海巡三等
105年
[海洋巡護科輪機組] 法學知識與英文(包括中華民國憲法、法學緒論、英文)
第 44 題
📖 題組：
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 chaos caused the extinction of dinosaurs and many other species, opening the way for the age of mammals－and ultimately humans. It also left a big hole in what is now southern Mexico. That hole is one of only three known of similar dimensions (the other two are Vredefort in South Africa and Sudbury in Canada). And this is odd. For, during the billions of years that Earth has had a solid crust, many more than three big asteroids might have been expected to have hit it. That thought led Brandon Johnson of the MIT and Timothy Bowling of Purdue University in Indiana, to wonder how many other craters have vanished, either by erosion or by being swallowed into Earth’s interior as its crust moves around, and therefore whether it is likely that some have survived and been overlooked. They have just published their analysis in Geology. Earth’s crust formed more than 4 billion years ago, but the oldest surviving blocks of it large enough to harbor craters date back only 3.5 billion years. What is known of the sizes and orbits of modern asteroids suggests that, if things 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 take seven, over the past 3.5 billion years. Such impacts may have been more common in the past, when more big asteroids were around. Allowing for this, Earth would have been hit by 113, give or take 11, of them. Either way, a lot of craters are missing.
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 chaos caused the extinction of dinosaurs and many other species, opening the way for the age of mammals－and ultimately humans. It also left a big hole in what is now southern Mexico. That hole is one of only three known of similar dimensions (the other two are Vredefort in South Africa and Sudbury in Canada). And this is odd. For, during the billions of years that Earth has had a solid crust, many more than three big asteroids might have been expected to have hit it. That thought led Brandon Johnson of the MIT and Timothy Bowling of Purdue University in Indiana, to wonder how many other craters have vanished, either by erosion or by being swallowed into Earth’s interior as its crust moves around, and therefore whether it is likely that some have survived and been overlooked. They have just published their analysis in Geology. Earth’s crust formed more than 4 billion years ago, but the oldest surviving blocks of it large enough to harbor craters date back only 3.5 billion years. What is known of the sizes and orbits of modern asteroids suggests that, if things 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 take seven, over the past 3.5 billion years. Such impacts may have been more common in the past, when more big asteroids were around. Allowing for this, Earth would have been hit by 113, give or take 11, of them. Either way, a lot of craters are missing.
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.
思路引導 VIP
請回頭掃描文章中出現的所有長度單位（如 km）。接著問問自己：這個數字是在描述「撞擊地球的那顆石頭」，還是在描述「撞擊後留下的那個大洞」？有沒有哪一個數字是專門用來標註「墨西哥那個洞」的大小呢？
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AI 詳解
AI 專屬家教
哇！你表現得真棒，觀察力非常細心喔！
你答對了這題，這代表你是一位很會抓重點的閱讀者，沒有被文章中多個數字給搞混呢！
- 一起來確認觀念喔：在文章第一段，$10\text{km}$ 指的是「隕石自己的直徑」。而第三段提到的 $7.4\text{km}$ 和 $85\text{km}$，其實是用來定義「大型隕石」以及它「預期會造成的坑洞」的一般性標準。雖然文章有提到墨西哥那邊有個「大洞（big hole）」，但你仔細看，文章從來都沒有直接說出那個墨西哥坑洞的實際尺寸喔。所以，選擇 (D) 就是最正確的答案了！
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