- The solid portion of the earth on which we live is called the Lithosphere. The word Litho is originated from the Greek language, Lithos meaning stone.
- The gaseous layers that surround the earth, is the Atmosphere. The word Atmos is originated from the Greek language, meaning Vapor.
- The area covered by water is called the Hydrosphere, and it comprises water in all its forms. The word Hudor is originated from the Greek language, meaning Water.
- The Biosphere is the narrow zone where the land, water and air are found together and it contains all forms of life. The word Bios is originated from the Greek language, meaning Life.
- The lithosphere comprises the rocks of the earth’s crust and the thin layers of soil that contain nutrient elements which sustain organisms.
- There are two main division of the earth’s surface. The large landmasses are known as the continents and the huge water bodies are called the ocean basins.
- The highest mountain peak Mt. Everest is 8,848 metres above the sea level. The greatest depth of 11,022 meters is recorded at Mariana Trench in the Pacific Ocean.
- There are 7 major continents. They are Asia, Europe, Africa, North America, South America, Australia and Antarctica. The greater part of the land mass lies in the Northern Hemisphere.
- Asia is the largest continent. It covers about 1/3rd of the total land area of the earth. It is in the Eastern Hemisphere. The Tropic of Cancer passes through the Continent. Asia is separated from the Europe by the Ural mountains on the west.
- Europe lies to the west of Asia. The Arctic circle passes through it. It is bound by water bodies on 3 sides.
- Africa is the second largest continent after Asia. The Equator or 0o latitude runs almost through the middle of the continent. A large part of it lies in the N. Hemisphere. It is the only continent through which the Tropic of Cancer, the Equator and the Tropic of Capricorn The Sahara desert, the world’s largest hot desert, is located in Africa. It is bound on all sides by oceans and seas.
- North America is the third largest continent of the world. It is linked to South America by a very narrow strip of land called the Isthmus of Panama. The continent completely lies in the Northern and Western Hemisphere. Three oceans surround this continent.
# Isthmus – A narrow strip of land joining two landmasses.
# Strait – A strait is a narrow passage of water connecting two large water bodies like seas and oceans.
- South America lies mostly in Southern Hemisphere. The Andes, world’s longest mountain range runs through its length from north to south. It has the world’s largest river, the Amazon.
- Australia is the smallest continent that lies entirely in the Southern Hemisphere. It is an island continent.
- Antarctica, completely in the Southern Hemisphere, is a huge continent. The South pole lies almost at the centre of this continent. The research stations of India in Antarctica are Maitri and Dakshin Gangotri.
Oceans: Oceans are the major part of hydrosphere.
- The oceans are always moving. The three chief movements of ocean waters are the waves, the tides and the ocean currents.
- The four major oceans are the Pacific Ocean, the Atlantic Ocean, the Indian Ocean and the Arctic Ocean, in order of their size.
- The Pacific ocean is spread over one-third of the earth. Asia, Australia, North and South Americas surround it.
- The Atlantic ocean 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 Atlantic ocean is highly intended. This irregular and indented coastline provides ideal location for natural harbors and ports. From the point of view of commerce, it is the busiest ocean.
- The Indian ocean is almost triangular in shape. In the North, it is bound by Asia, in the west by Africa and in the east by Australia.
- 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 Bering Strait. It is bound by northern coasts of North America and Eurasia.
- The atmosphere extends up to a height of about 1,600 kms. The atmosphere is divided into five layers based on composition, temperature and other properties.
- These layers starting from earth’s surface are called the troposphere, the stratosphere, the mesosphere, the thermosphere and the exosphere.
- The density of the atmosphere varies with height. It is maximum at the sea level and decreases rapidly as we go up. The temperature also decreases as we go upwards. The pressure also varies from place to place.
- Moving air is known as wind.
Biosphere – the Domain of Life:
- The organisms in the biosphere may broadly be divided into the plant kingdom and the animal kingdom. The three domains of the earth interact with each other and affect each other in some way or the other.