Official name : Antarctica
Area: 14,000,000 square kilometers (5,405,430 square miles)
Highest point on mainland: Vinson Massif (5,140 meters/16,864 feet)
Lowest point on land: Bentley Subglacial Trench (2,540 meters/8,333 feet below sea level)
Hemispheres: Southern, Eastern, and Western
Time zone: Each research station chooses its own time zone (usually based on its home country)
Longest distances: Longest distance traversing the South Pole 5,339 kilometers (3,337 miles); shortest distance traversing the South Pole 1,234 kilometers (771 miles)
Land boundaries: None
Coastline: 17,968 kilometers (11,164 miles)
Territorial sea limits: None
The continent of Antarctica is almost entirely south of the Antarctic Circle (66.5°S), surrounded by the Southern Ocean. Both the geographic and magnetic South Poles are located on the continent. With a total area of about 14,000,000 square kilometers (5,405,430 square miles), Antarctica ranks fifth in size among the world's continents, larger than Australia or Europe. It is slightly less than one-and-one-half times the size of the United States.
Antarctica is unique. It is a continent, but it has no native population or government. It does not belong to any one nation, but parts of Antarctica are claimed by seven different countries: Argentina, Australia, Chile, France, New Zealand, Norway, and the United Kingdom. The international community, however, does not recognize their claims, and they cannot enforce them under the terms of the Antarctic Treaty, which has been signed by forty-five nations of the world. First signed in 1961 by twelve nations, the treaty specifies that "Antarctica shall be used for peaceful purposes only." As of 2002, twenty-seven nations held consulting member status in the international treaty agreements protecting Antarctica.
The average annual temperature in the interior is a frigid -57°C (-71°F), with a mean summer temperature of -40°C (-40°F) and an average winter temperature of -68°C (-90°F). In the coastal areas, the mean summer temperature is 0°C (32°F). McMurdo Station near the Ross Ice Shelf in East Antarctica has the most moderate climate, with a mean winter temperature of -9°C (16°F). The lowest temperature ever recorded on Earth was at Vostok, East Antarctica, where the mercury dipped to -89°C (-129°F) in 1983.
Since the 1950s, scientists have recorded an overall increase in temperature on Antarctica of about 2°C (4°F), which is much more than the increase in overall temperature elsewhere in the world. Five of the largest ice shelves have shrunk in size during this time period. Some scientists speculate that this is an early sign of global warming caused by human activity, but this theory has not been proven.
Antarctica has continuous daylight from mid-September to mid-March and six months of continuous darkness from mid-March to mid-September. During the daylight months, the continent receives more solar radiation than equatorial regions. Observation has shown that the layer of high-atmosphere ozone that helps reflect harmful solar radiation away from Earth's surface is thin to nonexistent over Antarctica. The ozone hole varies in size from season to season, but it appears to be expanding. Many blame human activity for this hole in the ozone, but the exact causes are unknown.
Most of the continent receives less than 5 centimeters (2 inches) of precipitation annually, in the form of snow.
Antarctica is generally described as having two parts, West Antarctica and East Antarctica. West Antarctica lies directly south of the South American continent and includes the Antarctic Peninsula, which extends farther north than any other part of the continent. East Antarctica is the larger region; it lies south of the southern tips of Africa and Australia. East and West Antarctica are separated by the Transantarctic Mountains.
About 98 percent of the land area is permanently covered with ice. The remainder is exposed barren rock. Antarctica is generally mountainous, with elevations typically ranging from 2,000 to 4,000 meters (6,600 to 13,200 feet). Mountain peaks rise to heights in excess of 5,000 meters (16,500 feet).
There are no native vertebrate animals on Antarctica. The ocean waters surrounding Antarctica support several species of whale, seals (including the crabeater, elephant, and leopard seal), and about a dozen species of birds, the best-known of which are two varieties of penguin, the Adélie and Emperor. Penguins are birds, but they cannot fly.
