Landforms and Landscapes - 16 ARTICLES 16 IMAGES 7 VIDEOS For Years 6-8 This Pack contains: Humanities and Social Sciences ...
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Britannica LaunchPacks | Landforms and Landscapes
Landforms and Landscapes
For Years 6-8
This Pack contains:
16 ARTICLES
16 IMAGES
7 VIDEOS
© 2020 Encyclopædia Britannica, Inc. 1 of 90
Britannica LaunchPacks | Landforms and Landscapes Antarctica The icy continent surrounding the South Pole is called Antarctica. Its name means “opposite to the Arctic,” referring to the region around the North Pole. Antarctica is the fifth in size among the continents, larger than Europe and Australia. It is a cold and forbidding land that has no permanent human population and is almost devoid of animal or plant life. However, the ocean surrounding Antarctica teems with life. A map of Antarctica highlights the major geographic regions, ice sheets, and research stations (with … Encyclopædia Britannica, Inc. Gentoo penguins live in Antarctica. Paul Souders—Stone/Getty Images © 2020 Encyclopædia Britannica, Inc. 2 of 90
Britannica LaunchPacks | Landforms and Landscapes Researchers study the Ross Ice Shelf at the Bay of Whales, Antarctica. Michael Van Woert/NOAA NESDIS, ORA Ice and stormy seas kept anyone from seeing Antarctica until about 1820. In 1950 more than half the continent still had not been seen. Now airplanes and tractors have taken people to most parts of Antarctica, and satellite photographs have revealed the rest. But Antarctica remains a frontier, and much is yet to be learned about it. Almost no one goes to Antarctica except scientists and some adventurous tourists. The continent has natural resources that someday may be used, but the harsh environment of the area makes them difficult to exploit. Countries interested in Antarctica have signed a treaty that reserves the region for science and other peaceful purposes. © 2020 Encyclopædia Britannica, Inc. 3 of 90
Britannica LaunchPacks | Landforms and Landscapes The Land Paradise Bay is a harbor on the Antarctic Peninsula. © Jupiterimages—Photos.com/Getty Images Antarctica covers an area of about 5.5 million square miles (14.2 million square kilometers). It would be essentially circular except for the Antarctic Peninsula and two indentations created by the Ross Sea and the Weddell Sea. The Antarctic Peninsula forms an 800-mile (1,300-kilometer) northward extension of Antarctica toward the southern tip of South America, about 600 miles (970 kilometers) away. The enormous Beardmore Glacier extends across the Transantarctic Mountains of central Antarctica. Commander Jim Waldron USNR—Antarctic Photo Library/National Science Foundation An ice sheet covers nearly all of Antarctica. At its thickest point the ice sheet is 15,670 feet (4,776 meters) deep—almost 3 miles (5 kilometers). It averages 7,000 to 8,000 feet (2,100 to 2,400 meters) thick, making Antarctica the continent with the highest mean elevation. This ice sheet contains 90 percent of the world’s ice and 70 percent of the world’s fresh water. © 2020 Encyclopædia Britannica, Inc. 4 of 90
Britannica LaunchPacks | Landforms and Landscapes An iceberg floats in the waters off Antarctica. iStockphoto/Thinkstock This picture shows the edge of an ice shelf in Antarctica. An ice shelf is a thick mass of floating… © Armin Rose/Shutterstock.com The Antarctic ice was formed from the snows of millions of years that fell on the land, layer on layer. The weight of new snow squeezes the old snow underneath until it turns to a substance called firn, then ice. As the ice piles up, it moves toward the coast like batter spreading in a pan. The moving ice forms into glaciers, rivers of ice that flow into the sea. Pieces of the floating glaciers break off from time to time, a process called calving. These icebergs float north until they reach warm water, break into pieces, and melt. Icebergs as large as 40 by 30 miles (64 by 48 kilometers) have been sighted, but most are smaller. In some places the floating glaciers stay attached to the land and continue to grow until they become ice shelves. The Ross Ice Shelf alone is about the size of Canada’s Yukon Territory and averages 1,100 feet (330 meters) thick. The Transantarctic Mountains divide Antarctica into eastern and western parts. The mountains stretch … Hannes Grobe © 2020 Encyclopædia Britannica, Inc. 5 of 90
Britannica LaunchPacks | Landforms and Landscapes The Transantarctic Mountains extend for more than 2,000 miles (3,200 kilometers) across the continent, dividing the ice sheet into two parts. The larger, eastern part—called East Antarctica—rests on land that is mostly above sea level. It has been there at least 14 million years. The smaller, western part—called West Antarctica—is on land that is mostly below sea level. Other mountain ranges include the Prince Charles Mountains and smaller groups near the coasts. The Antarctic Peninsula has many mountains. The Ellsworth Mountains are Antarctica’s highest, the Vinson Massif rising 16,050 feet (4,892 meters) above sea level. Mountains with only their peaks showing through the ice (called nunataks) are found in some areas. Several active volcanoes on the continent provide spectacular and scenic landforms at many places and are located near the Antarctic Peninsula and in the Transantarctic Mountains. Only about 2 percent of Antarctica is free from ice. These unusual land areas, called oases, generally are near the coast and include the dry valleys of southern Victoria Land and the Bunger Oasis in Wilkes Land. High rims at the end of the valleys prevent entry of large glaciers. The warm local climate melts the ends of smaller glaciers extending into the valleys. In October 2016, 24 countries and the European Union agreed to establish the world's largest marine… © Behind the News Surrounding Antarctica is a cold water mass called the Southern, or Antarctic, Ocean. It contains what were once considered the southern parts of the Pacific, the Atlantic, and the Indian oceans. The Ross and Weddell seas are extensions of the Southern Ocean. The Antarctic Convergence, which encircles Antarctica roughly 1,000 miles (1,600 kilometers) off the coast, divides the cold southern water mass from warmer waters to the north. The Antarctic Circumpolar Current, the world’s largest ocean current, moves eastward around the continent at an average speed of about half a knot (1 kilometer per hour). Sea ice up to 10 feet (3 meters) thick forms outward from the continent every winter, making a belt 300 to 1,000 miles (500 to 1,600 kilometers) wide. Even in summer the sea ice belt is 100 to 500 miles (160 to 800 kilometers) wide in most places. The aurora australis, or southern lights, glow in the skies over Antarctica in winter. © AbleStock.com/Jupiterimages © 2020 Encyclopædia Britannica, Inc. 6 of 90
