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Greater and Lesser Antarctica and the lost continent of Gondwanaland

Posted in Exploration, Geography, Nature, Wildlife on Thursday, 9 August 2012

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This edited article about Antarctica originally appeared in Look and Learn issue number 762 published on 21st August 1976.

Surveying Antarctica, picture, image, illustration

Surveying Antarctica by Graham Coton

Hundreds of millions of years ago, it is believed that two great continents existed, one in the north and one covering a vast area in the Southern Hemisphere. Then, during a period of great volcanic activity, these land masses broke up and drifted apart, leaving the continents as they appear now.

Parts of the southern continent, according to this theory, are now incorporated in Australia, Africa and South America. Another fragment forms the main part of the ice-bound continent of Antarctica. Evidence of the latter having originated in this way is found in the rocks of which it is composed, including coal-seams. These show a striking resemblance to strata existing in the other southern continents.

The North and South Polar regions receive far less of the sun’s heat than the other zones of the earth’s surface. During part of the Polar winter the sun does not rise at all, because of the angle at which the earth’s axis is tilted. Even during the summer period of continuous daylight, the sun remains low in the sky.

Understandably, the Polar regions are extremely cold, and are permanently capped with ice. But there are important differences between the two. The North Pole is covered by sea, on which the ice floats as a great “raft”. But, of the area within the Antarctic Circle, some three-quarters is covered by land and forms the continent of Antarctica.

Lacking the comparative warmth of the water that covers the North Pole, the Antarctic is much colder, and carries a much thicker covering of ice. This averages 6,000 feet (1,800m), and in parts is twice as deep. The South Pole itself stands on an ice plateau approximately 9,500 feet (2,900m) above the rock bed. The average temperature there is less than minus 50 degrees centigrade, and much lower temperatures have been recorded.

The Antarctic continent comprises two parts. The greater represents what is supposed to be the fragment of Gondwanaland, the ancient southern continent. Its semi-circular coastline faces northwards towards New Zealand at one extremity, and towards the central Atlantic at the other. At its widest it is some 2,700 miles (4,320km) across.

Joined to this main mass is Lesser Antarctica. This tapers into a narrow peninsula, extending beyond the Antarctic Circle towards South America, only about 700 miles (1,120km) distant. The mountains of Graham Land, in the peninsula, are thought to be an extension of the Andes Range.

Geological evidence shows that Lesser Antarctica is a relatively late addition to the continent. Much of it is low-lying. If the ice cover were to melt away, the peninsula would remain above sea-level, but the rest of Lesser Antarctica would be submerged, with its higher peaks forming an archipelago of islands.

The visible surface of Antarctica is largely a waste of ice, in places riven by crevasses, and in others broken by the protruding peaks of half-buried mountains. Among the loftier mountains is the still active volcano, Erebus, close to McMurdo Sound.

The ice-cap, built up over many hundreds of thousands of years from layers of unthawed snow, tends always to move outwards under its own weight. Some of it reaches the sea in broad sheets; some is channelled into troughs between mountains to form valley glaciers. As the ice breaks off, it floats away in the form of icebergs.

Along the coastline, the ice presents an almost unbroken front of ice-cliffs, often 200 feet high. The true coastline may be hidden under ice many miles inland.

Comparatively little of the continent’s true surface is visible above the ice. In summer some rocky patches and ledges on the coast become exposed, providing precious breeding grounds for penguins, petrels and other species of birds. All but the emperor penguin migrate as winter approaches. The female emperor actually lays her single egg in the depths of the sunless winter, on the sea ice surrounding the coast.

Summer-breeding penguins of the Antarctic include the little Adelie penguin and the ringed penguin; but most penguins have their homes in sub-Antarctic islands such as South Georgia or the South Orkneys.

Plant-life in the Antarctic mainland is confined almost entirely to lichens and mosses, though rare specimens of grasses and of a small flowering plant, the Antarctic pink, have been found. With no vegetation to live on, and such a severe climate, it is natural that true land animals should be scarce.

The largest land creature is a wingless fly, the Belgica Antarctica, a mere half-inch in length. Other, much smaller, insects also exist there, finding “oases” of moisture and warmth in hollows and under rocks. When these refuges freeze up, the insects simply become dormant till warmer weather returns.

If the land of Antarctica is almost barren, the seas that surround it support an abundant population. These waters have been described as a “soup”, so rich are they in plankton. Plant plankton feeds animal plankton, including the shrimp-like crustaceans called krill. The latter provide food for many species of fish, and for marine mammals, such as whales and the crab-eater seal. The fish in their turn feed seals, penguins and other sea-birds.

For most of us, mention of the South Pole brings to mind the early days of Antarctic exploration, and especially the tragic deaths of Captain Scott and his companions in 1912. Today the Pole is no longer the almost inaccessible spot that it used to be. It is now the permanent home of a United States research station, easily reached by air.

In 1959, a number of countries signed a treaty, agreeing not to press any territorial claims in Antarctica, and to cooperate in scientific research. As well as the U.S.A., the U.S.S.R., Britain, Australia and other countries have scientific missions active in the region.

The result is that much is now known that was not known before. Especially important has been the work of measuring the ice depths, and investigating the rock underlying the ice. Measurement of the ice can be done by “seismic” sounding – detonating an explosion on the surface, and recording the time taken for the sound waves to “bounce” back from the rock. Radar is also used for this purpose.

It is possible that one day Antarctica may furnish homes for large numbers of the world’s swelling population. For the present, it remains a desert of ice; fascinating to scientists, and grimly beautiful in its way, but as inhospitable as in the days before aircraft and snow tractors opened it up to modern exploration.

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