Glacial motion is the motion of glaciers, which can be likened to rivers of ice. It has played an important role in sculpting many landscapes. Most lakes in the world occupy basins scoured out by glaciers. Glacial motion can be fast (up to 30 metres per day (98 ft/d), observed on Jakobshavn Isbræ in Greenland) or slow (0.5 metres per year (20 in/year) on small glaciers or in the center of ice sheets), but is typically around 25 centimetres per day (9.8 in/d).