2020年8月15日雅思阅读真题+题目+答案：How deserts are formed

2020年8月15日雅思阅读真题+题目+答案：How deserts are formed

A A desert is a barren area of landscape where little precipitation occurs and consequently living conditions are hostile for plant and animal life. Deserts have been defined and classified in a number of ways, generally combining total precipitation, number of days on which this falls, temperature, and humidity, and sometimes additional factors. In some areas, the deserts are separated by rivers, mountains or other landforms and in other areas, the borders of deserts cannot be determined.

B The raising of livestock is a major economic activity in semiarid lands, where grasses are generally the dominant type of natural vegetation. The consequences of an excessive number of livestock grazing in an area are the reduction of the vegetation cover and the trampling and pulverization of the soil. This is usually followed by the drying of the soil and accelerated erosion.

C Sand and dust storms are natural events that occur in arid regions where the land is not protected by a covering of vegetation. Dust storms usually start in desert margins rather than the deserts themselves where the finer materials have already been blown away. As a steady wind begins to blow, fine particles lying on the exposed ground begin to vibrate. At greater wind speeds, some particles are lifted into the air stream. When they land, they strike other particles which may be jerked into the air in their turn, starting a chain reaction. Once ejected, these particles move in one of three possible ways, depending on their size, shape and density.

D The cultivation of crops has expanded into progressively drier regions as population densities have grown. These regions are especially likely to have periods of severe dryness, so that crop failures are common. Since the raising of most crops necessitates the prior removal of the natural vegetation, crop failures leave extensive tracts of land devoid of a plant cover and susceptible to wind and water erosion.

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雅思阅读真题题目：

Questions 14-20 Matching

Which paragraph contains the following information?

14. the reference of irregular movement of particles 

15. an account that a productive-land turned into a desert in 20th century 

16. the types of deserts 

17. the method of tackling the problems of deserts 

18. the effect of migration on desertification 

19. the lack of agreement among the scientists about the causes of desertification 

20. the example of the fatal effects of faming practice 

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