The Green Sahara - HCT

The Green Sahara - HCT Passage 1 The Green Sahara 1 The Sahara sets a new standard for dry land, where relative humidity can drop into the low single digit and there are places where it rains only once in a century. There are people living there who reach the end of their lives without ever seeing water come from the sky. Even in the Sahara’s wettest areas, it may rain twice in a week and then not rain again for several years. Although temperatures can rise as high as 50 to 55 º C, making the Sahara one of the hottest places on earth, it is the dryness and not the heat which makes a place like the Sahara a desert. However, there can be huge variations in temperature in the Sahara. While temperatures in excess of 55 ? C have been recorded in the summer, frost can be seen in winter. The Sahara can also be very windy and result in powerful sandstorms which can be unpleasant or even dangerous for those caught up in them. 2 The Sahara is also the world’s largest desert. It covers most of North Africa, more than a third of the continent, and an area around the same size as the United States. However, satellite photographs have shown that the Sahara regularly shrinks and grows. In the early 1980’s the Sahara’s southern edge expanded into the Sahel, a dry band that separates the desert from the savannah. However, by the mid 1980’s this area was green and wet again. 3 Yet beneath the Sahara are vast aquifers of fresh water, enough liquid to fill a small sea. It is fossil water, a treasure laid down in prehistoric times, some of it possibly a million years old. Just 6,000 years ago, the Sahara was a very different place from what it is today: it was green. Prehistoric rock art in the Sahara shows something very surprising: hippopotamuses, which need year- round water to survive. “We don’t have much evidence of a tropical paradise out there, but we had something perfectly livable,” said Jennifer Smith, a geologist at Washington University in St. Louis. “We are learning, and only in recent years, that some climate changes in the past have been as rapid as anything that we see today,” said Robert Giegengack, a University of Pennsylvania geologist. 4 The green Sahara was the product of the migration of the monsoon. The monsoon is the seasonal rain which affects India and parts of Africa every year. In the same way that ice ages come and go, so too do monsoons migrate north and south. The dynamics of the earth’s motion are responsible as the tilt of the Earth’s axis varies in a regular cycle. Sometimes the planet is more tilted towards the sun, sometimes less so. The axis also wobbles like a spinning top. The date on which the Earth is closest to the sun also operates in a cycle. At times when the Northern Hemisphere tilts sharply 1 towards the sun and the planet makes its closest approach, the increased amount of sunlight during the summer months in this area can cause the African monsoon (which presently occurs between the Equator and roughly 17?N latitude) to move to the north. This is exactly what happened 10,000 years ago, flooding large parts of North Africa. 5 Around 5,000 years ago the monsoon shifted dramatically southwards again. The prehistoric inhabitants of the Sahara discovered that their usually green surroundings were undergoing something worse than a drought. It is about then that they may have migrated towards the Nile Valley, where Egyptian culture started to flourish at about the same time. 6 As the land dried out and the vegetation decreased, the soil lost its ability to hold water when it did rain. Fewer clouds formed from evaporation, and when it did rain, the water washed away and evaporated quickly. There was a kind of runaway drying effect. By 4,000 years ago, the Sahara had become what it is today, although it is still changing. 7 No-one knows how human-driven climate change may alter the Sahara in the future. It is something which scientists can ponder while they are sipping bottled fossil water pumped from underground. “It is the best water in Egypt,” Giegengack says – clean, refreshing mineral water. If you want to drink something good, try the ancient buried treasure of the Sahara. 8 Despite the heat and the lack of rainfall, the Sahara has a remarkable range of wildlife. Some of the mammal species found there include gazelle, baboons, hyenas and jackals. The Sahara also contains over 300 species of migratory birds while common birds include ostriches, secretary birds and eagles. There are, in addition, numerous reptiles, including crocodiles and the feared cobra. 