The core of the Earth is not a perfect sphere, it has mountains and valleys at the boundary of the mantle. This is what, at least, a group of researchers from the "California Institute of Technology" announced last December at the meeting of the American Geophysical Union. The team led by Olafur Gudmundson comes to this conclusion after analyzing earthquakes.
The mantle is a region of molten stones between the thin crust of the Earth and the liquid core of nickel/iron. The border map has been completed with a technique called seismic tomography. This technique is similar to that used by doctors to get pictures of the brain. To complete the image, the pressure waves of earthquakes that cross the core have been used. According to data collected by geologists, the nucleus is located in central Central America and Asia, located in eastern Australia, northeast of the Pacific.
However, the "valleys" have been detected in the southwest Pacific, the East Indies, Europe and Mexico. The mountains and valleys are the result of the traffic of a conflictive mantle. They fall into the dense cold rock, producing depressions. However, hot light stones climb carrying the core towed.