Geography Reference
In-Depth Information
its base actually lies below the sea level, and its edges transform into floating ice shelves.
The WAIS is believed to contain about 10% of the total volume of the Antarctic ice sheet,
and some two million cubic kilometres of ice press down on the underlying bedrock. While
the net result has been to depress the baseline, the ice can flow at different rates over the
bedrock depending on local topographies. This subterranean variability is of interest to
scientists because of concerns that the WAIS may not be stable. If the WAIS disintegrates,
then global sea levels could rise some 3-4 metres. In 2006, the British Antarctic Survey
(BAS) warned about the possible collapse of this ice sheet, and noted that there was a
danger that a tipping point might be reached thereafter accelerating ice sheet degenera-
tion. Evidence for this change comes from research into a number of glaciers within the
WAIS, coupled with observations about ocean circulation patterns around Western Antarc-
tica that have reported a rise in ice mass loss in the period between 1996 and 2006.
East Antarctica lies on the other side of the 3,500-kilometre-long Trans-Antarctic Moun-
tains, closer to the Indian Ocean. Geologically, the eastern portion is a stable ancient
shield of Precambrian rock, similar in nature to that found in South America, South Africa,
India, and Australia. It is here that the oldest rocks in Antarctica have been found, some
dated to 3,900 million years ago. East Antarctica is covered by the East Antarctic Ice Sheet
(EAIS), and rests on a large landmass, unlike the marine-based WAIS. It is a thicker and
larger ice sheet, with a thickness of up to 4,800 metres. The South Pole is to be found on
the EAIS, and beneath it lie spectacular sub-glacial lakes such as Vostok - about the size
of Lake Ontario, stretching some 50 kilometres in length, and possibly created some two
to three million years ago. East Antarctica is the largest and coolest portion of the polar
continent, stretching from Queen Maud Land and encompassing the vast polar plateau in-
cluding Wilkes Land and Victoria Land. The future stability of this part of the continent
depends inter alia on ozone concentration coupled with weather patterns, including the po-
lar vortex which helps to trap cold air near the South Pole.
The Antarctic coastline is immensely varied, rising steeply in places such as the mountain-
ous Antarctic Peninsula and areas adjacent to the Ross Sea. Immense ice cliffs are to be
found along much of the East Antarctic coastline. In other regions, floating ice shelves such
as the Brunt Ice Shelf and the Ronne Ice Shelf represent the end point of glaciers flowing
out towards the sea. Beyond the Antarctic coastline, the continental shelf falls sharply into
tectonically active ocean basins, which lie anywhere between 3,000 to 6,000 metres depth.
Volcanoes are to be found onshore and offshore, even if most are concentrated in western
Antarctica.
