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Hurricane of rock

点击量:   时间:2019-03-07 11:05:08

A SWIRLING vortex of molten rock has been found 3000 kilometres beneath the North Pole. The Earth’s magnetic field is thought to be generated by circulation in its molten outer core. By looking at historical measurements of the magnetic field, geophysicists Peter Olson and Jonathan Aurnou of Johns Hopkins University in Baltimore, Maryland, traced a flow of around a quarter of a degree a year in a region 2400 kilometres across (Nature, vol 402, p 170). “It has the structure of a giant hurricane,