Question: Why does the crust subside slightly on either side of a melting glacier? Need Assignment Help? Crust under the glacier rises as the ice melts. This allows crust on either side of the glacier to move to areas under the glacier. Crust under the glacier rises as the ice melts. This allows mantle on either side of the glacier to move to areas under the glacier. Mantle under the glacier rises as the ice melts. This allows crust on either side of the glacier to move to areas under the glacier. Mantle under the glacier rises as the ice melts. This allows mantle on either side of the glacier to move to areas under the glacier. Ice under the glacier rises as the crust moves. This allows mantle on either side of the glacier to move to areas under the glacier.