As several valley glaciers pile up as they are being pulled down they from a large valley glacier. Valley glaciers are pulled by pressure therefore they don't flow, instead they crack. These great cracks are called crevasses. Crevasses also occur near the edges when one part of the glacier moves faster than other parts. Another kind of glacier is a Continental glacier.
Continental glaciers are huge sheets of ice that cover thousands of square kilometers.
Two such glaciers are called icecaps. Icecaps cover most of Antarctica and Greenland. Icecaps are shaped like domes. Their movements are caused by their great weight. Glacial Erosion Glacial erosion is caused when gravel and pieces of rock are frozen into the ice at the bottom of a glacier.