Britannica LaunchPacks | Landforms and Landscapes Antarctica has three points that are called South Poles. The best known is the geographic South Pole, at 90° S latitude on the axis of Earth’s rotation. In the early 1990s the geomagnetic South Pole, which moves, was located at about 78° S, 108° E, in East Antarctica; it is the center of the Southern Hemisphere auroras. The magnetic South Pole is the area toward which compasses point; it is just off the Adélie Coast at about 66° S, 139° E, and moves a few miles to the northwest each year. Antarctica does not have 24-hour periods broken into days and nights. This is because the continent lies almost entirely south of the line of latitude of 66.5° S, which is known as the Antarctic Circle. Because of the tilt of Earth’ s axis as it revolves around the Sun, the Antarctic Circle has one day each year when the Sun does not set (the summer solstice, December 21 or 22) and one day when the Sun does not rise (the winter solstice, June 21 or 22). The number of days without sunset or sunrise increases southward from the Antarctic Circle. At the South Pole the Sun rises on about September 21 and moves in a circular path upward until December 21, when it reaches about 23.5° above the horizon. Then it circles downward until it sets on about March 22. This “day,” or summer, is six months long. From March 22 until September 21 the South Pole is dark, and Antarctica has its long “night,” or winter. According to scientific theory, some 200 million years ago Antarctica was joined to South America, Africa, India, and Australia in a single large continent called Gondwana. There was no ice sheet, and trees and large animals flourished. Today, only geological formations, coal beds, and fossils remain as clues to Antarctica’s warm past. Climate Antarctica is the coldest continent. The world’s record low temperature of –128.6 °F (–89.2 °C) was recorded there. The mean annual temperature of the interior is –70 °F (–57 °C). The coast is warmer. Monthly mean temperatures at McMurdo Station range from –18° F (–28 °C) in August to 27 °F (–3 °C) in January. Along the Antarctic Peninsula temperatures have been as high as 59 ° F (15 °C). A person walks in the wind at a camp in Antarctica. FLPA/SuperStock Because it is such a large area of extreme cold, Antarctica plays an important role in global atmospheric circulation. In the tropics the Sun warms the air, causing it to rise and move toward the poles. When these air masses arrive over Antarctica, they cool, become heavier, and fall from the high interior of the continent toward the sea, making some Antarctic coasts the windiest places in the world. Winds on the Adélie Coast in the winter of 1912 to 1913 averaged 40 miles (64 kilometers) per hour 64 percent of the time, and gusts of nearly 200 miles (320 kilometers) per hour have been recorded. © 2020 Encyclopædia Britannica, Inc. 7 of 90
Britannica LaunchPacks | Landforms and Landscapes Antarctica’s interior is one of the world’s major cold deserts. Precipitation (if melted) averages only 1 to 2 inches (2.5 to 5 centimeters) a year. Plant and Animal Life Antarctic hair grass (Deschampsia antarctica) is one of only two flowering plants that grow in… Lomvi2 The severe climate has kept Antarctica nearly devoid of life. Plants are limited almost entirely to primitive types that are capable of surviving lengthy winter periods of total or near-total darkness during which photosynthesis cannot take place. The most common plants are lichens, which comprise about 350 species. Mosses and liverworts grow mostly in ice-free areas along the coast. Two species of flowering plants—a grass and an herb— are found on the peninsula and a few islands. More widespread than plants are numerous types of bacteria, algae, and fungi such as yeasts and molds. The native land animals are limited to arthropods (such as insects), which become inactive during the coldest months. Nearly all the species are found only in Antarctica. These springtails, midges, mites, lice, and fleas live generally along the coast among plant colonies. Some species live as parasites on birds and seals. The immense numbers of birds and seals that live in Antarctica are, properly speaking, sea animals. They spend most of their time in or over the water, where they get their food. These animals come ashore only to establish rookeries and breed. Emperor penguins can be found around the entire coastline of Antarctica. © Photos.com/Jupiterimages © 2020 Encyclopædia Britannica, Inc. 8 of 90
Britannica LaunchPacks | Landforms and Landscapes About 45 species of birds live south of the Antarctic Convergence. Two penguin species—the emperor and the Adélie—are distributed widely around the entire coastline. Gentoo and chinstrap penguins occupy Antarctic Peninsula coasts and some islands. Penguins are excellent swimmers and catch and eat their food—mostly krill (a shrimplike animal) and fishes—underwater. The animal life of Antarctica includes Adélie penguins and leopard seals. Stockbyte/Thinkstock Sea mammals native to Antarctica include seals, porpoises, dolphins, and whales. Four species of seals breed almost exclusively in the Antarctic. They are the Weddell seal, which ranges as far south as the sea does and can dive as deep as 2,000 feet (600 meters) for nearly an hour; the crabeater seal, which spends most of its time around pack ice (sea ice); the leopard seal, which favors penguins as its food; and the Ross seal, rarely seen. Other Antarctic species include the fur seal and the huge elephant seal. Most populous is the crabeater, whose numbers are estimated to be in the millions. Among the whales of Antarctic waters are the killer whale, sperm whale, and rare bottle-nosed, or beaked, whale. A marine biologist examines specimens hauled up from the depths of the Southern (Antarctic) Ocean,… Contunico © ZDF Enterprises GmbH, Mainz Fishes peculiar to the Antarctic include the Antarctic cod and the icefish. These and other Antarctic fish have developed blood that enables them to live in seawater as cold as 28 ° F (–2 °C). © 2020 Encyclopædia Britannica, Inc. 9 of 90
Britannica LaunchPacks | Landforms and Landscapes Antarctic krill (Euphausia superba). Matt Wilson/Jay Clark/NOAA NMFS AFSC The most important single member of the Antarctic marine food chain is the krill. This crustacean looks like a small shrimp and exists in huge numbers; one vast swarm stretching several miles in length was observed from ships, and some biologists think the total population may be 5 billion tons or more. Krill eat small marine organisms called plankton and in turn are eaten in great numbers by squid, birds, seals, and whales. Economic Development Antarctica is so far from world markets, and its environment is so hostile, that little economic development has taken place. Also, little is known about the amounts of natural resources that exist there. But, if world shortages of food and energy products become severe, Antarctica may be more intensely explored. Because no one country governs the land, however, exploitation of the continent’s resources would raise questions of ownership. In addition, economic development would be limited by the Antarctic Treaty of 1959, which preserved the continent for scientific research, as well as later international agreements designed to protect its resources. The first people to make money by going to Antarctica were whalers and sealers. Seal hunters began catching Antarctic seals for their oil and fur in the late 1700s. Fur seals were reduced almost to extinction by the 1820s, at