Theory question 205
Weathering, Erosion and Mass Movement(a)(i) Differentiate between Erosion and Mass movement (ii) Name two features each of river erosion and mass movement. (b) Describe the factors that affect mass movement.
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(a)(i) Erosion is the wearing away and removal of rock material by moving agents such as rivers, wind, waves and ice; mass movement is the downslope movement of weathered material under the pull of gravity alone, without a transporting agent.
(ii) River erosion: V-shaped valley, gorge, waterfall, pothole, interlocking spurs, river cliff. Mass movement: landslide scar, terracettes, slump, scree/talus, mudflow deposits.
(b) Steepness of slope (steeper slopes move faster); amount of water lubricating the material (heavy rain); nature of rock and soil (loose, clayey or jointed material moves easily); vegetation cover (roots hold soil; clearing increases movement); depth of weathering; earthquakes and volcanic activity trigger movement; human activities (road cutting, mining, building on slopes); freezing and thawing.
Stress that gravity drives mass movement.