首页
外语
计算机
考研
公务员
职业资格
财经
工程
司法
医学
专升本
自考
实用职业技能
登录
外语
IMPACTS AND MASS EXTINCTIONS (1) Meteorites and impact craters bear witness to the fact that large impacts occasionally occu
IMPACTS AND MASS EXTINCTIONS (1) Meteorites and impact craters bear witness to the fact that large impacts occasionally occu
admin
2022-09-29
54
问题
IMPACTS AND MASS EXTINCTIONS
(1) Meteorites and impact craters bear witness to the fact that large impacts occasionally occur on Earth. Barringer Meteor Crater in the northern Arizona desert of the United States formed about 50,000 years ago when a metallic impactor roughly 50 meters across crashed to Earth with the explosive power of a 20-megaton hydrogen bomb. Although the crater is only slightly more than one kilometer across, an area covering hundreds of square kilometers was probably battered by the blast and ejecta—the debris ejected or displaced during the formation of an impact crater. Far bigger impacts have occurred, sometimes with
catastrophic
consequences for life on Earth.
(2) While collecting geological samples in Italy in 1978, the father-son team of Luis and Walter Alvarez discovered a thin layer of dark sediment that had apparently been deposited 65 million years ago—at about the same time that the dinosaurs and many other organisms suddenly became extinct. Subsequent studies found similar sediment deposited at the same time at many sites around the world. Careful analysis showed this worldwide sediment layer to be rich in iridium, an element that is rare on Earth’s surface. But iridium is common in primitive meteorites, which led the Alvarezes to a stunning conclusion: the extinction of the dinosaurs was caused by the impact of an asteroid or comet. This conclusion was not immediately accepted and still generates some controversy, but it now seems clear that a major impact
coincided with
the death of the dinosaurs. While the dinosaurs were the most famous victims of this mass extinction, it seems that up to 99 percent of all living things were killed and that 75 percent of all species living on Earth were wiped out at that time.
(3) How could an impact lead to mass extinction? The amount of iridium deposited worldwide suggests that the impactor must have been about 10 kilometers across. After a decade-long search, scientists identified what appears to be the impact crater from the event. Located off the coast of Mexico’s Yucatan peninsula, it is 200 kilometers across, which is close to what one would expect for a 10-kilometer impactor, and dates to 65 million years ago. Further evidence that the Yucatan crater is the right one comes from the distribution of small glassy spheres that formed when the molten impact ejecta solidified as it rained back to Earth. [A] More of these glassy spheres are found in regions near the crater, and careful study of their distribution suggests that the impactor crashed to Earth at a slight angle. [B] These pieces of once molten rock are evidence of an explosion powerful enough to instantly melt bedrock and propel it far from its origin. [C] The impact almost immediately sent a shower of debris raining across much of North and South America and generated huge waves that may have sloshed more than 1,000 kilometers inland. [D] Many North American species thus may have been wiped out shortly after impact. For the rest of the world, death may have come more slowly. Heat from the impact and returning ejecta probably ignited wildfires in forests around the world. Evidence of wildfires is found in the large amount of soot (a black powdery form of carbon produced when coal, wood, or oil is burned) that is also present in the iridium-rich sediment from 65 million years ago. The impact also sent huge quantities of dust high into the stratosphere, where it remained for several years, blocking out sunlight, cooling the surface, and affecting atmospheric chemistry. Plants died for lack of sunlight, and effects
propagated
throughout the food chain.
(4) Perhaps the most, astonishing fact is not that 75 percent of all species died, but that 25 percent survived. Among the survivors were a few small, rodent-like mammals. These mammals may have survived because they lived in underground burrows and managed to store enough food to outlast the long spell of cold, dark days. Small mammals had first arisen at about the same time as the dinosaurs, more than 100 million years earlier. But the sudden disappearance of the dominant dinosaurs made these mammals dominant.
The word "catastrophic" in the passage is closest in meaning to ________.
选项
A、widespread
B、disastrous
C、important
D、immediate
答案
B
解析
本题属于同汇题,考查考生对catastrophic的理解。题干所问单词意为“灾难性的”,B项disastrous同样意为“灾难性的”,为catastrophic的同义词,故选。A项widespread“广泛的”、C项important“重要的”和D项immediate“立刻的”均与catastrophic的意思相差甚远。
转载请注明原文地址:https://kaotiyun.com/show/aE5O777K
0
托福(TOEFL)
相关试题推荐
Completethenotesbelow.WriteNOMORETHANTHREEWORDSAND/ORANUMBERforeachanswer.
TransportfromBayswaterExampleDestinationHarbourCityExpresstrainleavesat【L1】________The【L2】________i
Choosethecorrectletter,A,B,orC.WhywasJeninvitedtotheprofessor’spersonalproject?
StrategiesforeffectiveuseoflecturesDosome【L25】________【L26】________andsitwhereyoucanseeandheareasily.Be【L27】___
TheTawnyOwlMost【L31】________owlspeciesinUKStronglynocturnalHabitatMainlylivesin【L32】________,butcanalsobeseeni
ChoosethecorrectletterA,BorC.Accordingtothelecturer,postgraduatecourseis
Choosethecorrectletter,A,BorC.WhyshouldHuntergiveacopyofplanstotheprofessor?
Whichofthefollowingdoesthepassagemainlydiscuss?Itcanbeinferredfromthelastparagraphthataglacier
TheprofessorexplainedmanydirectcausesofthemassextinctionsthatweresupposedlyproducedbytheK-Tasteroidimpact.Ind
随机试题
假设你是一家家电公司的客户服务部经理,负责处理顾客投诉并解决善后问题。你接到了一顾客电话,声称他购买的电器在保质期内出了故障,其原因是电器内部的零件中使用了二手产品,他保留了样品,要求你公司做出解释。请你给此顾客一封信,表明公司正视该问题并进行调查和处
与呼吸运动功能无关的是
建设工程施工劳务分包合同中,关于劳务报酬计取,下列说法不正确的是( )。
根据《税务行政复议规则(暂行)》规定,纳税人对()不服的案件应当先依法申请复议,对复议决定不服可以再依法向人民法院起诉。
工程师李某一次性获得设计费30000元,从其收入中支付中介费5000元,李某应缴纳的个人所得税为( )元。
在某高级小区里,有许多女性住户是“全职太太”,她们的主要任务就是照顾好丈夫和孩子的饮食起居,几乎没有自己的休闲时间。王正红就是这个群体中的一员,她在成为全职太太前是某小学的音乐教师。为了照顾这个家庭,她生了宝宝之后就放弃了原本稳定的教师工作,这让她感到很不
2012年度,某县政府在扫黄活动中抓获十余名涉嫌卖淫嫖娼的违法人员,为扩大教育警示作用,在公开处理的现场,警方逐一宣读涉案人员的姓名、出生日期和籍贯,并宣布处罚决定,然后游行示众。现场一千余人围观。该事件经媒体报道后引起广泛社会反响。有学者提出质疑,认为警
0,0.5,2,3,8,(),210
使用约束可以保证数据库中数据的正确性,其中【8】约束允许出现空值但不允许出现重复值。
A、晴天B、雨天C、寒冷D、大风B“这几天太潮湿”是关键词,潮湿的天气应该是雨天,所以选择B。
最新回复
(
0
)