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Ice sheets are bigger than Ice Shelves or Glacier s. 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, in places it melts 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 Stream s. 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 Antarctica. The Greenland ice sheet did not develop at all until the late Pliocene, but apparently developed ''very rapidly'' with the first continental Glaciation . This had the unusual effect of allowing Fossils of Plants that once grew on present-day Greenland to be much better preserved than with the slowly forming Antarctic ice sheet. ANTARCTIC ICE SHEET The the bed is in places more than 2500 m below sea level. It would be seabed if the ice sheet were not there. However, if the ice sheet were actually removed, isostatic rebound would occur and Antarctica would rise to an average height of 800m above sea level. GREENLAND ICE SHEET The Greenland ice sheet occupies about 82% of the surface of Greenland, and if melted would cause sea levels to rise by 7.2 metreshttp://www.grida.no/climate/ipcc_tar/wg1/412.htm#tab113. POSSIBLE EFFECTS OF GLOBAL WARMING If . REFERENCES |
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