About 98% of Antarctica is covered by the Antarctic ice sheet, a sheet of ice averaging at least 1.0 mile thick. The continent has about 90% of the world’s ice (and thereby about 70% of the world’s fresh water). If all of this ice were melted, sea levels would rise about 200 feet. In most of the interior of the continent, precipitation is very low, down to 0.8 inches per year; in a few “blue ice” areas precipitation is lower than mass loss by sublimation, and so the local mass balance is negative. In the dry valleys, the same effect occurs over a rock base, leading to a desiccated landscape.
West Antarctica is covered by the West Antarctic Ice Sheet. The sheet has been of recent concern because of the small possibility of its collapse. If the sheet were to break down, ocean levels would rise by several meters in a relatively geologically short period of time, perhaps a matter of centuries. Several Antarctic ice streams, which account for about 10% of the ice sheet, flow to one of the many Antarctic ice shelves.
East Antarctica lies on the Indian Ocean side of the Transantarctic Mountains and comprises Coats Land, Queen Maud Land, Enderby Land, Mac. Robertson Land, Wilkes Land, and Victoria Land. All but a small portion of this region lies within the Eastern Hemisphere. East Antarctica is largely covered by the East Antarctic Ice Sheet.
Vinson Massif, the highest peak in Antarctica at 16,050 feet, is located in the Ellsworth Mountains. Antarctica contains many other mountains, on both the main continent and the surrounding islands. Mount Erebus on Ross Island is the world’s southernmost active volcano. Another well-known volcano is found on Deception Island, which is famous for a giant eruption in 1970. Minor eruptions are frequent, and lava flow has been observed in recent years. Other dormant volcanoes may potentially be active. In 2004, a potentially active underwater volcano was found in the Antarctic Peninsula by American and Canadian researchers.
Antarctica is home to more than 70 lakes that lie at the base of the continental ice sheet. Lake Vostok, discovered beneath Russia’s Vostok Station in 1996, is the largest of these subglacial lakes. It was once believed that the lake had been sealed off for 500,000 to one million years, but a recent survey suggests that, every so often, there are large flows of water from one lake to another.
There is some evidence, in the form of ice cores drilled to about 1,300 feet) above the water line, that Lake Vostok’s waters may contain microbial life. The frozen surface of the lake shares similarities with Jupiter‘s moon, Europa. If life is discovered in Lake Vostok, it would strengthen the argument for the possibility of life on Europa. On 7 February 2008, a NASA team embarked on a mission to Lake Untersee, searching for extremophiles in its highly alkaline waters. If found, these resilient creatures could further bolster the argument for extraterrestrial life in extremely cold, methane-rich environments.