Abstract
Recent measurements by J. A. O'Keefe, A. Eckels, and R. K. Squires of the third zonal harmonic component of the earth's gravitational potential are used to determine the characteristics of a hypothetical convection current in the earth's mantle. The calculations are based on a convection theory developed by F. A. Vening Meinesz. The current's velocity is found to be 3.6 cm/yr, corresponding to an overturn time of 1.75×108 yr. The temperature perturbation is found to be 9.7°C. The flow is found to impose a distortion of 159 meters on the earth's crust and a distortion of 237 meters on the surface of the core. The mass loadings associated with these distortions were calculated as 5.3×107 dyne/cm2 at the top, and 8.9×107 dyne/cm2 at the bottom of the mantle. It is believed that the Vening Meinesz theory is capable of qualitatively explaining the results of O'Keefe and his co-workers. However, the required thermal efficiency is about 70 per cent, as compared with an estimated maximum of 4 per cent. It is considered improbable that convective efficiencies could be so large.
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