FEATURES PRODUCED BY DEPOSITION IN A DESERT

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    Coarse material deposited by the wind is deposited in the shape of hills or ridges called Dunes.

    The lightest material carried by the winds which will form a blanket covering the existing land and is called  Loess.           

A. Sand Dunes

        i) Live - Dunes that change their shape and move forward under the effects of

                    the wind. The speed at which they move varies according to the wind

                   speed and sand particle size.

 

     ii) Fixed - A dune whose shape and position are maintained over a long period of

                    time. Dunes would generally be fixed by vegetation or by opposing

                   winds.         

 

Types of Dunes:       

  1. Barchans    - crescent shaped and isolated ,                   

                         - windward slope convex                      

                         - leeward slope steep                    

                         - tails point downwind                   

                         - found in areas of little sand supply                    

                         - winds from same direction          

 

2. Parabolic     - reverse direction of Barchan

                               - found in more humid areas                     

                         - tails drag behind                     

                         - tails may hold vegetation          

3. Traverse     - found in areas with lots of sand

                               - look like waves in the sea          

4. Longitudinal - long, narrow, parallel                    

                          - lined up with the wind                     

                          - tops are rounded or pointed         

5. Blowout        - found on beaches                     

                           - lots of sand in area

                                 - winds from the same direction                    

                           - windward side hollowed out       

B. LOESS  The wind can carry dust-sized particles to be  deposited like a blanket over the existing land forms. Loess is very porous so that when it rains the rain sinks quickly through it. Streams can cut through loess and erode it easily.