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
考研
There are some earth phenomena you can count on, but the magnetic field, some say, is not one of them. It fluctuates in strength
There are some earth phenomena you can count on, but the magnetic field, some say, is not one of them. It fluctuates in strength
admin
2015-01-15
55
问题
There are some earth phenomena you can count on, but the magnetic field, some say, is not one of them. It fluctuates in strength, drifts from its axis, and every few 100,000 years undergoes a dramatic polarity reversal—a period when north pole becomes south pole and south pole becomes north pole. But how is the field generated, and why is it so unstable?
Groundbreaking research by two French geophysicists promises to shed some light on the mystery. Using 80 metres of deep sea sediment(沉淀物)core, they have obtained measurements of magnetic-field intensity that span 11 polarity reversals and four million years. The analysis reveals that intensity appears to fluctuate with a clear, well-defined rhythm. Although the strength of the magnetic field varies irregularly during the short terra, there seems to be an inevitable long-term decline preceding each polarity reversal. When the poles flip—a process that takes several hundred of thousand years—the magnetic field rapidly regains its strength and the cycle is repeated.
The results have caused a stir among geophysicists. The magnetic field is thought to originate from molten(熔化的)iron in the outer core, 3,000 kilometers beneath the earth’s surface. By studying mineral grains found in material ranging from rocks to clay articles, previous researchers have already been able to identify reversals dating back 170 million years, including the most recent switch 730,000 years ago. How and why they occur, however, has been widely debated. Several theories link polarity flips to external disasters such as meteor(陨星)impacts. But Peter Olson, a geophysicist at the Johns Hopkins University in Baltimore, says this is unlikely if the French researchers are right. In fact, Olson says intensity that predictably declines from one reversal to the next contradicts 90 percent of the models currently under study. If the results prove to be valid, geo-physicists will have a new theory to guide them in their quest to understand the earth’s inner physics. It certainly points the direction for future research.
The word "flip"(Line 7, Para. 2)most probably means______.
选项
A、decline
B、intensify
C、fluctuate
D、reverse
答案
D
解析
根据文章不难看出,the poles flip指的就是地球南北两极的转移、倒转;de—cline意为“倾斜;拒绝;跌落;衰败”,intensify意为“使强烈,增加强度;变强,增强”;fluctuate表示“波动,升降,涨落不定”;reverse意为“颠倒,倒转;反转,倒行”。可见,D项reverse的意思和flip最接近。
转载请注明原文地址:https://www.kaotiyun.com/show/Uqhi777K
0
在职申硕(同等学力)英语
相关试题推荐
Thewordscienceisheardsoofteninmoderntimesthatalmosteverybodyhassomenotionofitsmeaning.Ontheotherhand,its
AEachculturehasitsowndistinctiveBwaysofseeing,feeling,thinking,speaking,believing,andCjustlikenotwohumansare
Manyobserversbelievethatcountrywillremaininastateofchaosifitfailstosolveitschronicfoodshortageproblem.
Revengeisoneofthosethingsthateveryoneenjoys.Peopledon’tliketotalkaboutit,though.Justthesame,thereisnothing
Somepeoplefeelsadaboutglobalizationbecausetheybelieveitwill______Whatisthewriter’sattitudetowardsglobalizatio
Seniorcitizensareadvisedtogoinforsomecreativeactivitiestokeepthemselvesmentallyyoung.
Whywasthehydraulicfuelpumpsealimportantforthespaceshuttle?WhichofthefollowingisNOTTRUEaccordingtowhatVoss
(That)thewoman(wassaying)wassoimportantthatIaskedeveryone(tostop)talkingand(listen).
Wewantyoutodescribealltheeventsofthatmorninginsequencewithoutanydelay.
Daltonwonderedwhytheheavierandlightergasesintheatmospheredidnotseparateasoilandwaterdo.Hefinallyconcludedt
随机试题
下列哪种疾病可出现急性腹痛
A.左心室增大B.右心室增大C.左心房增大D.右心房增大E.左心房、心室均增大在左侧位,心后间隙消失,提示
A.血清GOT增高B.脾肿大C.颜面蝶形红斑D.病理性Q波E.抗链“O”升高风湿热可以有
关于酶原与酶原激活的叙述,正确的是
存款合同的内容包括()。
下列各项中,不得与破产债权相抵销的有()。
患者,男,75岁,心功能不全,听力下降明显,护士在与其交流时应特别注意应用哪种沟通技巧?()
在学科教学中进行学习策略训练,要遵循的原则有()
据某省2013年国民经济和社会发展统计公报资料,该省人民生活和社会保障稳步提高。(一)城乡居民收入稳步增长。全年农民人均纯收入8781元,比上年增长12.2%;城镇居民人均可支配收入21873元,增加10.1%。农村居民恩格尔系数42.3%,城镇居民恩格
毛泽东第一次系统地阐述社会主义社会矛盾问题的著作是()。
最新回复
(
0
)