Desert landscapes dominated by wind

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Desert landscapes dominated by wind

  1. 1. Desert LandscapesDominated by Wind
  2. 2. “We don’t survive the desert, we live here” - Pima Indian
  3. 3. Deserts: where & why Earth’s dry regions: 30% of all land 2 climate types of dry regions: ◦ desert (arid) ◦ steppe (semi-arid, surrounds deserts) Question:How much rain do deserts get every year? ◦ Sahara Desert receives as little as 2mm and as much as 100mm of precipitation per year
  4. 4. Climate Graphs – Semi-arid and AridWhat do you notice about the minimum and maximum temperatures?What do you notice about the amount of precipitation?
  5. 5. Deserts: where & why What causes deserts? Global distribution of ◦ air pressure ◦ wind Relationship between ◦ rainfall ◦ evaporation
  6. 6. Deserts: where & why Low-latitude deserts ◦ Tropic of Cancer ◦ Tropic of Capricorn In contrast…. ◦ Equator:  hot air  rises to 15-20 km  low pressure belt
  7. 7. Deserts: where & why
  8. 8. Deserts: where & why
  9. 9. Deserts: where & why
  10. 10. Deserts: where & why
  11. 11. Deserts: where & why Middle-latitude deserts (ie. 45°N) ◦ exist in rain shadows.
  12. 12. Deserts: where & whyMiddle-latitude deserts
  13. 13. The Great Basin Basin (valley) and Range (mountains) topography ◦ mountainous desert landscape ◦ Nevada, Arizona, California, Utah ◦ Death Valley, Mojave Desert, Great Salt Lake
  14. 14. Great Salt Lake, Utah
  15. 15. Evaporation > Precipitation Playa: ephemeral (not existing all year long) lake beds that consist of salt and mud flats Spotted Lake, just outside of Osoyoos, BC
  16. 16. Wind erosion + deposition Wind erosion: Important in arid environments Example…Sand dune shape depends on: ◦ Flat or hilly? ◦ How much sand? ◦ Winds steady or intermittent? ◦ Wind direction constant? ◦ Vegetation present?
  17. 17. Wind erosion Desert pavement
  18. 18. Wind erosion Deflation: the process of wind removing silt and sand-sized particles
  19. 19. Wind erosion + deposition Ergs: seas of dunes
  20. 20. Wind erosion + deposition Sand dune formation
  21. 21. Wind erosion Ventifacts: rocks abraded, pitted, polished by windblown sand
  22. 22. Wind Deposition Loess from Aeolian (or Eolian) transportation: ◦ Deposit of wind- blown silt and clay in angular grains and weakly cemented by calcite ◦ Develop rich, fertile soils
  23. 23. Water Erosion Wadi: a dried up river bed that only has water during rainy season Town of WadiTiwi, Oman
  24. 24. Water Erosion  Hoodoos (or fairy chimneys): column of soft sedimentary rock often with resistant layer of “cap” rock on top  Water flows through badlands causing further erosion to theBryce Canyon National Park, Utah spires
  25. 25. Water ErosionFairy chimneys that people still live inside in Cappadocia,Turkey
  26. 26. Water Erosion  Antelope Slot Canyons, Page, AZ  Flash floods from localized thunderstorms carry sediments that abrade and polish the sandstone
  27. 27. Water ErosionMesa: a flat-topped “table” formed bydifferential erosion of softer rockunderneath a layer of “cap” rock
  28. 28. Water Erosion Butte: a smaller version of a mesa
  29. 29. Water Erosion  Pedestal rock: softer rock erodes quicker than resistant “cap” rock
  30. 30. Water DepositionAlluvial Fan: deposition of sediments as rivers or flashfloods leave mountain ranges and spread into thevalley
  31. 31. Water Deposition Bajada: several adjacent alluvial fans that have merged together

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