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
2023-10-19
65
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/3112554.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
TheBritishgovernmentrecentlyannouncedaproposaltointroducehealthcar
艾滋病的主要传播途径为A.母婴传播 B.共同进餐 C.握手 D.拥抱 E
可适用于各级公路的面层类型是()。A.沥青混凝土路面 B.水泥混凝土路面
关于级配碎石的最大干密度和最佳含水率试验,以下分析正确的是()。A.击实法
下列关于腹部损伤的描述正确的是A.肝、脾损伤的主要临床表现为弥漫性腹膜炎 B.
根据《社会保险法》,下列人员中,属于自愿参保人的是()。A.未签订劳动合同的自
下列哪种说法是错误的?( ) A.通过互联网将国家秘密非法发送给境外的机构的
流动资金贷款是指银行向()发放的用于满足个人控制的企业(包括个体工商户)生产经营
结构化产品市场中的投资者或者某个机构的交易员,其参与的目的在于从产品定价偏差中获
某公司对海关征收滞纳金的行为不服,可以向上一级海关提起行政复议,也可以直接到人
最新回复
(
0
)