SS3 Second Term Geography Lesson Note – Mass Movement

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WEEK 3 

TOPIC: MASS MOVEMENT

CONTENT:

(1) MEANING OF MASS MOVEMENT

(2) FACTORS THAT INFLUENCE MASS MOVEMENT

(3) TYPES OF MASS MOVEMENT

SUB – TOPIC 1: MEANING OF MASS MOVEMENT AND FACTORS INFLUENCING IT

Mass movement can be defined as the movement of weathered materials down slope under the force or influence of gravity. Such movement may be slow, gradual or sudden depending on the steepness of the slope. The size or weight of weathered materials determines the speed of the movement. Usually, rain water serves as lubricant to the weathered materials or debris. It is otherwise known as mass wasting.

FACTORS THAT AFFECT MASS MOVEMENT

1. The gradient or steepness of slopes: The rate of movement of materials is naturally faster on steeper slopes than on gentle slopes. Mass movement is pronounced in areas with steep slopes where the weathered layer is deep and the weathered materials are loose.
2. The nature and weight of materials: Mass movement is rapid on steep slopes where the weathered layer is quite deep and the materials are loosely held together. Permeable rocks are more prone to mass movement than the impermeable rocks. The lighter the weight of materials carried the faster the movement and vice versa.
3. Vegetation cover: Absence of vegetation encourages mass movement while presence of vegetation discourages or reduces mass movement.
4. Climatic conditions or the presence of lubricating moisture: The amount and nature of rainfall and snow fall determine how much moisture would be available to saturate the weathered materials on a given slope. Heavy rainfall or alternate freeze-thaw condition promotes mass movement.
5. Human activities: These are activities of man such as mining, road construction, over-grazing by animals and deforestation which may take place on steep slopes and encourage the production of mass movement.
6. Earthquakes and volcanic eruptions: Mass movement is encouraged if there are earthquakes and volcanic eruptions.

EVALUATION

1. Explain mass movement
2. Outline the factors that affect mass movement

SUB – TOPIC 2: TYPES OF MASS MOVEMENT

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