The geologic evolution of Antarctica has followed a course similar to that of the other southern continents. The earliest chapters in Antarctica’s rather fragmentary record extend far back, perhaps as much as 3 billion years, into early Precambrian time. Similarity in patterns of crustal and biological evolution in the southern continents can be traced back some 150 million years, and evolutionary courses began to diverge conspicuously by about 70 million years ago, late in the Mesozoic Era. Plant and animal migration routes that apparently had interconnected all the southern continents were largely cut off by the outset of the Cenozoic Era (about 66 million years ago). Antarctica became isolated with the opening of the Drake Passage between the continent and South America sometime between 49 million and 17 million years ago, a time when land mammals diversified and flourished elsewhere, populating all the other continents of the world. Antarctica had long been thought to be a migratory path for marsupials moving between southern continents in early Cenozoic time. But documentation for the theory was not discovered until 1982, when the first mammal remains, a marsupial fossil, were found on Seymour Island in the Weddell Sea. The subsequent growth of Antarctica’s ice sheets cut off any further migrations by land animals.


Now bathed by polar ice, Antarctica has abundant fossil evidence that its climate and terrain at one time supported far more populous flora and fauna than today’s few seedless plants and primitive insects. Much of Antarctica was densely forested in Mesozoic times (about 252 million to 66 million years ago), dominated by southern conifers of podocarps and araucarias, with undergrowth of rainforest-type ferns. Angiosperm trees, particularly the southern beech, Nothofagus, appeared during the Cretaceous Period (about 145 million to 66 million years ago). According to some scientists, the discovery of Nothofagus pollen in the Transantarctic Mountains that dates to approximately 3 million years ago suggests that Nothofagus may have lingered as Antarctica drifted poleward, cooled, and became glaciated. Remains of luxuriant extinct floras—as well as fossils of Mesozoic reptiles, dinosaurs, and amphibians—have been discovered, and these compare so closely to those of other southern continents that many geologists have postulated former contiguity of these lands in a single giant continent called Gondwana. Continental stratigraphic evidence and the dating of seafloors seem to indicate that the supercontinent broke apart along Jurassic rift faults 180 million to 160 million years ago and that fragments such as Africa and Australia separated from Antarctica in Jurassic to Cretaceous time (about 201 million to 66 million years ago) and in the early Cenozoic Era. Early stages of rifting were marked by immense outpourings of plateau lavas (Kirkpatrick Basalt, on Mount Kirkpatrick) and by related sill intrusions (Ferrar Dolerites) across Antarctica, including one of the world’s largest layered gabbroic igneous complexes, the DufekIntrusion, in the Pensacola Mountains.


Modern theory ties mobile zones to the interaction and jostling of immense crustal plates (see plate tectonics). Modern plate boundaries may be far different from ancient ones presumably marked by old fold belts. Ancient Antarctic mobile belts, such as are followed by today’s Transantarctic Mountains, terminate at continental margins abruptly, as if sliced off, and seemingly reappear in other lands across young ocean basins. Much research has been concentrated on attempting to match intercontinentally the detailed structure of opposed coasts, such as between Antarctica and Australia, in an effort to learn whether they had been actually connected before the latest cycle of crustal spreading from intervening mid-oceanic ridges. Similarities between ancient mobile belts now suggest to some geologists that Antarctica may even have been connected to southwestern North America more than 600 million years ago, in late Precambrian time.

South America has two major mountain systems of contrasting nature. Bordering the Pacific Ocean to the west, the geologically young cordilleras of the Andes extend along the entire continent from north to south. Stretching along the continent’s northern and eastern sides are the ancient Guiana and Brazilian highlands, which are much lower in elevation and slope gently to the west; farther south are the plateaus of Patagonia. Lowlands—the basins of the Orinoco, Amazon, and Paraguay-Paraná rivers and the plains of the Pampas—separate the highlands from one another. Taken as a whole, the relief of the continent shows a great imbalance: the major drainage divide is far to the west along the crest of the Andes. Thus, rain that falls only 100 miles (160 km) east of the Pacific may flow to the Atlantic Ocean, 2,500 miles (4,000 km) away.

