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Landforms of a Desert

Covering about 20 percent of the planet's surface, deserts are regions with very little precipitation, bare landscapes and little plant life. Although they are often thought of as covered only in sand, deserts can harbor a wide range of landforms. Desert landforms are created by different processes, such as weathering, evaporation, flooding and erosion.

Dunes
- Sand dunes cover less than one-third of desert regions.
  
  A dune forms when sand is deposited by the wind when it encounters an obstacle, such as a bush or rock. If they are not stabilized by plant life, dunes can be moved by the wind and migrate great distances. Transverse dunes are formed by constant wind from one direction. These dunes feature a gentle slope on the side exposed to the wind and steep slopes on their lee, or sheltered, side. They often break into smaller mounds as they get farther from the source of sand. Longitudinal dunes are ridges of sand that stretch in the direction of the wind. They feature roughly the same slope on both sides.
Playas
- Playas are the flattest and smoothest features on Earth. Composed of clay and silt, playas form in closed interior basins of arid areas. Water enters the basin during sudden floods and evaporates quickly, often in days or weeks. The evaporating water leaves behind sediment made of fine clay, sand and silt. This sediment builds up in the deeper part of the basin first, and then over thousands of years it spreads across the basin, forming a level surface.
  
  Playas are either wet or dry. In a wet playa, water drawn to the surface from a shallow water table leaves behind salt deposits as it evaporates, covering the playa in a salty crust. Dry playas are often covered by layers of dry mud deposited by flooding.
Alluvial Fan
- An alluvial fan is a cone-shaped formation created by sediment from water and mud flows where streams emerge from mountain sides. They fan out from a single point and feature wedges of grainy sediment and distinctive, radiating channels. Several alluvial fans may merge together, forming a single plain called a bajada. The locations where material is deposited can change over time, and areas of the alluvial fan may become overgrown with vegetation and minerals.
Badlands
- The term "badland" originated in North America and is thought to come from the French phrase "les mauvaises terres a traverser," meaning "bad lands to cross." French explorers applied this term to American Indian descriptions of several regions of the Great Plains. It is now used to classify landscapes from Canada to New Guinea.
  
  Badlands form in areas where sudden, intense rainstorms erode weak rock surfaces. The rapid erosion and infertile rock prevent plants from growing, and badlands take on a dramatic appearance consisting of maze-like gullies, tunnels, narrow cracks and spires called hoodoos.

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