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Antarctica is the fifth largest of the seven continents. It covers the South Pole, most of it is south of the Antarctic Circle at latitude 66° 30' south.
Antarctica is a very rough circular shape, the long arm of the Antarctic Peninsula stretches towards South America.
There are two large indentations, the Ross Sea, the Weddell Sea and their ice shelves.
The nearest other land is South America - 600 mls / 1000 km away, Australia 1550 mls / 2500 km away, and South Africa 2500 mls / 4000 km away.
The area of Antarctica is about 14.2 million sq km (about 5.5 million sq mls) in summer, approximately twice the size of Australia, one and a half times as big the USA and fifty times the size of the UK.
In the winter Antarctica doubles in size because sea ice forms around the coast.
The true boundary of Antarctica is not the coastline of the continent itself or the outlying islands, but the Antarctic Convergence.
A Desert is a place with less than 254 mm (10 in) of annual rainfall. This is what makes Antarctica a desert.
There is virtually no rainfall in Antarctica - it is so cold it only ever snows. Snowfall is measured in "water equivalent". This is the amount of water you would get if the snow was collected and melted.
Antarctica gets only about 50 mm (about 2 in) of "water equivalent" per year, this is less than the Sahara. This is more near the coasts but still only about 200 mm (8 in) in "water equivalent"
Heavy snowfall can happen when storms pick up moisture from the seas surrounding Antarctica and then drop this as snow along the coast.
The big difference in Antarctica is that unlike other deserts falling water (snow) doesn't evaporate. So even though there is only a small amount of snow falling, it doesn't go away again. Instead it builds up over hundreds and thousands of years into enormously thick ice sheets.
Antarctica is the coldest, and also the windiest continent. The lowest temperature ever recorded anywhere on earth, -89.2° C (-128.6° F) was on July 21st 1983 at the Russian base at the Southern Geomagnetic Pole.
This base is near to the "Pole of Inaccessibility". The point on the Antarctic continent that is the furthest from the sea in any direction, it is the most difficult or inaccessible place to get to. It is always one of, if not the coldest place on earth. As it far from any coast it is affected by the warming effect of the oceans less than anywhere else.
The continent is also battered by strong winds, calm periods are rare and last hours rather than days. A wind speed of 320 km/h (200 mph) was recorded at the French Dumont d'Urville base in July 1972.
Antarctica has "katabatic winds". These are caused as a result of the height and shape of the continent. Antarctica is a high (average 2300m) dome-shaped continent. Air cools and then starts to fall (the opposite of hot air rising) as it does so it flows down the slope from inland towards the coast, travelling many hundreds or thousands of miles driven largely by gravity.
As these katabatic winds reach the coast and flow over the surface of the sea, they produce a west-flowing ocean current known as the East Wind Drift. The rotation of the earth causes this wind flowing offshore from the land to produce an ocean current at a right-angle to the wind direction.
There are three climatic regions in Antarctica.
The interior of the continent is extremely cold with little snowfall.
The coastal areas have milder temperatures (though still very cold) and much higher precipitation rates (though still in the desert range).
The Antarctic Peninsula region which has a warmer and wetter climate, with above-freezing temperatures being common.
Here's a couple of shots of the Australian Mawson base that illustrate this: picture 1 picture 2
Blizzards are therefore common and frequently result in disorienting white-out conditions where everything in front of you becomes a white blanket with no distinguishable features - likened to walking along inside a ping-pong ball.
I recall a story of a day where the base doctor had gone out to visit a penguin rookery about two miles away. On the way back the weather had deteriorated and he found himself in a white-out. He thought he saw the base cook, going downhill rapidly on a sledge and waving to him from around 200-300 yards. A few footsteps later, he trod on what he had really seen - a penguin feather stuck in the snow about 10 yards away and blowing in the breeze! Yes, disorienting is definitely the right word!
|4/ What is the Antarctic landscape like?|
Antarctica consists of two main areas. East Antarctica (Greater Antarctica), and smaller West Antarctica (Lesser Antarctica) which also has the Antarctic Peninsula.
West Antarctica is an extension of the Andes mountains stretching from South America. It is thought that if the ice sheet were removed, West Antarctica would actually be a collection of islands.
More than 99 percent of Antarctica is covered with ice, this contains about 70 percent of the world's fresh water. The thick ice cover makes it the highest of all continents, with an average elevation of about 2300 m (about 7500 ft).
The highest point on the continent is Vinson Massif 4897 m (about 16 066 feet). The lowest point yet found is the Bentley Subglacial Trench (2499 m/8200 ft below sea level) in West Antarctica, this is a trench in the earth's crust well below sea-level, it is covered with more than 3000 m (more than 9840 ft) of ice and snow. Lower points may exist under the ice, but they have not yet been discovered.
