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  Weathering – disintegration and decomposition Weathering of material at or near the surface Mechanical weathering  Breaking of rocks into smaller.

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Presentation on theme: "  Weathering – disintegration and decomposition Weathering of material at or near the surface Mechanical weathering  Breaking of rocks into smaller."— Presentation transcript:

1   Weathering – disintegration and decomposition Weathering of material at or near the surface Mechanical weathering  Breaking of rocks into smaller pieces Frost wedging Unloading Biological activity Ex. Plant roots, burrowing animals Ex. Human activity Chemical weathering  Alters the internal structures of minerals.  Minerals altered by removing or adding elements.  Most important agent is water. Oxygen dissolved in water oxidizes Carbon dioxide (CO 2 ) in water forms carbonic acid (H 2 CO 3 ); alters material  Erosion – the incorporation and transportation Erosion of material by a mobile agent, usually water, wind, or ice. 1 Figure 4.5B: Igneous mass fracture Figure 4.4: Frost wedging 11: Erosion

2   Def : The downslope movement of rock, regolithregolith and soil under the direct influence of gravity  Gravity is the controlling force.  Important triggering factors:  Saturation of the material with water.  Destroys particle cohesion  Water adds weight Over-steepening of slopes.  Unconsolidated granular particles assume stable slope called the angle of repose.angle of repose  Stable slope angle different for various materials.  Over-steepened slopes are unstable. Removal of anchoring vegetation. Ground vibrations from earthquakes. Mass Wasting (Massive Landside, 3:21) Google Images: Landslide 2

3   Mud, earth, rock, debris, etc.  The movement of the material:  Fall (free-fall of pieces)  Slide (material moves along a well- defined surface)  Flow (material moves as a viscous fluid)  Rate of movement: slow or fast  Mud, earth, rock, debris, etc.  The movement of the material:  Fall (free-fall of pieces)  Slide (material moves along a well- defined surface)  Flow (material moves as a viscous fluid)  Rate of movement: slow or fast Processes Google Images: Mass Wasting 3

4   Process types defined by rate of movement, fast or slow.  Creep: slow movement of soil and regolith downhill  Causes fences and utility poles to tilt.  Slump : rapid movement along a curved surface.  Occur along over-steepened slopes.  Rockslide : bedrock moves rapidly downslope.  Debris flow: rapid flow of debris with water.  Often confined to channels.  Problems in dry areas with heavy rains.  Lahars: volcanic material debris flow.  Earthflow: rapid, hillsides in humid regions. Types Google Images: Mass Wasting 4


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