In 2000, the International Hydrographic Association drew boundaries for a new ocean, called the Southern Ocean, that encompasses all of the water south of 60° latitude. Since this decision, the ocean surrounding Antarctica has been called the Southern Ocean. Due to the great temperature differences between the ice and the open ocean, as well as the lack of any land to impede them, powerful winds blow across the Southern Ocean and the southernmost parts of the surrounding oceans.
The Southern Ocean is home to the Antarctic Circumpolar Current. This ocean current flows east completely around the earth in a great circle just to the north of Antarctica. The current is the most powerful on earth, and it is unique in that it is unimpeded by landforms as it travels around the globe. The current tends to keep cold water to the south, near Antarctica, and holds warmer water back to the north, with a relatively sharp boundary flowing down the middle of the current known as the Antarctic Convergence.
Both the geographic and magnetic south poles are located on the continent of Antarctica. Earth's two geographic poles are designated as 90°N latitude/0° longitude (North Pole) and 90°S latitude/0° longitude (South Pole).
Earth's magnetic poles represent the two nearly opposite ends of the planet where the earth's magnetic intensity is the greatest. These locations are different than the geographic poles. The South Magnetic Pole is located at 66°S latitude and 139°E longitude on the Adélie Coast of Antarctica. The North Magnetic Pole is located at 78°N latitude and 104°W longitude in the Queen Elizabeth Islands of northern Canada.
All of the Antarctic seas are inlets of the Southern Ocean. The Bellingshausen Sea lies off the western coast of the Antarctic Peninsula. It is named for Russian explorer Fabian von Bellingshausen, the first person to sail completely around Antarctica in 1819–21. His expedition also gave names to Queen Maud Land and Peter I Island. Off of West Antarctica is the Amundsen Sea, named for the Norwegian explorer Roald Amundsen, who was the first explorer to reach the South Pole.
The Ross Sea lies off the coast of the Ross Ice Shelf directly south of New Zealand. Both are named for Sir James C. Ross, an explorer in the region in 1839–43 from the United Kingdom. The Weddell Sea is named for the British explorer James Weddell, who conducted an exploration in 1823. It is the body of water east of the Antarctic Peninsula.
The Drake Passage lies between Antarctica and South America, which is located hundreds of miles to the north of Antarctica.
Antarctica's largest island, Alexander Island (43,200 square kilometers/16,700 square miles), is separated from the Antarctic Peninsula by the George VI Sound, although thick ice sheets connect the two land masses. There are dozens of smaller islands in the Bellingshausen Sea and Amundsen Seas, including Thurston, Siple, Carney, and Charcot Islands. Further north along the Antarctic Peninsula is Adelaide Island and the Palmer Archipelago. Most of these islands are connected to the mainland mass by ice.
Berkner Island (3,880 square kilometers/1,500 square miles), covered by the Ronne and Filchner Ice Shelves, lies in the McCarthy Inlet of the Weddell Sea. Roosevelt Island is the largest land mass found within the Ross Sea, but it is completely covered by the Ross Ice Shelf. Ross Island is smaller, but it has access to the ocean in the summer months.
The South Shetland Islands, situated between Antarctica and the southern tip of South America, include Deception Island and King George I Island, among others. Deception Island lies in an active volcanic field known as the Branfield Rift. It is a horseshoe-shaped island with a central caldera (a crater formed by the eruption of a volcano) that has a surface area of about 26 square kilometers (10 square miles) and is breached at one end to be accessible from the open sea. The water of the caldera is heated by underground volcanic activity and has at times reached the boiling point. Also lying in the ocean between Antarctica and South America are the South Orkney Islands, South Georgia, and the South Sandwich Islands. Zavadovski Island in the South Sandwich Islands is home to one of the largest penguin colonies in the world—with a population estimated at two million penguins.
Even during the summer, only a few coastal areas are ever free of ice, including parts of Wilkes Land in East Antarctica and parts of the Antarctic Peninsula. During the winter, the ocean around Antarctica freezes, surrounding the continent with ice that expands far out to sea. As winter proceeds, the ice surrounding the Antarctic land mass grows at the rate of about 103,600 square kilometers (40,000 square miles) per day. By the heart of winter, it is roughly six times larger than normal, expanding the effective size of the continent to 33,000,000 square kilometers (13,000,000 square miles).