which point the sealers started hunting elephant seals. The hunting of elephant seals continued until 1964, when some 20 countries signed measures to protect the plants and animals of Antarctica. The Convention for the Conservation of Antarctic Seals, signed in 1972, established guidelines for any future sealing. It prohibits the taking of fur, elephant, and Ross seals and limits the annual catch of crabeater, leopard, and Weddell seals. Whaling began in Antarctic waters in the 19th century. The industry enlarged greatly in the early 1900s, when steamships, harpoon guns, and shore processing stations (notably at South Georgia) were introduced. During the 1912–13 season 10,760 whales were caught. After that time nearly all the whales caught in the world were caught in Antarctic waters. In 1931, a peak year, 40,199 whales were caught in the Antarctic, while only 1,124 were caught in the rest of the world. So many whales were caught that their numbers declined, just as had those of the seals. The industry declined after 1960. In the 1980–81 season fewer than 6,000 whales were caught in the Antarctic; all were minke whales, a relatively small-sized species also called the lesser rorqual. In 1986 the International Whaling Commission banned commercial whaling, though Japan continues to take Antarctic whales in the name of scientific research. The Soviet Union began commercial fishing on a large scale in 1967. Within a decade, intensive fishing led to severe declines in the numbers of Antarctic cod and other types of fish. Krill fishing began in the early 1970s and grew rapidly over the next decade. In response to these threats to the Antarctic ecosystem, multiple countries signed the Convention on the Conservation of Antarctic Marine Living Resources in 1982. This agreement—an © 2020 Encyclopædia Britannica, Inc. 10 of 90
Britannica LaunchPacks | Landforms and Landscapes addition to the Antarctic Treaty—set catch limits on krill, finfish, and other marine animals. After a period of decline, krill harvests increased again in the early 21st century as a source of food for the growing aquaculture (fish farming) industry. Petroleum and other minerals have never been exploited in Antarctica. Minerals have been found in great variety on the continent but almost always in small amounts. Only two large mineral deposits have been found: iron ore in the Prince Charles Mountains and coal in the Transantarctic Mountains. However, it would cost too much to get these materials to market to make them economically attractive. Large reserves of petroleum may exist in Antarctica, and oil has generally been considered to be the most likely prospect for exploitation. Little exploration has been done, however, and even if reserves were found, extraction would be difficult. The edge of the Antarctic continental shelf is 1,000 to 3,000 feet (300 to 900 meters) deep, much deeper than the world average continental shelf depth of about 600 feet (200 meters), and Antarctica’s icebergs would threaten drill rigs. Also, the environmental impact of spills would be greater in Antarctica because low temperatures retard the growth of biological organisms that reduce crude oil to environmentally harmless components. Even as these economic barriers discouraged mining in Antarctica, the Antarctic Treaty countries took an additional step to prevent the practice. In 1991 they signed a protocol to the treaty that prohibited the exploitation of mineral resources in Antarctica for 50 years. The protocol took effect in 1998, meaning that mining was banned until 2048. Some people have devised ingenious schemes for towing Antarctic icebergs north to serve as a source of fresh water. As with the continent’s other potential resources, however, delivery costs would be too high to make these plans economically feasible. A cruise ship with tourists approaches the Lemaire Channel at the Antarctic Peninsula, in… © Andrew Peacock—Stone/Getty Images Antarctica has abundant scenic resources, and it seems likely that they have greater potential for economic development than do mineral and biological resources. Commercial tourist visits to Antarctica began in the 1950s. Between 1958 and 1980 an estimated 16,600 passengers on 80 cruise ships visited places along the Antarctic Peninsula and in the Ross Sea. Tourism continued on a small scale until the 1990s, when the number of visitors began to multiply more quickly. In the early 21st century, the continent typically received a few tens of thousands of visitors each year. Most visitors come to the northern Antarctic Peninsula aboard cruise ships. A small but growing number of more adventurous tourists have ventured into or across the continental interior by ski, dog team, or private aircraft. New technologies for landing large wheeled aircraft on inland ice sheets have opened possibilities for tourist facilities in many parts of Antarctica. Permanent accommodations for tourists ashore seem inevitable, especially © 2020 Encyclopædia Britannica, Inc. 11 of 90
Britannica LaunchPacks | Landforms and Landscapes in the Antarctic Peninsula. The flourishing tourist industry, however, has few controls under Antarctic Treaty regulations. Parties to the treaty are studying effects of tourism in order to provide regulations for ensuring protection of Antarctica’s highly sensitive ecosystem. Safeguarding penguin rookeries that particularly attract tourist photographers is of special concern. Problems created by the increasing tourism include sewage and waste disposal and the need for search and rescue facilities (a few tourist ships have gone aground or have been trapped in ice, requiring help). Political and International Relations Because it has never had permanent human settlements, Antarctica has had an unusual political history. Seven countries have claimed pie-shaped sectors of territory centering on the South Pole. Three of the claimed sectors overlap on the Antarctic Peninsula. One sector is unclaimed. Most other countries do not recognize these claims. The United States policy, for example, is that the mere discovery of lands does not support a valid claim unless the discovery is followed by actual settlement. Also, like many other countries, the United States reserves all rights resulting from its explorations and discoveries. This unsettled situation might have continued had it not been for a surge of scientific interest in Antarctica that developed in the mid-1950s. At that time scientists of 12 countries decided to make research in Antarctica the major portion of a large investigation, the International Geophysical Year. The 12 countries were Argentina, Australia, Belgium, Chile, France, Japan, New Zealand, Norway, South Africa, the Soviet Union, the United Kingdom, and the United States. When this program was completed in 1958, these countries decided to continue their research programs in Antarctica. Much of the research had been achieved through international cooperation, and the 12 countries carried their new, friendly ties from science into politics. They met in Washington, D.C., in 1959 to sign the Antarctic Treaty. The treaty reserved the region for peaceful purposes, especially scientific research. It prohibits nuclear weapons and disposal of radioactive waste on the continent, and it does not allow military activities there except to support science and other peaceful pursuits. The treaty does not recognize or dispute the territorial claims of any country, but it also does not allow any new claims to be made. It allows members to inspect each others’ installations, encourages the exchange of personnel, and requires each country to report to the others on its plans and results. The Antarctic Treaty did not address all possible activities in Antarctica—for example, it included nothing about sharing the continent’s natural resources. It did, however, provide for regular meetings to further its objectives. At these meetings the original treaty countries, as well as others that later signed the agreement, have agreed on conservation plans and on responsible collection and sharing of resources. Scientific Research © 2020 Encyclopædia Britannica, Inc. 12 of 90
