INTERIOR OF THE EARTH

No one has ever visited the interior of the Earth due to extreme temperature. However, on the basis of certain artificial, empirical and natural factors like volcanic eruptions, temperature, pressure, seismic waves and so on, scientists have been able to describe the interior of the Earth.

Our Earth comprises three main divisions namely the crust, mantle and the core. These divisions were made on the basis of certain factors. 

On the basis of temperature, it can be explained as follows:

1. Various information available from findings of bore holes and deep mining suggest that temperature increases from the surface of the Earth at the rate of 2-3 degree Celsius for every 160 metres. Thus, the crust which extends up to 700 kilometres is relatively cooler compared to the mantle and the core. 

2. Due to the presence of radioactive minerals in the uppermost layer of the Earth, here the rate of increase in temperature is more. On the basis of this fact,scientists have calculated the temperature at the core to be around 6000 degree Celsius.

3. The temperature on the surface of the Earth remains stable and cooler due to the presence of atmosphere. 

4. The mantle which is in the plastic state has a very  high temperature that is observed in volcanic eruptions. 

On the basis of composition

1. The interior of the Earth can be explained on the basis of the nature of elements found below the Earth's crust with lighter elements forming the crust and the denser elements settling downwards due to pressure. 

2. According to Suess, three main zones of different matter exist.

    SIAL- Consisting of mainly silicon and aluminium and other elements like silicates of sodium,           potassium and aluminium, SIAL layer constitutes the continental crust. Its density is around 2.9. 

    SIMA- Having a density of 2.9-4.7, the oceanic crust is made up of the SIMA layer. The                     predominant elements constituting it are Silicon and Magnesium. 

    NIFE- This comprises the zone where the denser materials like nickel, iron etc. are found. They           can be observed on the basis of volcanic eruptions when lava comes out containing these heavier         materials. Its density is around 11. 

The magnetic property of the Earth's interior can be explained through the presence of iron. 

On the basis of the States of Matter

1. Our Earth's interior consists of all states of matter very evident through the observation of lava coming out during volcanic eruptions. 

2. The uppermost layer that is the crust exists in the solid state. It is basaltic solid in nature. 

3. The second layer that is the mantle exists in the plastic, semi liquid state. It can be supported with the observation of volcanoes. Also, seismic waves indicate the presence of a liquid layer just below the solid crustal layer as secondary waves do not pass through the liquid layer. 

4. The core exists in the solid state due to high pressure and density of the matter in the core being the maximum. An important evidence that points to this fact is the reflection of seismic waves off the boundary of the inner core.