The
lithospheric flexure (also called
regional isostasy) is the process by which the
lithosphere (rigid outer layer of the Earth) bends under the action of forces such as the weight of a growing orogen or changes in ice thickness related to (de)glaciations. The lithosphere is a thin, outer, rigid layer of the Earth resting on the
asthenosphere, a viscous layer that in geological time scales behaves as a viscous fluid. Thus, when loaded, the lithosphere progressively reaches an
isostatic equilibrium, which is the name of the
Archimedes principle applied to these geological settings.