Kelso Dunes form the largest field of windblown sand in the Mojave Desert, covering about 45 square miles with ridges rising up to 650 feet above the surrounding land. Part of a broader eastern Mojave sand transport system, the dunes were built from sand derived largely from granitic rocks and from the Mojave River sink near Afton Canyon, then trapped in the Soda Lake-Kelso basin. Their present form reflects repeated climate shifts over roughly the last 25,000 years, with five stacked dune sets recording drier periods. The dunes are also known for booming sand and for specialized desert species adapted to loose sand.