問題詳情

請依下文回答第 44 題至第 47 題 Some 66m years ago Earth was hit by a space rock reckoned to have been 10km across. The resulting chaoscaused the extinction of dinosaurs and many other species, opening the way for the age of mammals－and ultimatelyhumans. It also left a big hole in what is now southern Mexico. That hole is one of only three known of similardimensions (the other two are Vredefort in South Africa and Sudbury in Canada). And this is odd. For, during thebillions of years that Earth has had a solid crust, many more than three big asteroids might have been expected to havehit it. That thought led Brandon Johnson of the MIT and Timothy Bowling of Purdue University in Indiana, to wonderhow many other craters have vanished, either by erosion or by being swallowed into Earth’s interior as its crust movesaround, and therefore whether it is likely that some have survived and been overlooked. They have just published theiranalysis in Geology. Earth’s crust formed more than 4 billion years ago, but the oldest surviving blocks of it large enough to harborcraters date back only 3.5 billion years. What is known of the sizes and orbits of modern asteroids suggests that, ifthings have not changed over the aeons, about 14 big asteroids (defined as having a diameter of more than 7.4km,which would cause a crater at least 85km in diameter) should hit Earth every billion years. That means 49, give or takeseven, over the past 3.5 billion years. Such impacts may have been more common in the past, when more big asteroidswere around. Allowing for this, Earth would have been hit by 113, give or take 11, of them. Either way, a lot of cratersare missing.
44 How large is the crater created in southern Mexico by the asteroid 66m years ago?
(A)10km across in diameter.
(B)85km in diameter.
(C)7.4km in diameter.
(D)Not mentioned in the article. 

參考答案

答案：D
難度：困難0.351351
統計：A(57),B(9),C(5),D(39),E(0)

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