Antarctica

Positioned asymmetrically around the South Pole and largely south of the Antarctic Circle (one of the five major circles of latitude that mark maps of the world), Antarctica is surrounded by the Southern Ocean. Rivers exist in Antarctica; the longest is the Onyx. Antarctica covers more than 14.2 million km (5,500,000 sq mi), almost double the area of Australia, making it the fifth-largest continent, and comparable to the surface area of Pluto. Its coastline is almost 18,000 km (11,200 mi) long. as of 1983, of the four coastal types, 44% of the coast is floating ice in the form of an ice shelf, 38% consists of ice walls that rest on rock, 13% is ice streams or the edge of glaciers, and the remaining 5% is exposed rock.

The lakes that lie at the base of the continental ice sheet occur mainly in the McMurdo Dry Valleys or various oases. Lake Vostok, discovered beneath Russia's Vostok Station, is the largest subglacial lake globally and one of the largest lakes in the world. It was once believed that the lake had been sealed off for millions of years. Scientists now estimate its water is replaced by the slow melting and freezing of ice caps every 13,000 years. During the summer, the ice at the edges of the lakes can melt, and liquid moats temporarily form. Antarctica has both saline and freshwater lakes.

Antarctica is divided into West Antarctica and East Antarctica by the Transantarctic Mountains, which stretch from Victoria Land to the Ross Sea. The vast majority of Antarctica is covered by the Antarctic ice sheet, which averages 1.9 km (1.2 mi) in thickness. The ice sheet extends to all but a few oases, which, with the exception of the McMurdo Dry Valleys, are located in coastal areas. Several Antarctic ice streams flow to one of the many Antarctic ice shelves, a process described by ice-sheet dynamics.

East Antarctica comprises Coats Land, Queen Maud Land, Enderby Land, Mac. Robertson Land, Wilkes Land, and Victoria Land. All but a small portion of the region lies within the Eastern Hemisphere. East Antarctica is largely covered by the East Antarctic Ice Sheet. There are numerous islands surrounding Antarctica, most of which are volcanic and very young by geological standards. …

From the end of the Neoproterozoic era to the Cretaceous, Antarctica was part of the supercontinent Gondwana. The Neoproterozoic fusion of Antarctica into Gondwana likely resulted in extensive mountain formation. Modern Antarctica was formed as Gondwana gradually broke apart beginning in the Early Jurassic, around 183 Ma. For a large proportion of the Phanerozoic, Antarctica had a relatively temperate climate, and it was covered in forests, despite being at high latitude for most of the last 400 million years.

During the Cambrian period, Gondwana had a mild climate. Mountainous areas of Antarctica may have undergone extensive erosion during the early Palaeozoic. From the Cambrian to the Devonian, Antarctica drifted to from being situated in the tropics to being situated at high temperate latitudes, and partly within the Antarctic Circle by the end of the Devonian. The Mid-Late Devonian Aztec Siltstone in Victoria Land has yielded an important fauna of early jawed fish, and also (along with the underlying Beacon Heights Orthoquartzite) indicates that Antarctica had by this time been colonised by vegetation, including lycopods. Pollen records indicate that during the Late Devonian, Antarctica was colonised by the progymnosperm Archaeopteris, one of the first large woody trees.

Antarctica became glaciated during the Late Paleozoic icehouse beginning at the end of the Devonian period (360 Ma), though glaciation would substantially increase during the late Carboniferous. It drifted closer to the South Pole, and the climate cooled, though flora remained. After deglaciation during the latter half of the Early Permian, the land became dominated by glossopterids (an extinct group of seed plants with no close living relatives), most prominently Glossopteris, a tree interpreted as growing in waterlogged soils, which formed extensive coal deposits.

Other plants found in Antarctica during the Permian include Cordaitales, sphenopsids, ferns, and lycophytes. At the end of the Permian, the climate became drier and hotter over much of Gondwana, and the glossopterid forest ecosystems collapsed as part of the Permian–Triassic extinction event. There is no evidence of any tetrapods (terrestrial vertebrates) having lived in Antarctica during the Paleozoic.

The continued warming dried out much of Gondwana. …

The first semi-permanent inhabitants of regions near Antarctica (areas situated south of the Antarctic Convergence) were British and American sealers who used to spend a year or more on South Georgia, from 1786 onward. During the whaling era, which lasted until 1966, the population of the island varied from over 1,000 in the summer (over 2,000 in some years) to some 200 in the winter. Most of the whalers were Norwegian, with an increasing proportion from Britain. The first child born in the southern polar region was a Norwegian girl, Solveig Gunbjørg Jacobsen, born in Grytviken on 8 October 1913. Emilio Marcos Palma was the first person born on the Antarctic mainland at the Esperanza Base of the Argentine Army, on 7 January 1978.

