Like an onion, the Earth has several layers. The outermost layer, the Earth’s crust, has an average depth of about 40 km. 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 2900 km. Due to the heat inside the Earth, the mantle consists 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 and 5000 degree Celcius.
