(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 m...

Answer Details

(a)(i) Difference between Erosion and Mass movement:

Erosion is the wearing away and removal of rock waste from one place to another by a moving transporting agent such as running water, wind, ice or waves. Mass movement (mass wasting) is the down-slope movement of rock waste and soil under the direct pull of gravity, without a separate transporting agent carrying the material away.

(a)(ii) Two features each:

• Features of river erosion: waterfalls and rapids; V-shaped valleys and gorges (also potholes, river cliffs).
• Features of mass movement: landslides; soil creep terracettes (also scree/talus slopes, slumps, mudflows).

(b) Factors that affect mass movement:

• Gradient (steepness) of slope: the steeper the slope, the stronger the pull of gravity down-slope and the faster and more likely the movement.
• Water content: water adds weight and lubricates the material, reducing friction; saturated soil moves easily as mudflows and slumps, so heavy rain triggers movement.
• Nature of the material: loose, unconsolidated or weathered material moves more readily than solid, coherent rock; the size and cohesion of particles matter.
• Vegetation cover: plant roots bind the soil and hold it in place, so bare slopes are far more prone to movement than well-vegetated ones.
• Underlying rock structure: where rock layers dip in the same direction as the slope, and along planes of weakness (joints, bedding), sliding is encouraged.
• Human activity and earth tremors: undercutting slopes for roads or building, overloading, and vibrations from earthquakes or blasting can set off movement.