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.