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Global Dry Climate Distribution

Explore the geologic processes and landscape evolution in dry climates, including weathering, role of water, desert streams, wind erosion, and types of wind deposits.

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Global Dry Climate Distribution

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  1. Global Dry Climate Distribution

  2. Deserts • Geologic processes in arid climates • Weathering • Not as effective as in humid regions • Mechanical weathering forms unaltered rock and mineral fragments • Some chemical weathering does occur • Clay forms • Thin soil forms

  3. Deserts • Geologic processes in arid climates • Role of water in arid climates • Streams are dry most of the time • Desert streams are said to be ephemeral • Flow only during periods of rainfall • Different names are used for desert streams including wash, arroyo, wadi, donga, and nullah

  4. Deserts • Geologic processes in arid climates • Role of water in arid climates • Desert rainfall • Rain often occurs as heavy showers • Causes flash floods • Poorly integrated drainage • Most erosional work in a desert is done by running water

  5. Desert Stream Channel

  6. Deserts • Basin and range: the evolution of a desert landscape • Uplifted crustal blocks • Interior drainage into basins produces • Alluvial fans and bajadas • Playas and playa lakes

  7. Deserts • Basin and range: the evolution of a desert landscape • Erosion of mountain mass causes local relief to continually diminish • Eventually mountains are reduced to a few large bedrock knobs called inselbergs projecting above a sediment-filled basin

  8. Landscape Evolution in a Basin and Range Region

  9. Deserts • Wind erosion • Deflation • Lifting of loose material • Produces • Blowouts • Desert pavement • Abrasion

  10. Formation of Desert Pavement

  11. Deserts • Types of wind deposits • Loess • Deposits of windblown silt • Extensive blanket deposits • Primary sources are deserts and glacial stratified drift

  12. Deserts • Types of wind deposits • Sand dunes • Mounds and ridges of sand formed from the wind’s bed load • Characteristic features • Slip face – the leeward slope of the dune • Cross beds – sloping layers of sand in the dune

  13. Deserts • Types of wind deposits • Sand dunes • Types of sand dunes • Barchan dunes • Transverse dunes • Longitudinal dunes • Parabolic dunes • Star dunes

  14. Sand Dune Types

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