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Science 10 November 2006:
Vol. 314. no. 5801, p. 889
DOI: 10.1126/science.314.5801.889b
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This Week in Science

The Earth's inner core grows slowly from the solidification of the outer core, and the heat released helps drive convection in the outer core and fuels the magnetic dynamo. Wen (p. 967, published online 28 September) measured the inner core's growth directly in one spot using seismic compression waves reflected off the inner core boundary. Similar waves received at seismic stations in Russia and Kyrgyzstan after a pair of earthquakes in 1993 and 2003 were tens of milliseconds earlier in the later earthquake, which indicates that this part of the inner-core boundary had grown by about 1 kilometer in a decade. This speed is much greater than predicted by the thermal history model of the core. Such a rapid change may indicate either differential rotation of an irregular inner core boundary or nonuniform growth of the inner core.




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Science. ISSN 0036-8075 (print), 1095-9203 (online)