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Meteorite Impact and Dinosaur Extinction
(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.
(2) If an impact is large enough, it can disturb the environment of the entire Earth and cause an ecological catastrophe. The best-documented 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 10 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.
(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 Yucatán region of Mexico. The crater, now deeply buried in sediment, was originally about 200 kilometers in diameter.
(4) This impact released an enormous amount of energy, excavating a crater about twice as large as the lunar crater Tycho. The explosion lifted about 100 trillion tons of dust into the atmosphere, as can be determined by measuring the thickness of the sediment layer formed when this dust settled to the surface. Such a quantity of material would have blocked the sunlight completely from reaching the surface, plunging Earth into a period 30 of cold and darkness that lasted at least several months. The explosion is also calculated to have produced vast quantities of nitric acid and melted rock that sprayed out over much of Earth, starting widespread fires that must have consumed most terrestrial forests and grassland. Presumably, those environmental disasters could have been responsible for the mass extinction, including the death of the dinosaurs.
(5) Several other mass extinctions in the geological record have been tentatively identified with large impacts, but none is so dramatic as the Cretaceous event. But even without such specific documentation, it is clear that impacts of this size do occur and that their results can be catastrophic. What is a catastrophe for one group of living things, however, 40 may create opportunities for another group. Following each mass extinction, there is a sudden evolutionary burst as new species develop to fill the ecological niches opened by the event.
(6) Impacts by meteorites represent one mechanism that could cause global catastrophes and seriously influence the evolution of life all over the planet. According to some estimates, the majority of all extinctions of species may be due to such impacts. Such a perspective fundamentally changes our view of biological evolution. The standard criterion for the survival of a species is its success in competing with other species and adapting to slowly changing environments. Yet an equally important criterion is the ability of a species to survive random global ecological catastrophes due to impacts.
(7) Earth is a target in a cosmic shooting gallery, subject to random violent events that were unsuspected a few decades ago. In 1991 the United States Congress asked NASA to investigate the hazard posed today by large impacts on Earth. The group conducting the 55 study concluded from a detailed analysis that impacts from meteorites can indeed be hazardous. Although there is always some risk that a large impact could occur, careful study shows that this risk is quite small.
Take the quiz after reading the passage:https://www.examtime.com/p/1018847-TOEFL-Practice-Quiz--See-Passage-1--quizzes
(Narrator) Listen to a conversation between a student and her basketball coach and then answer the questions. (Male coach) Hi, Elizabeth. (Female student) Hey, Coach. I just thought I’d stop by to see what I missed while I was gone. (Male coach) Well, we’ve been working real hard on our plan for the next game . . . I’ve asked Susan to go over it with you before practice this afternoon, so you’ll know what we’re doing. (Female student) Okay. (Male coach) By the way, how did your brother’s wedding go? (Female student) Oh, it was beautiful. And the whole family was there. I saw aunts and uncles and cousins I hadn’t seen in years. (Male coach) So it was worth the trip. (Female student) Oh definitely. I’m sorry I had to miss practice, though. I feel bad about that. (Male coach) Family’s very important. (Female student) Yep. Okay, I guess I’ll see you this afternoon at practice, then. (Male coach) Just a minute. There are a couple of other things I need to tell you. (Female student) Oh, okay. (Male coach) Uh . . . First, everybody’s getting a new team jacket. (Female student) Wow. How did that happen? (Male coach) A woman who played here about 20, 25 years ago came through town a few weeks ago and saw a game, and said she wanted to do something for the team, so . . . (Female student) So she’s buying us new jackets? (Male coach) Yep. (Female student) Wow, that’s really nice of her. (Male coach) Yes, it is. It’s great that former players still care so much about our school and our basketball program . . . Anyway you need to fill out an order form. I’ll give it to you now, and you can bring it back this afternoon. I’ve got the forms from the other players, so as soon as I get yours we can order. Maybe we’ll have the jackets by the next game. (Female student) OK. (Male coach) Great. And the next thing is, you know Mary’s transferring to another college next week, so we’ll need someone to take over her role as captain for the second half of the season. And the other players unanimously picked you to take over as captain when Mary leaves. (Female student) Wow. I saw everybody this morning, and nobody said a word. (Male coach) They wanted me to tell you. So, do you accept? (Female student) Of course! But Susan’s a much better player than I am. I’m really surprised they didn’t pick her. (Male coach) They think you’re the right one. You’ll have to ask them their thoughts. (Female student) Okay . . . I guess one of the first things I’ll have to do as captain is make sure we get a thank-you card out to the lady who’s buying us the jackets. (Male coach) Good idea. I have her address here somewhere. (Female student) And I’ll make sure the whole team signs it. (Male coach) Good. That’s all the news there is. I think that’s it for now. Oh, let me get you that order form.