Almost half of the coastal regions are covered by ice shelves, which are formed as thick fields of ice branch out into the ocean. The ice shelves meet the bottom of the ocean near the shores but narrow into surface ice sheets (with water beneath them) as they stretch away from the land. The shelves extend out into the water for hundreds of kilometers.
The Ross Sea and the Weddell Sea both contain enormous ice shelves. The Ross Ice Shelf in the sea of the same name is the larger of the two, with an area of roughly 336,770 square kilometers (130,100 square miles). The Ronne, Filchner, Larsen, and Riiser-Larsen Ice Shelves are all found in the Weddell Sea.
West Antarctica has a highly irregular coastline, with many small peninsulas and inlets, most of them ice-covered. The S-shaped Antarctic Peninsula extends far to the northeast. It comes closer to another continent (South America) than any other part of Antarctica. Away from the Weddell and Ross Seas, East Antarctica has a much more regular coastline than the western part of the continent. It arcs in a rough half circle from one sea to the other. Since this coast is much closer to the Antarctic Circle than that of West Antarctica, its ice shelves are smaller. The Amery Ice Shelf, along the East Antarctic coast, envelops most of Prydz Bay, that coastline's only significant indentation. East Antarctica extends north slightly beyond the Antarctic Circle at both Cape Ann and Cape Poinsett. The Shackleton Ice Shelf lies not far from the second of these capes. Cape Adare marks the point where the East Antarctic coast curves sharply inwards to form one side of the Ross Sea.
While a large portion of the world's fresh water is located on Antarctica, it is present mostly in the form of ice. Non-frozen water does exist, however, in the lakes beneath the ice. These lakes are believed to be at least 30 meters (100 feet) deep. Scientists are studying these lakes to determine whether they support any marine life. To conduct their experiments, they must use exceptionally sterile methods to collect specimens in order to avoid contaminating the glacial environment.
The discovery of the geographic South Pole is a story of one of the most famous exploration "races" in history. British adventurer Robert F. Scott set out to be the first person to reach the South Pole in 1909. At the same time, unbeknownst to Scott, Norwegian explorer Roald Amundsen was making secret plans to try the trip himself. When Amundsen set sail in 1910, he told his crew and government that he was on his way to the North Pole. Shortly after setting off, he switched directions and the race began. Amundsen reached the pole first, on December 14, 1911, and he set up a small tent and a flag to mark the occasion. This is what Scott saw when he arrived only a few weeks later on January 18, 1912. Unlike Amundsen, Scott and his crew did not survive the trip back from the South Pole. Today, the research station located at the South Pole is named in honor of these two explorers.
Antarctica's largest known lake, Lake Vostok (26,000 square kilometers/10,000 square miles), is approximately the same size as North America's Lake Erie, but it is buried under 3.5 kilometers (2.8 miles) of ice. Other lakes found in the McMurdo Dry Valleys include Lake Vanda, Lake Brownworth, Lake Fryxell, Lake Bonney, and Lake Hoare. These lakes are fed by runoff from the glaciers that lie in the deepest mountain valleys. During the summer, the air temperatures warm to about the freezing point (0°C/32°F), causing the glaciers to melt slightly and to send water flowing into small streams for a few weeks before the temperature again drops below freezing. The stream flow feeds the lakes, which lie beneath 3 meters (10 feet) of permanent ice cover.
The only river of any significance in Antarctica is the Onyx River. With a length of about 25 kilometers (20 miles), it is the largest of the streams that flow during the summer months. The Onyx River flows into Lake Vanda.
Due to the lack of precipitation, the entire continent is technically considered a desert, despite the fact that it holds more than two-thirds of the world's fresh water. By definition, a desert is any barren land with very little rainfall, extreme temperatures (both hot and cold), and sparse vegetation. This definition can include a permanently cold region, such as Antarctica.
