It is not that baffling that at the center of the Earth lies the inner core. According to seismologic studies, it is a solid sphere comprised of iron-nickel alloy and has a radius of about 1,220 kilometers or about 785 miles.

In divine theories, it was believed that Hell is found within the center of the Earth. There are other notions that the Earth's core is hollow as suggested in the Hollow Earth Theory. However, both have not gained scientific basis or proof.

Discovery and history of the inner core

Believed to have a temperature hotter than the sun, Inge Lehmann discovered the inner core in 1936. This was via his observations on the seismic waves which generated earthquakes. There are claims that the inner core transmits shear waves which are barely detectable by seismographs.

It is surrounded by the outer core which is in liquid state thus only compressional waves can pass through it.

It has been suggested that the inner core is freezing and growing out of the outer core. According to J. A. Jacobs, it is estimated to cool at about 100 degrees Centigrade per billion years.

Before, the whole core itself was believed to be molten and its age lies at about 2 to 4 billion years. This makes it younger than the Earth and it was not around during the formation of the solar system.

Temperature and composition

The temperature of the inner core is estimated to reach 5,700 Kelvin and a pressure of about 3 million atmospheric units. Since the inner core is made up of nickel-iron alloy, this makes it reasonable for the element to exist in there since its melting temperature increases in such a high pressure.

Francis Birch stated that there may be 10 percent of other elements present in the inner core, though they are lighter and not that abundant.

Other things related with the inner core

It is not certain if the inner core revolves the same rate as that of the Earth or not. All that is known is that its growth gives it a significant role in providing the Earth its magnetic field.

There also exist speculations that the inner core has deformities explaining why there are areas that have higher seismic waves than others. In a seismological study in 1990 it is claimed that the changing properties in seismic waves denotes a super-rotation of the inner core.