The cryosphere is made up of all the frozen water in the world. Cryosphere features form anywhere on earth that is above the snowline—the lowest elevation where snow remains year-round. Glaciers, sea ice (polar ice caps and ice bergs), and permafrost make up most of the cryosphere. Snow cover and ice on fresh water bodies account for the rest (see illustration at left).

Glaciers are large, land-based masses of ice. They persist over years and centuries, but are not necessarily permanent features—they can grow, shrink, and even disappear as the climate changes.

Glacier Formation
Glaciers form in the cold climates found at high elevations and high (polar) latitudes. High elevation glaciers are found in North and South America and even on equatorial mountains in Africa and Indonesia. There, winter snows never melt—instead, they persist in layers thick enough to weigh heavily on underlying snow, compacting the ice crystals below. These dense ice crystals absorb all other colors but blue, giving glaciers their characteristic deep blue hue.

The vast majority of glaciers are found near the poles. Antarctica has nearly 14 million square kilometers of glaciers—over 91% of the world's glacial ice! Greenland has another 7.9% (1.8 million square kilometers). The remaining fraction (0.7%) exists in the ice fields and glaciers of the Americas, Europe, and Asia.

In the high (polar) latitudes, heavy winter snows often compress glaciers, creating dense ice fields which can cover vast areas of land. Glaciers gain mass from winter snows that compress the ice beneath to form glacier ice. The crystals in glacier ice can grow to be as large as baseballs.

Next: Glacial Advance and Retreat