The Eastern and Western halves of Antarctica are separated by the Transantarctic Mountains. This range of mountains stretches across the entire continent, large portions of them being buried under the ice cover. If you stood on the great Antarctic ice sheet all you would see would be ice and snow (and your friend taking a photograph of you standing on the great Antarctic ice sheet). It would be similar to being on the surface of the sea above an underwater mountain range.
It would be far from a continuous smooth sheet though. The ice sheet is continuously moving towards the coast under the influence of gravity.
Glaciers, huge rivers of ice carry the ice from the interior of the continent forming ice shelves at the coasts. Where a glacier is moving, the ice cracks and breaks, underlying rock and different streams meeting that move at different speeds add to the chaos.
This makes the ice sheet very dangerous in places as it is broken up by great crevasse fields with some cracks hundreds of feet deep and frequently covered by flimsy bridges formed of blown snow.
In places, you may see a "Nunatak" an outcrop of rock where one of the taller parts of the Transantarctic mountains peek up through the ice sheet. Like islands in mid-ocean that start as underwater mountains.
Amazingly sometimes such nunataks can be home to birds such as snow petrels that build their nests here. This is despite them being isolated unproductive pieces of rock surrounded by miles and miles of cold sterile ice field.
Nunataks are very useful to geologists as they give a sample of what the rock is like in that area, where most of it is covered by hundreds or thousands of meters of ice.
Large tabular icebergs form at the coasts as the edges of the ice shelves and glaciers calve off into the sea. An ice shelf is formed where a large glacier or even several glaciers begin to float when they meet the sea.
The largest ice shelf, the Ross Ice Shelf, is the size of the American state of Texas. Ice shelves produce the largest icebergs (called tabular as they table-like, flat, on top) as the ice is gently fed onto the surface of the sea before eventually breaking off and becoming free floating.
There are at least two active volcanoes in Antarctica, Mount Erebus (3794 m/12,448 ft) is the highest and has a permanent molten lava lake. The other is on Deception Island, situated just north of the Antarctic Peninsula, a popular stop-off for tourist ships where it is possible to have a warm bath in the volcanically warmed waters while being surrounded by Antarctic ice and penguins.
It is thought that there may be some areas of volcanism under the ice sheet. In some places glaciers and ice streams are flowing very quickly, possibly caused by them being lubricated from underneath by flowing water formed by volcanic activity melting the ice.
|5/ What kinds of plants and animals are there in Antarctica?|
Antarctica has no trees or bushes at all, not even the short stunted ones you get in the arctic. Vegetation is limited to about 350 species of mostly lichens, mosses, and algae. There are lush beds of such vegetation in some parts of the Antarctic Peninsula. Lichens have been discovered growing on isolated mountains within 475 km (295 mls) of the South Pole.
In some places bare rocks are colonised by the vibrant red, orange and yellow growth of lichens. Where rock is uncovered by ice for large parts of the summer, green lichens that grow to a few centimetres high can give the impression from a distance of a field of dark grass (albeit a bit tatty). Three species of flowering plants are also found on the Antarctic Peninsula.
In some places in the Antarctic continent such as in the dry valleys, rather than growing on rocks, some algae actually grow in the rock. Conditions are so harsh, particularly from strong, drying winds and from blown sand and dust, that it is easier to live in the rock despite low light levels, than it is exposed at the surface.
There are no land based vertebrate animals in Antarctica. All the vertebrates there are dependent on the sea for feeding or are migratory and leave the continent when the winter arrives.
The largest truly Antarctic land animals therefore are invertebrates only a few of millimetres in size. These animals, mites, ticks and nematode worms tolerate the low temperatures in the winter by becoming frozen in ice under rocks and stones.
They have antifreeze in their bodies and stop all motion and bodily functions while frozen, becoming active again when the ice finally warms up sufficiently to melt. These animals live largely in the Antarctic Peninsula.
The oceans surrounding the continent on the other hand are teeming with great quantities of life. Large numbers of whales feed on the rich marine life, especially krill. Six species of seals and 12 species of birds live and breed in the Antarctic. Crabeater seals are the second most numerous large mammal on the planet after humans and the population of krill has been estimated as outweighing the human population.
The most famous inhabitant of Antarctica is of course the penguin. A flightless bird, but excellent swimmer, penguins live on pack ice and in the oceans around Antarctica. They breed on the land or ice surfaces along the coast and on islands. Best known and most typical are the Adelie and emperor penguins.
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