托福阅读常考话题及练习题推荐一：冰川（2）

Paragraph 1: It has long been accepted that the Americas were colonized by a migration of peoples from Asia, slowly traveling across a land bridge called Beringia (now the Bering Strait between northeastern Asia and Alaska) during the last Ice Age. The first water craft theory about this migration was that around 11,000-12,000 years ago there was an ice-free corridor stretching from eastern Beringia to the areas of North America south of the great northern glaciers. It was this midcontinental corridor between two massive ice sheets–the Laurentide to the east and the Cordilleran to the west–that enabled the southward migration. But belief in this ice-free corridor began to crumble when paleoecologist Glen MacDonald demonstrated that some of the most important radiocarbon dates used to support the existence of an ice-free corridor were incorrect. He persuasively argued that such an ice-free corridor did not exist until much later, when the continental ice began its final retreat.

1. According to paragraph 1, the theory that people first migrated to the Americans by way of an ice-free corridor was seriously called into question by

A. paleoecologist Glen MacDonald's argument that the original migration occurred much later than had previously been believed

B. the demonstration that certain previously accepted radiocarbon dates were incorrect

C. evidence that the continental ice began its final retreat much later than had previously been believed

D. research showing that the ice-free corridor was not as long lasting as had been widely assumed

2. The word “persuasively” in the passage is closest in meaning to

A. aggressively

B. inflexibly

C. convincingly

D. carefully

► Paragraph 2: Support is growing for the alternative theory that people using watercraft, possibly skin boats, moved southward from Beringia along the Gulf of Alaska and then southward along the Northwest coast of North America possibly as early as 16,000 years ago. This route would have enabled humans to enter southern areas of the Americas prior to the melting of the continental glaciers. Until the early 1970s, most archaeologists did not consider the coast a possible migration route into the Americas because geologists originally believed that during the last Ice Age the entire Northwest Coast was covered by glacial ice. It had been assumed that the ice extended westward from the Alaskan/Canadian mountains to the very edge of the continental shelf, the flat, submerged part of the continent that extends into the ocean. This would have created a barrier of ice extending from the Alaska Peninsula, through the Gulf of Alaska and southward along the Northwest Coast of north America to what is today the state of Washington.

3. Paragraph 2 begins by presenting a theory and then goes on to

A. discuss why the theory was rapidly accepted but then rejected

B. present the evidence on which the theory was based

C. cite evidence that now shows that the theory is incorrect

D. explain why the theory was not initially considered plausible

4. The phrase “prior to” is closest in meaning to

A. before

B. immediately after

C. during

D. in spite of

5. Paragraph 2 supports the idea that, before the 1970s, most archaeologists held which of the following views about the earliest people to reach the Americas?

A. They could not have sailed directly from Beringia to Alaska and then southward because, it was thought, glacial ice covered the entire coastal region.

B. They were not aware that the climate would continue to become milder.

C. They would have had no interest in migrating southward from Beringia until after the continental glaciers had begun to melt.

D. They lacked the navigational skills and appropriate boats needed long-distance trips.

► Paragraph 3: The most influential proponent of the coastal migration route has been Canadian archaeologist Knut Fladmark. He theorized that with the use of watercraft, people gradually colonized unglaciated refuges and areas along the continental shelf exposed by the lower sea level. Fladmark’s hypothesis received additional support form from the fact that the greatest diversity in native American languages occurs along the west coast of the Americas, suggesting that this region has been settled the longest.

6. 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 to leave out essential information.

A. Because this region has been settled the longest, it also displays the greatest diversity in Native American languages.

B. Fladmark's hypothesis states that the west coast of the Americas has been settled longer than any other region.

C. The fact that the greatest diversity of Native American languages occurs along the west coast of the Americans lends strength to Fladmark’s hypothesis.

D. According to Fladmark, Native American languages have survived the longest along the west coast of the Americas.

► Paragraph 4：More recent geologic studies documented deglaciation and the existence of ice-free areas throughout major coastal areas of British Columbia, Canada, by 13,000 years ago. Research now indicates that sizable areas of southeastern Alaska along the inner continental shelf were not covered by ice toward the end of the last Ice Age. One study suggests that except for a 250-mile coastal area between southwestern British Columbia and Washington State, the Northwest Coast of North America was largely free of ice by approximately 16,000 years ago. Vast areas along the coast may have been deglaciated beginning around 16,000 years ago, possibly providing a coastal corridor for the movement of plants, animals, and humans sometime between 13,000 and 14,000 years ago.

7. The author's purpose in paragraph 4 is to

A. indicate that a number of recent geologic studies seem to provide support for the coastal hypothesis

B. indicate that coastal and inland migrations may have happened simultaneously

C. explain why humans may have reached America's northwest coast before animals and plants did

D. show that the coastal hypothesis may explain how people first reached Alaska but it cannot explain how people reached areas like modern British Columbia and Washington State

8. The word “Vast” in the passage is closest in meaning to

A. Frozen

B. Various

C. Isolated

D. Huge

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