NCERT / CBSE NOTES : Chapter Summary
Major Landforms of the Earth
The earth is made up of land, water and air. These form three domains of the earth—the lithosphere, the hydrosphere, and the atmosphere. All these three domains combine to form the life-giving domain of the earth, called the Biosphere. The biosphere is the narrow zone of contact between land, water, and air where life exists.
Humans affect the balance of the biosphere by:
- Gases and smoke emitted from factories and vehicles are released in the air. The quantity of gases like carbon monoxide, dust and smoke has increased in the air, leading to air pollution.
- Waste water and chemicals from residences and factories are disposed in rivers, lakes and ponds. This has resulted in water pollution.
Human activities have also affected our natural resources:
- Reckless cutting down of forests and clearing green areas for construction and agricultural purposes has resulted in land pollution.
- Less trees means less oxygen and more carbon dioxide in the air. More carbon dioxide has resulted in global warming.
A mountain is a high natural landform that projects above the surrounding land, in a limited area. It is only when the natural elevation of a landform is more than 1000 feet high above the sea level; it is termed as a mountain.
The peaks of many high mountains are snow-capped because the temperature dips below zero beyond a certain height. Owing to the extreme cold, the rivers in some mountains are permanently frozen. Such rivers of ice are called glaciers.
Mountains have been found under the sea also. Owing to the steep slopes, relatively less land is available for farming in the mountains. People in the mountainous regions practice terrace cultivation. A mountain range is the term used for mountains arranged in a line.
- Fold mountains,
- Block mountains and
- Volcanic mountains
Fold mountains are a result of folding and are formed when collision occurs between two parts of the earth’s crust. The oldest fold mountain system is found right here in India: The Aravali range.
Block mountains form when large areas of rock lying beneath the surface deposits of soil are broken and displaced in a vertical direction. The displacement of rocks results in elevated blocks known as horsts and lowered blocks known as grabens.
Volcanic mountains are formed because of volcanic activity. Glaciers in the mountains are source of water for many rivers. This water is stored in reservoirs and used by us for irrigation and generation of hydro-electricity.
Mountains act as storehouses of water for human beings. River valleys and terraces are used for cultivation of crops. Cardamom is produced through terrace cultivation. Mountains are also home to a variety of species of plants and animals. Therefore, tourists are also attracted to mountains for their scenic beauty.
The steep slopes of the mountains attract people who are involved in sports like paragliding, hand gliding, river rafting and skiing.
A plateau is an elevated land with a flat top, bound by steep slopes on one or more sides. A plateau is also called a tableland. Plateaus cover about 45% of the earth’s surface.
Examples of plateaus are:
- The Deccan Plateau in India,
- The East African Plateau in Kenya, Tanzania and Uganda,
- The Western Plateau in Australia and
- The Tibet Plateau in East Asia
The Deccan Plateau of India is one of the oldest plateaus on the earth’s surface. The Tibet Plateau, is the youngest, highest and largest plateau in the world. Plateaus are formed by lava, rivers or wind.
Lava erupting from cracks on the earth’s surface spreads in the surrounding areas, then cools down, and eventually forms plateaus. Plateaus formed by lava are called lava plateaus.
As rivers flow down the slopes of high mountains, they carry stones and sand with the water. This results in the erosion of the mountains and formation of table lands or plateaus. Plateaus are created when winds wear away the side of an uplifted region and carry the debris to far-off places.
Plateaus are rich in mineral deposits, such as gold and iron. Waterfalls are fairly common in plateau regions. This is because there are often spots where river water falls from great heights. These waterfalls have added to the tourist attractions of these areas.
Lava plateaus have a high percentage of productive black soil containing calcium and magnesium carbonates. Crops like maize, cotton, ragi and chilli grow well in the black soil of plateau regions. The Deccan Plateau, which is a lava plateau, has an extensive deposit of black soil.
Tourists are attracted to plateaus for the beautiful scenery, flora and fauna.
Plains are large stretches of flat land on the earth’s surface. The elevation of plains is generally limited to about 200 metres above the mean sea level. While some plains are extremely level, there are plains which have a rolling surface. Plains cover about 55% of the earth’s area.
Most plains have low elevation. However, some plains, are highly elevated from sea level. These types of plains are called high plains. Plains are the most popular areas for human habitation.
Plains are formed by the erosion and deposition caused by rivers and their tributaries. Plains formed by the river deposits are called riverine plains or alluvial plains.
Plains are important for agriculture. This is because the soil deposited on plains in the form of sediments is fertile. The flat surface of plains is suitable for the cultivation of crops. Due to the flat surface, it is easier to build a transport network on the plains.
Flatness of plans makes it is easier for people to build houses as well. It is easier to live on the plains than in the mountains. Human beings need to be careful in their use of land so that it can be used by future generations as well.