The balance between changes within the Earth's crust and mantle, where material is displaced in response to an increase (isostatic depression) or decrease (isostatic rebound) in mass at any point on the Earth's surface above. Such changes are frequently caused by advances or retreats of glaciers. ------------------ J-L Jökulhlaup A glacier outburst flood resulting from the failure of a glacier-ice-dam, glacier-sediment-dam, or from the melting of glacier ice by a volcanic eruption (Icelandic).

concept of a density/mass equilibrium within the lithosphere that "floats" on the asthenosphere. Changes in mass, such as loading and unloading by ice or water bodies, cause depression or rebound of the lithosphere.