A plain is an extensive area of level or gentle undulating land, usually a few metres above the sea-level.
In this situation, height differences are small. Plains are certainly the most important and populous landforms because the world population lives on them. Some plains have fertile soils and they are extensively cultivated for agricultural purposes.
TYPES OF PLAINS
- Structural Plains: These are relatively undisturbed horizontal surface of the earth, formed by bedded sedimentary rocks. Examples include the Russian platform, central lowland of Australia and the Great plain of United States of America.
- Erosional Plains: These plains are formed by the agents of denudation such as rivers, wind, rain, glacier and ocean waves which wear out irregular rock surfaces and smoothen them. Plains, resulting from the action of these agents of denudation are called Peneplains while those formed when wind blows and reduces a highland to a flat or level but a gentle land is called An example of Peneplain is the Great Lakes plain of the Hudson Bay area, North America and that of the Pediplain include Reg and Hamada of Sahara Desert.
- Depositional plains: These are plains formed by the deposition of materials or sediments transported there by the various agents of transportation such as rivers, winds, waves and glacier. When this action is effected, the following features then emerge:
- Alluvial Plains: These are formed from the deposition of sediments eroded from the upper course of a river to the lower course of that river. The deposited materials on the lower course of the river form the alluvial plain.
- Flood Plains: These are also formed from the deposition of sediments eroded from the upper course of a river and deposited on the lower course, especially when the river overflows its banks. It can also be formed from deposition of sediments carried by running water e.g. floods.
- Deltaic Plains: These are formed from the deposition of sediments brought down by a river onto the mouth of that river. Alluvial, flood and deltaic plains are all rich and fertile soils which are very good for serious farming activities.
- Outwash Plains: These are formed from the deposition of materials brought down by glaciers.
- Aeolian Plains: These are formed in arid or desert and semi-arid regions where wind-blown sand is deposited to form an extensive plain.
- Lacustrine Plains: These are formed from the deposition of sediments which cover the beds of lakes that have become dry.
- Coastal Plains: These are formed from the deposition of sediments brought by ocean waves on the continental shelf. Coastal plains can also be formed by the uplift of part of the sea-floor bordering a continent.
IMPORTANCE OF PLAINS
- Plains, especially level ones are good for human habitation. Population and settlements are usually concentrated on plains.
- Some plains are rich sources of minerals like petroleum and coal.
- Plains, especially depositional plains are rich fertile soils which favor intensive agriculture.
- Plains generally favor communication as roads, railway, and airports are better built on level lands.
- In areas of low rainfall, rearing of animals is carried out in plains as they favor the growth of pasture.
- Rivers in plains provide water for drinking and transportation.
- Rivers in plains (basins) provide jobs e.g. fishing.
- Plains are centres of population concentration, e.g. the flood plains of rivers.
- It supports concentration of manufacturing industries.
DISADVANTAGES OF PLAINS
- Plains are not good areas for protection during war as they are easy for an invading enemy to overrun.
- Some plains, especially in delta areas may be flooded with water and this reduces human activities.
- Some may pose serious barrier to communication, especially in areas flooded by excess water either from river or after rain. It therefore increases the cost of developing such areas e.g. construction of flyovers.
- Some plains may be barren e.g. outwash plains in some parts of Netherlands may be water-logged.