|Board||CBSE Board, UP board, JAC board, HBSE Board, Bihar Board, PSEB board, RBSE Board, UBSE Board|
|Subject||GEOGRAPHY | Social Science|
|Chapter Name||Major Domains of the Earth|
|Topic||Major Domains of the Earth CBSE Class 6 GEOGRAPHY Chapter 5 Notes|
|Especially Designed Notes for||CBSE, ICSE, IAS, NET, NRA, UPSC, SSC, NDA, All Govt. Exam|
Major Domains of the Earth
- The earth is the only planet which has life due to presence of life supporting elements like land, water and air on it.
- These three elements make life possible on earth. These are called domains.
Components of the Environment
The surface of the earth is a complex zone, in which the three main components of the environment meet, interact and overlap each other.
The three main components of the environment are:
- Lithosphere’ is made-up of solid rock surface of the earth’s crust and the thin layers of soil that contain nutrient elements, essential for life.
- There are two main divisions of the earth’s surface.
- The large landmasses are known as the continents and the massive water bodies are called ocean basins.
- All the oceans of the world are connected with one another.
- The level of seawater remains the same everywhere in the world.
- Elevation of land is measured from the level of the seawater, which is taken as zero.
- The highest mountain peak of the world is Mount Everest that is 8,848 metres above the sea level, while the deepest point of the earth is recorded at Mariana Trench in the Pacific ocean with the depth of 11,022 metres.
- Continents are separated by large water bodies and the greater part of the landmass lies in the Northern hemisphere.
- There are seven major continents:
- It is the largest continent and covers about one-third of the total land area of the world.
- Asia lies in the Eastern hemisphere.
- The tropic of Cancer passes through this continent.
- Asia is separated from Europe by the Ural mountains on the West part of it.
- This continent lies to the West of Asia and is much smaller in size than Asia.
- The Arctic Circle passes through it. It is bound by the water bodies on three sides.
- It is the second largest continent after Asia.
- The 0° latitude or Equator passes almost through the middle of this continent.
- It is the only continent through which the tropic of Cancer, the Equator and the tropic of Capricorn pass.
- A large part of Africa lies in the Northern hemisphere.
- The largest hot desert of the world (Sahara Desert) is located here.
- The Nile river, which is the longest river of the world, flows through Africa.
- The continent is bound on all sides by oceans and seas
- It is the third largest continent of the world.
- It is linked with South America by a narrow strip of land called three oceans.
- “Isthmus of Panama”. The continent lies totally in the Northern and Western hemisphere, and is surrounded by Three oceans.
- It lies mostly in the Southern hemisphere.
- The world’s longest mountain range Andes’ runs from North to South through its entire length.
- This continent has the world’s largest river named ‘Amazon’
- It lies completely in the Southern hemisphere and is the smallest continent.
- It is called an island continent, as it is surrounded on all sides by the oceans and seas.
- It is a huge continent, completely lies in the Southern hemisphere.
- The South Pole lies almost at the centre of the continent.
- The continent remains permanently ice-covered due to its position in the South Polar region.
- There are no permanent human settlements.
- Many countries have established their research stations in Antarctica.
- India also has established research stations in Antarctica, i.e. Maitri and Dakshin Gangotri.
- More than 71 per cent of the earth is covered with water and 29 per cent with land.
- The earth is called the blue planet due to excess of water cover.
- More than 97 per cent of the earth’s water is present in the oceans.
- A large proportion of the rest of the water is present in the form of ice sheets and glaciers or under ground water, and only a very small percentage is available as fresh water for human consumption.
- Oceans are the major part of hydrosphere.
- They are all interconnected.
- The ocean waters are always moving The three main movements of ocean waters are: (i) the waves (ii) the tides (iii) the ocean currents. There are five major oceans.
(i) Pacific Ocean
- The Pacific ocean is the largest ocean spread over one-third of the earth.
- Mariana Trench, the deepest part of the earth, lies in the Pacific ocean.
- The shape of the Pacific ocean is almost circular.
- Asia, Australia, North and South Americas surround it.
