansion of the national monument to encompass both high elevations and more land in the lower dune ecosystem will help to ensure that ecological connectivity perpetuates nature's way. And that the Great Sand Dunes National Monument and Preserve will still be there for our children's children — and all in our own backyard! Planning Your TripAccess Great Sand Dunes National Monument and Preserve via US 160 and CO 150 from the south, or from CO 17 and County Six Mile Lane (6-N Ln.) from the west. The monument is open 24 hours a day, 365 days a year; 719-378-6300; www.nps.gov/grsa/Unfortunately, the wonderful visitor center is under renovation — a good thing — until September or October 2004. However, a temporary trailer at the main parking lot houses a bookstore and a couple of exhibits. Learn about the archaeological digs in the area that reveal artifacts from native peoples who lived in the San Luis Valley 9,000 to 10,000 years ago, or about saber-toothed tigers, woolly mammoths, and 350-pound beavers that populated the valley after the last ice age. If you have a four-wheel-drive vehicle, consider driving the Medano Pass Road (Forest Road 235), which follows the creek through the dunes, up into the Sangre de Cristo Range and down to the beautiful Wet Mountain Valley. Camping facilities are available at the dunes, and there's a lot of room for car-camping in the Rio Grande and San Isabel National Forests. |
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