Isostatic constraints in 2-D gravity modelling

Abstract

In the modern geophysical context, isostatic equilibrium implies substantial equality of load at the top of the aesthenosphere ? that depth in the earth where the geotherm and the rock melting point curve approach each other quite closely and some degree of partial melting is considered to commence. Below this level (70 to 120 km) a sudden drop in viscosity by 2 or 3 orders of magnitude provides relative "fluidity" which facilitates pressure equalization by governing the freeboard of the overlying, relatively rigid lithosphere (or "plate"). Thus structural and topographic masses evident on the upper lithosphere surface are at least regionally compensated at, or somewhere above the aesthenosphere.