Chapter 5: Major Domains of the Earth
Social Science - Geography Notes for CBSE Class 6
Chapter Summary
- The Earth is a unique planet because it supports life. This is due to the presence of land, water, and air.
- The four major domains of the Earth are:
- Lithosphere: The solid portion of the Earth, consisting of the rocks of the Earth’s crust and the thin layers of soil.
- Hydrosphere: Comprises water in all its forms (ice, water, and water vapour), covering over 71% of the Earth’s surface.
- Atmosphere: The thin layer of air that surrounds the Earth.
- Biosphere: The narrow zone where land, water, and air interact to support life.
- Lithosphere
- The Earth’s surface is broadly divided into two main parts: the large landmasses known as continents and the huge water bodies called ocean basins.
- The seven major continents are Asia, Europe, Africa, North America, South America, Australia, and Antarctica.
- Asia: The largest continent, covering about one-third of the total land area of the Earth. It lies in the Eastern Hemisphere. The Tropic of Cancer passes through it. The Ural Mountains separate Asia from Europe, and the combined landmass is called Eurasia.
- Europe: Much smaller than Asia, located to the west of Asia. The Arctic Circle passes through it. It is bounded by water bodies on three sides.
- Africa: The second-largest continent. It is the only continent through which the Tropic of Cancer, the Equator, and the Tropic of Capricorn pass. The Sahara Desert, the world’s largest hot desert, is located here. The Nile River, the world's longest river, also flows through Africa. It is surrounded by oceans and seas on all sides.
- North America: The third-largest continent. It is linked to South America by a very narrow strip of land called the Isthmus of Panama. It lies entirely in the Northern and Western Hemispheres and is surrounded by three oceans.
- South America: Lies mostly in the Southern Hemisphere. The Andes, the world’s longest mountain range, runs almost through its entire length from north to south. The Amazon, the world’s largest river (by volume), flows in this continent.
- Australia: The smallest continent that lies entirely in the Southern Hemisphere. It is called an 'island continent' because it is surrounded on all sides by the ocean.
- Antarctica: Completely in the Southern Hemisphere and a huge continent. The South Pole lies almost at the centre of this continent. It is permanently covered with thick ice sheets and has no permanent human settlements. Many countries have research stations there, such as India's Maitri, Dakshin Gangotri, and Bharati.
- Hydrosphere
- The hydrosphere consists of water in all its forms. Over 71% of the Earth is covered with water, and 29% is land.
- More than 97% of the Earth’s water is found in the oceans and is too salty for human use. A very small percentage is available as fresh water in the form of ice sheets, glaciers, groundwater, and rivers and lakes.
- The major components of the hydrosphere are the oceans, which are interconnected. The five major oceans are the Pacific Ocean, the Atlantic Ocean, the Indian Ocean, the Southern Ocean, and the Arctic Ocean.
- Pacific Ocean: The largest ocean, covering one-third of the Earth. The Mariana Trench, the deepest part of the Earth, lies in the Pacific Ocean. It is almost circular in shape, with Asia, Australia, North and South Americas bordering it.
- Atlantic Ocean: The second-largest ocean, 'S' shaped. It is bordered by North and South Americas on the west and Europe and Africa on the east. Its coastline is highly indented, which is ideal for natural harbours and ports, making it the busiest ocean for commerce.
- Indian Ocean: The only ocean named after a country, India. It is almost triangular in shape. Asia borders it on the north, Africa on the west, and Australia on the east.
- Southern Ocean: Encircles the continent of Antarctica and extends northward to 60 degrees South latitude.
- Arctic Ocean: Located within the Arctic Circle and surrounds the North Pole. It is connected with the Pacific Ocean by a narrow stretch of shallow water known as the Bering Strait. It is bounded by northern coasts of North America and Eurasia.
- Atmosphere
- The Earth is surrounded by a thin layer of air called the atmosphere. It protects us from the harmful effects of the sun’s rays.
- The atmosphere extends up to a height of about 1,600 kilometres.
- It is composed mainly of nitrogen (78%) and oxygen (21%), with other gases like argon, carbon dioxide (0.03%), etc., making up the remaining 1%.
- Oxygen is vital for breathing, nitrogen helps in the growth of living organisms, and carbon dioxide absorbs heat radiated by the Earth, keeping the planet warm. It is also essential for plant growth.
- The density of the atmosphere varies with height, being highest near the surface and decreasing rapidly as one goes up.
- The atmosphere is divided into five layers based on composition, temperature, and other properties: Troposphere, Stratosphere, Mesosphere, Thermosphere, and Exosphere.
- Biosphere
- The biosphere is the narrow zone of contact between land, water, and air where all forms of life exist.
- It is in this zone that all living organisms, including humans, plants, and animals, interact with each other and with their environment.
- Living organisms in the biosphere are broadly divided into the plant kingdom and the animal kingdom.
- Changes within any of these three domains (lithosphere, hydrosphere, atmosphere) can affect the others, emphasizing the interconnectedness of Earth's systems. For example, cutting forests (lithosphere) affects the carbon dioxide content in the atmosphere and can lead to soil erosion.
Questions and Answers
1. What are the four major domains of the Earth?
Answer: The four major domains of the Earth are: Lithosphere, Hydrosphere, Atmosphere, and Biosphere.
2. Name the major continents of the Earth.
Answer: The seven major continents of the Earth are Asia, Europe, Africa, North America, South America, Australia, and Antarctica.
3. Name the two continents that lie entirely in the Southern Hemisphere.
Answer: Australia and Antarctica are the two continents that lie entirely in the Southern Hemisphere.
4. Name the different layers of atmosphere.
Answer: The different layers of the atmosphere are Troposphere, Stratosphere, Mesosphere, Thermosphere, and Exosphere.
5. Why is the Earth called the ‘blue planet’?
Answer: The Earth is called the ‘blue planet’ because more than 71% of its surface is covered with water, making it appear blue from space.
6. Why is the Northern Hemisphere called the ‘land hemisphere’?
Answer: The Northern Hemisphere is called the ‘land hemisphere’ because a larger portion of the Earth’s landmasses (continents) lies in this hemisphere compared to the Southern Hemisphere.
7. Why is the Biosphere important for living organisms?
Answer: The Biosphere is important for living organisms because it is the narrow zone where land, water, and air interact, making life possible. It provides the necessary conditions and resources for all forms of life to exist, grow, and reproduce.
Tick the correct answer.
1. The mountain range that separates Europe from Asia is
- (a) the Andes
- (b) the Himalayas
- (c) the Urals
Answer: (c) the Urals
2. The continent of North America is linked to South America by an
- (a) Isthmus
- (b) Strait
- (c) Canal
Answer: (a) Isthmus
3. The major constituent of atmosphere by percentage is
- (a) Nitrogen
- (b) Oxygen
- (c) Carbon dioxide
Answer: (a) Nitrogen
4. The Ocean that surrounds Antarctica is
- (a) the Pacific Ocean
- (b) the Indian Ocean
- (c) the Southern Ocean
Answer: (c) the Southern Ocean
5. The deepest point on the Earth is
- (a) Mount Everest
- (b) Mariana Trench
- (c) Indian Ocean
Answer: (b) Mariana Trench
Fill in the blanks.
1. The highest mountain peak on the Earth is __________.
Answer: Mount Everest
2. The __________ Desert is the world’s largest hot desert.
Answer: Sahara
3. The __________ is a narrow passage of water connecting two large water bodies.
Answer: Strait
4. The __________ is a narrow strip of land joining two landmasses.
Answer: Isthmus
5. The largest continent is __________.
Answer: Asia
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