9 For animals to survive in the Sahara, their bodies need to adapt to considerable variations in temperature. In order to cool down when the air around them heats up, mammals tend to pant, burrow underground, wallow in pools, or sweat. Sweating releases a lot of water, a more precious commodity in today’s harsh Sahara than it was 6000 years ago when there was enough water for hippos to wallow in. Camels do sweat, but not as much as most animals, and they can keep it to a minimum to conserve water. The main reason they can do this is that they are able to withstand significant fluctuations in body temperature – more than 5 º C – that could kill other animals, including humans. A camel’s body temperature rises during the day, sometimes above 41ºC, but can then fall to as low as 35 º F at night. (954 words), Flesch/Kincaid 11.0, Readability 49.8 2 Passage 1 Questions 1 – 5: True/False/No Information Read the texts and look at the statements below. Write: T if the statement is true F if the statement is false NI if the information is not given 1 The temperature in the Sahara remains constant throughout the year. 2 Monsoons migrate due to the movement of the Earth. 3 The Sahara is about the same size as the US. 4 The Sahara was green 5000 years ago. 5 Camels do not sweat as much as most other animals. Questions 6 – 10: Vocabulary in context Choose the best answer closest in meaning to the following: 6 shrinks (paragraph 1) a) gets smaller b) gets bigger c) separates d) dies 7 migration (paragraph 4) a) stillness b) danger c) result d) movement 8 flourish (paragraph 5) a) migrate b) decrease c) disappear d) grow 3 9 range (paragraph 8) a) loss b) change c) variety d) species 10 burrow (paragraph 9) a) run b) tunnel c) breathe d) die Questions 11 – 15: Gapfill Fill in the gaps to make a summary of paragraph XXXXXX. Use the words in the box Some places in the Sahara only see rain once every ______________(11) years. Some people who live there all their lives without ever seeing_________.(12)The Sahara is one of the hottest places on our planet as the ________________ (13) can reach 55 C. It is known as a desert because it is so _____________ (14) rather than so hot. Powerful sandstorms occur as a result of the ____________________ .(15) temperature temperatures wind windy hundred fifty dangerous dryness ten rain raining dry 4 Passage 2 Discovery by Accident 1 In the long history of inventions, discoverers seem to fall into two classes: the first is the intelligent person who wants to find the solution to a problem; the second is the lucky one who appears to find something by accident. However, it has to be clear what is meant by "accident". The "accidental" part of many great discoveries is that something unusual happened when there was an observant person who observed what had happened and began work to find out why. 2 Consider the wheel, without which there would be no clocks nor motorcars, neither airplanes nor trains. Nevertheless, men had been making wheels for tens of thousands of years before someone thought of using them to make work easier. Skeletons of people who died fifty thousand years ago were discovered to be wearing little wheels as necklaces; wheels were painted on their pottery and carved on their bone tools. Their children must have played with small wheels, yet thousands of years had to pass before someone thought of making a larger wheel and fitting it to a sledge, thus making a cart. 3 During the First World War, Mr. Harry Brearley, a well-known expert in metals, was asked to investigate the problem of the "pitting" which spoiled gun barrels after they had been fired for a certain length of time. Minute holes, almost invisible to the naked eye, appeared on the surface. In his research, the first thing that Mr. Brearley did was to order a number of barrels to be made of new steel alloys. One of these alloys contained a higher percentage of chromium than had ever been used before. A gun barrel was made of this new "chromium steel," but the first shot fired through it broke it into many pieces. So the scraps were thrown onto the waste heap. A week or two afterwards, Mr. Brearley noticed that among the rusty scraps of metal, a few were still as bright as when they had left the foundry: these were the broken pieces of the chromium steel barrel. From this accidental discovery developed the enormous benefits of "stainless steel." 4 The same desire to find out why something happens is behind one of the most valuable inventions of all time; that of penicillin. A culture of deadly bacteria that Dr. Alexander Fleming was experimenting with became mouldy. He noticed that where the mould had formed, the deadly micro-organisms were dying fast. Had he found something which would actually kill the bacteria? With the help of some other scientists, he was able to cultivate the mould, which had been identified as Penicillium notatum. Eventually, 5 that mould was mass produced, and given to the world as the "wonder-drug," penicillin. 