ENV 3110 Aeolian revision by G87z6M

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									ENV3110 Dryland Environments
GY3091 Californian Drylands
GY3102 Geomorphology of Desert Environments




 Aeolian Geomorphology

  ENV 3110 ~ Aeolian Geomorphology
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Why are aeolian processes so
important in drylands?

Windier?
More sediment?
Greater sediment availability?




 ENV 3110 ~ Aeolian Geomorphology
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Deflation and Abrasion


Deflation: the removal by the wind of loose
 clastic particles
Abrasion: erosion by the wind of cohesive
 materials as a consequence of
 bombardment by wind-tranported particles




 ENV 3110 ~ Aeolian Geomorphology
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Landforms of wind erosion

Ventifact

Yardang

Pan

Stone pavement


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What are these?




ENV 3110 ~ Aeolian Geomorphology
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 Yardang
   A mound composed of generally
    cohesive sediment whose surface has
    been abraded (and perhaps deflated) by
    the wind into an aerodynamic shape




ENV 3110 ~ Aeolian Geomorphology
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What is this?




ENV 3110 ~ Aeolian Geomorphology
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  Stone pavement
  A pebbly covering of a finer soil, which
   may be formed partly in some
   circumstances by deflation of finer
   material




ENV 3110 ~ Aeolian Geomorphology
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                                   Stone
                                   Pavement




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ENV 3110 ~ Aeolian Geomorphology
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Classification of dunes




ENV 3110 ~ Aeolian Geomorphology
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 Fundamental Desert Sand Dune
 Types

       Dune type              Wind Regime     Mode of Transport


        Transverse                 Unimodal          Migrating

        Linear                     Bimodal           Extending

        Star                       Complex           Sedentary




ENV 3110 ~ Aeolian Geomorphology
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 Complete the diagram ...
 (Wasson & Hyde 1983)




ENV 3110 ~ Aeolian Geomorphology
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Dust storms
and dust haze




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ENV 3110 ~ Aeolian Geomorphology
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 Why so little work on dust
 until the 1980s?

Erosion of dust often leaves little clear
 evidence of occurrence.
Deposition of dust does not produce
 distinctive landforms. Often it leaves only
 thin, widespread mantles.



 ENV 3110 ~ Aeolian Geomorphology
                                               16
Loess

“A terrestrial windblown silt” (Pye, 1987,
  p.199)
commonly 50-75% quartz;
commonly buff colour, but also grey, red,
  brown, yellow;




 ENV 3110 ~ Aeolian Geomorphology
                                             17
Loess

typically modal size around 20-40 μm
 (sand content >20% termed “sandy
 loess”)
Syn- and post-depositional reworking is
 common;
angular and sub-angular grains.



 ENV 3110 ~ Aeolian Geomorphology
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Smalley & Krinsley (1978, p. 63)

“Glacial grinding is the only natural process
 which efficiently converts sand-sized quartz
 particles totally into a silt-sized product.”




 ENV 3110 ~ Aeolian Geomorphology
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Chinese loess




ENV 3110 ~ Aeolian Geomorphology
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Mapping loess occurrence




    1984



ENV 3110 ~ Aeolian Geomorphology
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Mapping loess occurrence




     1988



ENV 3110 ~ Aeolian Geomorphology
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Peridesert loess: Matmata Plateau, Tunisia




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