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2015年12月英语六级考试全套模拟卷9

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参加2015年12月英语四六级考试的同学想必已经开始为此做准备了，文都四六级考试网小编整理了一些英语六级模拟题供大家练习，希望有助于大家复习。

　　Part II Reading Comprehension (35 minutes)

　　Directions: There are 4 reading passages in this part. Each passage is followed by some questions or unfinished statements. For each of them there are four choices marked A., B., C. and D. You should decide on the best choice and mark the corresponding letter on the Answer Sheet with a single line through the center.

　　Questions 21 to 25 are based on the following passage:

　　For all their great diversity of shapes and sizes, glaciers can be divided into two essential types: valley glaciers, which flow downhill from mountains and are shaped by the constraints of topography(地貌), and ice sheets, which flow outward in all directions from dome—like centers of accumulated ice to cover vast expanse of terrain. Whatever their type, most glaciers are remnants of great shrouds of ice that covered the earth eons ago. In a few of these glaciers the oldest ice is very ancient indeed; the age of parts of the Antarctic sheet may exceed 500,000 years.

　　Glaciers are born in rocky womb above the snow line, where there is sufficient winter snowfall and summer cold for snow to survive the annual melting. The long gestation period of a glacier begins with the accumulation and gradual transformation of snow flakes. Soon after they reach the ground, complex snowflakes are reduced to compact, roughly spherical ice crystals, and the basic components of a glacier. As new layers of snow and firn, snow that survives the melting of the previous summer, accumulate, they squeeze out most of the air bubbles trapped within and between the crystals below. This process of recrystallization continues throughout the life of the glacier.

　　The length of time required for the creation of glacier ice depends mainly upon the temperature and the rate of snowfall. In Iceland, where snowfall is heavy and summer temperatures are high enough to produce plenty of melt—water, glacier ice may come into being in a relatively short time—say, ten years. In parts of Antarctica, where snowfall is scant and the ice remains well below its melting temperature year round, the process may require hundreds of years.

　　The ice does not become a glacier until it moves under its own weight, and it cannot move significantly until it reaches a critical thickness—the point at which the weight of the piled—up layers overcomes the internal strength of the ice and the friction between the ice and the ground. This critical thickness is about 60 feet. The fastest moving glaciers have been gauged at not much more than two and a half miles per year, and some cover less than 1/100 inch in that same amount of time. But no matter how infinitesimal the flow, movement is what distinguishes a glacier from a mere mass of ice.

　　21. Which of the following is the most appropriate definition of glacier?

　　A. Glaciers fall into two basic categories: valley glaciers and ice sheets.

　　B. Glaciers are huge masses of ice that move under their own weight.

　　C. Glaciers either flow downhill from mountains or flow outward in all directions from dome—like centers of accumulated ice.

　　D. Glaciers are primarily formed in the rocky mountain tops above the snow line.

　　22. What is implied in the passage?

　　A. Glaciers can be divided into many categories according to their shapes and sizes.

　　B. Ice sheets move faster than valley glaciers.

　　C. It takes longer for glaciers to form in Antarctica than in Iceland.

　　D. Valley glaciers are not as old as ice sheets.

　　23. Why does the author mention the formation of glaciers in Iceland in the third paragraph?

　　A. Heavy snowfall and high summer temperatures make glaciers come into existence in a relatively short period of time in Iceland.