On the topography of the core-mantle interface

Abstract

Hypothetical contour maps of the topography of the core-mantle interface are presented, deduced under the assumption that this topography is largely responsible for the spherical harmonic components of the Earth's external gravitational field of degree n ≤ n∗. Lack of clearcut seismological evidence for undulations of the core-mantle interface indicates that n∗ < 8 and there is indirect geomagnetic evidence that n∗ ≥ 4. The vertical distance between the highest and the lowest points on these maps is 8.7 km when n∗ = 4, 30.9 km when n∗ = 6, and 132 km when n∗ = 0, the corresponding maximum horizontal stress variations being respectively, approximately 2 × 10 −3, 6 × 10 −3, and 3 × 10 −2 times the hydrostatic pressure.