Structure of EARTH'S interior

        The layer of the interior of earth is divided into three parts.

1. Crust

2. Mantle

3. Core (Outer core and Inner core)

The Outer Layer : The Crust

- It is the outermost and the thinnest layer of the earth. This layer has the least density and it's thickness varies about 8 to 40 km. Thickness of the crust is more under the continents and lesser under the oceans, while density of crust is lower than ocean.

- The Crust of the earth is rich in lighter minerals like silica and aluminium. Hence, this layer is also called as Sial (silica and aluminium). The average density of this layer is 2.7 .

The Middle Layer : The Mantle

- It is the intermediate layer of the earth in terms of both it's location and density. It is about 2900 km in thickness, composed of minerals in a semi solid state.

- It is divided further in two layer, upper mantle and lower mantle. The upper part of the mantle is called the Asthenosphere, which is about 250 km 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 .

The Inner Layer : The Core

- The Core is the innermost layer of the earth and occupies it's center. 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.

- This layer is also known as Nife (nickel and iron), because this layer contain large concentration of iron and nickel. Temperature of the core is between 2200°C and 2750°C. Density of this part of the earth is 12.6 to 13.0 gm/cm³ and is many times greater than the average density of the earth 5.53 gm/cm³

EARTH'S MAGNETIC FIELD

          Magnetic fields are produced by the motion of electrical charges. The origin of the earth's magnetic fields thought to be associated with electrical currents produced by the coupling of convective effects and rotation in the spinning liquid metallic outer core of iron and nickel. This mechanism is termed as the Dynamic Effect.