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Deserts and Arid Regions

Deserts and Arid Regions. Desert. Region with low precipitation Usually less than 25 cm of rain per year Distribution Most related to descending air masses Belts at 30 o North & South latitude Rain shadow of mountains Great distance from oceans Tropical coasts next to cold ocean currents

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Deserts and Arid Regions

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  1. Deserts and Arid Regions

  2. Desert • Region with low precipitation • Usually less than 25 cm of rain per year • Distribution • Most related to descending air masses • Belts at 30o North & South latitude • Rain shadow of mountains • Great distance from oceans • Tropical coasts next to cold ocean currents • Polar desserts

  3. Some characteristics of deserts • Lack of through-flowing streams • Internal drainage • Desert thunderstorms • Flash floods • Mudflows

  4. Some characteristics of deserts • Stream channels normally dry • Covered with sand & gravel • Narrow canyons with vertical walls • Resistance of rocks to weathering • Desert topography typically steep and angular

  5. Desert Features in S.W. United States • Mojave Desert, CA • Basin and Range, NV • Colorado Plateau

  6. Numbers indicate rainfall

  7. Alluvial Fans

  8. Desert Features in S.W. United States • Colorado Plateau • Mostly flat-lying sedimentary beds • Plateaus, mesas, buttes

  9. Wind Action • Strong in desert because: • Low humidity • Great temperature ranges • More effective because of lack of vegetation • Effective erosion in deserts because sediment is dry

  10. Wind Erosion and Transportation • Dust storms • Sand • Moves along ground- saltation • Sandstorms • Sandblasting up to 1 meter • Ventifact • Deflation Pavement • Blowout

  11. Wind Deposition • Loess • Sand Dunes • Well-sorted, well-rounded sand grains • Slip face • Angle of repose • Wind ripples

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