Sand Blast

Visitors have a great time playing and hiking in Great Sand Dunes National Park in, of all places, Colorado.

Cover Story

July 03, 2005|By Robert Cross | Robert Cross,Chicago Tribune

All it needs is a camel, maybe a Bedouin tent, or a couple of date palms. The place is that deserty.

Great Sand Dunes National Park is centered on mounds of sand that go for 30 square miles, right up against the sort of Colorado landscape one has every reason to expect: mountains with snow on top, rushing creeks, cactus, sagebrush, aspens, cottonwoods and ranchland dotted with grazing bison.

The sand is what catches attention, some of it piled nearly eight stories high, magnificent but highly incongruous -- as if Hollywood remade Lawrence of Arabia as a Western.

The Great Sand Dunes area has fascinated people since they first laid eyes on it. Last year, the dunes earned a promotion to national park from their former rank as national monument, due to some land acquisition and a few new national-park-level facilities.

I found the dunes mesmerizing when I first saw them some 20 years ago, and when I revisited them again last fall, I observed that they hadn't lost a grain of magnificence. Up close, they resemble a trans-planted desert from Africa or the Middle East, changing colors and forming shadows, rippling and shifting.

They almost deserve to remain a mystery, one of those natural phenomena too majestic for human comprehension. But, of course, people have almost figured out why those dunes appeared -- almost, but not quite.

Carol Sperling, the park's interpretive officer, started the explanation by pointing out that the modernistic visitor center where we were sitting is on the east side of the Great Sand Dunes. To the west are the San Juan Mountains, and farther east are the Sangre de Cristos. The land beneath the visitor center and under the dunes is the San Luis Valley. This is a portion of the Rocky Mountains' front range.

The sands started to accumulate around 12,000 years ago, although the exact time still eludes scientists.

"The geologic explanation that's accepted right now," Sperling said, "is that most of the material started over there in the San Juans and was brought down out of those mountains by various streams that went across the valley floor."

Most of the material in the dunes matches the material in the rocks of the San Juan Mountains. Streams and prevailing southwesterly winds push the material up against the Sangre de Cristo Mountains. Those mountains and occasional gusts of northerly winds hold the sand in place.

"The part that's not totally clear right now is what happened in between the time the material was getting out to the valley floor and ending up over here." Sperling waved toward the immense wall of sand outside her office window.

"This is just a supposition," she said, "but it sounds pretty plausible, based on what we can see, that there was a big, long, skinny series of lakes that might have been wetlands or seasonal lakes and that the sand ended up in those bodies of water."

After the lakes dried up, goes the theory, the sand was free to pile up against the Sangre de Cristos, leaving the impressive dunes we see today.

Playing in the sand

The visitor center where Sperling works is filled with fascinating displays, including a device that shows how various wind patterns play across a miniature San Luis Valley. Walls of photographs provide a peek at the many faces of the Great Sand Dunes -- pink in the morning and afternoon, purple at dusk or littered with seemingly improbable clumps of snow.

I drove up the road to a parking lot where I could begin a trek across the dunes. Others were far ahead of me, mere specks on a broad surface that midafternoon sunshine rendered a soft beige.

The recreational possibilities of the Great Sand Dunes weren't lost on the people who showed up that day. Two little boys slid down the slopes on plastic disks. Several visitors walked their dogs, and other folks walked themselves.

Hiking on sand thoroughly engages the calves and thighs; the footing shifts constantly and often abruptly. Shoes sink in. I envied those who made it all the way to the top of High Dune, as it's called, but I settled for a lesser, unnamed summit.

Besides missing the heights of High Dune, I also came in the wrong season for water sports. "In spring, Medano Creek is like a Mecca for people who are desperate for the beach but live in Colorado and don't get to the coast very much," Sperling had told me.

Not far from the dune field parking lot, I could see the dry, shallow trench identified as a section of Medano Creek. The creek skirts the east and south sides of the dune mass. In April, May and June, melting snow from the mountains turns Medano Creek into a sort of river.

It might get as deep as 18 inches and move with an energetic current. Little underwater dunes form, and when they become tall enough, water crashes over their crests, causing surf that breaks about every 20 seconds. This is called surge flow.

And right next to it is a beach as natural as beaches get. Bring your folding chair and that inflatable ball.

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