Let's Get 7 in IELTS

IT'S not just the sphere of culture that has an east-west divide. The Earth's 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's Institute of Geophysics in Paris and his team suggest that the anomaly may be due to subterranean "cyclones" 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.

Aubert's 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.

wonky搖晃的
hemisphere 地球的半球;半球體
seismic地震的;因地震而引起的
phenomenon現象;非凡的人,傑出的人才
baffle阻礙,阻擋
numerical數字的;以數字表示的;數值的
anomaly【天】近點角;反常(事物);異常(現象); 不規則;破格
subterranean地下的
cyclone旋風;暴風;龍卷風
swirl打旋,旋轉;捲曲,盤繞
alignment 隊列,一直線;調準,校直;結盟;組合