Applying the concept of isostatic adjustment, we should expect that when weight is added to the crust, it will respond by subsiding, and when weight is removed, it vill rebound. (Visual ize what happens when a ship's cargo is loaded or unloaded.) Evi. dence for crustal subsidence followed by crustal rebound is provided by Ice Age glaciers. When continental ice sheets occu pied portions of North America during the pleistocene epoch, the added weight of 3-kilometer-thick masses of ice caused down warping of Earth's crust by hundreds ofmeters. In the 8,000 years since this last ice sheet melted, gradual uplift of as much as 330 meters(1,000 feet) has occurred in Canada's Hudson Bay region, where the thickest ice had accumulated