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PHYSICAL GEOGRAPHY Weathering, Mass Wasting & Erosion C.J. Cox
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–Weathering - –the tearing down process reshaping the lithosphere
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–UPLIFTING –TEARING DOWN –gradational processes
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Weathering, Mass Wasting & Erosion Weathering - the tearing down process –breakdown of materials –Most landscapes are a combination of mechanical and chemical weathering Mass Wasting - massive movement of materials downslope Erosion - the removal of material
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Weathering Breakdown of materials Regolith - (greek) –rhegos (blanket) –lithos (rock) –Loose material above the bedrock caused by weathing
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Weathering Weathering occurs much faster along cracks or joints and faults –Exfoiliation unloading of overlying pressure slabs separating –Disintegration- rock falls, splits crumbles granite -> sand (granular disintegration)
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Exfoiliation Disintegration-
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–Frost Wedging –Joint Block Separation
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Mechanical Weathering Breakdown of rocks without change to chemical composition Frost Wedging - water expands as it freezes and breaks apart rocks Salt Wedging - pitted surfaces Thermal Weathering - extremes of temperatures on rocks –outer part is heated & expands during the day –at night outer rock contracts –inner part remains cool
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– Thermal Weathering –Salt Wedging
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Mechanical Weathering Breakdown of rocks with change to chemical composition Organic - plant roots and small burrowing animals break up rocks Unloading - abrasive action of water, wind and ice –less pressure on surface causes expansion & fracturing
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Chemical Weathering Rocks break up because of chemical composition change Decomposition - alterations in chemical composition Carbonation - CO2 & H20 = carbonic acid –carbonic acid dissolves limestone & creates caverns –feldspar -> clay Oxidation - rusting (requires water)
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Chemical Weathering Rocks break up because of chemical composition change Hydrolysis - moisture in rock cavities H20 & salts =acids which cause the break down of rock Solution - water dissolving rock particles –limestone
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Mass Wasting Movement of materials downslope in response to the Angle of Repose Soil Creep - slow movement found on gentle slopes Slumping and Earth Flows - forms of earth collapse caused by water logged soils Mud Flows - rapid movement of moisture saturated soil often occur after violent storms
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–Slumping - Earth flow
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–Soil Creep into terrasettes
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Mass Wasting Movement of materials downslope in response to the Angle of Repose Solifluction - slow downslope movement of materials found in higher latitudes
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Mass Wasting Movement of materials downslope in response to the Angle of Repose Rock Falls - loosened fragments of rocks known as talus fall down slope talus slopes Landslides - massive movement of materials occuring on steep face slopes Avalanche - down slope movement of snow, ice, or rock
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Agents of Erosion Water (most significant) Ice (Glaciers) Wind (arid regions where there is little vegetation)
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–Water Erosion
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–Ice Erosion
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–Wind Erosion
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Weathering, Mass Wasting & Erosion Weathering - the tearing down process –breakdown of materials Mass Wasting - massive movement of materials downslope Erosion - the removal of material
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PHYSICAL GEOGRAPHY Lithosphere Weathering, Mass Wasting & Erosion Chapter 13 C.J. Cox
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