Ice formation is a large mass of frozen water. Ice formations include glaciers, icebergs, and sea ice.
A glacier is a large mass of ice formed from packed snow. Glaciers flow slowly under the influence of gravity. Large glaciers, called ice sheets and icecaps, flow outward in many directions from their centers. An ice sheet, the largest type of glacier, covers an area greater than 19,300 square miles (50,000 square kilometers). Ice sheets can measure more than 2 miles (3 kilometers) thick. Huge ice sheets cover most of Antarctica and Greenland. An icecap covers an area of 19,300 square miles or less. An ice shelf is a broad, flat area of an ice sheet or icecap that pushes out over the sea but remains attached to land.
Long, narrow glaciers called valley glaciers flow through valleys in mountainous areas. Some valley glaciers flow out of the mountains and onto flatter ground. Such a glacier can spread out to form a rounded lump of ice known as a piedmont glacier.
When a glacier flows into the sea, huge chunks of ice can break off and fall into the water. These floating chunks of freshwater ice are called icebergs. Some icebergs measure many miles or kilometers across.
Sea ice is seawater that freezes in the cold air and frigid water temperatures found at high latitudes. Sea ice often forms large floating chunks called floes. These floes can freeze together to form masses called pack ice. Sea ice covers some bays in Antarctica and about half the area of the Arctic Ocean the year around. In winter, ice covers the entire surface of the Arctic Ocean. Winter sea ice extends far from the coast of Antarctica, doubling the area of the continent. In spring, some sea ice breaks into floes that move with the wind and ocean currents and melt away in summer.
