Aeolian landforms in deserts

Aeolian landforms in deserts

Wind, as an external force, plays an important role in shaping deserts.

Geography

Keywords

wind, landform, desert, dune, sand dune, sand, erosion, mushroom rock, mesa, surface, external forces, oasis, physical geography, geomorphology, geography

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Aeolian processes depend on certain conditions related to climate, vegetation and geology. Wind shapes the Earth’s surface most effectively in arid regions where there is sparse vegetation and a surface covered with grains of sediment. Such regions include areas partly anchored by vegetation as well as arid, semi-arid, glacial and coastal areas.

Even if it reaches a high speed, wind can only transport small grains of sand that are no more than 2 mm (0.1 in) in diameter. Larger particles are transported along the surface through creeping, smaller ones are conveyed through saltation (that is through bouncing and hopping along the ground), and the smallest ones are carried through the air by suspension. Most particles are transported through saltation which does not lift them higher than 10 cm (3.9 in).

Wind in the desert engages in erosion and construction . Erosion can occur in several ways. One form of erosion is deflation, which takes place when the wind removes sand particles from the ground, resulting in depressions of various sizes called blowouts (or deflation basins). Another form of erosion is abrasion, during which the sand transported by the wind erodes rocks, while the sand grains themselves are also eroded in the process. Abraded rock formations include rock mushrooms, hoodoos, and sphinx yardangs as well as mesas and plateaus.

Once the wind dies down, it deposits sediment, creating different landforms. This process is called aeolian accumulation. Freely moving aeolian landforms are formed where there is no vegetation. These include longitudinal dunes, star dunes, crescent-shaped barchans and transverse dunes, which are barchans joined together laterally.

Desert and semidesert areas occupy a large part of the Earth's total land surface. About one third of the desert areas are covered with sand. Sand seas are rapidly changing areas. Wind erosion and sand encroachment pose serious problems. Sand can cover oases, arable lands and roads, and wind erodes the surface, thereby damaging agricultural lands. Due to climate change, larger and larger areas are becoming more arid and losing vegetation; this is desertification. They are thereby becoming more vulnerable to wind erosion.

  • - Particles smaller than 0.08 mm (0.003 in) are transported by the wind this way: they are airborne.
  • 10 cm (3.9 in)

  • - A tall, thin column of relatively soft rock of variable thickness, topped by harder, less easily eroded stone. Erosional patterns (deeper lines and ridges showing rock layers of alternating hardness) characterize this rock formation.

  • - These dunes are formed in areas with ample sand by barchans joining together laterally. They are a couple of meters tall and the distance between their ridges is a couple of hundred meters.
  • - They are the most common type of dune in sandy deserts. They are parallel to the prevailing wind direction. Their length ranges from hundreds of meters to several kilometers. The permanently blowing desert winds transform into helical roll vortices parallel to one another sweeping out sand from the inter-dune corridors and depositing it in the sheltered troughs.
  • - These crescent-shaped dunes are formed in areas with limited supply of sand. Their gently sloping convex side is facing into the wind, while the steeper slope, the leeward side or slip face, is sheltered from the wind. Their height ranges from tens of centimeters to tens of meters. They can migrate several meters a year without changing their shape.

  • - Particles smaller than 0.08 mm (0.003 in) are transported by the wind this way: they are airborne.
  • 10 cm (3.9 in)
  • - A tall, thin column of relatively soft rock of variable thickness, topped by harder, less easily eroded stone. Erosional patterns (deeper lines and ridges showing rock layers of alternating hardness) characterize this rock formation.
  • - These dunes are formed in areas with ample sand by barchans joining together laterally. They are a couple of meters tall and the distance between their ridges is a couple of hundred meters.
  • - They are the most common type of dune in sandy deserts. They are parallel to the prevailing wind direction. Their length ranges from hundreds of meters to several kilometers. The permanently blowing desert winds transform into helical roll vortices parallel to one another sweeping out sand from the inter-dune corridors and depositing it in the sheltered troughs.
  • - These crescent-shaped dunes are formed in areas with limited supply of sand. Their gently sloping convex side is facing into the wind, while the steeper slope, the leeward side or slip face, is sheltered from the wind. Their height ranges from tens of centimeters to tens of meters. They can migrate several meters a year without changing their shape.

Narration

Aeolian processes depend on certain conditions related to climate, vegetation and geology. Wind shapes the Earth’s surface most effectively in arid regions where there is sparse vegetation and a surface covered with grains of sediment. Such regions include areas partly anchored by vegetation as well as arid, semi-arid, glacial and coastal areas.

Even if it reaches a high speed, wind can only transport small grains of sand that are no more than 2 mm (0.1 in) in diameter. Larger particles are transported along the surface through creeping, smaller ones are conveyed through saltation (that is through bouncing and hopping along the ground), and the smallest ones are carried through the air by suspension. Most particles are transported through saltation which does not lift them higher than 10 cm (3.9 in).

Wind in the desert engages in erosion and construction . Erosion can occur in several ways. One form of erosion is deflation, which takes place when the wind removes sand particles from the ground, resulting in depressions of various sizes called blowouts (or deflation basins). Another form of erosion is abrasion, during which the sand transported by the wind erodes rocks, while the sand grains themselves are also eroded in the process. Abraded rock formations include rock mushrooms, hoodoos, and sphinx yardangs as well as mesas and plateaus.

Once the wind dies down, it deposits sediment, creating different landforms. This process is called aeolian accumulation. Freely moving aeolian landforms are formed where there is no vegetation. These include longitudinal dunes, star dunes, crescent-shaped barchans and transverse dunes, which are barchans joined together laterally.

Desert and semidesert areas occupy a large part of the Earth's total land surface. About one third of the desert areas are covered with sand. Sand seas are rapidly changing areas. Wind erosion and sand encroachment pose serious problems. Sand can cover oases, arable lands and roads, and wind erodes the surface, thereby damaging agricultural lands. Due to climate change, larger and larger areas are becoming more arid and losing vegetation; this is desertification. They are thereby becoming more vulnerable to wind erosion.

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