AridEolian Landscapes

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Arid/Eolian Landscapes

• Reminders
• Test next Tuesday in class
• Review next Monday, 6 PM, TRAP 204

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T. S. Ida

• Odd timing?
• Named November storm 1/2 years
• 150 fatalities in Central America
• Major US risk?
• Wind damage
• Flooding
• Storm surge
• Tornadoes
• Lightning

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More Ida

• What is storm surge?
• What is Idas future?

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Arid and Eolian Landscapes
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The only true Climatic Landscape

• Processes and landscapes of BW regions

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Arid and Semi-arid

• Boundary is statistical

Sahel
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Desert Characteristics

• What makes a desert, desert?
• Climate
• Biota
• Processes
• Landforms

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Desert landscapes

• US Southwest desert landscapes are dominated by
• Wind-related features
• Weathering-related features
• Water (stream) related features
• Water (wave) related features
• All of the above to similar degrees

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Arid Lands Weathering

• Dry air temperature extremes
• Seasonal to rare precipitation
• Rock weathering along fractures
• Positive feedback enlarges residuals

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• Weathering

• Desert Pavement

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Ayers Rock, Australia
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Arid Fluvial?

• Streams are ephemeral, but powerful
• Significant in mountainous deserts

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Mountainous Deserts The Basin and Range

• Normal (tensional) faulting
• Helena to LA
• Rain shadow deserts

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Death Valley
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B R Evolution
Idaho

• Active fault blocks
• Broad pediments
• Erosional remnants

Nevada
Arizona
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Basin Ranges
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Playa Lakes

• Sediments and salts

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Racetrack Playa
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Pluvial Lakes

• More in Glacial
• More rain, less evap.
• Lake sediments and shores

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Colorado Plateau (Scarp/mesa)
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Erosion of Horizontal Strata

• Resistant
• Sandstone
• Limestone (?)
• Basalt
• Non-resistant
• Shale
• NOTE NOT restricted to arid regions!

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Monument Valley
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Wind as an Agent

• Like water, but weaker
• Moves gravel, sand, silt, clay
• Traction, saltation, and suspended load

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Dust storm
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Wind Erosion

• Deflation
• Desert pavement
• Abrasion
• Ventifacts

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Sand Transport

• By saltation, near the ground
• Limited by wind velocity
• Winds faster near dune crest
• Negative feedback constant dune height
• Dunes migrate!

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Slip Face (angle of repose)
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Types of Sand Dunes

• Barchan
• Low sand
• One wind
• Transverse
• High sand
• One wind
• Seif
• Two winds

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Barchan Dunes
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Transverse Dunes
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Seif (Longitudinal) Dunes
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Star Dunes

• How do these form?
• Seasonally variable winds!

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Sand and Vegetation

• Vegetation stabilizes sand
• Coastal foredunes (N.Z.)

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Where does the dust go?

• Clay? World-wide (ocean floor sediment)
• Silt? 100s of km Loess

FARMLAND!
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Loess Deposits

• Bluffs
• Caves