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An ice sheet is a mass of glacier ice that covers surrounding terrain and is greater than 50,000 km2 (20,000 mile), thus also known as continental glacier. The only current ice sheets are in Antarctica and Greenland; during the last glacial period at Last Glacial Maximum(LGM) the Laurentide ice sheet covered much of Canada and North America, the Weichselian ice sheet covered northern Europe and the Patagonian ice sheet covered southern South America.
(c. 95,000 and c. 20,000 years before the present day)
Weichselian (northern Europe) Ice Sheet
(Approximately 20,000 years ago)
(About 18,000-17,500 years ago)
Ice sheets are bigger than ice shelves or alpine glaciers. Masses of ice covering less than 50,000 km2 are termed an ice cap. An ice cap will typically feed a series of glaciers around its periphery.
Although the surface is cold, the base of an ice sheet is generally warmer due to geothermal heat. In places, melting occurs and the melt-water lubricates the ice sheet so that it flows more rapidly. This process produces fast-flowing channels in the ice sheet — these are ice streams.
The present-day polar ice sheets are relatively young in geological terms.
The Antarctic Ice Sheet first formed as a small ice cap (maybe several) in the
early Oligocene, but retreating and advancing many times until the Pliocene,
when it came to occupy almost all of
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