THE EARTH IS ROUND ,IT has been known for more than 2000 years,but we were able to actually see this much later only when we flew into space .The Earth is made up of rocks, soils ,and water.It is surrounded by an air cover called the atmosphere. INTERNAL STRUCTURE OF THE EARTH .-Like an Onion Earth has several layers.The outer most layer, the Earth's crust,has an average depth of 40 k.m.As compared with the diameter of the Earth ,which is around,12,700 km,the Earth's crust is very small.It is primarily made up of solid rocks.Below the crust is the mantle reaching to a depth of about 2900km.Due to the heat inside the earth ,the mantle consist of solid and molten rocks..Below the mantle is core,made up of Iron and Nickle.The deeper one travels inside the Earth ,the hotter it is .The temperature in the core is