1. Geoid: the actual equipotential surface at sea level

3. Image Name : ww15mgh Boundaries : Lat -90N to 90N ; Lon 0E to 360E Color Scale, Upper (Red) : 85.4 meters and higher Color Scale, Lower (Magenta) :-107.0 meters and lower Data Max value : 85.4 meters Data Min value :-107.0 meters Illuminated from the : East This is an image generated from 15'x15' geoid undulations covering the planet Earth. These undulations represent the NIMA/GSFC WGS-84 EGM96 15' Geoid Height File. This file is a global grid of undulations generated from: (a) the EGM96 spherical harmonic coefficients and (b) correction terms that convert pseudo-height anomalies on the ellipsoid to geoid undulations.

4. Density contrasts cause geoid upward deflection But motion of blob in mantle causes deflection in density contrasts at surface and internal boundaries (depending on viscosity) Internal mass effects upon geoid From: Hager, 1984