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
27
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.
According to paragraph 4, all of the following are true of the animals that survived the impact EXCEPT________.
选项
A、they probably had a lot of food stored up.
B、many lived underground.
C、most were relatively new species.
D、they tended to be small.
答案
C
解析
本题属于否定事实信息题,问根据第4段,哪项关于撞击中幸存的动物的叙述不正确。本题可用排除法。第4段第2句提到,幸存的物种是一些小型啮齿动物(a few small…mammals)。对应D项。接着第3句提到它们幸存的原因:一、生活在地下洞穴中,对应B项;二、储存了足够的食物,对应A项。故A、B、D三项均可在原文找到依据,不符合题意,本题选C项。
转载请注明原文地址:https://kaotiyun.com/show/SE5O777K
0
托福(TOEFL)
相关试题推荐
TransportfromBayswaterExampleDestinationHarbourCityExpresstrainleavesat【L1】________The【L2】________i
Labelthemapbelow.Writethecorrectletter,A-L,nexttoQuestions11-16.Studentdormitory
Whatspecialconditionsapplytothefollowingrides?ChooseFOURanswersfromtheboxandwritethecorrectletter,A-F,nextt
StrategiesforeffectiveuseoflecturesDosome【L25】________【L26】________andsitwhereyoucanseeandheareasily.Be【L27】___
Choosethecorrectletter,A,BorC.Thetutorclaimsshedoesnotunderstandwhether
ImpactofUrbanizationTheeffectsofurbanization:Example:intheU.S.only【L31】________oflandbuiltonlossof【L32】________
ImpactofUrbanizationTheeffectsofurbanization:Example:intheU.S.only【L31】________oflandbuiltonlossof【L32】________
ChooseTWOletters,A-E.WhichTWOproblemsdoesGroveridentifyconcerningthelecturers?APunctuality.BOrganisation.C
Whichofthefollowingdoesthepassagemainlydiscuss?Intemperateglaciers,whereiswaterfound?
Whydoestheprofessorbeginthelecturebydescribingthedestructiveforceofanasteroidimpact?
随机试题
The______sizeofanairplaneintheskyissmallerthantheairplanereallyis.
—Haveyoubeenpaidforthepainting?—Yes,Iremember______$60forit.
下列哪项不是肉毒梭菌的特
A.痰厥B.食厥C.血厥D.气厥E.暑厥
人群作为一个整体对传染病易感程度称为一种疾病从一个宿主传播给其他宿主的难易性称为
微机视屏显示终端(VDT)操作人员,由于静态负荷,频繁操纵键盘,头部经常转动,手臂悬空,最易引起
土地增值税实行()税率。
2019年3月,某审计组对丙上市公司2018年度财务收支情况进行审计。有关固定资产业务审计的情况和资料如下:1.审计人员对该公司固定资产的内部控制进行测评后,确定实质性测试的范围和重点。2.2018年1月至5月,该公司对旧厂房进行改扩建,有关情况如下
下列各项中,影响利润总额的有()。
下列不属于前期物业管理期间物业服务企业从事的活动和提供的服务的是()。
最新回复
(
0
)