Most individuals are inspired by the mountain vistas and wildlife found in our National Park System. However, being a soil scientist, I usually have my head down looking at interesting soils and soil-forming factors occurring at these special places. Water and wind erosion of soils have been going on since the beginning of time. When they happen, they change the landscape – sometimes dramatically. Great Sand Dunes in Colorado is an example of these two powerful acts of nature coming together. This National Park has the tallest sand dunes in North America, with peaks of 750 feet!
Great Sand Dunes National Park is located in the San Luis Valley, between the San Juan and Sangre de Cristo Mountains. Great Sand Dunes National Park is not just sand. It includes wetlands, forests, grass and shrub lands, and agriculture. These are all supported by soils formed from erosion of the two mountain ranges surrounding the valley.
Soil erosion is often associated with land degradation and viewed as a negative. When someone says erosion, my mind usually thinks of the Dust Bowl (wind) and the Gulf of Mexico Dead Zone (water). However, all soil was formed from erosional processes – and still is today! The rocks that degrade and become soil are known as “parent material.”*
At the Great Sand Dunes National Park, the processes of wind and water erosion are in perfect concert. Historically, the original sand came from soil deposits from the Rio Grande River. Even more erosional sediment “soil” comes by water erosion from mountain streams each year. Some of the soil in the dunes has traveled from the 13,000 to 14,000 foot peaks of the Sangre de Cristo Mountains!
But, there is a daily fight between wind and water at Great Dunes that’s an even bigger event. Water brings in sand, wind blows it back out: The water erodes the sand back to the southern portion of the dune field by Sand Creek (western edge of the dune field) and Medano Creek (eastern edge of the dune field). But, the sand is again blown back to the northeast by predominate southwesterly winds, and the erosional cycle continues. The easterly winds help create the dunes, too – especially their renowned height. And, it’s the wind that rebuilds the dunes every day!
Erosion has created some of our other greatest national treasures including the Grand Canyon (Arizona) and Bryce Canyon (Utah).
Usually, soil scientists encourage national park visitors to stay on the designated paths. This is because valuable soil microbes and other animals live in the soil, and walking off the path can lead to soil compaction, and destruction of natural habitats. To read more, visit here.
At Great Sand Dunes National Park, the erosional process rebuilds the dunes every day. So if you go, walk anywhere on the dune field. You may leave temporary footprints, but the continuous erosional processes there will make sure you leave no foot prints for tomorrow. The next day’s visitors will be able to experience this unique erosional and soil forming system.
Answered by Aaron DeJoia, Duraroot
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*To learn more about soil-forming processes, check out this Soils Matter blog: https://soilsmatter.wordpress.com/2014/12/11/what-ingredients-make-up-soil/