The ranges of the Andes Mountains, about 5,500 miles (8,900 km) long and second only to the Himalayas in average elevation, constitute a formidable and continuous barrier, with many summits exceeding 20,000 feet (6,100 metres). The Venezuelan Andes—the northernmost range of the system—run parallel to the Caribbean Sea coast in Venezuela west of Caracas, before turning to the southwest and entering Colombia. In Colombia the Andes—which trend generally to the north and south—form three distinct ranges: the Cordilleras Oriental, Central, and Occidental. The valley of the Magdalena River, between the Oriental and the Central ranges, and the valley of the Cauca River, between the Central and the Occidental ranges, are huge rift valleys formed by faulting rather than by erosion. An aerial view of the Andes in Colombia shows, within relatively short distances, a succession of hot lowlands interspersed with high ranges with snowcapped peaks.In Ecuador the Andes form two parallel cordilleras, one facing the Pacific and the other descending abruptly eastward toward the Amazon basin, crowned by towering peaks. Between the ranges lies a series of high basins. Three cordilleras run through Peru and are known by Peruvians as the Eastern Cordillera; the Central, or Blanca (“White”), Cordillera, named for the glaciated summit of Mount Huascarán, the country’s highest peak, which rises to 22,025 feet (6,713 metres); and the Western, or Negra (“Black”), Cordillera, which has no snowcapped summits.

South of Lima, Peru, and extending through western Bolivia, the Andes branch into two distinct ranges. Between them lies the Altiplano, a vast complex of high plateaus between about 12,000 and 15,000 feet (3,700 and 4,600 metres) in elevation and as much as 125 miles (200 km) wide. The Altiplano forms a maze of depressions, hills, and vast plains without equivalent except in Tibet. Water accumulates in closed basins to form marshes and lakes, the largest of which is Lake Titicaca on the border of Peru and Bolivia. That central region of the Andes has been dissected by several rivers, all of which have cut spectacular gorges down the eastern slopes.Farther to the south—along the border between Chile and Argentina—the Andes form a single but lofty chain with many of the system’s highest peaks, including Mount Aconcagua, which, at 22,831 feet (6,959 metres), is the highest point on the continent and in the Western Hemisphere; south of Aconcagua, elevations gradually diminish. In southern Chile part of the cordillera descends beneath the sea, forming innumerable islands with steep slopes. The Andes have been deeply carved by glaciers, particularly in the south. Ice masses still occupy some 1,900 square miles (4,900 square km), constituting a huge ice cap with long terminal tongues running into piedmont lakes or into the sea. The Andes are studded with numerous volcanoes that are part of the Circum-Pacific volcanic chain, often called the Ring of Fire. Earthquakes are frequent. Almost every major city has been devastated at least once by earthquake, even along the coastal plains, where clear signs of recent vertical movement are visible. Antarctica, with an average elevation of about 7,200 feet (2,200 metres) above sea level, is the world’s highest continent. (Asia, the next, averages about 3,000 feet.) The vast ice sheets of East Antarctica reach heights of 11,500 feet or more in four main centres: Dome A (Argus) at 81° S, 77° E; Dome C at 75° S, 125° E; Dome Fuji at 77° S, 40° E; and Vostok station at 77° S, 104° E. Without its ice, however, Antarctica would probably average little more than about 1,500 feet. It would then consist of a far smaller continent (East Antarctica) and a nearby island archipelago. A vast lowland plain between 90° E and 150° E (today’s Polar and Wilkes subglacial basins) would be fringed by the ranges of the Transantarctic Mountains and of the Gamburtsev Mountains, 6,500 to 13,000 feet high. The rest might be a hilly to mountainous terrain. Relief in general would be great, with elevations ranging from 16,066 feet (4,897 metres) at Vinson Massif in the Sentinel Range, the highest point in Antarctica, to more than 8,200 feet below sea level in an adjoining marine trough to the west (Bentley Subglacial Trench). Areas that are now called “lands,” including most of Ellsworth Land and Marie Byrd Land, would be beneath the sea.


