Geoid Anomalies -- from Eric Weisstein's World of Physics

A change in the height of a portion of the geoid compared to its height for the majority of the body. On Earth, substantial geoid anomalies are found at subduction zones and hotspots. In continental regions, they do not correlate with topography because of isostatic compensation Eric Weisstein's World of Astronomy. On both Venus and Mars, however, geoid anomalies are correlated with topography.