![]() ![]() Olympus on the Olympic Peninsula in the state of Washington. A small ice cap called Snow Dome is near Mt. Ice cap glaciers are smaller versions of ice sheets that cover less than 50,000 km 2 and usually occupy higher elevations and may cover tops of mountains. Cross-sectional view of both Greenland and Antarctic ice sheets drawn to scale for size comparison (Source: Steve Earle) Vatnajökull ice cap in Iceland The cross-sectional diagram comparing the Greenland and Antarctica ice sheets illustrates the size difference between the two. It s weight depresses the Antarctic bedrock to below sea level in many places. The thickest parts of the Antarctic ice sheetare over 4,000 m eters thick ( >13,000 ft or 2.5 mi). The Antarctic Ice Sheet is eve n larger and covers almost the entire continent. The Greenland Ice Sheet is the largest ice mass in the Northern Hemisphere with an extensive surface area of over 2 million sq km ( 1,242,700 sq mi ) and an average thickness of up to 1 5 00 m eters ( 5, 0 00 ft, almost a mile ). Earth’s largest ice sheets are located on Greenland and Antarctica. I ce sheets, also called continental glaciers, form across millions of square kilo meters of land and are thousands of meters thick. Thickness of Greenland ice sheet in meters (Source: Eric Gaba). A lpine glaciers may also form at lower elevations in areas that receive high annual precipitation such as the Olympic Peninsula in Washi ngton state. Most alpine glaciers are located in the world’s major mountain ranges such as the Andes, Rockies, Alps, and Himalayas, usually occupying long, narrow valleys. There are three general types of glaciers : a lpine or valley glaciers, ice sheets, and ice caps. T hese s mall air pockets provide record s of the past atmosphere composition. Solid g lacial ice still retains a fair amount of void space which traps the air buried with the snow. As the firn continues to be buri ed, compress ed, and recrystalliz es, the void space s become smaller and the ice becomes less porous, e ventually turn ing into glacier ice. As the old snow gets buried by more new snow, the older snow layers compact into firn, or névé, a granular mass of ice crystals. The amount of void space between the snow grains diminishes. Over repeated seasons of perennial snow, the snow settles, compacts, and bonds with underlying layers. ![]() A thin accumulation of p erennial snow is a snow field. ![]() P erennial snow is a snow accumulat ion that lasts all year. Thus there is an accumulation of snow that builds up into deep layers. Glaciers form when repeated annual snow fall accumulates deep layers of snow that are not completely melted in the summer. 14.1 Glacier Formation Glacier in the Bernese Alps. Glaciers also occur in low lying areas such as Greenland and Antarctica that remain extremely cold year-round. These enormous masses of ice usually form in mountainous areas that experience cold temperatures and high precipitation. Glaciers cover about 10% of the Earth’s surface and are powerful erosional agents that sculpt the planet’s surface. In contrast, m asses ice floating on the ocean are icebergs, although they may have had their origin in glaciers. Glaciers are l arge accumulations of ice that exist year-round on the land surface. This ice exists primarily in two forms, glaciers and icebergs. T he Earth’s cryosphere, or ice, has a unique set of erosional and depositional features compared to it s hydrosphere, or liquid water. Describe the history and causes of past glaciations and their relationship to climate, sea-level changes, and isostatic rebound.Identify glacial erosional and depositional landforms and interpret their origin describe glacial lakes.Describe glacial budget describe the zones of accumulation, equilibrium, and melting.Describe how glaciers form, move, and create landforms.Differentiate the different types of glaciers and contrast them with sea ice bergs.14 GlaciersĪt the end of this chapter, students should be able to: Avalanche Lake in Glacier National Park, Montana is an example of a glacially-carved cirque basin. ![]()
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