Results 1 to 2 of 2

Thread: Landforms shaped by Wind

  1. #1
    Senior Member RAMBO's Avatar
    Join Date
    Oct 2015
    Location
    FARIDS,IRAN
    Posts
    1,659

    Landforms shaped by Wind

    Areas where there is little or no vegetation are usually the most effected places that experience shaping due to wind. This happens when the wind picks up weathered rock materials and uses them to sand-blast larger rock structures on the zone closet to the ground. The formation of rock-strewn reg surfaces has resulted in the removal of finer material by wind. The wind also plays an important role in moving and reshaping dunes. Examples of landforms that are obvious in deserts are rock pedestals, Yardangs, Desert pavements, Deflation hollows, Oasis and Sand dunes.


    Rock Pedestals

    Rock pedestals are landforms created by abrasion in which grains cut away the base of rock structures but leaves their tips intact. This is due to wind-borne sand grains following bouncing trajectories that carry sand as high as 1m above the ground.



    Deflation Hollows

    When the sand is carried away over long distances by the wind, depressions are formed in the area from which is lands in. These depressions are called deflation hollows and are commonly found in non-mountainous arid regions. Deflation hollows are an example of wind erosion causing deflation yet these depressions also tend to collect rainwater and hold this water for a time depending on evaporation rates through the stones.



    Oasis

    Oasis' are found in the middle of deserts as fertile spots containing one or more springs surrounded by vegetation. This is caused by a variety of different temperature extremes causing islands of life. This outcome is due to oasis usually been located in parts of the desert where the elevation is low enough meaning the water table is underneath the surface, allowing life to grow through their roots extending into the moist land. Water is able to run right through the sand as it is holey hence why the water can stay underneath the surface especially when large quantities of sand is moved due to wind erosion.



    Sand Dunes

    There are two different types of sand dunes which are the barchan dunes and seif dunes. These are differentiated as barchan dunes are produced by the action of wind predominately convex facing from one direction forming crescent-shaped dunes , whereas the seif dunes are long and narrow or can be a chain of dunes. These dunes are generally orientated in a direction parallel to the wind or in a direction in which have been the result of two or more winds blowing at acute angles to each other. Wind directions can also alter the series of peaks, gaps, steepness and the face of the sides. These sand dunes are mostly found in open deserts and rest on a base of a sand sheet. Sand dunes are a result of deposition processes.



    Yardangs

    Similarly Yardangs are also the result of sand grains pushed by persistent winds to form low ridges of sand carved in soft rock. This is commonly found in flat deserts where steady winds blow away dust and silt. Higher front faces of Yardangs are undercut as erosion is concentrated in the lower areas because wind driven sand stays near the ground. These are an example of erosional landforms



    Desert Pavements

    Pavements are commonly covered with stones rather than sand. This may be due to the wind blowing away the finest material leaving the stones behind as they are the bigger particles and remain as a lag deposit or may be through various physical processes including the soil in the ground as the fine materials are moved down beneath the pebbles. This results in the stones remaining on top. Desert pavements can be used as mulch for plants or as a shelter for ants and rodents
    Last edited by RAMBO; 12-12-2016 at 12:53 PM.

  2. #2
    Senior Member RAMBO's Avatar
    Join Date
    Oct 2015
    Location
    FARIDS,IRAN
    Posts
    1,659
    Transportation processes - Wind


    Wind transports rubble near the surface by ‘saltation’. Saltation refers to short jumps of grains displaced from the surface caused by the force of wind. As the grains fall back to the surface they may disturb other grains that then get carried by wind until they collide with ground. This then leads to the process continuing on, leading to dislodge of other particles.





    Deflation


    Deflation is the lowering of the land surface due to removal of fine-grained particles by the wind. Deflation concentrates the rougher grained particles at the surface, eventually resulting in a surface composed only of the coarser grained remains that cannot be transported by the wind. This type of surface created is called a desert pavement.


    Dunes - Linear

    Linear Dunes are long straight dunes that form in areas with a limited sand supply and converging wind directions.





    Dunes - Parabolic


    Parabolic are "U" shaped dunes with an open end facing upwind. They are usually stabilized by vegetation, and occur where there is abundant vegetation, a constant wind direction, and an abundant sand supply. They are common in coastal areas.


    Sand Dunes

    Sand dunes form when there is

    1. a large supply of sand

    2. a steady wind

    3. Some kind of obstacle such as vegetation, rocks, or fences, to trap some of the sand.

    Sand dunes form when moving air slows down on the downwind side of an obstacle. The sand grains drop out and form a mound that becomes a dune.











Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •