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week 13 deserts - Deserts Wind aeolian processes-Deserts...

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Deserts, Wind, aeolian processes, -Deserts cover about 1/3 of the Earth’s land surface Common fallacies about deserts: - Lifeless - hot - endless expanses of sand - wind is dominant erosion process
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Extremely arid = more that 12 consecutive months without precip Arid lands < 250 mm/yr Semi-arid lands (steppes) = 250-500 mm
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Weathering in Dry environments -well-developed soils in humid regions reflect chemical weathering - deserts have thing soils, mechanical weathering dominates - lack of moisture=low chemical weathering -Some chemical weathering creates thin oxidized soils
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-Desert streams are usually ephemeral - rains mostly don’t soak in - flash floods - lack of veg= great erosion - wash or arroyo - Wadi or Donga or Nullah
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-Desert streams lack extensive systems of tributaries - non-ephemeral desert streams usually start outside - lack of permanent streams creates internal drainage - alluvial fans - Bajada - playa lakes - playa
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Cold Deserts - Both polar regions receive little precip - Little available atmospheric moisture, ice - liquid water restricted to the surface by permafrost - low rates of chemical erosion
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