What Are Six Types of Glaciers?
A glacier is a large perennial body of ice formed when snow is repeatedly deposited and, over time, turned to ice. Although the vast majority of glacial ice is stored at the poles, glaciers can be found on every other continent in the world. Glacier morphology, or the shape it assumes, is influenced by a number of factors including the underlying topography, precipitation and temperature. Moreover, the overwhelming mass of glaciers coupled with their gradual movement makes them primary forces in shaping the landscape -- carving out massive valleys and eroding whole mountain ranges over centuries.
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Ice Sheets
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Ice sheets are the largest form of glacier, being by definition 19,305 square miles or larger. Found only in Antarctica and Greenland, ice sheets are continental in size and are unrestrained by their underlying topography. The ice sheet covering Antarctica, for instance, is known to be more than 13,799 feet deep in some places.
Ice Caps
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Ice caps have essentially the same form as ice sheets, but are considerably smaller -- 19,305 miles or less. Ice caps can be found at both polar and sub-polar regions, usually in high-altitude flat areas such as the top of a mountain range. Like ice sheets, the flow of ice caps is unrestrained by the underlying topography and its ice migrates from its highest point to its periphery.
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Ice Fields
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Ice fields are similar to ice caps, but their flow is influenced by the underlying topography. Ice fields are typically located atop a mountain range with high levels of precipitation. Ice fields begin forming on basins or plateaus and, because of gravity, feed numerous outlet glaciers. A famous example is the Columbia Glacier, which covers a portion of the Canadian Rockies between Banff and Jasper and feeds eight glaciers, including the Athabasca Glacier
Mountain Glaciers
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Mountain glaciers are typically found on high-altitude peaks and will result either from large amounts of precipitation or flow from a nearby ice field. The topography of the mountain will determine the flow of ice and the shape of the glacier.
Valley Glaciers
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Valley glaciers are formed from mountain glaciers. As ice accumulates, the bottom layer will mix with the underlying sediment while water will accumulate as a result of glacial run-off and melting from geothermal heat. As a result of the overwhelming mass of the glacier and this lubricated bottom layer, gravity will compel the glacier to move down the mountain, assuming the ablation point -- the point where melted ice is not replaced -- is not reached. Over time, glacial shear -- the abrasion of glaciers on the floor and side of the mountain -- will widen valleys and deposit sediment at the base.
Piedmont Glaciers
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Piedmont glaciers are created when steep, narrow valley glaciers spill out onto flat expanses. As they spread across the plains, the ice forms lobes -- fan like shapes caused by the repeated advance and retreat of glaciers. The best-known and largest piedmont glacier is the Malaspina Glacier, located in Alaska. Here, the ice spills out into the coastal plain, covering an expanse of 3,107 miles.
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References
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