Fig 1: Temperature profile of the inner Earth

The main reasons for the increase in heat and temperature in the interior of the earth are the following:

1. Radioactive disintegration within rocks which liberates heat

2. Internal and external forces (gravitational pull, weight of overlying rocks etc.)

3. Chemical reactions

It is tempting to think that under the conditions of this enormous temperature in the interior of the earth nothing can be found in solid state. Under such conditions all existing rocks should be either in liquid or gaseous state. But it is not so. Along with the increase in temperature with depth, pressure too increases in the interior of the earth. This pressure is lacs of times more than the pressure exercised by atmospheric layers on the surface of the water in oceans. For this reason due to enormous pressure, liquid state rocks of the core have the properties of solids. It is possible that these rocks might be in plastic state. It is why these rocks have elasticity. Due to the pressure of overlying layers on the earth’s interior these rocks do look solid upto 2900 kilometers’ depth. Sometimes due to lessening of overlying pressure, the rocks in the interior melt down and the fluid comes to the surface or is in the process of finding its way to the surface of the earth. A volcanic eruption is one such example.