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GEOSCIENCES BY PETER J. SMITH Department of Earth Sciences Open University Milton Keynes, U.K. " A recent redetermination of solar composition showed that the Sun’s Fe abundance is 40% higher than previously thought and that Fe/Si and Ca/Al atomic ratios are 30% to 40% higher than chrondritic values. These new data require a fundamental re-evaluation of the. composition of the Earth’s mantle, which is likely to be chemically layered. The lower mantle, in particular, must be much r

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BY PETER J. SMITH Department of Earth Sciences Open University Milton Keynes, U.K.

" A recent redetermination of solar composition showed that the Sun’s Fe abundance is 40% higher than previously thought and that Fe/Si and Ca/Al atomic ratios are 30% to 40% higher than chrondritic values. These new data require a fundamental re-evaluation of the. composition of the Earth’s mantle, which is likely to be chemically layered. The lower mantle, in particular, must be much richer in FeO than hitherto supposed.

D.L. Anderson, “Composition of the Earth,” Science, 243, 367-70, 20 January 1989.

" The complex borderzone (1000km x 150km) in Turkey, within which the Turkish, Arabian, Iranian, and Eurasian lithospheric plates interact, is surprisingly quiescent, only three earthquakes of magnitude 6.6 or greater having occurred there this century. However, a search of historical records back to 1500 A.D. shows that seismic activity was much more intense in the ...

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