Conversation Section:
(Male professor) Today I’d like to introduce you to a novel that some critics consider the finest detective novel ever written. It was also the first. We’re talking about The Moonstone by Wilkie Collins. Now, there are other detective stories that preceded The Moonstone historically—Um, notably the work of Poe . . . Edgar Allen Poe’s stories, such as “The Murders in the Rue Morgue” and . . . “The Purloined Letter.” Now these were short stories that featured a detective . . . uh, probably the first to do that. But The Moonstone, which follows them by about twenty years—it was published in 1868—this is the first full-length detective novel ever written.Now, in The Moonstone - if you read it as . . . uh, come to it as a contemporary reader— what’s interesting is that most of the features you find in almost any detective novel are in fact already present. Uh, its hard at this juncture to read this novel and realize that no one had ever done that before, because it all seems so strikingly familiar. It’s, it’s really a wonderful novel and I recommend it, even just as a fun book to read, if you’ve never read it. Um, so in The Moonstone, as I said, Collins did much to establish the conventions of the detective genre. I'm not gonna go into the plot at length, but, you know, the basic set is ... there's this diamond of great ... of great value, a country house, the diamond mysteriously disappears in the middle of the night, uh, the local police are brought in, in an attempt to solve the crime, and they mess it up completely, and then the true hero of the book arrives. That's Sergeant Cuff. Now, Cuff, this extraordinarily important character . . . well, let me try to give you a sense of who Sergeant Cuff is, by first describing the regular police. And this is the dynamic that you’re going to see throughout the history of the detective novel, where you have the regular cops—who are well-meaning, but officious and bumblingly inept—and they are countered by a figure who’s eccentric, analytical, brilliant, and . . . and able to solve the crime. So, first the regular police get called in to solve the mystery—Um, in this case, detective, uh, Superintendent Seegrave. When Superintendent Seegrave comes in, he orders his minions around, they bumble, and they actually make a mess of the investigation, which you’ll see repeated—um, you’ll see this pattern repeated, particularly in the Sherlock Holmes stories of a few years later where, uh, Inspector Lestrade, this well-meaning idiot, is always countered, uh, by Sherlock Holmes, who’s a genius.So, now Cuff arrives. Cuff is the man who’s coming to solve the mystery, and again he has a lot of the characteristics that future detectives throughout the history of this genre will have. He’s eccentric. He has a hobby that he’s obsessive about—in this . . . in his case, it’s the love of roses. He’s a fanatic about the breeding of roses; and here think of Nero Wolfe and his orchids, Sherlock Holmes and his violin, a lot of those later classic detective heroes have this kind of outside interest that they . . . they go to as a kind of antidote to the evil and misery they encounter in their daily lives. At one point, Cuff says he likes his roses because they offer solace, uh, an escape, from the world of crime he typically operates in. Now, these detective heroes . . . they have this characteristic of being smart, incredibly smart, but of not appearing to be smart. And most importantly, from a kind of existential point of view, these detectives see things that other people do not see. And that’s why the detective is such an important figure, I think, in our modern imagination. In the case of The Moonstone—I don’t want to say too much here and spoil it for you—but the clue that’s key to . . . the solving of the crime is a smeared bit of paint in a doorway. Of course, the regular police have missed this paint smear or made some sort of unwarranted assumption about it. Cuff sees this smear of paint—this paint, the place where the paint is smeared—and realizes that from this one smear of paint you can actually deduce the whole situation . . . the whole world. And that’s what the hero in a detective novel like this . . . brings to it that the other characters don’t—it’s this ability to, uh, see meaning where others see no meaning and to bring order . . . to where it seems there is no order.
Lecture Transcript
Take the quiz after reading this passage along with passage 3:https://www.examtime.com/en-US/p/1020794
Take the quiz after reading this passage along with passage 2:https://www.examtime.com/en-US/p/1020794
Passge 1
passage 2
passage 3
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