PHYSICAL GEOGRAPHY Weathering, Mass Wasting & Erosion C.J. Cox

–Weathering - –the tearing down process reshaping the lithosphere

–UPLIFTING –TEARING DOWN –gradational processes

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

Weathering Breakdown of materials Regolith - (greek) –rhegos (blanket) –lithos (rock) –Loose material above the bedrock caused by weathing

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)

Exfoiliation Disintegration-

–Frost Wedging –Joint Block Separation

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

– Thermal Weathering –Salt Wedging

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

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)

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

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

–Slumping - Earth flow

–Soil Creep into terrasettes

Mass Wasting Movement of materials downslope in response to the Angle of Repose Solifluction - slow downslope movement of materials found in higher latitudes

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

Agents of Erosion Water (most significant) Ice (Glaciers) Wind (arid regions where there is little vegetation)

–Water Erosion

–Ice Erosion

–Wind Erosion

Weathering, Mass Wasting & Erosion Weathering - the tearing down process –breakdown of materials Mass Wasting - massive movement of materials downslope Erosion - the removal of material

PHYSICAL GEOGRAPHY Lithosphere Weathering, Mass Wasting & Erosion Chapter 13 C.J. Cox