Earth's inner core – discoveries and conjectures |
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| Authors: | Paul G Richards |
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| Institution: | the Natural Sciences in the Lamont-Doherty Earth Observatory and Department of Earth and Environmental Sciences, Columbia University, Palisades, NY 10964, USA. |
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| Abstract: | The inner core has long been recognized as a part of the process by which fluid core convection is maintained and as an influence upon the magnetic field. Evidence from several seismological studies in recent years has mounted to indicate that the inner core has anisotropic velocities with large-scale (degree one) variation in strength of the differences from isotropy, and fine-scale (a few kilometres) inhomogeneities of structure. Indications have also been found of systematic changes in the travel time of seismic waves passing through the inner core – which have been interpreted as evidence that the inner core is rotating in an easterly direction, relative to the mantle, at a rate fast enough to be perceived on human timescales. The rate has been dismissed as too slow or physically impossible, but additional evidence has accumulated in support of what may be an emerging consensus that the inner core has a super-rotation of a few tenths of a degree per year. |
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