新编大学英语教程第四册Unit 08

Seen from space, the astronauts tell us, the most distinctive¹ feature of our planet is the ice sheet of Antarctica which “radiates light like a great white lantern across the bottom of the world”.This ice sheet covers 5,500,000 square miles (an area greater than the United States and Central America combined); it averages more 7,000 feet in thickness ; it contains more than 90 per cent of the world’s ice and snow, and if suddenly it melted the oceans would rise to such a height that every other person on earth woud be drowned. Antarctica is in fact out planet’s largest and most spectacular natural phenomenon.

Yet 160 years ago no one had ever set eyes on this vast continent, let alone set foot on it; and even today man’s tenure² of it is unsure and his knowledge comparatively slight. To understand why , we need to appreciate the sort of place Antarctica is.

People used to regard the Arctic and the Antarctic as much alike. In fact their differences outweigh³ their similarities. The Arctic is closely hemmed⁴ in by the populatedlandmasses of Europe,America and Asia ; the Antarctic in contrast is in splendid isolation⁵, divided from the nearest land by vast reaches of the most tempestuous⁶ seas on earth. Another big difference is the climate. We are so liclined to think of both the Arctic and Antarctic as cold , that we tend to forget how much colder the latter is. North of the Arctic Cirele tens of thousands of families live in comfort all the year round; hundreds of children are born every year . South of the Antarctic Circle . in contrast , there is no habitation that a man can describe as home; the only plants are a handful of mosses⁷ and lichens⁸; the only landlife simple one-celled creatures and wingless flies; no human child has ever been born there.

It is not hard to see why. The basic essentials to life are rainfall, warmth and a degree of stillness. The Arctic, and times, provides all three; the Antarctic seldom provides any-witness the descriptions of those who have been there:

As regards precipitation the Southern Continent is a desert with an annual fall no greater than the outback of Australia. The exact accumulation is difficult to measure because of the common occurrence of blown snow, but the central area certainly receives less than five centimetres per uear; and there may well be places close to the Pole where snow has never fallen. (U.S Weather Bureau)

Antarctica is by far the coldest place on earth; weather stations have reported temperatures of -88°C,more than 20°below those recorded anywhere else. In this sort of cold if you try to burn a candle the flame becomes obscured by a hood⁹ of wax, if you drop a steel bar it is likely to shatter like glass, tin disintegrates¹⁰ into loose granules, mercury freezes into a solid metal, and if you haul up a fish through a hole in the ice within five seconds it is frozen so solid that it has to be cut with a saw.(John Becjervaose)

All those who have set foot in Antarctica agree that its main and most cruel characteristic is wind . When we wintered in Adelie Land the wind on 5th July blew nonstop for eight hours at an average speed of 107 mph; gusts¹¹ were recorded of over 150 mph,and the average wind speed of the month was 63.3. In these conditions it was possible to stand for more than a few seconds, and then only by leaning forward at an angle of 45°!(Douglas Mawson)

It is worth remembering that wind is as injurious to human health as cold; for by disrupting the cushion of warmth which is trapped by pores and hairs of the skin, each knot of wind has an effect on life equal to a drop of one degree in temperature. So whereas a man can live quite happily at -20°in the still air, when the temperature is -20°and the wind speed 60 knots knots he will very quickly die. Small wonder that whereas in the eighteenth and early nineteenth centuries man swiftly explored and occupied the rest of his planet, the southernmost continent remained inviolate¹².

Yet climate by itself was not the main drawback to the unveiling of Antarctica; an even greater drawbaack, at least in the early stages, was the nature of the sea—the Southern Ocean—which surrounds it .

By Ian Cameron

The Underworld 

Let us take a brief look at the planet on which we live. As Earth hurtles through space at a speed of 70,000 miles an hour , it spins, as we all know, on its axis¹³, which causes it to be flattened¹⁴ at the Poles. Thus if you were to stand at sea level at the North or South Pole you would be 13 miles nearer the centre of the earth than if you stood on the Equator.

The earth is made up of three major layers—a central core, probably metallic¹⁵, some 4,000 miles across, a surrounding layer of compressed rock ,and to top it all a very thin skin of softer rock, only about 20 to 40 miles thick—that’s about as thin as the skin of an apple,talking in relative terms.

The pressure on the central core is unimaginable. It has been calculated that at the centre it is 60 million pounds to the square inch, and this at a temperature of perhaps 10,000 degrees Fahrenheit¹⁶. The earth’s interior, therefore, would seem to be of l iquid metal—and evidence for this is given by the behaviour of earthquakes.

When an earthquake occurs, shock waves radiate from the centre just as waves radiate outwards¹⁷ from the point where a stone drops into a pond. And these waves pulsate¹⁸ through the earth’s various layers. Some waves descend¹⁹ vertically²⁰ and pass right through the earth, providing evidence for the existence of the core and an indication that it is fluid rather than solid. Thus , with their sensitive instruments, the scientists who study earthquakes, the seismologists ,can in effect X-ray the earth.

Northern India, and more especially that part of Northern Pakistan known as Baluchistan, is a particularly active seismic²¹ area. In Baluchistan one of the greatest earthquake disasters of modern times occurred in 1935, when the town of Quetta was destroyed and 30,000 people lost their lives. Today , Quetta is the home of a geophysical observatory²² where scientists make a special study of earthquakes. One of the practical tasks of these seismologists in Quetta has been to calculate ways of making buildings sage²³ against earthquake tremors²⁴, and nowadays all houses in the town are built according to seven approved designs. As a result, in a great earthquake near Quetta only a few years ago, practically all the buildings stood up and no lives were lost.

Iceland is one of the most active volcanic²⁵ regions of the world . And it was to Iceland that Jules Verme semt the hero of his book A Journey to the Centre of the Earth.This intrepid²⁶ explorer clambered down the opening of an extinct volcano and followed its windings²⁷ until he reached the earth’s core. There he found great oceans, and continents with vegetation. This conception of a hollow earth we now know to be false. In the 100 years since Jules Verne published his book, the science of vulcanology , as it is called, has made great strides. But even so the deepest man has yet penetrated²⁸ is about 10,000 feet.This hole, the Robinson Deep mine in South Africa , barely scratches the surface; so great is the heat at 10,000 feet that were it not for an elaborate air-conditioning system , the miners working there would be roasted. Oil borings down to 20,000 feet have shown that the deeper they go, the hotter it becomes.

The temperature of the earth at the centre is estimated to be anything between 3,000 and 11,000 degrees Fahrenheit. Some scientists believe that this tremendous heat is caused by the breaking-down of radio-active elements, which release large amounts of energy and compensate²⁹ for the loss of heat from the earath’s surface. If this theory is correct , then we are all living on top of a natural atomic powerhouse.

By Radio UNESCO