<P> Post-glacial rebound (also called either isostatic rebound or crustal rebound) is the rise of land masses that were depressed by the huge weight of ice sheets during the last glacial period, through a process known as isostatic depression . Post-glacial rebound and isostatic depression are different parts of a process known as either glacial isostasy, glacial isostatic adjustment, or glacioisostasy . Glacioisostasy is the solid Earth deformation associated with changes in ice mass distribution . The most obvious and direct effects of post-glacial rebound are readily apparent in parts of Northern Eurasia, Northern America, Patagonia, and Antarctica . However, through processes known as ocean siphoning and continental levering, the effects of post-glacial rebound on sea level are felt globally far from the locations of current and former ice sheets . </P> <P> During the last glacial period, much of northern Europe, Asia, North America, Greenland and Antarctica was covered by ice sheets . The ice was as thick as three kilometres during the last glacial maximum about 20,000 years ago . The enormous weight of this ice caused the surface of the Earth's crust to deform and warp downward, forcing the viscoelastic mantle material to flow away from the loaded region . At the end of each glacial period when the glaciers retreated, the removal of the weight from the depressed land led to slow (and still ongoing) uplift or rebound of the land and the return flow of mantle material back under the deglaciated area . Due to the extreme viscosity of the mantle, it will take many thousands of years for the land to reach an equilibrium level . </P>

If an area experiences glacial rebound it means that