by Mitch Battros - Earth Changes Media                      September 17th, 2013

Earth's inner and outer core is shifting as they respond to Earth's magnetic field. A recent study published in the scientific journal Proceedings of the National Academy of Sciences, show for the first time - that scientists have been able to link the way the inner core spins to the behavior of the outer core. The planet behaves in this way because it is responding to the Earth's geomagnetic field. Scientists interpret the dynamics of the core of the Earth, as the source of our planet's magnetic field.

The fact that the Earth's internal magnetic field changes slowly, over a timescale of decades, means that the electromagnetic force responsible for pushing the inner and outer cores will itself change over time. This may explain fluctuations in the predominantly eastwards rotation of the inner core, a phenomenon reported for the last 50 years by Tkalcić et al. in a recent study published in Nature Geoscience.

Earth may have experienced a magnetic field rotation within the last 3,000 years. Research based on archaeological artifacts and rocks, with ages of hundreds to thousands of years, suggest that the drift direction has not always been westwards: some periods of eastwards motion may have occurred in the last 3,000 years. Viewed within the conclusions of the new model, this suggests that the inner core may have undergone a westwards rotation in such periods.

The Earth's inner core, made up of solid iron, ‘super-rotates' 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 solid iron inner core is about the size of the Moon. It is surrounded by the liquid outer core, an iron alloy, whose convection-driven movement generates the geomagnetic field.

In the last few decades, seismometers measuring earthquakes travelling through the Earth's core have identified an eastwards, or super-rotation of the solid inner core, relative to Earth's surface.

"The magnetic field pushes eastwards on the inner core, causing it to spin faster than the Earth, but it also pushes in the opposite direction in the liquid outer core, which creates a westward motion." says Dr Philip Livermore, of the School of Earth and Environment at the University of Leeds. 

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