Earth's inner core spins at changing speed: scientists

BEIJING, May 14 (Xinhuanet) – Earth’s inner core actually spins at speed which can fluctuate over time, according to foundings in the journal Nature Geoscience online Tuesday.

Earth's solid-metal inner core is a key component of the planet, helping to give rise to the magnetic field that protects us from harmful space radiation.

But its remoteness from the planet's surface means there is difficulty to find out the going-ons down there.

One way scientists learn about it is by analyzing acoustic waves from earthquakes that ripple through the inner core as they pass through the planet.

By seismic observations and computer models of the Earth's innards, Tkalcic and his collaborators, geoscientists at Stanford University in California, found the speed at which the inner core spins apparently fluctuates over the course of approximately decades between 1961 and 2007.

The inner core on average rotates eastward. At the speeds it travels, it might on average complete a revolution every 750 to 1,440 years, they found.

However, the speeds appear unstable, which makes it uncertain just how long it actually takes to finish a turn on its axis, Tkalcic said.