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The surface of the Earth is not uniform everywhere at some places; it is elevated at other it is level. This variation is called relief. The relief features on the Earth’s surface are broadly grouped into Mountains, Plateaus and Plains. 1). Mountains: These are highest landforms and occupy about one-fourth of the total land area of the Earth. Mountains have peaks rising more than 900 meters from their base. Himalaya are young mountains, while Aravalis are old mountains. 2). Plateaus: A Plateau is a highland with a flat area on its top, unlike a mountain. It is also called table land. The Plateau of Tibet in Asia, surrounded by mountain ranges is the highest Plateau of the World, 3). Plains: a relatively flat and low lying land surface with almost no difference between its highest and lowest points is a Plain. They are also called Low Lands. 4). Hydrosphere: About 71 percent of Earth’s surface is covered with water. This portion of the Earth is known as Hydrosphere. The depth of ocean water is about 3800 meters, while the average height of the land is about 840 meters. REALMS OF THE EARTH: 1). Lithosphere: The landmasses, which provide a home for humans, animals and plants represent the solid realm. It is called Lithosphere. The solid outer crust of the Earth, Composed of rocks and minerals is called Lithosphere. 2). Hydrosphere: The oceans and seas which fill the large depressions on the Earth’s surface, represent the liquid realm. It is called Hydrosphere. 3). Atmosphere: A vast expanse of air around the Earth represents the gaseous realm. It is called Atmosphere. 4). Biosphere: A narrow zone of contact between land, water and air is called the Biosphere. Important Facts:: a). Europe and Asia are a continuous landmass separated by Ural Mountains. They are called Eurasia. b). Africa: Africa is the 2nd largest continent which is separated from Asia by the Suez Canal. c). North and South America have been separated by Panama Canal. d). Australia is also known as the Island Continent. e). Antarctica is permanently covered under a thick sheet of snow and ice and hence called white continent. f). About two-third of the land surface lies north of the Equator. MOTIONS OF THE EARTH: 1). Rotation is called the daily motion of the Earth .The phenomena of alternating day and night is possible only due to the rotation of the Earth. 2). The light before Sunrise is called dawn. 3). The time or half darkness before sunset is called dusk. 4). Days and nights are not of the same length. This variation is due to the inclination if the Earth’s axis. 5). Revolution is called the annual motion of the Earth. The earth revolves in the anticlockwise direction at a speed of about 1, 00,000 kilometres per hour. 6). Equinox: It is one of the two dates in a year when day and night are of equal length due to the Sun being overhead at the Equator. Government of India approved Job portal For fast updates of Govt jobs and Bank Jobs in India. Bansal Academy is best for UGC NET Life Science Coaching in Chandigarh
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