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WEEK 1
TOPIC: MOUNTAINS
CONTENT:
- Meaning and Types of Mountain.
- Mode of formation and characteristics.
- Importance of mountains
The major land forms of the world include: (i) Mountains (ii) Plateaux and (iii) Plains.
Sub-Topic 1: Meaning and Types of Mountains.
Definition of Mountains
Mountains can be defined as the great elevated land surfaces resulting from intense action of internal forces. There are four types of mountains namely:- (i) Fold mountains (ii) Block mountains (iii) Volcanic mountains and (iv) Residual mountains.
EVALUATION:
- What is mountain?
- State types of mountains.
Sub-Topic 2: FOLD MOUNTAINS
Mode of formation:
Fold Mountains are formed by large scale horizontal earth movement as a result of stress and compressional forces which cause the expansion or contraction of some parts of the earth. The compressional forces produce wrinkling or folding of the crust of the earth. The up folds of the wrinkles are anticlines while the down folds are called syncline.
Upfold and Downfold
A fold may be simple, but where the compressional forces are complex, it results in asymmetrical folding. When pushed further, it forms an over-fold; an overfold later forms a recumbent fold. Where there are cracks or faults in extreme folding. It forms over thrust fold.
FOLDING AND TYPES OF FOLD
Folding is the large-scale deformation of vast sedimentary layers of the earth’s crust by compressional forces acting horizontally along the surface layers of the earth.
TYPES OF FOLD.
(i) Simple or Symmetrical.
(ii) Asymmetrical or Inclined.
(iii) Overfold/Recumbent.
(iv) Overthrust.
Simple fold: Occurs when compressional force applied from both sides are equal. Each of the two sides is known as limb.
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