Glaciers alter the landscape through erosion of the soil and rocks over which they pass. This erosion process leaves a vertical-walled valley similar to an amphitheater at the glacier's sources, according to Reference.com. As they travel through V-shaped valleys, glaciers transform the valley into a U-shape, grinding away cliffs and the bases of slopes. If the ocean fills these valleys, they become fjords.
As a glacier erodes away the valley, it often leaves the outlets of tributary valleys hanging hundreds of feet above their former inlets. With stream-containing valleys, this forms cascades and waterfalls. When a glacier travel over elevations, it leaves the approaching side smooth while the lee sides remain rough.
As the glacier erodes the ground, it also picks up the debris, carrying them both within and under the ice. This material gives the glacier even more abrasive power to cut through the landscape. However, as temperatures warm and the ice melts, the debris becomes deposits known as moraines, till or drift that also affect the landscape.
Even considering the effects of global warming, glaciers contain over 3/4 of the fresh water in the world. They form above the snow line where compacted snow becomes ice pellets. The weight of these pellets presses on those below, forcing out air and compacting the ice, so glaciers take on a blue color, an indicator of their density. Ultimately, however, it's the force of gravity that causes glaciers to move across the landscape.