Department of Earth Science
Open University
Milton Keynes, U.K.

" New seismic data from Australia combined with earlier world data indicate that, depending on the precise assumptions made about the earth’s outer liquid core, the solid inner core has an ellipticity of 1.9 x 10^-3 to 5.6 x 10^-3 . This corresponds to a polar flattening of 1.6 to 5.0 km.

A. Souriau, M. Souriau, “Ellipticity and density at the inner core boundary from subcritical PKiKP and PcP data,” Geophysical Journal International, 98,39-54, July 1989. (Australian National University, Canberra)

Along the East Pacific Rise, slip rates of transform faults do not exceed 145 km per million years. Where spreading is faster than this, microplates, propagating rifts, and overlapping spreading centers form in preference to transform faults. The physical reason for this phenomenon is unclear.

D.F. Naar, R.N. Hey, “Speed limit for oceanic...

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