Antarctic

Antarctica An ice sheet covers nearly all of Antarctica. At its thickest point the ice sheet is 15,670 feet (4,776 meters) deep. Its average elevation is estimated at between 7,000 and 8,000 feet (2,100 to 2,400 meters) above sea level. The continent covers about 5.4 million square miles (14 million square kilometers). Its ice sheet contains 90 percent of the world's ice and 70 percent of the world's fresh water. The continent has two unequal parts. The larger is generally known as East Antarctica while the smaller is West Antarctica. The Transantarctic Mountains separate East and West Antarctica. Other mountain ranges include the Prince Charles Mountains and smaller ranges near the coasts. Mountains with only their peaks showing through the ice, known as nunataks, are found in some areas. Several active volcanoes are located near the Antarctic Peninsula and in the Transantarctic Mountains. West Antarctica includes the Antarctic Peninsula, an 800-mile (1,300kilometer) extension of the continent that juts northward towards the southern tip of South America. The Antarctic Peninsula has many mountain ranges. It includes the Vinson Massif. At 16,066 feet (4,897 meters) above sea level, the Vinson Massif is the highest peak in Antarctica. Surrounding Antarctica are the southern parts of the Pacific, the Atlantic, and the Indian oceans. Around the coast of the continent, glaciers continually “calve,” or break off, icebergs into the sea. These icebergs float north until they reach warm water, break into pieces, and melt. In some places, however, the floating glaciers stay attached to the land and

continue to grow until they become ice shelves. The Ross Ice Shelf is one example. It averages 1,000 feet (300 meters) thick. About 2 percent of Antarctica is ice-free. These unusual land areas, called oases, are mostly found near the coast. They include the dry valleys of southern Victoria Land and the Bunger Oasis in Wilkes Land. Antarctica does not have 24-hour periods divided into days and nights. At the South Pole the sun rises on about September 21 and moves in a circular path upward until December 21. 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 “night,” or winter.

Clim ate Antarctica is the coldest continent. The world's record low temperature (-128.6° F; -89.2° C) was recorded in this region. The average annual temperature in the interiors is -70° F (-57° C). The coast is, however, warmer. Along the Antarctic Peninsula temperatures can rise up to 59° F (15° C). Antarctica's interior is one of the world's major cold deserts. Rainfall on the continent averages only 1 to 2 inches (2.5 to 5 centimeters) a year.

Pl an ts and A nima ls The extremely cold climate of Antarctica has kept the continent almost empty of life. The exceptions in terms of plants are mosses and liverworts that grow in some ice-free areas along the coast and two species of flowering plants that grow on the peninsula. Native land animals are limited to certain species of arthropods, or insectlike animals. Nearly all the species discovered on the continent are found only in Antarctica. These include springtails, midges, and mites. About 45 species of birds live on the continent. The emperor and the Adélie penguins are found in large numbers around the entire coastline.

Gentoo and chinstrap penguins occupy the Antarctic Peninsula coasts and some islands. Four species of seals breed in the Antarctic. They are the Weddell seal, the crabeater seal, the leopard seal, and the Ross seal. Other Antarctic species include the fur seal and the huge elephant seal. Fishes limited to the Antarctic include the Antarctic cod and the icefish. The Antarctic waters are also home to the killer whale, sperm whale, and rare bottle-nosed, or beaked, whale, and the pygmy right whale. Seven species of baleen, or whalebone, whales also inhabit the waters. The most important single member of the food chain in the Antarctic is the krill. It looks like a small shrimp and exists in huge numbers; some biologists think that there may be 5 billion or more of krills. They eat small marine plants and animals and in turn are eaten in great numbers by squid, birds, seals, and whales.