However glaciers require more than cold weather to form. To form a glacier it is necessary to have sufficient precipitation, as snow, to persist year around. Glaciers move, but slowly - witness the ancient corpse found in an Alpine glacier recently. Flow rates are greatest in the center of the ice mass, least at rock contacts. Crevasses and their arrangements reflect the stresses on the brittle ice.
Rock glaciers are less important sub-type.
Alpine glaciers are in mountains. Piedmont glaciers are formed by two or more coalescing alpine glaciers entering a flatter area. Continental ice sheets, such as Antarctica and Greenland, have well over a km of ice slowly moving seaward over a landmass. Drumlins are low ice-shaped hills of till, of various sizes, some are about 30 m high and 1 km long and include Bunker Hill. Kettles and kames are topographic features associated with ground moraines, as are stratified drift deposits such as eskers, formed by under-ice streams.