### STRUCTURE OF THE EARTH

**INTERIOR OF THE EARTH** can be discussed in **THREE LAYERS**-

**1. CRUST
    2.  MANTLE &
    3. CORE**

![lll.png](https://steemitimages.com/DQmck7XyPDx6HMbPqpTpaNwP2Jwc7qBYCqEejaQueAuNWKi/lll.png)

### Crust
It is the outermost solid part of the Earth. It is brittle in nature. Because, during an earthquake, it is the crust that breaks easily. causing a **FAULT**. The more and more the density of material increases as we go more and more deep. So, materials available in the crust  level have low density. The thickness of the crust varies under the **Oceanic** and the **Continental** areas. 
The mean thickness of **OCEANIC CRUST** is 5 km.
Whereas the **CONTINENTAL CRUST** is around 30 km. 

![lll.png](https://steemitimages.com/DQmS1pwXQ9BssHZjgcUjp7hJezLVbe4r9w7tYoLmxemsUHB/lll.png)

### Mantle

The second layer is the mantle. Right from the end of the crust and the beginning of outer core it is 2900 km deep and divided into **TWO** parts-

**Upper mantle**- it is also called ***ASTHENOSPHERE*** and upper mantle and crust together called the ***LITHOSPHERE***.  **Astheno** means *weak* and due to this weakness the magma finds way to the surface during *volcanic eruption*. Thickness of the *lithosphere* is 200 km. 

![lll.png](https://steemitimages.com/DQmVw2kc6F3vZNJkgERhtDfto9LPAzRekpbNARtMdNWik5f/lll.png)

**Lower mantle**- This layer is also responsible for all of earth's *volcanic* and *seismic* activity. Because 2900 km thickness is pretty specious area for the formation of such natural catastrophe. Because, after some laboratory tests it has found that temperature under 100-200 km of earth surface is very high that the rocks are in **Molten State**.


![lll.png](https://steemitimages.com/DQmYxjqeFWRLpPNmxVAmtbs2on1Wae6rb58G96L8UC4mu8k/lll.png)

### Core 

It is the immediate next layer of the **Mantle** part of the earth. Density of the materials in this layer is 3500 km. And divided into **TWO** parts-

**OUTER Core**- This part is generally in liquid state. The depth is 2300 km and consists of Ni *(nickel)* and Fe *(iron)*. Because of these two chemical constituents this layer is also known as Nife layer. The highest temperature in this layer is around 4000-5000 degrees Celsius.
 
![lll.png](https://steemitimages.com/DQmSmd7m49pGeTZgK9fct6bZ9brHDSAYtBb1SGW8hKMZHud/lll.png)

**INNER Core**- This part is generally in solid state. The depth is 1200 km and consists of Fe *(iron)* mainly. The temperature goes to 5000-7000 degrees Celsius.

### THIS PICTURE DESCRIBES THE SUMMARY OF THE WHOLE TOPIC
![lll.png](https://steemitimages.com/DQmXt8y74UbckHfHZo639h4ZHg64av4TpHN7HQJqJoC6adU/lll.png)
### References
1. The Earth's Layer, [Oregon State University](http://volcano.oregonstate.edu/earths-layers-lesson-1)
2. Structure of the earth, [Handy Geography](https://handygeography.wordpress.com/gcse/the-restless-earth-revision-materials/structure-of-the-earth/)
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