Scientists at the University of Leeds have solved a 300-year-old riddle about which direction the centre of the earth spins. The Earth´s inner core, made up of solid iron, ´superrotates´ in an eastward direction – meaning it spins faster than the rest of the planet – while the outer core, comprising mainly molten iron, spins westwards at a slower pace.

The findings, published in Proceedings of the National Academy of Sciences, help scientists to interpret the dynamics of the core of the Earth, the source of our planet´s magnetic field.

The magnetic field pushes eastwards on the inner core, causing it to spin faster than Earth, but it also pushes in the opposite direction in the liquid outer core, which creates a westward motion. The earth´s solid inner core spins eastward at an incredibly fast pace, while the molten outer core rotates the other way, but much slower.

The study was a collaboration between the University of Leeds and the Swiss Federal Institute of Technology, Zurich. The full paper, P.W. Livermore, R. Hollerbach and A. Jackson, "Electromagnetically driven westward drift and inner-core superrotation in Earth´s core" available to download.