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SAT考试9月每日精选题(48)

2017年09月26日 12:02:10来源:SAT考试网
导读:今天,让我们继续进行SAT考试9月每日精选题练习,深入的了解SAT,提升SAT知识。趁这次机会,正在紧张备考的你可以检验一下自己的水平,发现自己的问题,有目的的提升更加有效哦!不要走开,练习即将开始!

>>SAT考试练习:SAT考试9月每日精选题(48)

>>SAT考试辅导:精品课程高端指导

Critical Reading>Select an Answer

Four billion years ago, Earth's continents began taking shape. Scientists long held that this process unfolded gradually. It would have taken millions of years for granite, the primary component of the continental crust, to form in the mantle and migrate to the upper crust, they reasoned. But new research suggests that these events may have proceeded at rather a different pace. According to a report published in the journal Nature, the emergence of granite occurred by way of swift, dynamic and possibly catastrophic events lasting from 1,000 to 100,000 years.

Geologist Alexander Cruden of the University of Toronto and his colleagues turned to experimental studies—melting rock samples, for example—to explore how granite magma forms and how fast it can move. Their results proved surprising. "In the past we thought that granite magma, which cools and crystallizes to form very large granite intrusions, moved up through kilometers of crust as large, solid blobs at rates of about a meter per year," Cruden says. "But we've found that magma actually has quite low viscosity and is relatively runny. Because it is runny, it is able to channel its way from the mantle and lower crust through fractures and cracks that are as small as one meter thick."

According to this model, granite intrusions in Greenland or the Canadian Shield, depending on their size, would have taken only thousands of years to form, which is extraordinarily fast from a geological point of view, Cruden notes.

The first paragraph of this passage serves primarily to __________

(A) introduce two competing explanations of a natural phenomenon.

(B) establish the validity of evidence supporting a new scientific theory.

(C) compare and contrast two perspectives on a recent discovery.

(D) present a detailed timeline of advances in a field of study.

小编提醒各位参加准备sat考试的同学,仔细看完以上的sat考试官网题目,然后再看下面的SAT题目答案更有效哦。

答案:A

解析:

Choice A is the best answer. The first paragraphpresents two different explanations for theformation of Earth's continents. The idea "longheld" by scientists is that the formation "unfoldedgradually" over "millions of years." The other idea, sparked by recent research, is that theformation occurred in a relatively "swift" period of "1,000 to 100,000 years."

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