首页
登录
职称英语
The dinosaurs are dead.They ruled the world for millions of years—but on
The dinosaurs are dead.They ruled the world for millions of years—but on
游客
2024-08-19
18
管理
问题
The dinosaurs are dead.They ruled the world for millions of years—but once the last one died, that was it.There were no more Maiasaura to nurture reptile babies, no fierce Tyrannosaurus, no more spiked Ankylosaurus.
Dinosaurs are just one of many groups of animals that no longer exist.Scientists don’t always know why animals become extinct.They try to look at different kinds of evidence for answers.The first place scientists look is rocks.Rocks reveal the unusual conditions that might have taken place while the animals lived.
One popular explanation for the disappearance of dinosaurs is that a large asteroid (小行星)hit Earth 65 million years ago.Dust from the impact could have spread over the whole planet.The dust would have dimmed the sun and killed many plants.Animals that ate plants would have starved, causing the animals that preyed on them to die off also.
If an asteroid collision really happened, scientists would find iridium (铱,化学元素)in rocks that are about 65 million years old.This rare element is added to Earth’s crust when asteroids hit Earth.It just so happens that around the world, many rocks created at that time do have high amounts of iridium.An asteroid impact would have blown a huge hole in Earth’s surface.In fact, a giant crater (大坑) was found just off the coast of Mexico.Scientists believe it is about 65 million years old.
Scientists know that dinosaurs vanished around the same time as this asteroid collision.Are the two events related? To find out, scientists need to study the bones of animals that lived then.
Dinosaurs were not the only animals alive when the asteroid struck Earth.What happened to other groups of creatures? Most frogs, for example, were not affected by the disaster.Most fish were fine too, as were lizards and mammals.Why did these animals go on living, when dinosaurs did not? Is it possible that the dinosaurs disappeared for a different reason?
Scientists have found fewer and fewer species of dinosaur fossils from the years before dinosaurs vanished altogether.This suggests that dinosaurs disappeared slowly, over thousands and millions of years, not in one crash of an asteroid.It’s possible that dinosaurs did not compete well with the clever, warmblooded mammals that ere increasing in numbers on Earth.
Right now no one can say for sure what caused the death of the dinosaurs.There’s a lot more work to do—in many areas of science. [br] Where was the giant crater found?
选项
答案
It was found off the coast of Mexico.
解析
转载请注明原文地址:https://tihaiku.com/zcyy/3727124.html
相关试题推荐
Singleandlookingforlove?Howaboutadvertisingyourselftomillionsofp
Singleandlookingforlove?Howaboutadvertisingyourselftomillionsofp
Thedinosaursaredead.Theyruledtheworldformillionsofyears—buton
ThedinosaursprobablybecameextinctafteragiantasteroidhittheEarthabout
Millionsoftelevisionsetsandoldcomputermonitorstakentocivicamenity
Millionsoftelevisionsetsandoldcomputermonitorstakentocivicamenity
Millionsoftelevisionsetsandoldcomputermonitorstakentocivicamenity
Millionsoftelevisionsetsandoldcomputermonitorstakentocivicamenity
Millionsoftelevisionsetsandoldcomputermonitorstakentocivicamenity
Millionsoftelevisionsetsandoldcomputermonitorstakentocivicamenity
随机试题
IntheUnitedStates,PresidentBarackObamahasreversedlong-standingDemo
Toachorusofangryshoutsandinsults,a【C1】______(wealth)Chicagocouple
Hearingwewill_______candies,thechildrensuddenlygatheraroundus.A、assign
教育的本质决定了高校的基本职能是()。A.培养人才 B.科学研究 C.服务
建立最广泛的统一战线,首先是由中国半殖民地半封建社会的阶级状况所决定的。近代中国
共用题干 资料2013年3月,甲、乙、丙、丁发起设立A科技股份有限公司(以下简
亚非国家和地区第一次在没有殖民国家参加的情况下召开的会议是()。A.开罗宣言
王某妻子早亡。其独自抚养儿子王勇和女儿王芳。王勇在与张萍结婚三年后去世。两人并未
( )是订立合同所必须经过的程序,是一方当事人以缔结合同为目的,向对方当事人所
(2016年真题)某商住地产项目,一至四层为商业服务设施(包括中餐餐饮),五层及
最新回复
(
0
)