(a) Define the term mass wasting (b) Describe two types of mass wasting (c) State three effects of mass wasting

Answer Details

(a) Definition of mass wasting

Mass wasting (mass movement) is the downslope movement of weathered rock materials, soil and debris under the direct influence of gravity, without the help of a transporting agent such as running water, wind or ice. It ranges from slow, gradual creep to sudden, rapid falls and slides.

(b) Two types of mass wasting

1. Soil creep: This is the very slow, almost imperceptible downhill movement of soil and fine rock particles on gentle slopes. Individual particles move a little at a time as the soil is alternately wetted and dried, heated and cooled, or frozen and thawed. It is shown by tilted poles, bent tree trunks and small soil terraces.
2. Landslide (rock/debris slide): This is the rapid, sudden movement of a large mass of rock, soil and debris down a steep slope. It occurs when the slope becomes unstable, often after heavy rain saturates the material or after an earthquake, and the mass slides or falls quickly along a slip surface. (Other types include earthflow, mudflow and rockfall.)

(c) Three effects of mass wasting

1. It destroys farmland, buildings, roads and other property, and can bury or kill people and animals.
2. It lowers slopes and alters the shape of the landscape, exposing bare rock and forming scars and heaps of debris at the foot of slopes.
3. It can block rivers and roads and, by removing the topsoil, reduces soil fertility and encourages further erosion.