Applied Geomorphology
Lecture 8: Arid (Eolian) Landforms
Cycle of Landform Development
• Initiated by tectonics: Normal Faulting resulting
from lateral extension of lithosphere
• Alluvial
Fans
• Playa
Lakes
• Inselbergs
• Bajada
• Pediment
(Bajada)
(Inselbergs)
Arid Landform Stages of
Development
• Early
– Alluvial Fans
– Flat Divides
• Middle
– Rounded Divides
– Bajada
– Playa Lakes
• Late
– Inselbergs
– Pediment
Alluvial
Fan
Example
(Early
Stage)
Middle Stage Arid
Late
Stage
Arid
Wind (Eolian) Landforms
• Produced solely by wind action
• Transported material:
– Bed Load: Sand (<= 2mm)
– Suspended Load: Silt and Clay (<=.062mm)
• No dissolved load
Global Wind Patterns
• Coriolis effect deflects wind direction
• Driven by convection
Arid and Semi-Arid Regions
• Occur at 30 degrees
latitude or in
rainshadows
Wind Velocity
• A velocity of 50 kph is required to produce
significant movement of sand by wind
Effects of Eolian Transport
• Rounding of grains
• Adds a “frosted” appearance to sand
grains
Wind Erosion Products
• Ventifacts: faceted
pebbles
Wind Erosion Landforms
• Deflation: removal of
topsoil by intense
wind erosion lowers
elevation of region
Wind Erosion Landforms
• Desert
pavement:
result of
deflation
Wind Erosion Landforms
• Desert varnish:
concentration of
insoluble products on
land surface
Wind Erosion Landforms
• Dry wash: stream
channel of intermittent
stream
Wind Erosion Landforms
• Hoodoos: erosional
remnants that are
spire-shaped
Wind Erosion Landforms
• Playa Lakes: due to rapid erosion and elevated
base levels
Arid Vegetation
• Sparse concentration
• Shallow roots
• Not effective for erosion
control
Sand 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 Types
•
•
•
•
Barchan
Blowout
Transverse
Linear