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ENV3110 Dryland Environments GY3091 Californian Drylands GY3102 Geomorphology of Desert Environments

ENV3110 Dryland Environments GY3091 Californian Drylands GY3102 Geomorphology of Desert Environments. Aeolian Geomorphology. Why are aeolian processes so important in drylands?. Windier? More sediment? Greater sediment availability?. Deflation and Abrasion.

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ENV3110 Dryland Environments GY3091 Californian Drylands GY3102 Geomorphology of Desert Environments

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  1. ENV3110Dryland EnvironmentsGY3091Californian DrylandsGY3102Geomorphology of Desert Environments Aeolian Geomorphology ENV 3110 ~ Aeolian Geomorphology

  2. Why are aeolian processes so important in drylands? • Windier? • More sediment? • Greater sediment availability? ENV 3110 ~ Aeolian Geomorphology

  3. 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

  4. Landforms of wind erosion • Ventifact • Yardang • Pan • Stone pavement ENV 3110 ~ Aeolian Geomorphology

  5. What are these? ENV 3110 ~ Aeolian Geomorphology

  6. 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

  7. What is this? ENV 3110 ~ Aeolian Geomorphology

  8. 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

  9. Stone Pavement ENV 3110 ~ Aeolian Geomorphology

  10. ENV 3110 ~ Aeolian Geomorphology

  11. Classification of dunes ENV 3110 ~ Aeolian Geomorphology

  12. Fundamental Desert Sand Dune Types Dune type Wind Regime Mode of Transport Transverse Linear Star Unimodal Bimodal Complex Migrating Extending Sedentary ENV 3110 ~ Aeolian Geomorphology

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

  14. Dust storms and dust haze ENV 3110 ~ Aeolian Geomorphology

  15. ENV 3110 ~ Aeolian Geomorphology

  16. 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

  17. 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

  18. 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

  19. 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

  20. Chinese loess ENV 3110 ~ Aeolian Geomorphology

  21. Mapping loess occurrence 1984 ENV 3110 ~ Aeolian Geomorphology

  22. Mapping loess occurrence 1988 ENV 3110 ~ Aeolian Geomorphology

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

  24. ENV 3110 ~ Aeolian Geomorphology

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