Britannica LaunchPacks | Landforms and Landscapes Palmer Station is a research station that was built by the United States. It is located on Anvers… Christopher Michel The government of Norway owns a research station in Queen Maud Land, Antarctica. Scientists live and … Islarsh The International Geophysical Year (IGY) of 1957–58 began the modern era of scientific investigation of Antarctica. It established multiple year-round stations on the continent, including one at the geographic South Pole and one at the geomagnetic South Pole. Since then numerous Antarctic Treaty countries have carried out continuous scientific studies. A nonpolitical body called the Scientific Committee on Antarctic Research, or SCAR, coordinates the international scientific effort in Antarctica. The scientific knowledge of Antarctica gained during and after IGY far outweighs that learned in the preceding millennia. This progress has been made possible by advances in technology, including jet aircraft, turbine- powered helicopters, ski-planes, and polar-orbiting satellites that automatically collect data across the continent and transmit it to a base collection station. A computer-enhanced map, taken from satellite observations of ozone levels in the atmosphere over… NASA Ozone Watch © 2020 Encyclopædia Britannica, Inc. 13 of 90
Britannica LaunchPacks | Landforms and Landscapes Researchers launch a balloon carrying an ozonesonde, an instrument that measures ozone in the… NOAA The research carried out in Antarctica encompass virtually all the physical sciences. Biologists, geologists, oceanographers, geophysicists, astronomers, glaciologists, and meteorologists conduct experiments there that cannot be duplicated anywhere else. Many important problems with relevance for the entire Earth are best studied in the polar region. One example is ozone depletion, the gradual thinning of Earth’s protective ozone layer in the upper atmosphere. In 1985 researchers reported that since 1977 the ozone over Antarctica had decreased rapidly in the springtime. Scientists found that this seasonal “ozone hole” resulted from the presence of man-made chemical compounds known as chlorofluorocarbons (CFCs), which were widely used in industry. This discovery led to strict regulations on the use of CFCs. An image produced by NASA shows locations on Antarctica where temperatures increased between 1959… GSFC Scientific Visualization Studio/NASA © 2020 Encyclopædia Britannica, Inc. 14 of 90
Britannica LaunchPacks | Landforms and Landscapes A map shows the extent of collapse of the Larsen Ice Shelf in Antarctica. The Larsen A Ice Shelf… Encyclopædia Britannica, Inc. Another crucial research subject with worldwide implications is global warming. The effects of this gradual rise in Earth’s surface temperatures are most visible at the poles. West Antarctica is one of the fastest-warming places on Earth. The collapse of much of the Larsen Ice Shelf, part of the Antarctic Peninsula, between 1995 and 2002 was largely attributed to climate changes resulting from rising air temperatures. Continued melting of the glaciers and ice sheets of Antarctica could contribute to a dangerous rise in the global sea level. The impact of global warming was a main goal of the International Polar Year of 2007–08, an international research project focused on Antarctica and the Arctic. History of Exploration An engraving based on a sketch by Charles Wilkes shows his men on the Antarctic ice. From Narrative of the United States Exploring Expedition by Charles Wilkes, U.S.N., Vol. II, 1849 The first expedition to come close to Antarctica took place from 1772 through 1775. The English navigator James Cook sailed around the continent and came within 100 miles (160 kilometers) of it. Land was seen about 1820, when separate British, American, and Russian expeditions all claimed first sightings. In 1821 the American sealer John Davis made the first recorded landing on Antarctica, at Hughes Bay, on the Antarctic Peninsula. In the Antarctic summer of 1839–40 a U.S. Navy expedition headed by Charles Wilkes mapped 1,500 miles (2,400 kilometers) along the coast of East Antarctica. The next summer James Clark Ross of Great Britain sailed into the Ross Sea, traveling as far south as a ship can go. The first recorded landing on mainland Antarctica was on Cape Adare in 1895, and the first group to spend a winter there did so from March 1898 to March 1899. © 2020 Encyclopædia Britannica, Inc. 15 of 90
Britannica LaunchPacks | Landforms and Landscapes Beginning in the early 20th century, several explorers set out to reach the South Pole. Roald… Encyclopædia Britannica, Inc. Encyclopædia Britannica, Inc. © 2020 Encyclopædia Britannica, Inc. 16 of 90
Britannica LaunchPacks | Landforms and Landscapes Roald Amundsen, 1923. UPI/Bettmann The struggle inland and toward the geographic South Pole began with the first expedition by Robert F. Scott of Great Britain in 1901–04. A fellow Englishman, Ernest Shackleton, led an expedition that came within 112 miles (97 nautical miles, or 180 kilometers) of the pole in 1909. But the first person to reach the pole was Roald Amundsen of Norway on December 14, 1911. On another Antarctic expedition Scott arrived at the pole just a month later; he died on March 29, 1912, trying to return to the coast. Richard E. Byrd. © N. G. Thwaites—Hulton Archive/Getty Images These early expeditions relied on sail power, dog power, and human power for their transportation. The mechanical age arrived on November 16, 1928, when George Hubert Wilkins, leading an American expedition, made an airplane flight from Deception Island. On November 29, 1929, Richard E. Byrd of the United States flew a three-motor Ford plane over the South Pole. Byrd also explored parts of Antarctica by air and on the surface in 1933–35 and 1939–41 and commanded the largest single expedition to Antarctica yet attempted—the U.S. Navy’ © 2020 Encyclopædia Britannica, Inc. 17 of 90
