To explore the earth, we have to explore the 6400 km radius of Earth. Starting from center to outer layer of earth, it is composed of four different layers. All these layers have different properties, composition, and characteristics that effects the processes occurring outside and inside the earth.
Four layers of earth are :
1. The Inner Core -
This is the deepest layer of earth having thickness of about 1200 to 1500 km. The temperature of the layer is about 5500 degree celsius. Generally it is made up of iron and nickel , but the pressure is so high that is why it is in solid state.
2. Outer core -
This layer lies between inner core and mantle, and is 2200 km thick. It has very hot temperature of about 6100 degree Celsius. Liquid iron and Nickel spins when the planet rotates, which is responsible for earth's magnetic field, that protects us from sun's solar radiation. Without magnetic field our planet resembles the Mars.
3. Mantle -
This layer lies beneath the crest and have up to 2900 km of thickness. It consists of hot, dense, iron, magnesium and silicon rich solid rocks. Mantle is semi-liquid and makes about 84% of earth's volume. Further, mantle is divided into 3 zones i.e.
- Lithosphere is upper part of mantle. It has thickness of about 100 km and consists of 15 major tectonic plates.
- Asthenosphere is fluid zone of mantle, which allows the above lying tectonic plates to move across earth.
- Mesosphere is deepest part of mantle. It consists of rigid rocks, which cannot flow because of its high and pressure.
4. Crest-
this is the topmost layer of earth, having 5-70 km thickness where the temperature ranges from 500-1000 degree Celsius. It is made up of solid rock (Basalt and Granite). Two types of crest are :
- Oceanic crest (5-7 km thick) is denser, thinner and composed of Basalt
- Continental Crest (35-70 km thick) is less dense, thick and composed of Granite.