雅思阅读第036套P3- Living Dunes阅读段落 3你应该花大约 20 分钟的时间来 回答问题 27-40， 这些问题基于阅读以下页面上的第 3 篇文章。 活沙丘当您想到沙丘时，您可能会想到一堆没有生命的沙子。但沙丘实际上是动态的自然结构。他们成长、转变和旅行。他们爬着活的东西。一些沙丘甚至会唱歌。 A 尽管沙丘只不过是一堆风吹过的沙子，但它可以翻过树木和建筑物，无情地穿过高速公路，吞噬沿途的车辆，并威胁到非洲、中东和中国的农作物和工厂。在某些地方，杀手沙丘甚至会卷入并吞没城镇。整个村庄都消失在沙子下。在少数情况下政府为流离失所者建造了新村庄，却发现新村庄本身在几年后就被掩埋了。防止沙丘淹没城市和农业区已成为联合国环境规划署的优先事项。 乙 Some of the most significant experimental measurements on sand movement were performed by Ralph Bagnold, a British engineer who worked in Egypt prior to World War II. Bagnold investigated the physics of particles moving through the atmosphere and deposited by wind. He recognised two basic dune types, the crescentic dune, which he called “barchan,” and the linear dune, which he called longitudinal or “sief ’ (Arabic for “sword”). The crescentic barchan dune is the most common type of sand dune. As its name suggests, this dune is shaped like a crescent moon with points at each end, and it is usually wider than it is long. Some types of barchan dunes move faster over desert surfaces than any other type of dune. The linear dune is straighter than the crescentic dune with ridges as its prominent feature. Unlike crescentic dunes, linear dunes are longer than they are wide—in fact, some are more than 100 miles (about 160 kilometers) long. Dunes can also be comprised of smaller dunes of different types, called complex dunes. C 尽管沙丘形成的动力学复杂，Bagnold 指出，沙丘通常需要以下三点才能形成：在植被稀少的地区（通常在海岸或干涸的河流、湖泊中）有大量松散的沙子或海床；吹动沙粒的风或微风；还有一个障碍物，它可能像石头一样小，也可能像树一样大，它会导致沙子失去动力并沉降。在这三个变量合并的地方，形成了一个沙丘。 D 当风把沙子卷起来时，沙子会移动，但通常只高出地面一两英寸，直到有障碍物使它停止。最重的颗粒靠在障碍物上，形成一个小脊或隆起。较轻的颗粒会沉积在障碍物的另一侧。风继续将沙子移动到沙堆的顶部，直到沙堆变得如此陡峭以至于它在自身重量下坍塌。当崩塌的沙子达到适当的陡度以保持沙丘稳定时，它就会停止。沙子在迎风面向上移动到沙丘顶部的重复循环，然后从沙丘的滑动面滑落，使沙丘向前移动，沿着风吹的方向移动。 E Depending on the speed and direction of the wind and the weight of the local sand, dunes will develop into different shapes and sizes. Stronger winds tend to make taller dunes; gentler winds tend to spread them out. If the direction of the wind generally is the same over the years, dunes gradually shift in that direction. But a dune is “a curi-ously dynamic creature”, wrote Farouk El-Baz in National Geographic. Once formed, a dune can grow, change shape, move with the wind and even breed new dunes. Some of these offspring may be carried on the back of the mother dune. Others are bom and race downwind, outpacing their parents. F Sand dunes even can be heard 'singing’ in more than 30 locations worldwide, and in each place the sounds have their own characteristic frequency, or note. When the thirteenth century explorer Marco Polo encountered the weird and wonderful noises made by desert sand dunes, he attributed them to evil spirits. The sound is unearthly. The volume is also unnerving. Adding to the tone’s otherworldliness is the inability of the human ear to localise the source of the noise. Stéphane Douady of the French national research agency CNRS and his colleagues have been delving deeper into dunes in Morocco, Chile, China and Oman, and believe they can now explain the exact mechanism behind this acoustic phenomenon. G 该小组将沙子拖回实验室，并将其设置在带有自动推板的通道中。沙子仍在歌唱，证明沙丘本身不需要充当声音的共鸣体，因为 som研究ers had theorised. To make the booming sound, the grains have to be of a small range of sizes, all alike in shape: well-rounded. Douady’s key discovery was that this synchronised frequency—which determines the tone of sound—is the result of the grain size. The larger the grain, the lower the key. He has successfully predicted the notes emitted by dunes in Morocco, Chile and the US simply by measuring the size of the grains they contain. Douady also discovered that the singing grains had some kind of varnish or a smooth coating of various minerals: silicon, iron and manganese, which probably formed on the sand when the dunes once lay beneath an ancient ocean. But in the muted grains this coat had been worn away, which explains why only some dunes can sing. He admits he is unsure exactly what role the coating plays in producing the noise. The mysterious dunes, it seems, aren’t quite ready yet to give up all of their secrets. SECTION 3: QUESTIONS 27-40 Questions 27-33Reading passage 3 has seven paragraphs, A-G. Choose the correct heading for paragraphs A-G from the list of headings below. Write the correct number, i-x, in boxes 27-33 on your answer sheet.
27 ____________ Paragraph A 28 ____________ Paragraph B 29 ____________ Paragraph C 30 ____________ Paragraph D 31 ____________ Paragraph E 32 ____________ Paragraph F 33 ____________ Paragraph G Questions 34-36Complete the sentences below. Choose ONE WORD ONLY from the passage for each answer. Write your answers in boxes 34-36 on your answer sheet. 34 _________________ dune is said to have long ridges that can extend hundreds of miles. According to Bagnold, an 35 _________________ is needed to stop the sand from movingbefore a dune can form. Stéphane Douady believes the singing of dunes is not a spiritual phenomenon, but purely 36 _________________. Questions 37-40Complete the summary below. Choose ONE WORD ONLY from the passage for each answer. Write your answers in boxes 37-40 on your answer sheet.
|
|
|
