PHYSICAL GEOGRAPHY Weathering, Mass Wasting & Erosion - PowerPoint PPT Presentation

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PHYSICAL GEOGRAPHY Weathering, Mass Wasting & Erosion

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  1. PHYSICAL GEOGRAPHYWeathering, Mass Wasting & Erosion C.J. Cox

  2. Weathering - • the tearing down process reshaping the lithosphere

  3. UPLIFTING TEARING DOWN gradational processes

  4. 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

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

  6. 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)

  7. Exfoiliation Disintegration-

  8. Joint Block Separation Frost Wedging

  9. Mechanical WeatheringBreakdown 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

  10. Thermal Weathering Salt Wedging

  11. 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

  12. Chemical WeatheringRocks 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)

  13. Chemical WeatheringRocks 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

  14. 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

  15. Slumping - Earth flow

  16. Soil Creep into terrasettes

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

  18. 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

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

  20. Water Erosion

  21. Ice Erosion

  22. Wind Erosion

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

  24. PHYSICAL GEOGRAPHYLithosphereWeathering, Mass Wasting & Erosion Chapter 13 C.J. Cox