Seismologists Xiaodong Song from Columbia University's Lamont-Doherty Earth Observatory and Don Helmberger of the California Institute of Technology published their study of the structure of the earth's core in the October 30 issue of the journal Science . These findings are likely to affect the current model of how the earth, and its magnetic field, formed.
Earthquakes generate seismic waves that can be measured as they cross the globe.
Song and Helmberger studied seismic waves from earthquakes in the South Atlantic Ocean that passed through the earth's core traveling northward to seismographs in Alaska and Canada. These waves moved faster than seismic waves that traveled from those same southern earthquakes to seismographs in Korea. The pair narrowed down the source of these alterations to the inner core. There they found a point of transition 120 miles into the inner core above which the core was no longer anisotropic. It was, instead, isotropic, meaning that seismic waves could travel at the same speed in any direction.