Thermal History of the Earth


PROF. ARTHUR HOLMES has written to me to point out that I have misunderstood his meaning in his recent paper on the above subject1. In this paper he states (p. 187 and Fig. 9, p. 179) that the condition for permanent convection currents to be possible in the earth's crust below a certain depth is that the adiabatic and freezing point gradients of the fluid substratum should become tangential at that depth. I assumed that he meant that, if the actual numerical values of the two gradients at various depths were plotted against the depth, the two resulting curves would touch at the critical depth, and that consequently if the freezing point gradient were greater above this depth it would also be greater again below it.

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  1. 1

    J. Washington Acad. Sciences, 23, No. 4, April 1933.

  2. 2

    Sci. Proc. Roy. Dub. Soc., 21, (N.S.), No. 2, 10, Jan. 1934.

  3. 3

    Jeffreys, H. "The Earth.", 2nd Ed., p. 141; and Poole, H. H. and Poole, J. H. J., Phil. Mag., p. 666, March 1928.

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