London, August 12 : French scientists have come up with an explanation for why the Earth's inner core of solid iron behaves differently in the western hemisphere and the eastern hemisphere, transmitting seismic waves faster in the eastern side than in the west.
Julien Aubert and his colleagues at the French national research centre's Institute of Geophysics in Paris say that this anomaly may be due to subterranean "cyclones" found in parts of the liquid iron outer core.
The researchers say that such swirling cyclones drag cooler material from the top of the outer core right down to the bottom, where iron is gradually crystallising onto the solid inner core.
They further say that the cooling causes crystals to form more quickly, and with random alignments, reports New Scientist magazine.
That, according to the researchers, makes the material stronger, which in turn means it is able to carry seismic waves more quickly.
Aubert reckons that most of the iron cyclones would have been found below Asia for the past 300 million years, and thus most of the cooling effect would have been in the eastern hemisphere.
The researcher says that, over time, the inner core has grown by about 100 kilometres, and on the eastern side of the core that layer should have formed from the fast-transmission crystals.