Major Landform Features

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Welcome to class! 

In today’s class, we will be talking about major landform features. Enjoy the class!

Major Landform Features

Mountains

Mountains are greatly elevated land surfaces resulting from the intense action of internal forces. They have steep slopes and show distinct peaks. Mountains are classified according to their mode of formation, resulting in four major types of mountains. These are

1. Fold mountains
2. Block Mountains
3. Volcanic Mountains and
4. Residual mountain

• Fold mountains:

Characteristics

They contain old hard rocks with steep sides. They have wrinkling or folding appearance and show distinct peaks of great heights. Fold Mountains exist in layered form. They are soft and have anticlines and synclines.

Folding shortens the earth’s crust. They form the most widespread type of  Mountains and are noted for active volcanoes. They form the highest Mountain ranges. Examples of Fold Mountains include the Himalayas, Rockies, Andes Alps and the Atlas Mountains

Mode of formation

They are formed by large- scale horizontal earth movement as a result of stress and compressional forces which cause expansion or contraction of some parts of the earth. Such stresses, therefore, subject the rocks to compressional forces.

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 a syncline.

A fold may be simple, but where the compressional forces are complex, it results in asymmetrical folding. When pushed further, it forms an overfold, an overfold later forms a recumbent fold. In some cause, faults or cracks result in extreme folding to form over thrust fold.

• Block mountains:

Characteristics

Block Mountains are made up of old hard rocks with flat or slightly sloping surfaces. They have steep sides. They are associated with rift valleys. Examples pf Block Mountains include Hunsruck Mountain, Voges Mountain and the Black Forest of the Rhine land. Example of the rift valley is the East African rift valley system which is about 4.800km

Mode of formation

Block Mountains are formed when the earth cracks due to faulting. Faulting may result from tensional forces or compressional forces. Tensional forces are those that tend to pull the earth’s crust apart, and they result in a normal fault while the Compressional forces are those that shorten the crust to produce a reverse or thrust fault.

Therefore, if a block of rock between two normal faults rises or the land on either side of the block subsides, a block mountain or Horst is formed. At times, a block in between two faults may subside, so that rift valley or graben is formed. The slopes and height of Block Mountains are modified by agents of denudation.

Evaluation

1. Mention any three types of mountain
2. Block mountain is also called?…..
3. The rift valley is associated with ……. mountain?

• Volcanic mountain:

Characteristics

Volcanic Mountains are made up of lava. They have irregular sides with a conical shape. Materials that make up volcanic mountains include ash, volcanic bombs, and cinders etc which are arranged in layers. Examples include Mt. Fuji (Japan), Mt. Mayon (Philippines), Mts Kilimanjaro, Kenya, Elgon, Ruwenzori and Cameroon (all in Africa)

Mode of formation

Volcanic Mountains are formed from volcanoes which are built from materials (molten magma) ejected through fissures or vents in the earth’s crust. The material also includes molten lava, volcanic bombs, cinders, ash, dust and liquid mud. They fall around the vent in successive layers, building up an extensive volcanic cone. Volcanic Mountain is also called Mountain of accumulation  

• Residual mountain:

Characteristic

Residual Mountains are formed from the remains of already existing mountains. They have irregular surfaces with steep sides. They occur in varying heights and sizes and are caused by agents of denudation. Examples include Mt Manodnock (U.S.A), Highlands of Scotland, Highlands of Scandinavia and Decon Plateau.

Mode of formation

Residual Mountains are formed from already existing mountains which are lowered or reduce by agents of denudation such as running water, ice and wind. Residual mountains are, therefore, the remains of the existing mountains. Some hard and the very resistant parts of the existing mountains remain after the lowering of the upper part. This remaining part is called residual mountains which are also called mountains of denudation

Importance or uses of mountains

1. Sources of Minerals
2.  Formation of Rainfall
3. For Transhumance
4. Climatic Barriers
5. For Defence
6. As Tourist Centers
7. Construction of Hydro-electric Power
8. As Wind-breaks

Disadvantages of mountains

1. It causes a barrier to communication
2. It prevents human habitation
3. Mountains promote soil erosion
4. Mountains occupy the good land that could have been used for other useful things
5. Mountain soil is poor in nutrients.

General evaluation

1. Volcanic and residual mountains are also called   ……… and………….
2. Mention two examples of a volcanic mountain.
3. Give four importance of mountains to man.
4. What is a highland?
5. Give an example of a highland.

Reading assignment

Essential Geography pages 31-33.

Theory

1. With a diagram, explain the formation of any one type of mountain.
2. List three advantages and two disadvantages of mountains.

 

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