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OU GEOG 1114 - Deserts
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GEOG 1114 1stEdition Lecture 27Outline of Last Lecture -Landforms-Wind erosion-Requirement for wind erosion-Aeolian Landforms-Rock ArchesOutline of Current Lecture -Deserts-Mechanical weathering-Desert landforms-Desertification-Differential WeatheringCurrent Lecture Deserts: Specialized environment reflecting the interrelationships between a variety of factorsMechanical weatheringThin soil – thin or absent, exposing bedrockAbundance of sand – allows water to infiltrate, transport and shape the sands.PPTN – can be brief but intense; flash floodsDESERT STREAMS CHANNELS; EPHEMERAL (INTERMITTENET) STREAM BEDSWind – shifts sandsThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.Landforms: Ergs: seas of sand, large area covered with and in dune formation from wind. Sahara, Namibia – Arabian deserts. Reg: Stony desertErg Sea of sandReg Surface covered with coarse gravel, pebbles, or bouldersDesertification: Expanding of desert conditions due to land degradation and water removal (human activity) Climate Change: Prevalent in Africa, Middle East, Australia, Chile and Peru, India, Mexico.Estimates of 8,100 square miles are decertified each year.Affects on human population: growth and agricultural Landforms of Differential Weathering:Differential Weathering of Sedimentary Rocks TypesShale: Mechanically weak, easily fragmented into thin flakesChemically weathers into impermeable clay soils – easily cut by stream channels. Most erodible of all rock typesEvolves into lowlands, dissected slopes at the base if high hills or found in valley floor where it’s carried away as bed loadSandstone: Either weak or strong depending on the type of materialTypically hard in semi-arid environments.Often porous permitting water to soak into it and reduces run-off. Erodes slowly. Frequently forms ledges or cliffs or hills rising above areas of shale of limestone.Landforms of Differential Weathering of Sedimentary Rocks.Pinnacles (columnar), Buttes (Small surface areas and cliffs that rise above surroundings), Mesas (Larger flattop landforms: associated with horizontal strata – resistant sandstone form cap rock), Plateaus (larger then mesas) Cuesta (Spanish slope) – Ridge formed by gently dipping sedimentary rock. Have a steep slope where rock is exposed. Exposed rock is resistant to erosion.Hogback ridges – Steeply tilted strata of rock protruding from the surrounding area. Name comes from the ridge resembling the high, knobby spine between the shoulders of a hog. The two strata that compose a hogback are different types of sedimentary rock with differing weathering rates Badlands – barren terrain of easily eroded rock, eroded by fluvial processes. Overland flows from occasional rains develop tiny rills that expand into ravines or gullies. Characterized by maze of ravines and gullies, lifeless and nearly impassableMesa/scarp terrain – Associated with horizontal strata. Variable resistance to erosion in strata.Plateaus and stripped plains.Weathering of Limestone in Semi-Arid environmentsLittle water available to dissolve limestone. Limestone acts as resistant rock forming cuesta, mesas and hogbacks. Can also outcrop and be very resistant to


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OU GEOG 1114 - Deserts

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