External structure of the Earth
It has been known for more than 2000 years that the earth is round,But we were able to actually see this much later only when we flew into space.
The knowledge why we don't fall from the earth is much more recent.A journey as described by author jules verne in his book journey to the centre of the earth was,after all,impossible.Only one thing was known : The earth is made up of soil,rocks and water.
Today we know that the earth is also surrounded by an air cover called atmosphere.
Internal structure of the earth
Like an onion, the earth has several layers.The outer most layer, the earth crust has an average depth of about 40 km. As compared with the diameter of the earth, which is around 12,700km,the earth crust is very small. It is primarily made up of solid rocks, below the crust is the mantle consist of solid and molten rocks. Below the mantle is the core,made up of iron and nickel.The deeper one travels inside the earth,the hotter it is.
The temperature in the core is between 4000 5000°C.
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