(ii) Atlantic ocean
- The Atlantic ocean, the second largest ocean, is ‘S’ shaped with highly indented coastline, which provides ideal location for natural harbours and ports.
- From the point of view of commerce, it is the busiest ocean.
- It is flanked by the North and South Americas on the Western side, and Europe and Africa on the Eastern side.
(iii) Indian Ocean
- The Indian ocean is the only ocean that is named after a country i.e. India.
- The shape of the ocean is triangular.
- The ocean in the North is bound by Asia, in the West by Africa and in the Fast by Australia.
(iv) The Southern Ocean
- The Southern ocean encircles the Antarctica continent and extends Northward to 60 degress South latitude.
(V) Arctic Ocean
- The Arctic occan is located within the Arctic Circle and surrounds the North Pole.
- It is connected with the Pacific ocean by a narrow stretch of shallow water, which is called Berring strait’.
- It is bound by Northern coasts of North America and Eurasia.
- A strait is a narrow passage of water connecting two large water bodies like seas and oceans.
- The earth is surrounded by a layer of gas called the atmosphere.
- This thin cover of air is considered an integral and essential aspect of the planet.
- This layer provides us with the air we breathe and also protects us from the harmful effects of sun’s rays.
- The atmosphere extends upto a height of about 1,600 kms.
- The atmosphere is divided into five layers based on composition, temperature and other properties.
- These layers are called the troposphere, the stratosphere, the mesosphere, the thermosphere and the exosphere (starting from earth’s surface).
The atmosphere is composed mainly of the following gases as per their volume
- Nitrogen-78 per cent
- Oxygen- 21per cent
- Carbon dioxide, argon and others- 1per cent
(Note- Nitrogen and oxygen make up about 99 per cent of clean, dry air)
- Oxygen is important for breathing, nitrogen for growth of living beings while carbon dioxide is important for absorption of heat radiated by the earth to keep it warm and for respiration of plants.
- The density of the atmosphere is maximum at the sea level and decreases as going up.
- The temperature also decreases as going upwards.
- The air pressure also varies from place to place.
- Air moves from high pressure to low pressure and the movement of it is called wind.
Biosphere-The Domain of Life
- The biosphere is the narrow unique zone of contact between the land, water and air, where life exist.
- There are several organisms found here from microbes and bacteria to large mammals.
- All the living organisms are linked with each other and with biosphere for survival.
- The living organisms in biosphere can be broadly divided into the plant kingdom and the animal kingdom.
- The three domains of the earth are interlinked with each other and affect each other.
For example cutting of forests for fulfilling our needs and demands of wood, or clearing land for cultivation may lead to fast removal of soil from slopes.
- Likewise, earth’s surface may be changed due to natural calamities like earthquakes, landslides etc.
- For example there could be submergence of land, as happened in the case of Tsunami recently.
- Parts of Andaman and Nicobar islands were submerged under water.
- Besides this, discharge of waste water and material into water bodies makes the water contaminated and unsuitable for all living beings.
- Air is also polluted by emission from industries, thermal power plants and vehicles.
- Carbon dioxide (CO2) is an important constituent of air, but if the amount of CO2, increases, it leads to increase in global temperatures.
- This is termed as global warming.
- So, it is essential to limit the over-consumption of resources of the earth to maintain the balance of nature between the domains of the lithosphere, the atmosphere and the hydrosphere.
One word meaning
- Lithosphere It is the solid portion of the earth on which we live.
- Continents The large landmasses are known as the continents.
- Ocean basins The massive water bodies are called ocean basins.
- Sea level The elevation of land is measured from the level of sea water, which is taken as zero and called sea level.
- Isthmus It is a narrow strip of land that joins two landmasses.
- Hydrosphere Hydrosphere comprises all forms of water like- ice, water and water vapour.
- Strait It is a narrow stretch of shallow water, which connects two large water bodies.
- Atmosphere It is the gaseous layer that surrounds the earth.
- Biosphere It contains all forms of life and is a narrow zone, where land, water and air are found together.
- Global warming The increasing temperature of the earth due to carbon dioxide is called global warming.