IT鈥橲 not just the sphere of culture that has an east-west divide. The Earth鈥檚 inner core of solid iron also behaves differently in each hemisphere, transmitting seismic waves faster in the eastern side than in the west.
The phenomenon has baffled scientists, but now numerical simulations developed by Julien Aubert of the French national research centre鈥檚 Institute of Geophysics in Paris and his team suggest that the anomaly may be due to subterranean 鈥渃yclones鈥� found in parts of the liquid iron outer core.
These 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. This cooling causes crystals to form more quickly and with random alignments. That makes the material stronger, which in turn means it is able to carry seismic waves more quickly.
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Aubert鈥檚 work indicates that for the past 300 million years most of these iron cyclones will have been found below Asia, so most of the cooling effect will have been in the eastern hemisphere. Over that 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.
