Unformatted text preview: ph 1: There is increasing evidence that the impacts of meteorites have had important effects on Earth, particularly in the field of biological evolution. Such impacts continue to pose a natural hazard to life on Earth. Twice in the twentieth century, large meteorite objects are known to have collided with Earth.
1. The word in the passage is closest in the meaning to pose ○Claim
Paragraph 2: If an impact is large enough, it can disturb the environment of the entire Earth and cause an ecological catastrophe. The bestdocumented such impact took place 65 million years ago at the end of the Cretaceous period of geological history. This break in Earth's history is marked by a mass extinction, when as many as half the species on the planet became extinct. While there are a dozen or more mass extinctions in the geological record, the Cretaceous mass extinction has always intrigued paleontologists because it marks the end of the age of the dinosaurs. For tens of millions of years, those great creatures had flourished. Then, suddenly, they disappeared.
2. In paragraph 2, why does the author include the information that dinosaurs had flourished for tens of millions of years and then suddenly disappeared? ○To support the claim that the mass extinction at the end of the Cretaceous is the bestdocumented of the dozen or so mass extinctions in the geological record ○To explain why as many as half of the species on Earth at the time are believed to have become extinct at the end of the Cretaceous ○To explain why paleontologists have always been intrigued by the mass extinction at the end of the Cretaceous ○To provide evidence that an impact can be large enough to disturb the environment of the entire planet and cause an ecological disaster
Paragraph 3: The body that impacted Earth at the end of the Cretaceous period was a meteorite with a mass of more than a trillion tons and a diameter of at least 10 kilometers. Scientists first identified this impact in 1980 from the worldwide layer of sediment deposited from the dust cloud that enveloped the planet after the impact. This sediment layer is enriched in the rare metal iridium and other elements that are relatively abundant in a meteorite but very rare in the crust of Earth. Even diluted by the terrestrial material excavated from the crater, this component of meteorites is easily identified. By 1990 geologists had located the impact site itself in the Yucat region of Mexico. The crater, now deeply buried in sediment, was originally about 200 kilometers in diameter. 3. Which of the following can be inferred from paragraph 3 about the location of the meteorite impact in Mexico? ○The location of the impact site in Mexico was kept secret by geologists from 1980 to 1990.
○It was a well-known fact that the impact had occurred in the Yucat region.
○Geologists knew that there had been an impact before they knew where it had occurred.
[email protected] 在在在在在在 www.liuwenyong.c...
View Full Document
This note was uploaded on 09/17/2013 for the course LANGUAGE 13DL208 taught by Professor Wang during the Fall '13 term at East China Normal University.
- Fall '13