The layer of interior of earth is divided into three parts.
The Crust – The Outer Layer:
- Crust interior layer of earth is the outermost and thinner layer of the earth. This layer has the least density and its thickness varies about 0 to 100 km.
- Thickness of the crust is more under the continents and lesser under the oceans, while density of crust is ower than oceans. It forming the crust of the earth are rich in lighter minerals like silica and aluminium. Hence, this layer is also called as Sial (silica and aluminium). The average density of crust layer is 2.7 times the density of water.
The Mantle – The Middle Layer:
- Mantle is the intermediate layer of the Earth in terms of both its location and density. It is about 2900 km in thickness, composed of minerals in a semi solid state.
- Mantle layer is further divided into two layers, upper mantle and lower mantle. The upper part of the mantle is called the asthenosphere, which is about 250 kn thick.
- Due to presence of minerals like silica and magnesium in the rocks forming this layer of the Earth, the mantle layer is also known as Sima (silica and magnesium). The average density of this layer is about 5.68 times the density of water.
The Core – The Inner Layer:
- Core is the innermost layer of the Earth and occupies its centre. It is about 3500 km in radius.
- The core is further divided in two layers : outer core and inner core.
- The outer part of the core is believed to have the properties of a liquid and the innermost part of the core (about 1255 km in radius) may be called solid or crystal line.