Only two of the world's continents lie entirely within the Southern Hemisphere: Australia and Antarctica. Australia lies relatively close to the equator, while Antarctica is situated about the South Geographic Pole.
Antarctica is almost entirely covered by an ice sheet. At its thickest the ice is over 4 km deep, and beneath it there is a hidden landscape of mountains, valleys and plains. This dome-shaped ice sheet has been formed by the accumulation of snow over hundreds of thousands of years. The ice generally flows from the centre of the continent towards the surrounding ocean, and the Antarctic has thousands of glaciers extending into the sea. Great pieces of ice break away at the coast and drift away as icebergs. Huge icebergs, some larger than the Australian Capital Territory, have been observed, although normally they are several hundred metres to several kilometres in length.
During the winter months it becomes so cold that the sea surrounding Antarctica freezes for hundreds of kilometres offshore. This ice breaks up to form pack-ice which, under the action of winds and currents, is constantly changing form and distribution.
While the ice comprises about 98% of Antarctica’s surface, there are areas of bare rock, the greatest rock exposures being in the Antarctic Peninsula and the Transantarctic Mountains. The most significant ice-free areas of the Australian Antarctic Territory (AAT) are the Bunger Hills and the Vestfold Hills near Davis.
Except for coastal peaks, only the highest Antarctic mountains show above the icecap, some by only a few hundred metres. The highest point is the Vinson Massif at 5140 m above sea-level. The extensive Prince Charles Mountains inland of Mawson and the Transantarctic Mountains in the Eastern Sector contain the highest peaks in the AAT. The AAT also contains the world's largest glacier, the Lambert Glacier.
The Southern Ocean, which surrounds Antarctica, consists of the southernmost parts of the Atlantic, Indian and Pacific Oceans. In the sub-Antarctic, between 50°S and 60°S, there are many small islands. Some of them, like Australia’s Heard Island, are almost completely capped by glaciers, while others, such as Macquarie Island, are ice-free and have no permanent snow cover.
Australia holds territorial claims for 42% of the Antarctic continent. Six other countries also claim territory in Antarctica, but have all agreed to put their claims to one side and cooperate with other countries in studying and conserving Antarctica for the benefit of the world through the Antarctic Treaty system.
The Australian claim is based on a long historical association with this part of Antarctica. Australia’s Douglas Mawson (later Sir Douglas Mawson) led a group of Australians and New Zealanders in the 1911 to 1914 Australasian Antarctic Expedition which had bases at Commonwealth Bay, south of Tasmania, and the Shackleton Ice Shelf south of Perth. This expedition explored extensively along the coast near the bases and claimed this land was claimed as British territory. In 1933, sovereignty over this land was transferred from Britain to Australia.
That part of the Territory in the Antarctic seas which comprises all the islands and territories, other than Adélie Land, situated south of the 60th degree south latitude and lying between the 160th degree east longitude and the 45th degree east longitude, is hereby declared to be accepted by the Commonwealth as a Territory under the authority of the Commonwealth, by the name of the Australian Antarctic Territory.