5 Behind the great rubber industry of today lies a story of one man's search and of his lucky discovery by accident. Charles Goodyear was an American who had been trying for years to find a way in which rubber could be made to produce a hard, non-sticky and yet elastic substance. Rubber, in its natural state, is hard when cold and soft and sticky when heated. One day, by chance, Goodyear dropped a small piece of rubber on to a stove at the same time that a piece of sulphur slipped out of his hand. The smell of burning rubber mixed with burning sulphur was horrible and he quickly got a knife to scrape the mess from the stove top. As he scraped away, bits of boiling rubber were thrown on to a plate. When it had cooled down, a different sort of rubber was found. It was cold and yet pliable and was not sticky, even when it was reheated. Goodyear had invented - by accident - the basic method of preparing rubber for commercial use. He had invented the process that we now call "vulcanizing." 6 The vulcanized pneumatic tyre had been patented forty years before John Dunlop rediscovered it quite accidentally and through it laid the foundations for his immense rubber empire. Dunlop, a veterinary surgeon or animal doctor, had bought his small son a tricycle. In those days – more than seventy years ago - tricycles had solid wheels and riding was rather bumpy. Although Dunlop gained the recognition, it was Robert Thompson who invented the first vulcanized rubber pneumatic tyre, which he patented in 1845. This invention actually worked rather well, but was hampered by the fact that it proved too expensive to become a commercial success. 7 Mr Dunlop began looking around for some type of cushioning to protect his young son from the shocks of an uneven road. He wondered what would happen if he cut off a length of rubber garden hose, just sufficient to encircle a tricycle wheel, closed the ends of the tube, and pumped air into it. The tube was only tied on to the wheel with cord, at first. The idea was an instant success, and Dunlop at once saw the enormous possibilities of fitting his "pneumatic" tires to tricycles, and bicycles for grown-ups as well. 8 It is said that when Elias Howe's wife complained to him that her sewing machine did not work properly, he dreamed one night that a man was chasing him with a shiny spear which had a hole in the point. Howe woke up terrified but terribly excited. He had found the answer to the problem of making the lock stitch on a sewing machine, a problem which had puzzled every inventor before. Put the eye or hole in the point of the needle. There have been improvements since, but Elias Howe's basic idea remains the one on which the modern sewing machine works. 6 9 All these inventions had one thing in common: the inventor initially made the discovery by observation and questioning. Adapted from SLA Reading Clinic Words: 983 Flesch/ Kincaid 10.8 Readability 55.8 7 Passage 2 Questions 16 – 20: Matching Match the following titles to the correct paragraph e.g. Using bacteria Ans: para 4 16 The vulcanized tyre para ___ 17 Categories of inventions para ___ 18 A fortunate discovery para ___ 19 Slow development para ___ 20 A smoother ride para ___ Questions 21 – 25: Multiple Choice Choose the correct answer to the following questions: 21 "Accidental" discoveries mean more than discoveries by chance because there has to be a) a need for something the inventor is looking for b) someone present who notices what has happened and wants to find out why c) an expert to ask for help from other scientists d) a solution to the problem 22 The discovery of stainless steel was the result of a) years of research by a metal expert to find stainless steel b) an accidental detection of scraps of metal that had not rusted c) a combination of the knowledge of several men in this field d) the first World War 23 Alexander Fleming discovered a) penicillin b) culture 8 c) mould d) bacteria 24 Charles Goodyear was the American who invented a method for making a) rubber hard when cold b) a pneumatic tire c) rubber pliable even when cold d) a stove 25 The problem of making the lock stitch on a sewing machine was solved as a result of a) a dream b) many months of hard work c) improving the machine d) Elias Howe’s wife Questions 26 – 30: Short answers Answer the following questions. Write NO MORE THAN SIX words. 26 How do we know how long wheels have been in existence? 27 When did Brearley make his accidental discovery? 28 Who rediscovered the pneumatic tyre? 29 What is another name for an animal doctor? 30 Whose basic idea has not changed? 9 READING ANSWER KEY Abu Dhabi Men’s College 1 16 2 17 3 18 4 19 5 20 6 21 7 22 8 23 9 24 10 25 11 26 12 27 13 28 14 29 15 30 Raw Score ……………………… % ……………………… 10