The Earth is a spherical planet whose surface is covered with hard rocks and soil. It is found that the Earth is composed of three layers. The outer layer is the crust. The middle layer of the Earth is mantle. It is composed of solid rock with certain portion of molten rocks called magma. The centre most layer of the Earth is the core. It is the densest part of the planet. The outer core is a layer composed of molten iron, whereas the inner core is solid and extremely hot (5500°C).