Earth 

​Planet Earth→

all Introduction:

★Earth is the planet where we stay. It’s our home planet. It is about 4.5 billion years old. The planetary system in which earth resides is called as Solar system as the Sun is the star around which all planets revolves. Milky Way is the name of the galaxy which is the home of our Solar System. Earth is situated at the third position from the Sun after Mercury and Venus. Earth is 6th largest body in the Solar system after Sun, Jupiter, Saturn, Uranus and Neptune. Earth revolves around the Sun continuously and time taken to complete one such revolution around the sun is called a year. Earth’s axis of rotation is tilted 23.45 degrees with respect to the plane of Earth’s orbit around sun. While revolving around the sun it also rotates around itself. The time taken by earth to complete one rotation around itself is called as a day. Earth has a natural satellite revolving around it. We call it The Moon. Earth Internal Structure: collapse Earth has a layered structure. Main distinctive layers of the earth are as shown in above picture. Crust: The outermost layer which we can touch, dig and explore is called Crust. The depth of crust ranges from 5Km to 70km. It is very thick on the land(continental crust) and thin at the bottom of the ocean(oceanic crust). The lithosphere, which is the rigid outermost shell of a planet (the crust and upper mantle), is broken up into tectonic plates. Mantle: Mantle is the second distinctive layer of the earth. It is the thickest layer and its average thickness is 2850Km. It contains most of the mass of the earth. Mantle comprises nearly 84% of the Earth’s volume and 67% of its mass. The lowest part of the mantle next to the core-mantle boundary is known as the D layer. Although solid, the high temperatures within the mantle cause the silicate material to be sufficiently ductile that it can flow on very long timescales. Convection of the mantle is expressed at the surface through the motions of tectonic plates. Core:The innermost part of the earth is called as core. core’s composition is predominantly iron. The core is thus believed to largely be composed of iron (80%), along with nickel and one or more light elements. As a result taken as a whole, the Earth’s chemical composition by mass iron has the highest percentage. The liquid outer core surrounds the inner core and is believed to be composed of iron mixed with nickel and trace amounts of lighter elements. The Earth’s main magnetic field is associated with electric currents in the molten outer core. Earth’s atmosphere: collapse Earth is surrounded by the layers of gases to make atmosphere of Earth. These gases are retained to earth’s surrounding by earth’s gravitational pull. By volume air’s(excluding water vapor) composition is as follows: Nitrogen78.09% Oxygen20.95% Argon0.92% Carbon Dioxide0.04% Other Gases

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