The solid core that measures about 1,500 miles in diameter is spinning about one-quarter to one-half degree faster, per year, than the rest of the world, scientists from Columbia University's Lamont-Doherty Earth Observatory and the University of Illinois at Urbana-Champaign report in Friday's issue of the journal Science.
The spin of the Earth's core is an important part of the dynamo that created the planet's magnetic field, and researcher Xiaodong Song said he believes magnetic interaction is responsible for the different rates of spin.
The faster spin of the core was proposed in 1996 by two of the current study's authors, Paul Richards of Lamont-Doherty and Song, now an associate professor at Illinois.
The researchers studied the travel times of earthquake waves through the Earth, analyzing what are called couplets. Those are earthquakes that originate within a half-mile or so of one another but at different times.