Discover how wind builds, shapes, and moves mountains of sand.
Dunes are dynamic landforms created when wind carries loose grains and deposits them in repeating patterns across deserts and coasts.
Weathering and ancient sediments supply countless grains.
Learn MoreGrains bounce, roll, and fly across the ground.
Learn MoreWind direction and sand supply create distinctive forms.
Learn MoreSand climbs gentle slopes and tumbles down steep faces.
Learn MoreSpecialized plants and animals inhabit shifting ground.
Learn MoreFragile surfaces need protection from disturbance.
Learn MoreSand begins as rock broken into smaller pieces by water, wind, temperature changes, and chemical weathering. Rivers and ancient lakes may carry and deposit these grains before dry conditions expose them to wind. Some desert sand comes from eroded sandstone, while other grains are remnants of distant mountains or old shorelines. Contrary to a common picture of deserts, only part of the world's desert area is covered by dunes; much of it consists of rock, gravel, or compacted soil.
Wind sorts and moves loose sediment according to grain size and wind speed. Fine dust can rise high into the atmosphere and travel across continents. Heavier sand usually stays near the surface, bouncing in a process called saltation or rolling and sliding along the ground. Each landing grain may knock another into motion. When wind slows behind a rock, plant, or rise in the land, grains settle. Continued deposition can turn a small pile into a growing dune.
Dune shape records the behavior of wind and sand. Crescent-shaped barchan dunes often form where sand is limited and wind blows mainly from one direction. Long linear dunes may develop where winds approach from alternating directions. Star dunes grow tall arms under winds that vary through the year, while transverse dunes form ridges across the main wind direction where sand is abundant. Real dune fields can combine forms as weather and sediment supplies change.
On a typical dune, wind pushes grains up a broad windward slope. Sand collects near the crest until it becomes unstable and slides down the steeper sheltered side, called the slip face. Repeating this process shifts the whole dune downwind. Smaller dunes generally move faster than large ones. Vegetation, moisture, and changing winds may slow or redirect movement. Scientists compare photographs and satellite images to measure dune migration and understand how landscapes change over time.
A shifting dune can be hot, dry, and difficult to anchor in, yet it supports adapted life. Grasses may grow long roots and continue upward when partly buried. Insects, lizards, snakes, and small mammals burrow beneath the surface to escape heat and predators. Tracks left overnight reveal activity that daytime visitors might miss. Plants slow the wind and trap additional sand, gradually creating more stable habitat, while animals move seeds and nutrients through the dune ecosystem.
Dune surfaces can be damaged by repeated vehicle traffic, construction, mining, or heavy foot use. Breaking plant cover may restart erosion and remove shelter for wildlife. Conservation measures include designated paths, vehicle limits, protected habitat, and restoration with suitable native plants. Managers must also allow natural sand movement, because fixing every dune in place can disrupt the processes that created the landscape. Monitoring helps balance recreation, nearby communities, and the needs of dune species.