The hydrosphere, liquid water, is the single most important agent of erosion and deposition. The cryosphere, the solid state of water in the form of ice also has its own unique erosional and depositional features. Large accumulations of year-round ice on the land surface are called glaciers. Masses of ice floating on the ocean as sea ice or icebergs are not glaciers, although they may have had their origin in glaciers.
Glaciers cover about 10% of the surface of the Earth, and are powerful erosional agents that sculpt the planet’s surface. Glaciers form when more snow accumulates over a long span of time than melts and eventually turns into ice. This usually occurs in mountainous areas that have both cold temperatures and high precipitation. But snow can also accumulate and turn into ice in extremely cold low lying areas such as Greenland and Antarctica. This chapter focuses on types of glaciers, how glaciers function, erosional and depositional landforms created by glaciers, and how glaciers are connected to past climates and modern day climate change.