Sand dunes with the Sangre de Cristo Mountains in the background, Great Sand Dunes National Park and Preserve, Colorado

Sand dunes with the Sangre de Cristo Mountains in the background, Great Sand Dunes National Park and Preserve, Colorado

© Tim Fitzharris/Minden Pictures - 2020-09-13

Sand Natural environment Nature Dune Desert Erg Sky Aeolian landform Geology Wilderness Landscape Singing sand Morning Mountain Ecoregion Sahara Mountain range Terrain Shadow Geological phenomenon Cloud Hill Formation Ridge Tundra