Britannica LaunchPacks | Landforms and Landscapes s Operation High Jump in 1946–47. Thirteen ships, 25 airplanes, and thousands of men made surveys almost all the way around the continent. Vivian Ernest Fuchs, center, with fellow expedition team members W. Stanley Moss (immediately left… © The Estate of William Stanley Moss; reproduced by permission Shackleton made the first attempt at an overland crossing of Antarctica in 1914. His ship was caught and crushed, however, in ice in the Weddell Sea. The idea of an overland crossing lay dormant for several decades until it came to fruition during International Geophysical Year with the British Commonwealth Trans-Antarctic Expedition led by Vivian Ernest Fuchs. Using tracked vehicles and aided by aerial flights, the party left Shackleton Base on Filchner Ice Shelf on November 24, 1957, and by way of the South Pole reached the New Zealand Scott Base on Ross Island on March 2, 1958. In 1979–81 the continent was again crossed as part of the British Transglobe Expedition, which made the first polar circumnavigation of the world. In 1990 a six-man international expedition led by the American Will Steger completed a 221-day trek across Antarctica using dogsleds. At more than 3,700 miles (6,000 kilometers), it was the longest dogsled trek, as well as the first unmechanized passage through the South Pole. (See alsopolar exploration; world exploration at a glance.) Guy G. GuthridgeEd. Additional Reading DEWEY, JENNIFER. Antarctic Journal: Four Months at the Bottom of the World (HarperCollins, 2001).GOGERLY, LIZ. Amundsen and Scott’s Race to the South Pole (Heinemann, 2007).HACKWELL, W.J. Desert of Ice (Scribner, 1991). KALMAN, BOBBIE, AND REBECCA SJONGER. Explore Antarctica (Crabtree, 2007).MYERS, W.D. Antarctica: Journeys to the South Pole (Scholastic, 2004).PRINGLE, L.P. Antarctica: The Last Unspoiled Continent (Simon & Schuster, 1992). ROBERSON, DENNIS. Antarctica (Lucent, 2003).WOODS, MICHAEL. Science on Ice: Research in the Antarctic (Millbrook, 1995). Citation (MLA style): "Antarctica." Britannica LaunchPacks: Landforms and Landscapes, Encyclopædia Britannica, 23 Nov. 2021. packs. eb.com.au. Accessed 10 Apr. 2022. While every effort has been made to follow citation style rules, there may be some discrepancies. Please refer to the appropriate style manual or other sources if you have any questions. © 2020 Encyclopædia Britannica, Inc. 18 of 90
Britannica LaunchPacks | Landforms and Landscapes coast The area where the sea and land meet is called a coast. The coasts of the world measure about 312,000 kilometres (193,000 miles) in total. Coastal areas are also known as shores and seasides. They form unique habitats where a range of animals and plants survive in a challenging environment. There are many different types of coast. They may be sandy, rocky, muddy or covered in shingle. Some have steep cliffs that are buffeted by waves, while others are broad stretches of land that alternate between being wet and dry as the tides go in and out. How Coasts Are Formed Coasts have changed over millions of years. They are affected by geological events such as volcanic activity, ice ages and changes in sea levels. Two other factors that affect the shape and type of coast are erosion and deposition. Erosion Erosion is the wearing away of rocks or soil by the action of water, wind or ice. At the coastline, waves force pockets of air against rocks, which expand and explode, causing damage to the rocks over time. The continual force of waves against rocks and soil also wears them down, breaking them up into smaller and smaller fragments. Water that gets trapped in cracks and crevices can freeze in cold weather, causing more damage when it expands, forcing cracks to open wider. Plants, animals and humans can also cause coastal erosion. Sea arches, like this one in Dorset, England, are formed by wave erosion. Photos.com/Getty Images © 2020 Encyclopædia Britannica, Inc. 19 of 90
Britannica LaunchPacks | Landforms and Landscapes Headlands and bays are features of coasts that are formed by erosion. Waves wear down different… Encyclopædia Britannica, Inc./Patrick O'Neill Riley Erosion at the coast can result in the formation of features such as sea caves, arches, bays and coves. One important effect of coastal erosion can be the loss of land and homes when cliffs fall into the sea. Deposition Deposition is the laying down of materials, such as rocks, stones, gravel, sand and mud. As rivers reach the shoreline they widen and lose much of their energy. When this happens, the load of materials they have been transporting is dropped to the bottom of the river bed or in the sea. Sandy beaches, estuaries, sand bars, spits, deltas and lagoons are the result of deposition. Animals and Plants The living organisms that inhabit coasts form part of a special ecosystem. These animals and plants have to cope with extreme weather conditions of wind and rain, salty water, tides and waves. For this reason many coastal organisms do not live anywhere else. Rocky shores are high-energy habitats where waves pummel the coast, making it difficult for animals to live there. However, when the tide goes out, rock pools provide sanctuaries for small crabs and soft-bodied animals such as sea anemones. Shelled animals, such as mussels and barnacles, attach themselves firmly to the rocks, and can withstand the biggest waves. Jellyfish and shells can sometimes be found washed up on the shore, particularly after a storm at sea. Seaweed such as brown kelp and bladderwrack are common at coasts and sea lettuce forms a bright green, slimy carpet on smooth rocks. Multicoloured lichens cover exposed rocks above the waves. On sandy beaches, lugworms live beneath the water: their holes and wormcasts are the only sign of their presence when the tide goes out. In drier zones, such as sand dunes and clifftops, spiky marram grass, sea lavender and pink thrift grow. Sea birds often roost in coastal areas and the nests of terns and plovers can be found on rocky shores. Herring gulls, black-headed gulls, redshanks and common terns are amongst the many types of bird that visit coasts in search of food. Large birds, such as the peregrine falcon, build their nests on cliff faces. Fossils The erosion of a coast can have unexpected benefits, revealing clues to the types of animals and plants that lived in the area millions of years ago. Fossils, or remains, of ammonites and other marine animals can be found on the Northumbrian and Dorset coasts of England, for example. The soft cliffs of East Anglia and the Isle of Wight have been eroded to reveal many ancient remains of animals that lived long ago, including dinosaurs, woolly mammoths and sharks. Coasts and People Over thousands of years, coasts have proved to be good places to live, and human ancestors are known to have set up home by the sea. The water is full of life, such as fish and shellfish, so it provided a plentiful source of food. Caves and cliffs offered shelter from the weather and from predators such as wolves. Coastal Settlements © 2020 Encyclopædia Britannica, Inc. 20 of 90
