Earth Science: Earth – Ice Of the Poles and High Mountains
The flowing motion and pressure caused by the ice caps of the Poles and high mountain glaciers not only significantly shape the landscape but are also the Earth’s largest freshwater reservoir.
The appearance of the Earth today has been shaped by the major glaciation periods of the past two million years. More than one-third of the mainland, or about 21 million square miles (55 million km2), were once covered by an ice sheet. Today, only 5.8 million square miles (15 million km2) are still covered by the “eternal” ice. This accounts for about a tenth of the entire land mass.
All continents except Australia have mountain glaciers. Mountain glaciers are most common in Europe; however, even Mount Kilimanjaro, located near the Equator in Africa, is glaciated. Cold and dry regions in northern Alaska or the vast regions of Siberia do not have enough snow to form inland ice sheets. Overall, mountain glaciers cover 4 percent of the entire glaciated area; inland ice of the arctic polar regions, including Greenland, covers 11 percent; and the inland ice of Antarctica covers 85 percent.
High mountain glaciers and ice sheets
Valley glaciers are the best known type of glacier. The Aletsch Glacier, for example, is the longest glacier in the Alps. The Malaspina Glacier in southeast Alaska is a typical example of a piedmont glacier, where ice masses from the mountain valleys spread onto the adjacent lowland. Ice sheets covering large areas also exist in the mountains without following the course of a valley. One such plateau glacier is the Vatnajokull Glacier on Iceland. At about 720 cubic miles (3,000 km 3), it is the largest glacier in Europe.
Continental glaciers, sometimes called inland ice or ice sheets, are even larger. At times during the last 2.5 million years, they covered vast areas of Europe and North America. Today they are only found on Greenland and Antarctica. The ice sheet of Greenland covers an area of almost 700,000 square miles (1.8 million km2) and is more than 9,850 feet (3,000 m) thick. However, the ice sheet is melting, possibly losing up to 80 cubic miles (330 km3) of ice per year. The ice shield of the Antarctic is even more immense, with an area of about 4.9 million square miles (12.8 million km2) and a thickness of more than 13,120 feet (4,000 m).
Entire mountain ranges are buried underneath the ice. The few bare peaks that reach through the ice are referred to as “nunataks.” Large outlet glaciers move away from the inland ice toward the coast, where giant icebergs calve into the ocean. Glaciers flow at rates from several feet to a few miles per year. Temperate glaciers flow relatively quickly, due to a film of water created by the pressure on the bed of the glacier.
Colder glaciers, located above the firn line, move by deformation and at a much slower rate. Alpine glaciers typically cover a distance of about 100 to 500 feet (30 to 150 m) per year. Glaciers of the Himalaya move about six to thirteen feet (two to four m) a day. In the Antarctic, the cold and stiff ice only moves just over 16 feet (five m) per year.
ISSUES TO SOLVE
ICE-FREE FUTURE? According to the Intergovernmental Panel on Climate Change (IPCC), the area covered by snow was reduced by about 5 percent between 1980 and 2005 as a consequence of climate change.
The areas of Antarctica that are covered by pack ice are diminishing at a much quicker rate than expected. If this trend continues, the North Pole may become entirely ice-free by the year 2050. It is predicted that most Alpine glaciers will disappear by 2037.