TPO72阅读真题+题目+答案下载：The Impact Origin of Lunar Craters

TPO72阅读真题+题目+答案下载：The Impact Origin of Lunar Craters

From their discovery in 1609 until recently, lunar craters were almost unanimously thought to have volcanic origins, even though the topography of the Moon and its craters had been studied minutely by generations of observers. Dissenting voices, such as that of Robert Hooke, who postulated in 1665 that they were formed by the impact of meteors, did little to sway the majority opinion. The most serious challenge to the volcanic-formation hypothesis was made in 1893 by the geologist G. K. Gilbert. After analyzing the depth-to-diameter ratios of craters, Gilbert suggested that the craters could have been formed only by the impact of meteors. The central peaks that were commonly observed resulted from rebound of rock, in a similar manner to liquids (think of drops of water hitting a puddle). Bright rays surrounded many craters that were formed from material flung out during the impact---impact ejecta.

Although impacts with a surface can occur at all angles, from less than 5° to 90°, early experiments suggested that only vertical (90°) impacts were capable of producing circular craters. So the main argument against an impact mechanism for lunar crater formation was that only circular craters could be seen on the Moon. However, Gilbert himself showed that the average impact angle was 45° — in fact, very few impacts were close to vertical.

........余下托福TPO72阅读原文省略！

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

A confusing

B forceful

C opposing

D respected

2.The author mentions “drops of water hitting a puddle” in the passage for which of the following reasons?

A To illustrate the behavior of liquids under pressure

B To demonstrate common eruption patterns of volcanoes

C To help readers perceive flaws in G. K. Gilberf’s ideas

D To help readers imagine how lunar craters formed

3.According to paragraphs 1 and 2, which of the following seemed to disprove Gilbert’s theory of lunar crater creation?

A Only circular craters could be seen on the Moon.

B The impact of meteors striking the Moon could not be observed

C Impact craters like those on Earth are not visible on the Moon

D Materials surrounding the lunar craters were volcanic in origin

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