The Earth and major structural components of earth

EARTH 
The third farthest planet from the sun is earth. The earth rotates on its axis in about 24 hours.
The diameter of earth is 12756 km.The earth completes its rotation along its axis in 23.9 hour and one tip along its orbit in 365 days,6 hours and 9 minutes and 9.4 seconds. The orbit of the earth is not a circle but an ellipse. 
STRUCTURE OF THE EARTH 
The earth has four major structural components. 
1. The Crust 2.The Mantle 3.The Outer core 

4.The Inner Core.
THE CRUST
The upper most layer of the earth is called the crust. A solid and a complex layer of the lithosphere in both physical and chemical nature. The crust is composed of wide variety of rocks which are known as sedimentary rocks .The crust is further divided into ocean crust and continental crust. 
THE MANTLE: According to the various kinds of scientific evidences the upper mantle of the earth is made up of silicate minerals. The temperature increases rapidly with depth in outer of the earth. Due to high temperatures the rocks start melting .These molten rocks form the basis of lava which erupt from oceanic volcanoes. 
THE  CORE
The  core  starts  where  marked  physical  and  chemical  changes  occur  across  the over mantle  boundaries. 
The  outer  core is thought to be made of mixture of melted iron and nickle.In the inner core the mixture is thought to be nickel and iron alloy. 
ATMOSPHERE OF THE EARTH
The chief gases in the atmosphere of the earth are, 
Nitrogen 78.09% 
Oxygen 20.95% 
Argon 0.93% 
The  remaining  0.03%  is  made  of  carbon  dioxide,  small  quantities  of  neon,helium,ozone and  hydrogen  and  minute  traces  of krypton,methane,xenon and other gases. Another important constituent of the atmosphere is water vapor which makes up 4 percent by volume and 3 percent by weight. Life is not  possible  without  the  atmosphere  of  the  earth  Oxygen present  in  the  atmosphere  is  necessary  for  both  animals  and  plants  for respiration. Carbon dioxide is needed by the plants which use this gas in the process of photosynthesis. Water vapors present in the earth are necessary for the process of rain and other precipitation. 
The atmosphere is a valuable natural source of many gases that are widely needed in industry,argon for the purpose of welding and oxygen is required for hospitals and other metal industries. 
The  earth's  atmosphere  aloe  possesses  the  protective  role  against  the  dangerous  UV rays  and  other  high  radioactive  energy  from space. The atmosphere of the earth absorbs these radiations which are a cause of various health hazards.