Lowlands – SS1 Geography Lesson Note (First Term)

A plain, also called a lowland, is an extensive area of level or gently undulating land, usually a few metres above sea level. Plains are grouped into structural, erosional and depositional types, according to how they were formed. They are used for settlement, farming, mining and transport, but some are prone to flooding.

Behavioural objectives

By the end of the lesson, students should be able to:

• define a plain;
• name the three main types of plains and give an example of each;
• explain how structural, erosional and depositional plains are formed;
• list the categories of depositional plains;
• state the uses and disadvantages of plains.

What is a lowland (plain)?

A plain is an extensive area of level or gently undulating land, usually a few metres above sea level.

What are the types of plains?

1. Structural plains
2. Erosional plains
3. Depositional plains

Structural plains

Mode of formation: These are relatively undisturbed horizontal surfaces of the earth, formed by bedded sedimentary rocks. Examples include the Russian Platform and the Great Plains of the U.S.A.

Erosional plains

Mode of formation: These plains are formed by agents of denudation such as rivers, wind, rain, glaciers and ocean waves. These agents wear down irregular rock surfaces and smoothen them into plains.

Plains resulting from the action of these agents of denudation are called peneplains, while those formed when the wind blows and reduces a highland to a flat or level but gentle land are called pediplains. Examples of erosional plains include the Canadian Shield, and the Reg and Hamada of the Sahara desert.

Depositional plains

Mode of formation: These plains are formed by the deposition of materials or sediments transported by agents of transportation such as rivers, wind, waves and glaciers.

Depositional plains are grouped into the following categories:

1. Alluvial plains
2. Flood plains
3. Deltaic plains
4. Outwash plains
5. Aeolian plains
6. Lacustrine plains
7. Coastal plains

What are the importance and uses of plains?

1. Plains, especially level ones, are good for human habitation. Population and settlements are usually concentrated on plains.
2. Some plains are rich sources of minerals like petroleum and coal.
3. Plains, especially depositional plains, have rich fertile soils which favour intensive agriculture.
4. Plains generally favour the construction of roads, railways and airports.
5. In areas of low rainfall, animals are reared on plains because they favour the growth of pasture.
6. Rivers in plains provide water for drinking and transportation.
7. Rivers in plains provide jobs, for example fishing.

What are the disadvantages of plains?

1. Some plains, especially in delta areas, may be flooded with water, and this reduces human activities.
2. Some plains may pose a serious barrier to communication, especially because of water from rivers or after rain. This increases the cost of developing such areas, for example the construction of flyovers.

Evaluation

1. Define a plain.
2. Name the three types of plains and give one example of each.
3. How are depositional plains formed?
4. List four uses of plains.
5. State two disadvantages of plains.

Assignment

Name any five categories of depositional plains and explain why depositional plains favour intensive agriculture.