World Geography : Classification and Significance of Plains. ( UPSC )

• A plain is nothing but a low-lying relatively flat land surface with very gentle slope and minimum local relief.
• About 55% of the earth’s land surface is occupied by plains.

Classification of Plains

On the basis of their mode of formation, plains can be classified as:

1. Structural Plains
2. Erosional Plains
3. Depositional Plains

1. Structural Plain

• These plains are mainly formed by the upliftment of a part of the sea floor or continental shelf.
• They are located on the borders of almost all the major continents.
• The structural plains may also be formed by the subsidence of areas.
• Examples – Russian Platforms, Great plains of USA & Central lowlands of Australia.

2. Erosional Plain

• The erosional forces remove the disparities of the land by erosion and convert the land area into a flat and shapeless plain.

Erosion by the River

• Erode the high landmass and converts it into peniplain.
• The resistant rocks found everywhere are called Monadnac.

Erosion by Glacier

• Glacier erosion converts the highland section into a flat but relief plain.

Erosion by Wind

• Rocks in arid and semi-arid regions get disintegrated by weathering and get converted into particles.
• The winds carry these particles with them, due to which the rocky part gets eroded and turns into a plain.
• The resistant rocks found are called Inselberg.
• The plain formed on the mountain slopes is called pediplain.

Karst Plain

• Conversion of lime rocks into plain due to erosion by underground water.

3. Depositional Plains

• Various factors of erosion form the plains through the deposition process.

1. Alluvial Cone

• Rivers descending from the hill slopes form alluvial cones / alluvial fans on the foothills.
• This ground, made up of a pile of big pieces, is called Bhabar.

2. Flood Plain

• During floods, rivers flow over the embankments and form a flood plain, which has alluvial/trembling or alluvial soil.

3. Delta Plains

• When the rivers fall into the oceans, due to the slowdown in their velocity, they left deposition near the mouth, a triangular flat plain is formed which is called the delta plain.

4. Lacustrine Plain (Lake Plain)

• Plains formed due to deposition by rivers falling into lakes or drying up of lakes.

5. Lava Plains

• Plains formed by liquid lava emanating from a volcanic eruption.

6. Loess Plains

• By depositing sand particles wind forms the plain.

The Economic Significance of Plains

1. Fertile Soil

• The plains generally have deep and fertile soil.
• As they have a flat surface, the means of irrigation can be easily developed.
• That is why plains are called as the ‘Food baskets of the world’.

2. The Growth of Industries

• The rich agricultural resources, especially of alluvial plains, have helped in the growth of agro-based industries.
• Since the plains are thickly populated, plenty of labor is available for the intense cultivation and for supplying the workforce for the industries.

3. Expansion of means of Transportation

• The flat surface of plains favours the building of roads, airports and laying down railway lines.

4. Centres of Civilizations

• Plains are centres of many civilizations.

5. Setting up of Cities and Towns

• Easy means of transportation on land and the growth of agriculture and industries in plains have resulted in the setting up and expansion of cities and towns.