Britannica LaunchPacks | Landforms and Landscapes Coastal Settlements Many coastal areas began to develop and change about 15,000 years ago as the Ice Age was drawing to an end. The ice melted, sea levels rose and people were able to move north. They began to inhabit caves, often near the shore. The United Kingdom’s oldest-known dwelling has been discovered by archaeologists at a cliff edge at Howick, in Northumberland. The people who lived there, around 9,600 years ago, collected flints from the coast to make their tools. Travellers and Invaders Living by the sea enabled people to trade with travellers from overseas. Coastal communities have since maintained strong links with other countries. They often have diverse cultures and foods, which reflect the wide variety of peoples that have visited their shores. The Normans built Bamburgh Castle on the coast of Northumberland, England, so they could defend… Photos.com/Jupiterimages Unwelcome visitors, such as invaders, may also make their first appearance at coastal areas. For this reason, Britain’s coasts are peppered with castles and other military buildings which, through history, have provided a first line of defence against invasion. Dover Castle in south-east England was built on land that has been occupied as a defensive site since the Iron Age, at least 2,400 years ago. Bamburgh Castle in Northumberland was built by the Normans following their invasion in 1066. Pendennis Castle in Cornwall was built by Henry VIII to defend England against invasion by the Spanish and French. Changing Coastlines Structures called groins, or groynes, protect coastlines from the power of the waves. © Paul Cowan/Dreamstime.com © 2020 Encyclopædia Britannica, Inc. 21 of 90
Britannica LaunchPacks | Landforms and Landscapes Coasts are continually changing. Deposition and erosion form and reform the land. Other changes are the result of the movement of plates that make up Earth’s crusts (seeplate tectonics). In the long term, sea levels rise and fall because of this movement. Scientists have also predicted that changes in climate caused by global warming will cause sea levels to rise. An increase in marine pollution is also affecting coasts and their delicate ecosystems. Grasses help keep sand dunes in place. © ehrlif/stock.adobe.com In some places these changes can cause damage to buildings and can cause beaches to disappear. However, engineers have developed several different ways to protect coasts. Engineers can build structures to keep the waves from hitting the shore. They can also use the natural surroundings to help protect the coasts. They may replace sand that has been washed away, or they may restore sand dunes by planting grasses. The grasses help keep wind and water from blowing or washing the sand away. Citation (MLA style): "Coast." Britannica LaunchPacks: Landforms and Landscapes, Encyclopædia Britannica, 4 Mar. 2022. packs.eb. com.au. Accessed 10 Apr. 2022. While every effort has been made to follow citation style rules, there may be some discrepancies. Please refer to the appropriate style manual or other sources if you have any questions. desert Any barren region that supports very little life may be called a desert. More commonly, however, the term desert is reserved for regions that are barren because they are arid, or dry. Arid deserts receive little precipitation and are characterized by specialized plants that tolerate drought conditions and salty soils. Occupying some 20 percent of the Earth’s surface, deserts are one of the planet’s main types of ecosystems. They may or may not be hot, and their land features range from windswept expanses of loose sand to rugged mountains, bare rock, and plateaus strewn with gravel and boulders. © 2020 Encyclopædia Britannica, Inc. 22 of 90
Britannica LaunchPacks | Landforms and Landscapes Joshua trees and other yucca plants grow in the desert in Joshua Tree National Park in California. © Max Baumann/Shutterstock.com Climate and World Distribution Atacama Desert, Chile. Encyclopædia Britannica, Inc. Deserts are areas in which there is a shortage of moisture available for plants. There is no precise measure of how dry such an area must be to be called a desert. Characteristically, deserts receive an average of less than 10 inches (25 centimeters) of rain or other precipitation per year. Many deserts get less than half that amount of rain yearly, and some receive almost none. Regions with an average annual precipitation between some 10 and 16 inches (25 and 40 centimeters) are often called semideserts. But rainfall is not the only factor that influences how much water is available to support plants. The distribution of the rainfall throughout the year, the humidity of the air, and the temperature and amount of sunshine all play a role. Some definitions of deserts focus on the imbalance between the amount of precipitation received and the amount of moisture that could be lost through evaporation and through plants’ leaves. In the Sonoran Desert, in the southwestern United States and Mexico, for example, a year’s potential evaporation—the amount of evaporation that would occur if water were always present—is some 100 inches (250 centimeters). This is about 20 times the actual annual rainfall. Rainfall in deserts is not only scanty but also erratic. Most deserts have at least a few days of rain a year, but some may get no rain at all for several years or receive a year’s amount in one storm. For example, Iquique, in northern Chile, had no rain for a period of four years. The fifth year brought 0.6 inches (1.5 centimeters), making a five-year average of 0.12 inches (0.3 centimeter). At another time 2.5 inches (6.4 centimeters) fell in a single shower. © 2020 Encyclopædia Britannica, Inc. 23 of 90
Britannica LaunchPacks | Landforms and Landscapes Most of the world's hot deserts lie between 20° and 35° north and south of the equator. The main… Encyclopædia Britannica, Inc. There are two main types of arid desert: hot and temperate. Most of the Earth’s deserts are found between 20° and 35° in both north and south latitudes, near the Tropic of Cancer and the Tropic of Capricorn, respectively. Except for a couple of coastal deserts kept cool by ocean currents, these deserts are hot. They occupy subtropical regions that straddle a wet, tropical region around the equator. Because of the predominant air- circulation patterns, the air that descends into the subtropical regions has already rained out most of its moisture over the tropical lands. The air is also heated as it descends, which further prevents rain. Temperate deserts are found farther from the equator, in the middle latitudes. They occur mainly in Central Asia, with smaller areas in western North America, southeastern South America, and southern Australia. These deserts are generally separated from the coast by mountains or by great distance. Air picks up moisture from the ocean, but by the time it reaches these regions, it has lost much of its moisture over either the mountains or the land nearer the coast. Ice cap and tundra regions around the poles are sometimes called cold deserts. They have little precipitation, but the dearth of vegetation is caused chiefly by the cold. Temperatures range widely in deserts. In hot deserts, daytime air temperatures above 100° F (38° C) occur regularly in summer. Al Aziziyah, Libya, holds the record for the hottest temperature with a high of 136° F (57.8° C), while Death Valley, Calif., comes close with 134° F (56.7° C). Winters are cold in temperate deserts, located far from the equator. The Gobi, in Central Asia, for example, has an average low temperature of −40° F (−40° C) in January and an average high of 113° F (45° C) in July. The temperature drops sharply in the desert night. Dry air, cloudless skies, and bare, dry earth furnish ideal conditions for the cooling of air after sunset. A 24-hour range of 25 to 45 Fahrenheit degrees (14 to 25 Celsius degrees) is common, and it may exceed 60 to 70 Fahrenheit degrees (33 to 39 Celsius degrees). © 2020 Encyclopædia Britannica, Inc. 24 of 90
