GY301 Lecture7 Eolian - southalabama.edu · Cycle of Landform Development • Initiated by...
Transcript of GY301 Lecture7 Eolian - southalabama.edu · Cycle of Landform Development • Initiated by...
Applied GeomorphologyApplied Geomorphology
Lecture 8: Arid (Eolian) LandformsLecture 8: Arid (Eolian) Landforms
Cycle of Landform DevelopmentCycle of Landform Development
• Initiated by tectonics: Normal Faulting resulting from lateral extension of lithosphere
• Alluvial Fans
• Playa Lakes
• Inselbergs• Bajada• Pediment
(Inselbergs)
(Bajada)
Arid Landform Stages of Arid Landform Stages of DevelopmentDevelopment
• Early– Alluvial Fans– Flat Divides
• Middle– Rounded Divides– Bajada– Playa Lakes
• Late– Inselbergs– Pediment
Alluvial Alluvial Fan Fan
ExampleExample(Early (Early Stage)Stage)
Middle Stage AridMiddle Stage Arid
Late Late Stage Stage AridArid
Wind (Eolian) LandformsWind (Eolian) Landforms
• Produced solely by wind action• Transported material:
– Bed Load: Sand (<= 2mm)– Suspended Load: Silt and Clay (<=.062mm)
• No dissolved load
Global Wind PatternsGlobal Wind Patterns
• Coriolis effect deflects wind direction• Driven by convection
Arid and SemiArid and Semi--Arid RegionsArid Regions
• Occur at 30 degrees latitude or in rainshadows
Wind VelocityWind Velocity
• A velocity of 50 kph is required to produce significant movement of sand by wind
Effects of Eolian TransportEffects of Eolian Transport
• Rounding of grains• Adds a “frosted” appearance to sand
grains
Wind Erosion ProductsWind Erosion Products
• Ventifacts: faceted pebbles
Wind Erosion LandformsWind Erosion Landforms
• Deflation: removal of topsoil by intense wind erosion lowers elevation of region
Wind Erosion LandformsWind Erosion Landforms
• Desert pavement: result of deflation
Wind Erosion LandformsWind Erosion Landforms
• Desert varnish: concentration of insoluble products on land surface
Wind Erosion LandformsWind Erosion Landforms
• Dry wash: stream channel of intermittent stream
Wind Erosion LandformsWind Erosion Landforms
• Hoodoos: erosional remnants that are spire-shaped
Wind Erosion LandformsWind Erosion Landforms
• Playa Lakes: due to rapid erosion and elevated base levels
Arid VegetationArid Vegetation
• Sparse concentration• Shallow roots• Not effective for erosion
control
Sand Dune FormationSand Dune Formation• Asymmetric cross section:
– Windward slope: low angle slope facing wind direction
– Lee slope: high angle slope facing opposite the wind direction
• Cross-bedding forms when lee slope fails
Dune TypesDune Types
• Barchan• Blowout• Transverse• Linear