1 / 27

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:.

awen
Télécharger la présentation

Deserts

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  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

More Related