Sand dune

A hill or ridge of loose sand formed and reshaped by wind. Its shape and movement reflect the balance between wind, sand supply, and vegetation.

Saltation: The bouncing movement of sand grains carried by wind or flowing water. Bouncing grains strike the surface and set other grains moving across a dune.
Sand: Loose granular material composed mainly of mineral or rock particles within a defined size range. Dunes require a supply of grains small enough for wind to transport.
Barchan: A crescent-shaped dune with horns pointing downwind, typically formed where sand is scarce and winds are steady. Its curved planform is a classic expression of limited sand supply.
Coastal dune: A dune formed along a coast from sand supplied by beaches and transported by wind. Coastal dunes can store beach sand and reduce wave impacts during storms.
Dune grass: A group of grasses adapted to grow in mobile or coastal sand. Its roots trap sand and help dunes grow while reducing erosion.
Aeolian processes: Erosion, transport, and deposition caused by wind. These wind-driven processes build dunes and continually reshape their surfaces.
Wind: The movement of air relative to Earth's surface. Its speed and direction control where dune sand moves and accumulates.
Transverse dune: A ridge-shaped dune oriented roughly perpendicular to the prevailing wind, usually where sand is abundant. Its ridges show how plentiful sand builds across the wind direction.
Desertification: Land degradation in drylands caused by climatic variation and human activities. Shifting dunes can threaten infrastructure and fields in vulnerable drylands.
Desert pavement: A surface layer of closely packed stones left after finer particles are removed by wind. It contrasts with dunes, where loose sand remains mobile and accumulates.

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