The earth has an infinite variety of landforms. These landforms are a result of two processes. Within the earth, a continuous movement is taking place. The first or the internal process leads to the upliftment and sinking of the earth’s surface at several places. The second, or the external process is the continuous wearing down and rebuilding of the land surface. The wearing away of the earth’s surface is called erosion. The surface is being lowered by the process of erosion and rebuilt by the process of deposition. These two processes are carried out by running water, ice and wind.
- A mountain is any natural elevation of the earth’s surface.
- It may have a small summit and a broad base.
- It is considerably higher than the surrounding area.
- Some mountains are even higher than the clouds.
- The climate becomes colder when we go higher.
- In some mountains, there are permanently frozen rivers of ice.
- They are called glaciers.
- There are some mountains deep under the sea.
- Owing to harsh climate, less people live in the mountain areas.
- Since the slopes are steep, less land is available for farming.
- Mountains may be arranged in a line known as range.
- The Himalayas, the Alps and the Andes are mountain ranges of Asia, Europe and South America, respectively.
- Mountains vary in their heights and shape.
There are three types of mountains- Fold Mountains, Block Mountains and the Volcanic Mountains. The Himalayan Mountains and the Alps are young fold mountains with rugged relief and high conical peaks. The Aravali range in India is one of the oldest fold mountain systems in the world. The Appalachians in North America and the Ural mountains in Russia have rounded features and low elevation. They are very old fold mountains.
Block Mountains are created when large areas are broken and displaced vertically. The uplifted blocks are termed as horsts and the lowered blocks are called graben. The Rhine valley and the Vosges mountain in Europe are examples of such mountain systems.
Volcanic mountains are formed due to volcanic activity. Mt.Kilimanjaro in Africa and Mt.Fujiyama in Japan are examples of such mountains. Mountains are very useful. They are a storehouse of water. Many rivers have their source in the glaciers in the mountains. Reservoirs are made and the water is harnessed for the use of people.
Water from the mountains is also used for irrigation and generation of hydro-electricity. The river valleys and terraces are ideal for cultivation of crops. Mountains have a rich variety of flora and fauna. The forests provide fuel, fodder, shelter and other products like gum, raisins, etc.
- A plateau is an elevated flat land.
- It is a flat-topped tableland standing above the surrounding area.
- A plateau may have one or more sides with steep slopes.
- The height of plateaus often varies from a few hundred metres to several thousand metres. Plateaus, like mountains, may be young or old.
- The Deccan plateau in India is one of the oldest plateaus.
- The East African Plateau in Kenya, Tanzania and Uganda and the Western plateau of Australia are other examples.
- The Tibet plateau (Figure 5.1, p.31) is the highest plateau in the world with a height of 4,000 to 6,000 metres above the mean sea level.
- Plateaus are very useful because they are rich in mineral deposits.
- As a result, many of the mining areas in the world are located in the plateau areas.
- The African plateau is famous for gold and diamond mining.
- In India huge reserves of iron, coal and manganese are found in the Chhotanagpur plateau.
- In the plateau areas, there may be several waterfalls as the river falls from a great height.
- In India, the Hundru falls in the Chhotanagpur plateau on the river Subarnarekha and the Jog falls in Karnataka are examples of such waterfalls.
- The lava plateaus are rich in black soil that are fertile and good for cultivation.
- Many plateaus have scenic spots and are of great attraction to tourists.
- Plains are large stretches of flat land, not more than 200 metres above mean sea level.
- Some plains are extremely level and others may be slightly rolling and undulating.
- Most of the plains are formed by rivers and their tributaries.
- The rivers flow down the slopes of mountains and erode them.
- They carry forward the eroded material.
- Then they deposit their load consisting of stones, sand and silt along their courses and in their valleys.
- It is from these deposits that plains are formed.
- Plains are very fertile which makes it easier for construction of transport purposes.
- These plains are very thickly-populated regions of the world.
- Some of the largest plains made by the rivers are found in Asia and North America.
- For example, in Asia, these plains are formed by the Ganga and the Brahmaputra in India and the Yangtze in China.
- Plains are the most useful areas for human habitation.
- There is great concentration of people as more flat land is available for building houses, as well as for cultivation.
- Because of fertile soils, the land is highly productive for cultivation.
- In India too, the Indo-Gangetic plains are the most densely populated regions of the country.
Landforms and the People
- Humans have been living on different kinds of landforms in different ways.
- Life is difficult in mountainous areas.
- Plains provide much better conditions.
- It is easier to grow crops, build a house or a road in a plain than a mountain.
- Natural calamities such as earthquakes, volcanic eruptions, storms and floods cause widespread destruction.
- Quite often we use land for wasteful purposes, for example constructing houses on fertile land.
- Similarly, we throw garbage on land or in water making them dirty.