Isostatic depression is a phase of glacial
isostasy, along with
isostatic rebound. Glacial isostasy is the Earth's response to changing surface loads of ice and water during the expansion and contraction of large
ice sheets. The Earth's
asthenosphere acts
viscoelastically, flowing when exposed to loads and non-hydrostatic stress, such as ice sheets, for an extended period of time. The
Earth's crust is depressed by the product of thickness of ice and the ratio of ice and
mantle densities. This large ice load results in elastic deformation of the entire lithospheric mantle over the span of 10,000-100,000 years, with the load eventually supported by the
lithosphere after the limit of local isostatic depression has been attained. Glacial megalakes can form in regional depressions under the influence of glacial load. == Isostatic depression in Greenland ==