In Antarctica, glaciers (a large body of ice that moves over Earth's surface) completely cover the land beneath them, allowing only the most dramatic mountain peaks to poke through. Antarctica contains 90 percent of the world's natural ice total. Over land, it averages 2 kilometers (1.5 miles) thick, and is about 3.5 kilometers (3 miles) deep at its widest point. The East Antarctic glaciers are slightly larger than the West Antarctic glaciers. Some coastal areas support a few lichens during the summer months, but the ice sheets are otherwise barren.
Glaciers move over the land at a slow and steady pace. Dramatic formations and striations (stripes, believed to be remnants of volcanic ash) may be observed in the glaciers. The advancing edge of the glacier becomes a high sheer cliff as the top levels of ice push forward. The Antarctic polar ice cap moves an average of 10 meters (33 feet) each year.
In East Antarctica, the continent's largest valley glacier, the Lambert Glacier, lies over several mountain peaks that rise to 1,017 meters (3,355 feet). Massive sections of ice discharge from the Lambert Glacier to become part of the floating Amery Ice Shelf each year. Other noteworthy glaciers include the Skelton Glacier, Rennick Glacier, Recovery Glacier, and Beardmore Glacier.
Lying between the mountain peaks of the Transantarctic Mountains are Victoria Valley, Wright Valley, and Taylor Valley. These large, relatively ice-free territories are known collectively as the McMurdo Dry Valleys. They account for about 4,800 square kilometers (1,733 square miles) of dry land in an area measuring approximately 60 by 75 kilometers (48 by 60 miles). The valleys are ice-free because the mountains impede the flow of the sheet of ice that covers most of the rest of the continent. The valleys are filled with sandy, spongy gravel.
Dividing Antarctica into two regions, East Antarctica (Greater Antarctica) and West Antarctica (Lesser Antarctica), is the continent's major mountain range, the Transantarctic Mountains.
The Antarctic Peninsula, a finger of land jutting into the ocean from the mainland of West Antarctica, is also mountainous, with underlying volcanic activity. The Ellsworth Mountains of West Antarctica include the territory's highest point, the Vinson Massif (5,140 meters/16,864 feet). Other notable peaks in West Antarctica are Mount Sidley (4,181 meters/13,717 feet), Mount Jackson (4,189 meters/13,745 feet), and Mount Berlin (3,518 meters/11,543 feet).
East Antarctica features at least two active volcanoes, and scientists believe they will likely discover more that have peaks buried beneath the ice. Mount Erebus (3,794 meters/ 12,444 feet), one of the active volcanoes, is on Ross Island. Other notable peaks in East Antarctica are Mount Melbourne at 2,732 meters (9,016 feet) and the Gamgurtsev Subglacial Mountains at 4,030 meters (13,300 feet).
The Bentley Subglacial Trench, a canyon extending 2,540 meters (8,333 feet) below sea level, is covered by solid ice, making it the lowest point on Earth that is not underwater.
Even where it is not mountainous, Antarctica's elevations are high. Its average elevation of roughly 2,440 meters (8,000 feet) is greater than that of any other continent. As a consequence, most of the land areas outside of the mountain ranges can be considered to be plateaus. Covered by thick ice, most of these plateaus have no names. A few exceptions are the Hollick-Kenyon and Rockefeller Plateaus in West Antarctica, and the Polar Plateau over the South Pole in East Antarctica. The elevation of the South Pole is 2,835 meters (9,355 feet).
There are about seventy research stations on Antarctica that are operated by scientists from around the world. Only about half of these centers are used year-round; the others are occupied only during the summer months. Researchers come to Antarctica from many different fields of study, including astrophysics and astronomy, biology, meteorology, geology, oceanography, and biomedicine, among others. The largest research community is at McMurdo Station, governed by the United States and located on Hut Point Peninsula of Ross Island, which is the southernmost point of solid ground that is accessible by ship. There are more than one hundred structures in the complex, including a harbor, a landing strip, and the DASI (Degree Angular Scale Interferometer) telescope observation point for the study of cosmic microwave background radiation. Resident scientists number about twelve hundred people in the summer months and two hundred people in the winter.
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