Britannica LaunchPacks | Landforms and Landscapes Land Forms People get water at a well in the Thar (Great Indian) Desert, in western Rajasthan, India. © virdg/Fotolia Sagebrush blooms in the Chisos Mountains, in Big Bend National Park, in southwestern Texas. The park … © jamespharaon—iStock/Getty Images Desert areas differ greatly in their surface features, which range from mountains to plateaus to plains. The ground may be bare rock or be covered with sand, scattered boulders, or a “desert pavement” of coarse gravel and stones. Although sand dunes are spectacular features of deserts, they are not as common as generally believed. In the deserts of the southwestern United States, for example, dunes occupy less than 1 percent of the surface. In the most sandy of all deserts, the Arabian, dunes occupy only about 30 percent of the total area. If sand accumulations on plains are extensive and appear as a “sand sea,” they are called ergs. A more common type of desert consists of rugged mountains separated by basins called bolsons. The mountains receive most of the rains in downpours. As the water rushes down the steep slopes it cuts deep gullies and carries rock fragments, gravel, and sand to the bolson. These materials are freed from the water when it slows or evaporates, and they are deposited as cones or in fans of sediment called alluvial fans. The rugged forms produced in this way, such as the terrain in Death Valley, are termed badlands. Sometimes floodwaters make a temporary shallow lake in the basin. The temporary lakes that form in basins with no outlet are called playa lakes. Typically the water soon evaporates into the air or filtrates into the ground, leaving behind sediments of clay, silt, and sometimes salt. The flat-bottomed depression that is formed by the water is called a playa. In narrow basins, alluvial fans and badlands may extend to the edge of the playa. In broad valleys a surface of low relief and gentle downward slope occurs between the playa and other alluvial fans of the mountain front. Such a surface is called a desert flat or llano. © 2020 Encyclopædia Britannica, Inc. 25 of 90
Britannica LaunchPacks | Landforms and Landscapes Other deserts consist of rocky plateaus, called hammadas, separated by sand-filled basins. Here differences in altitude are usually slight. Many hammadas are broad, almost flat, dome-shaped areas. Where streams or wind wear away the weaker rocks, strong rock formations stand out boldly as mesas or cuestas. Pinnacles, needles, and arches carved in colored rocks lend fantastic beauty to the deserts of the American Southwest. Gullies are cut deep into the hammadas by the wearing force of the torrents. Gullies are known as wadis in Arabia and arroyos in the Southwest. Plants and Animals Plants in the deserts of Arizona have varying strategies to survive the dry conditions. Encyclopædia Britannica, Inc. Few parts of the desert are entirely barren. Where water seeps toward the surface, a great variety of plants spring up. After a rain low shrubs and grasses come to life. At blooming time, the plants are fragrant and bright with color. They grow quite far apart, instead of providing complete ground cover. Trees and large shrubs can be found in the desert, but they are not prominent in the driest regions. Learn about the saguaro cactus, a plant unique to the Sonoran Desert, as found in Saguaro National… Encyclopædia Britannica, Inc. Desert plants differ in the ways they are adapted to arid places. Some plants sprout when the rain falls, bloom quickly, ripen their seed in a few days, then wither and die. Other plants survive periods of water shortage by drying up and becoming physiologically inactive. When more water becomes available they swell up and resume activity. Some desert plants depend upon underground water and have long root systems, while others are able to absorb dew. Various adaptations of the leaves, such as smaller surface areas, help prevent the loss of moisture. In most species of cactus, for example, leaves are either absent or very small. Cacti and other © 2020 Encyclopædia Britannica, Inc. 26 of 90
Britannica LaunchPacks | Landforms and Landscapes succulent plants also store water in their thick, fleshy tissues to help them survive long dry periods. (See also sagebrush.) Animals live in all but the most barren stretches. The camel is the most useful domestic desert animal. Its physical structure permits it to travel far without water. Various wild mammals, birds, and reptiles of arid regions must get all their moisture from their food. In times of drought, many desert animals remain inactive for long periods. Others hide from the sun during the hottest daytime hours and come out at night to feed. More than half of desert animals live at least part of the time underground, where it is cooler and more humid. Another strategy is migration: many birds and other desert animals survive by regularly moving to areas that have recently received rain. People and Deserts Deserts are much less densely populated than other land areas. People can live and grow crops in the desert only at places where they can get water, called oases. In some spots ordinary shallow wells reach the water table, or the upper boundary of underground water, but usually groundwater lies at greater depths in deserts than in humid lands. In alluvial fans the water sinks deep into the porous material, but it may be reached by a well at the tip of the fan. In wadis, ordinary wells can usually tap a supply of good water. Oasis settlements therefore are most often found where wadis are numerous. Ergs into which many wadis drain may have a water supply. Desert shrubs in the hollows between the dunes signal its presence. Deep artesian wells may be bored where the rock structure holds water under pressure. In some oases an artesian spring flows through a crack in the rock. Streams that rise in rainy regions outside deserts bring the most generous supply of water for irrigation. All the large deserts except those of Australia are crossed by these so-called exotic rivers. The largest and best known of them are the Nile in Egypt, the Tigris and Euphrates in Iraq, the Indus in Pakistan, and the Colorado in the United States. Desert soils are usually productive when given water. They are coarse textured and highly mineralized. Most widely cultivated are the water-transported soils of floodplains and alluvial fans. Land is precious in oases, so it is intensively cultivated. In North African and Asian oases, the chief food crops are dates, figs, wheat, barley, rice, and beans. Oasis farmers also raise such crops as cotton and sugarcane. In the United States