TPO56阅读真题+题目+答案下载：Alfred Wegener's Theory of Continental Drift

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TPO56阅读真题+题目+答案下载：Alfred Wegener's Theory of Continental Drift

In 1912, the German geologist Alfred Wegener proposed that Earth's continents are mobile rafts of lighter crust that have shifted over time by plowing their way through the denser crust of the oceans. The theory, called continental drift, was partly motivated by the apparent fit, like puzzle pieces, of the coastlines of South America and Africa. Wegener first presented his theory of continental drift at a meeting and in a paper, and then as a book. The Origin of Continents and Oceans, published in 1915. He continued to write updated versions of this work until his death in an ill-fated expedition to Greenland in 1930. Wegener maintained that Earth is composed of concentric shells of increasing density from crust to core. The outermost shell is not continuous but made of continental blocks of lighter rock called sial (an acronym for silica- and aluminum-rich rock) floating in the denser sima (silica- and magnesia-rich rock) underlying the oceans. All the continents had been joined in the supercontinent of Pangaea. As the continent broke up, the pieces moving apart left bits behind, explaining the presence of nonvolcanic islands and island chains, according to Wegener. Where the moving pieces collided, mountains formed. They were thrust up either by the plowing of the continents through the sima, as in the case of the Andes, or by the colliding of two blocks of sial, as in the case of the Himalayas. As for the force driving continental drift, Wegener initially invoked Polfluchtkraft-a force causing flight from the poles as a result of Earth’s rotation-and later the tidal force resulting from the gravitational attraction between Earth and the Moon and Sun.

1.The word "updated" in the passage is closest in meaning to

A.required

B.popular

C.newer

D.various

2.According to paragraph 1, the presence of nonvolcanic islands was an indication to Wegener that

A.the sial was lighter than was once believed

B.a supercontinent that existed at one time broke apart

C.nonvolcanic islands were formed from the sima rather than the sial

D.island chains existed prior to the formation of the supercontinent Pangaea

3.Why are the Andes and Himalaya mountains mentioned in the discussion in paragraph 1?

A.To contrast the ways in which islands and mountains formed

B.To describe two ways in which movements of land formed mountains

C.To provide examples of mountain ranges that are no longer in their original locations

D.To explain the differences between sial and sima with well-known geographic areas

4.Which of the sentences below best expresses the essential information in the highlighted sentence in the passage? Incorrect choices change the meaning in important ways or leave out essential information.

A.Wegener's term “Polfluchtkraft" was first used to mean Earth's rotation and later the gravitational attraction between Earth and the Moon and Sun.

B.Continental drift required a powerful driving force that was created by the combination of Earth's rotation and tidal movements, which Wegener called “Polfluchtkraft."

C.At first Wegener believed that the movement of the continents was caused by Earth's rotationbut later came to believe that the drift was caused by powerful tides.

D.According to Wegener, the great force of continental drift first affected Earth's rotation at the poles and later also affected the gravitational force of Earth's tides.

One of the most influential geologists to join the mobilist camp, as the drifters school became known, was Arthur Holmes. Holmes recognized the importance of radioactive heat-which had recently been discovered-and realized that there must be a mechanism to remove it from Earth’s interior. That mechanism, he argued, is convection-the rising of less dense material and the sinking of more dense material. He went on to propose that the mantle (the part of Earth’s interior below the outer crust and above the core) convects in large, circulating patterns, and that this motion carries the continents across Earth’s surface. He also related crustal movement and mantle convection to the evolution of mountain belts. Wegener adopted Holmes's mechanism in the last rendition of his theory Holmes, for his part, presented his grand concept of a dynamic Earth in his influential and popular text Principles of Physical Geology, published in 1944.

.........省略若干字

5.What does paragraph 2 suggest about how Holmes influenced Wegener's thinking?

A.He encouraged Wegener to consult the geologists who formed the drifters school.

B.He convinced Wegener that the mantle contained a great deal of radioactive heat.

C.He demonstrated to Wegener that the density of geographic material was less important thanits pattern of movement.

D.He provided Wegener with a more accurate explanation of the mechanism by whichcontinents moved and mountains evolved.

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