Great Sand Dunes
By Barbara Berryman
Sand Dunes in Colorado! Nestled against the rugged Sangre de Cristo Mountains in the San Luis Valley, the Great Sand Dunes are a spectacular sight, a phenomenon of nature. These huge dunes, North America’s tallest at up to 750 feet, make up about 11 percent of a 330 square mile deposit of sand estimated to contain over 5 billion cubic meters of sand. Eroded from mountains, shattered by freezing and thawing, tumbled by streams and winds, the sand grains constantly cycle through the dunes system so its splendor never looks exactly the same from day to day, season to season, year to year. This wonder became a National Monument in 1932. The area’s designation as a National Park and Preserve happened in 2000; it was driven both by better knowledge of water’s many and complex roles there and our desire to protect the entire dunes system – dunes, mountains, creeks and wetlands.
On my visit last month, we had an additional reason to gasp as we approached the Dunes. As far as the eye could see, vast fields of wild sunflowers. In every direction. No words or photos can describe that joy inducing scene. With these yellow fields in front of the beige dunes in front of the shadow blue mountains, well… definitely a photographer’s dream. We obviously walked out onto the Dunes with the other tourists and discovered some people had set up camping chairs to just sit and take in the wonder of it, others climbed (which is really hard in squishy sand), and others tried out sand boarding or sand sledding.
Origin of the Dunes: The dunes are less than 440,000 years old. Wind and water move sand, continually forming and reforming the dunes. Most of the sand comes from the San Juan Mountains, over 65 miles to the west. Larger, rougher grains and pebbles come from the closer Sangre de Cristo Mountains. Sand and sediments from both these vast ranges originally was washed into a huge ancient lake that once covered the valley floor. As the lake receded, the exposed sand was blown by the predominant southwesterly winds toward the Sangre de Cristos where it built up, some washing back down toward the valley floor. Northeasterly storm winds that blast through mountain passes, then caused the dunes to pile back on themselves, thus creating North America’s tallest dunes.