Antarctica's population consists mostly of the staff of research stations in Antarctica (which are continuously maintained despite the population decline in the winter), although there are 2 all-civilian bases in Antarctica: the Esperanza Base and the Villa Las Estrellas base. The number of people conducting and supporting scientific research and other work on the continent and its nearby islands varies from about 1,200 in winter to about 4,800 in the summer, with an additional 136 people in the winter to 266 people in the summer from the 2 civilian bases (as of 2017). Some of the research stations are staffed year-round, the winter-over personnel typically arriving from their home countries for a one-year assignment. Christianity is the most common Antarctic religion, with 8 chapels of various Christian denominations located there; due to the difficulties involved with transporting religious officials to the continent most services are performed online. Antarctic English, a distinct variety of the English language, has been found to be spoken by people living on Antarctica and the subantarctic islands.

Antarctica's status is regulated by the 1959 Antarctic Treaty and other related agreements, collectively called the Antarctic Treaty System. Antarctica is defined as all land and ice shelves south of 60° S for the purposes of the Treaty System. The treaty was signed by twelve countries, including the Soviet Union, the United Kingdom, Argentina, Chile, Australia, and the United States. Since 1959, a further 42 countries have acceded to the treaty.

Countries can participate in decision-making if they can demonstrate that they do significant research on Antarctica; as of 2022, 29 countries have this 'consultative status'. Decisions are based on consensus, instead of a vote. The treaty set aside Antarctica as a scientific preserve and established freedom of scientific investigation and environmental protection. Several countries with research stations in Antarctica allow their citizens stationed in the continent to vote in their elections.

In 1539, the King of Spain, Charles V, created the Governorate of Terra Australis, which encompassed lands south of the Strait of Magellan and thus the then-hypothetical Antarctica, granting this Governorate to Pedro Sancho de la Hoz. Spain claimed all the territories to the south of the Strait of Magellan until the South Pole, with eastern and western borders to these claims specified in the Treaty of Tordesillas and Zaragoza respectively. In 1555 the claim was incorporated to Chile.

In the present, sovereignty over regions of Antarctica is claimed by seven different countries. While a few of these countries have mutually recognised each other's claims, the validity of the claims is not recognised universally. New claims on Antarctica have been suspended since 1959, although in 2015, Norway formally defined Queen Maud Land as including the unclaimed area between it and the South Pole.

The Argentine, British, and Chilean claims overlap and have caused friction. In 2012, after the British Foreign & Commonwealth Office designated a previously unnamed area Queen Elizabeth Land in tribute to Queen Elizabeth II's Diamond Jubilee, the Argentine government protested against the claim. The UK passed some of the areas it claimed to Australia and New Zealand after they achieved independence. The claims by Britain, Australia, New Zealand, France, and Norway do not overlap and are recognised by each other. …

Deposits of coal, hydrocarbons, iron ore, platinum, copper, chromium, nickel, gold, and other minerals have been found in Antarctica, but not in large enough quantities to extract. The Protocol on Environmental Protection to the Antarctic Treaty, which came into effect in 1998 and is due to be reviewed in 2048, restricts the exploitation of Antarctic resources, including minerals.

Tourists have been visiting Antarctica since 1957. Tourism is subject to the provisions of the Antarctic Treaty and Environmental Protocol; the self-regulatory body for the industry is the International Association of Antarctica Tour Operators. Tourists arrive by small or medium ship at specific scenic locations with accessible concentrations of iconic wildlife. Much Antarctic tourism is based around bird watching tours due to the high numbers of penguins on the continent. McDonald Beach is known to be a high-traffic area for tourists watching the Adélie penguin population there. Overland sightseeing flights operated out of Australia and New Zealand until the Mount Erebus disaster in 1979, when an Air New Zealand plane crashed into Mount Erebus, killing all of the 257 people on board. Qantas resumed commercial overflights to Antarctica from Australia in the mid-1990s.

Over 74,000 tourists visited the region during the 2019–2020 season, of which 18,500 travelled on cruise ships, but did not leave them to explore on land. Some nature conservation groups have expressed concern over the potential adverse effects caused by the influx of visitors, and have called for limits on the size of visiting cruise ships and a tourism quota. The primary response by Antarctic Treaty parties has been to develop guidelines that set landing limits, and closed or restricted zones on the more frequently visited sites.