"Well first off, glaciers are heavy and humongous. Currently the world's biggest is about 100km wide and 400km long. It's called the Lambert Glacier, and you'll find it only in Antarctica. But imagine the effect such a huge glacier has when it moves and rubs against the land! Indeed, when glaciers move, they sculpt the land by eroding the surface and pushing over rocks and debris. Over thousands of years they create spectacular landforms and pathways like valleys, moraines, erratics, and kettle lakes. Thus when glaciers move, they significantly change the land."