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Deserts

Deserts. Deserts: definition. A region which has an arid climate or where evaporation exceeds precipitation Steppe: region often adjacent to a desert Semiarid climate: irregular precipitation, enough to generate minimal plant growth. Desert and Steppe areas around the world:.

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Deserts

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  1. Deserts

  2. Deserts: definition • A region which has an arid climate or where evaporation exceeds precipitation • Steppe: region often adjacent to a desert • Semiarid climate: irregular precipitation, enough to generate minimal plant growth

  3. Desert and Steppe areas around the world:

  4. Cover a fifth of the earth’s surface Can be found at all altitudes and latitudes Four physical factors cause deserts : all are influenced by prevailing winds Continentality b. Lee side of mountains c. Cold ocean currents d. Prevailing winds Deserts:

  5. Prevailing Winds: • Found 30 n and s latitude due to the global wind circulation system • Descending air masses are compressed, warm and absorb moisture

  6. Lee Side:

  7. Coastal Location:

  8. Desert Erosion: Water • Seldom rains in desert regions • When it does massive DOWNPOUR or it’s called a FLASHFLOOD • Dry weathered soil, and minimal vegetation to anchor the soil causes rapid erosion • Rainwater carries sediment away and deposits it on the valley floor • Within 10 to 20 minutes the rain is gone and the water has evaporated

  9. Wind erosion processes: • Deflation ; is the removal of rock waste from the land by wind • Blowout or deflation hollow ; depression caused by deflation due to lack of vegetation to hold material down

  10. Landforms: created by water • Alluvial Fan: • Fan shaped delta formed at the foot of mountains in a desert valley • A Bajada is an apron of sediment resulting from a coalescence of alluvial fans

  11. Landforms : water • Playa Lake: • A temporary shallow lake formed in the central basin of a desert during a rare downpour • A Playa is the dry flat lake bed that remains

  12. Wind erosion processes: • Deflation: removal of rock waste from the land by the wind • Abrasion : “sandblasting” effect on materials caused by the impact with particles carried by the wind

  13. Bedload: • Saltation • Suspension • Particles are bounced along the ground or suspended in the air; both these process erode rock surfaces and carry material

  14. Sand Dunes: • Many different types but learn these: • Barchan: crescent shaped with convex portion facing the wind • Formed with a constant wind and limited sand supply

  15. Longitudinal or seif • Elongated in general direction of wind • Formed with slightly different wind directions and limited sand supply

  16. Inactive or stable dune: • Parabolic Dune: • Formed along coastlines or large lakes • Winds cause blowouts in sand resulting in a crescent shape with convex side facing the wind

  17. Reg Deserts: little sand

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