Major Domains of the Earth: Geography NCERT Notes for UPSC

Lithosphere

• The solid portion of the Earth is called the Lithosphere. It comprises the rocks of the Earth’s crust and the thin layers of soil that contain nutrient elements that sustain organisms.
• There are two main divisions of the Earth’s surface. Large land masses are known as continents while huge water bodies are called ocean basins.

Seven Major Continents on Earth

• Asia: It is the largest continent which comprises one-third area of the Earth. It lies in the Eastern Hemisphere. It is separated from Europe by the Ural Mountains on the west side. The Tropic of Cancer passes through it.

• Europe: It lies west of Asia. The Arctic Circle passes through it and it is surrounded by water bodies from three sides.
• Africa: It is second largest continent after Asia. All the three latitudes pass through this continent. World’s biggest desert Sahara is present on the northern part of the continent. It is the only continent which is bound by water from all sides of the continent. The world’s longest river Nile flows through this continent.
• North America: It is third largest continent which is linked to South America by a very narrow strip of land called the Isthmus of Panama. The continent lies completely in the Northern and Western Hemispheres. Three oceans surround this continent.
• South America: It lies mostly in the Southern Hemisphere. The Andes, the world’s longest mountain range, runs through its length from north to south. South America has the world’s largest river, the Amazon.
• Australia: It is the smallest continent that lies entirely in the Southern Hemisphere. It is surrounded on all sides by the oceans and seas. It is also called as island continent.
• Antarctica: It is a huge continent lying completely in the Southern Hemisphere. The South Pole lies almost at the centre of this continent. As it is located in the South Polar Region, it is permanently covered with thick ice sheets. There are no permanent human settlements. Many countries have research stations in Antarctica. India also has research stations there. These are named Maitri and Dakshin Gangotri.

Also Read: MISHTI Scheme for Mangrove Plantations

Atmosphere

• The thin layer of gas which surrounds the Earth is called the atmosphere.
• It extends up to a height of about 1,600 kilometres.
• The atmosphere is divided into five layers based on composition, temperature, and other properties. These layers starting from the Earth’s surface are called the troposphere, the stratosphere, the mesosphere, the thermosphere, and the exosphere.

• The atmosphere is composed mainly of Nitrogen and Oxygen, which make up about 99 per cent of clean, dry air. 
• Nitrogen 78 per cent, Oxygen 21 per cent and other gases like carbon dioxide, argon and others comprise 1 per cent by volume.

Hydrosphere

• The Hydrosphere comprises water in all its forms, i.e.  ice, water, water vapour, running water in ocean, river, underground water, etc.
• More than 71 per cent of the Earth is covered with water and 29 per cent is with land. That’s why the Earth is known as the “Blue Planet”.

Oceans

• Oceans are the major part of hydrosphere. They are all inter-connected and water in the ocean is always moving.
• The three chief movements of ocean waters are the waves, the tides, and the ocean currents.
• The five major oceans are the Pacific Ocean, the Atlantic Ocean, the Indian Ocean, the Southern Ocean, and the Arctic Ocean, in order of their size.
• The Pacific Ocean:  It is the largest ocean which is spread over one-third of the Earth. Mariana Trench, the deepest part of the Earth, lies in the Pacific Ocean. The Pacific Ocean is almost circular in shape. It is surrounded by Asia, Australia, North, and South America.
• The Atlantic Ocean: It is the second-largest ocean in the world. It is ‘S’ shaped. It is flanked by the North and South Americas on the western side, and Europe and Africa on the eastern side. The coastline of the Atlantic Ocean is highly indented. This irregular and indented coastline provides an ideal location for natural harbours and ports. From the point of view of commerce, it is the busiest Ocean.
• The Indian Ocean: It is the only ocean named after a country, that is, India. The shape of the ocean is almost triangular. In the north, it is bound by Asia, in the west by Africa, and in the east by Australia.
• The Southern Ocean: It encircles the continent of Antarctica and extends northward to 60 degrees south latitude. The Arctic Ocean 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 known as the Bering Strait. It is bound by the northern coasts of North America and Eurasia. 

Biosphere

It is the narrow zone where we find land, water and air together, which contains all forms of life.

Interesting terms and facts

• Strait: It is a narrow passage of water connecting two large water bodies like seas and ocean. E.g. Strait of Malacca, Palk Strait etc.
• Isthmus: A narrow strip of land joining two land masses. E.g. Isthmus of Panama.
• In the Greek language, Lithos means Stone; Atmos means Vapour; Hudor means Water; and Bios means Life.
• Edmund Hillary (New Zealand) and Tenzing Norgay Sherpa (India) were the first men to climb the highest mountain peak Mt. Everest on the planet Earth on 29th May, 1953. 
• Junko Tabei (Japan) was the first woman to reach the summit on 16th May, 1975. 
• The first Indian woman to climb the highest peak on 23rd May, 1984 was Bachendri Pal.

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