An ice-sheet, also called a continental glacier, is a large expanse of snow and ice covering a landmass; for example, Antarctica. Ice-sheets can cover entire mountain ranges and can spread across lowlands and oceans. The ice may become very thick: in Greenland and Antarctica there are places where the ice measures 3,000 meters (9.800 feet) in depth, An iceberg formed when ice breaks from the margins of such a sheet may be many square kilometers in area.

An ice-cap is a small ice-sheet, often in the shape of a flattened dome, which spreads over the mountains and valleys of polar islands. The floating ice fields surrounding the North Pole are sometimes incorrectly called an ice-cap.