A MODEL OF COMPENSATION OF TOPOGRAPHIC MASSES

The compilation of new global Mohorovicic ('Moho') topographic data enables the density contrast between the crust and mantle to be estimated. Assuming that this contrast is constant, the minimization of the external gravitational potential induced by the Earth's topographic masses and the Moho discontinuity yields the value of 0.28 g/cm3 for the density jump at the Moho. Moreover, it is shown that the Airy Heiskanen model of compensation only partly compensates the surface topographic masses. To fit the external gravitational potential, induced by the surface topography, the Pratt - Hayford concept of compensation has to be considered. Employing the dynamical flattening of the Earth, the minimum depth of compensation has been estimated at 100-150 km. This means that the topographic masses are compensated throughout the Earth's lithosphere at least.