Ice-scarred volcanoes, many still active, dot western Ellsworth Land, Marie Byrd Land, and sections of the coasts of the Antarctic Peninsula and Victoria Land, but principal activity is concentrated in the volcanic Scotia Arc. Only one volcano, Gaussberg (90° E), occurs along the entire coast of East Antarctica. Long dormant, Mount Erebus, on Ross Island, showed increased activity from the mid-1970s. Lava lakes have occasionally filled, but not overspilled, its crater, but the volcano’s activity has been closely monitored because Antarctica’s largest station (McMurdo Station, U.S.) lies on its lower flank. One of several violent eruptions of Deception Island, a volcanic caldera, in 1967–70 destroyed nearby British and Chilean stations. Whereas volcanoes of the Antarctic Peninsula and Scotia Arc are mineralogically similar to the volcanoes typical of the Pacific Ocean rim, the others in Antarctica are chemically like those of volcanoes along the East African Rift Valley.

Many species of Antarctic wildlife are unique to the southern region. Each of the major species shares a variety of adaptations that enables them to survive in the harsh environment. They all take their food from the sea that surrounds the continent; indeed, most live at the shore, although some breed on land.

Crabeater Seal: - The flightless birds - Penguins are able to withstand the extreme cold because of insulation provided by their short, densely-packed feathers forms a waterproof coat. A thick layer of fat or blubber also serves as an energy store. These adaptations, among others, enable them to minimize heat loss in icy cold waters so they can cope with the harsh Antarctic conditions.

Emperor Penguins: - Most of the seal pups can swim on the first day of their birth. Among the 35 varieties of the seals, 6 types live in Antarctica. They are Leopard seals, Crabeater seals, Ross seals, Weddell seals, Southern elephant seals & Antarctic fur seals.

Ross Seal: - Along with seals & penguins, whales also share the Antarctic waters. They belong to the family Cetacea, which includes about 75 species of huge whales, smaller dolphins & porpoises. The blue, fin, sei, humpback & minke whales migrate regularly in summers feeding on krill & small fish. These are the most dangerous of all the Antarctic animals.

Krill: - At the center of the Antarctic marine ecosystem is the krill. These are underwater shrimp like creatures up to 8 cm in length. They live on phytoplanktons, which grow in the warm sunlight in summer. Obviously these are the days when krill are found in unimaginable numbers. And why not? Imagine the female laying 2000 to 3000 eggs twice a year, which grow into adults in 2 or 3 years. One also may be surprised to notice that nearly 250 million tonnes of krill are consumed every year.

Antarctica also has a distinct variety of birds, which are distinguished by a thick layer of insulating fat under their skins & extensive fat deposits throughout their bodies. Their feathers provide excellent protection from the cold. There are 43 species of birds that breed within the limits of Antarctic convergence. The giant Albatrosses, the colorful shags, ferocious skuas & the small, white, pigeon like sheathbills are some of them. A variety of fresh water & saline lakes in Antarctica contain a limited range of aquatic life. The only vegetation observed here is mosses & lichens. They inhabit an exposed ground where moisture is available. Mosses grow rarely more than 100 mm deep even in most favorable conditions. Lichens are best adapted to survive at lower temperatures, & with less light & water. More than 300 species of non-marine algae are found under stones. They may form spectacular red, yellow or green patches on the areas of permanent snow.

A few species of mites, insects & invertebrates are also found at Antarctica. One must appreciate that even after the advent of man on this continent, the life here has remained as unspoilt & innocent as it was. And the credit for this mainly goes to the Antarctic treaty, which has played & is playing a pivotal role in the explorations of this continent.

Made from ❤️ by Divyesh Idhate