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Eolian
 

Eolian

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    Eolian Eolian Presentation Transcript

    • Wind Processes and Desert Landscapes
    • Overview
      • Eolian (Aeolian) processes
        • Erosion
          • deflation and abrasion
        • Transport
          • saltation and surface creep
        • Deposition
          • sand dunes and loess
      • Desert landscapes
    • Eolian Erosion
      • Abrasion
        • “ sandblasting”
          • ventifacts
      • Deflation
        • Occurs where there is a mixture of cobbles and gravel with finer material (typically sand)
        • Wind removes finer material, leaving only the cobbles and gravel (desert pavement)
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    • Eolian Transport
      • Suspension
      • Saltation
      • Creep
    • Eolian Deposition
      • Heavier material drops out of the wind before lighter materials
        • Sand deposited before silt and clay particles
      • Deposition of sand forms sand dunes
      • Deposition of clay and silt forms loess
    • Global Sandy Areas
    • Global Loess Deposits
    • Global Dry Regions
    • Dune Processes
    • Types of Sand Dunes
      • Several factors influence the formation of the various sand dune landforms
        • Strength of the wind
        • Prevailing wind vs. shifting winds
        • Presence of vegetation
        • Amount of sand present
      • Movement
        • Free Dunes
        • Tied Dunes
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    • Crescentic Dunes
      • Barchan
        • Free dunes
        • Scarce sand
        • Consistent and effective wind from one direction
        • Single slipface
        • Horns of crescent point downwind
      • Barchanoid Ridge
        • merged barchans
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      • Transverse dunes
        • Free dunes
        • Abundant sand supply
        • Less effective wind
        • Consistent direction of the wind
        • Single slipfaces
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      • Parabolic
        • Tied dune
        • Vegetation stabilizes movement
        • Consistent wind direction
        • multiple slipfaces
        • crescents point upwind
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    • Linear Dunes
      • Longitudinal
        • Winds variable in one direction
        • Ridge forms parallel to consistent wind direction
        • two slipfaces
        • 100 – 400 m tall, up to 100 km long
      • Seif
        • Sharp crest
        • shorter in height
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    • Star Dunes
      • Star Dunes
        • Winds variable in all directions
        • Multiple slipfaces
        • With effective winds, form high mounds
        • With less effective winds, form networks of connected sinuous arms
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    • Desert Landscapes
      • Arid areas are the largest climatic region on earth (35% of earth’s surface)
      • Fluvial features
        • Flash flooding
          • Washes, arroyos, wadis
          • Bursts of vegetation growth
        • Playas
          • interior drainage
          • salinization
        • Alluvial fans
          • bajadas
      • Landscape features
        • Adapted vegetation
        • Basin and Range Province
          • Horst and Graben, interior drainage, playas, alluvial fans
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    • Colorado River Issues
      • Headwaters originate in the Rocky Mountains
        • High levels of rainfall
        • Snow melt
      • Flows through an extremely arid area with few feeding tributaries
      • High demand on water means that often no water actually makes it to the sea
      • Flows through seven states, into Mexico
      • Beliefs on the river’s capacity based on a 400 year high mark (greatly overestimated)
      • Subject to a variety of political treaties and agreements regulating its flow
        • In many cases, quotas are exceeded, esp. with California
    • Desertification
      • Refers to the expansion of desert biomes due to a combination of poor agricultural practices and climate change
        • grazing has been identified as a major cause
      • As a global phenomenon, this idea has largely been falsified
        • Areas identified as “desertifying” were simply experiencing drought-like conditions, in conjunction with ENSO cycles; many have recovered
      • There are some areas where desertification has occurred, but it is not a global phenomenon
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