Arid Landforms
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Transcript of Arid Landforms
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Arid Landforms
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Introduction
1/3rdof earths landscape is arid
Common in deserts: Three types of
deserts i) hot deserts ii) Temperatedeserts and iii)cold deserts.
Aridity index is used(43% is arid)
Climate and plate tectonics- processAir currents shape the landscapes
Includes numerous types of sand dunes
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Basic ConceptsI. Most deserts exhibit highly angular landscapes.
mechanical weathering dominatesangular particles of weathered rock; bedrockoutcrops
little soil or vegetation to soften landscape
II. Softer, more rounded landscapes appear wheredeposition is predominant.
dunes
III. Desert rainfall is infrequent, intense, andunreliable.
intense flash flooding, intense erosionephemeral streams
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Characteristics of arid regions
Rainfall aperiodic, spotty in nature &torrential
Very high daily range of temperature(very hot in day & very cold in day) &also very high annual range oftemperature
Sparse vegetation, drainage is internal
Mechanical weathering is prominent
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Death Valley, July 15, 1999
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Las Vegas Flash Flood
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Types of DesertsErg - sea of sand
largest are in Sahara and Arabian Deserts, sandcovers about 20% of worlds deserts
vegetation rare
sand probably formed during more humidclimate
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Death Valley, California
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Types of DesertsReg - desert pavement of pebbles
and stonesall small materials and sand removed by wind
may be very thin coating of stones
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A gibber plain in Australia
Desert pavement
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Desert varnish -oxidation of iron andmanganese, useful for
dating desert surfaces
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DESERT FLUVIALPROCESSES/LANDFORMS
Fluvial Erosion - rare, intense flash floods.
steep slopes; steep-walled canyons; washes, wadis,arroyos, canyons.
fluvial systems decrease in discharge downstream
Fluvial Transportation - large amounts of rock and sandmoved short distances.
Fluvial Depositionwhere water slows on flat playasmaterial is deposited and sorted by size.
alluvial fans
rock debris in piedmont region
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Joshua Tree N.P.
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SlotCanyon
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TheNarrows,
Zion N.P.,Utah
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AEOLIAN (WIND)PROCESSES/LANDFORMS
Aeolian Erosion - much less effective than fluvial
deflation - the movement of small particles
abrasion - polishes and etches exposed surfaces
Aeolian Transportation - moves nothing bigger than sand
dust storms - can extend thousands of feet up
sand storms - only very near the surface
Aeolian Deposition - dunes form and shift where windsand terrain combine to slow the winds or block themovement of dunes.
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Dust Storm, Senegal
Sand Storm
AEOLIAN (WIND)
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AEOLIAN (WIND)PROCESSES/LANDFORMS
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Types of Dunes
BARCHAN
TRANSVERSE
DUNES
SEIFS
T f D
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Types of DunesBarchans - migrating crescent dune withhorns pointing downwind; form where strongwinds blow in a consistent direction. Movefast. Common in central Asia and Sahara. Canreach hundreds of feet in height.
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Transverse Dunes- parallel waves of crescent dunesperpendicular to wind direction; migrate downwind.Found in areas with large supply of sand.
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Seifs- multiple very long narrow, parallel dunes. May be causedin areas with at least two dominant wind directions. Can be tens
of miles long. Common outside of U.S.
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Namib Desert
Star Dunes
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BASIN ANDRANGE
TOPOGRAPHY
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Piedmont - gently sloping land that extendsout from base of mountains.
Pediment - sloping bedrock at base thatdevelops.
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Badwater, Death Valley, CA
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Playas
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Mesa and Scarp
Topography
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Differential Erosion
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Uluru (Ayers Rock), Australia
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Inselberg -island mountains riseabruptly out of desert landscapes
Bornhardt - highly resistant rocklandform; a type of inselberg.
Kata Tjuta (The Olgas), Australia
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Bornhardt, Arches National Park, Utah
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Delicate Arch,Arches National
Park, Utah