irrigated lands are mainly used for citrus fruits, dates, winter vegetables, and cotton. The proper development of critical water resources has focused on improving surface-water management techniques, improving control and storage of surface runoff, reducing loss from shallow aquifers, and desalting brackish waters. The buildup of salts in the soil has become a serious problem that is being studied in several nations. The introduction of cultivated plant species with greater salt tolerance, as has been done in Israel, seems to be a promising alternative to abandoning arid land. Humans have changed many desert environments. Irrigated lands have been extended by giant river-control systems. Oases once reached only by camel now have airports and gas stations for motor vehicles. Settlements have sprung up in deserts to obtain such valuable minerals as the petroleum of Saudi Arabia, Iraq, and Iran and the copper and other metals of arid North and South America. Typical desert minerals are soluble salts left behind by evaporation. Sodium nitrate, the most valuable, comes from the north Chile desert. The mismanagement or overuse of arid and semiarid lands can cause desertification, or the spread of desert environments. Excessive cultivation of the land, clearing away the vegetation, or exhausting the water supply © 2020 Encyclopædia Britannica, Inc. 27 of 90
Britannica LaunchPacks | Landforms and Landscapes can rob arid or semiarid land of its ability to sustain life. Factors such as long-term climate change or severe drought can also cause desertification. Charles William Finkl, Jr.Ed. Citation (MLA style): "Desert." Britannica LaunchPacks: Landforms and Landscapes, Encyclopædia Britannica, 4 Mar. 2022. packs.eb. com.au. Accessed 10 Apr. 2022. While every effort has been made to follow citation style rules, there may be some discrepancies. Please refer to the appropriate style manual or other sources if you have any questions. Echo Caves The Echo Caves are among the oldest caves in the world. These limestone caves are in the Molapong Valley in the South African province of Limpopo, about 6 miles (10 kilometers) west of Motlatse Canyon. The name derives from the echoes that are heard when rock formations within the caves are struck. The echoes can be heard outside the caves. The cave system is about 25 miles (40 kilometers) long, but its full extent is unknown. One of the largest rooms in the system is about 328 feet (100 meters) long and 190 feet (60 meters) high. The Madonna and Crystal Palace chambers are some of the latest discoveries. Visitors can go on guided tours. The caves have many impressive rock formations, including stalagmites and stalactites. A stalagmite is cone- shaped and rises up from the cave floor. A stalactite is a cone that hangs from the ceiling. People lived in the caves in prehistoric times. Cave dwellers may have used the rock formations as drums to warn each other when danger was near. Tools and other evidence of these early people are exhibited in a museum near the caves. There is also rock art in the caves that was made by the San people hundreds of years ago. The caves were unknown to European settlers in the region until 1923, when the owner of a farm called Klipfonteinhoek found them. When his cattle disappeared, the farmer wanted to find out what had happened to them. He discovered that the cattle had been going into the Echo Caves. The caves were not open to the public until 1960, after the completion of the Abel Erasmus Pass and the J.G. Strijdom Tunnel through the Drakensberg range. The caves were later declared a South African national monument. Citation (MLA style): "Echo Caves." Britannica LaunchPacks: Landforms and Landscapes, Encyclopædia Britannica, 17 Sep. 2018. packs.eb.com.au. Accessed 10 Apr. 2022. © 2020 Encyclopædia Britannica, Inc. 28 of 90
Britannica LaunchPacks | Landforms and Landscapes While every effort has been made to follow citation style rules, there may be some discrepancies. Please refer to the appropriate style manual or other sources if you have any questions. Great Victoria Desert An immense dry area known as the Great Victoria Desert stretches across southern Australia. It lies in the states of Western Australia and South Australia, between the Gibson Desert on the north and the Nullarbor Plain on the south. The Great Victoria Desert extends eastward from Kalgoorlie almost to the Stuart Range. It covers an area of about 250,000 square miles (647,000 square kilometers). Most of the desert consists of a vast expanse of sand dunes, though in some places a layer of tightly packed pebbles covers the ground. Great Victoria Desert, Australia. Encyclopædia Britannica, Inc. Spinifex grass grows in the Great Victoria Desert of southern Australia. © N Mrtgh/Shutterstock.com The Great Victoria Desert receives only about 6 to 10 inches (15 to 25 centimeters) of rain each year. The desert has very hot summers and cooler winters, when nighttime temperatures may drop below freezing. © 2020 Encyclopædia Britannica, Inc. 29 of 90
Britannica LaunchPacks | Landforms and Landscapes Grass of the genus Triodia (Spinifex) grows in parts of the desert, and there are also scattered acacia trees and shrubs. Wildlife includes reptiles such as skinks, geckos, monitor lizards, and copperhead snakes as well as mice, dingoes, and foxes. The Great Victoria Desert was named by the Australian explorer Ernest Giles, who led a party across it from east to west in 1875. Few people live in the desert. Some Australian Aboriginal people live in the eastern regions. The Australian government uses parts of the Great Victoria Desert to test weapons. There are several national parks and nature reserves in the area, including the Great Victoria Desert Nature Reserve and Nullarbor National Park. Citation (MLA style): "Great Victoria Desert." Britannica LaunchPacks: Landforms and Landscapes, Encyclopædia Britannica, 4 Mar. 2022. packs.eb.com.au. Accessed 10 Apr. 2022. While every effort has been made to follow citation style rules, there may be some discrepancies. Please refer to the appropriate style manual or other sources if you have any questions. Huang He (Yellow River) The main river of northern China, the Huang He (or Hwang Ho) is the second longest river in the country, after the Yangtze. It rises on the Plateau of Tibet and flows generally eastward, emptying into the Yellow Sea. Chinese historians routinely refer to the Huang He as the cradle of Chinese civilization. The river, its tributaries, and its valley have played an integral part in the history of China for more than 3,000 years. Along the middle and lower reaches of the system, Chinese civilization and agriculture first developed, and the earliest capitals of the dynastic era, Anyang and Luoyang, were located there. Control of the river and its drainage area provided the great surplus of grain required for China’s military and political expansion beginning in the Qin Dynasty (221– 207 BC). The Huang He (Yellow River) is the main river of northern China. It flows eastward from the Plateau… Encyclopædia Britannica, Inc. © 2020 Encyclopædia Britannica, Inc. 30 of 90
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