The inner core of the earth was discovered in 1936 by the seismologist Inge Lehmann. She discovered it by using observations of the earthquake-generated seismic waves. The inner core is in the form of a sphere. It is the smallest part of the subdivision of the earth; it represents 1 % of the volume of the earth. This part of the earth starts at about 6370 km and finishes at about 5500 km below the surface. The temperature in the inner core is approximately 5500ºC . The re are three factors that contribute to the heat generated in the inner core:
-The heat released by the colision of the particles during the formation of the earth.
-The heat given of whilest the iron solidified through cristilization.
-The heat released by the radioactive desintegration of the elements, for example uranium, thorium and potassium.
The pressure of the inner core is approximately 330 gigapascals. Because of the high pressure, the core is solid. The inner core is believed to be made out of nickel-iron alloy, it is also made out of some lighter elements (sulphur, carbon, oxygen, silicon and potassium). Many scientists expected that it would be homogeneous, they also thought that it would be made out of cristal iron. Scientisits have revealed that it is not completely uniform and contains large-scale stuctures that seismic waves pass more rapidly through than others. They also think that the inside has deformation patterns.
The photograph below explains where the inner core is situated within the earth.
