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
Scattered around the globe are more than 100 small regions of isolated volcanic activity known to geologists as hot spots. Unlik
Scattered around the globe are more than 100 small regions of isolated volcanic activity known to geologists as hot spots. Unlik
admin
2018-05-11
48
问题
Scattered around the globe are more than 100 small regions of isolated volcanic activity known to geologists as hot spots. Unlike most of the world’s volcanoes, they are not always found at the boundaries of the great drifting plates that make up the earth’s surface; on the contrary, many of them lie deep in the interior of a plate. Most of the hot spots move only slowly, and in some cases the movement of the plates past them has left trails of dead volcanoes. The hot spots and their volcanic trails are milestones that mark the passage of the plates.
That the plates are moving is now beyond dispute. Africa and South America, for example, are moving away from each other as new material is injected into the sea floor between them. The complementary coastlines and certain geological features that seem to span the ocean are reminders of where the two continents were once joined. The relative motion of the plates carrying these continents has been constructed in detail, but the motion of one plate with respect to another cannot readily be translated into motion with respect to the earth’s interior. It is not possible to determine whether both continents are moving in opposite directions or whether one continent is stationary and the other is drifting away from it. Hot spots, anchored in the deeper layers of the earth, provide the measuring instruments needed to resolve the question. From an analysis of the hot-spot population it appears that the African plate is stationary and that it has not moved during the past 30 million years.
The significance of hot spots is not confined to their role as a frame of reference. It now appears that they also have an important influence on the geophysical processes that propel the plates across the globe. When a continental plate comes to rest over a hot spot, the material rising from deeper layer creates a broad dome. As the dome grows, it develops deep fissures (cracks); in at least a few cases the continent may break entirely along some of these fissures, so that the hot spot initiates the formation of a new ocean. Thus just as earlier theories have explained the mobility of the continents, so hot spots may explain their mutability (inconstancy).
The passage is mainly about ______.
选项
A、the features of volcanic activities
B、the importance of the theory about drifting plates
C、the significance of hot spots in geophysical studies
D、the process of the formation of volcanoes
答案
C
解析
全文3个段落主要是围绕“热点对于地球物理学研究的意义”而展开的。故答案选C项。全篇共3段,第l段讲的是hot spots的定义与分布,第2段讲hot spots在大陆板块移动中的参照作用,第3段讲hot spots引起新海洋形成的地球物理意义。
转载请注明原文地址:https://kaotiyun.com/show/yZT7777K
0
大学英语六级
相关试题推荐
Wikipedia’sTrembling[A]Wikipediaisdying!Wikipediaisdying!That’sthelinerepeatedbythemediaeverysixmonthsorsosi
A、Tohavethemdrawagraphofthetestscoresofthetestinggroup.B、Toconfirmonlycomingtothelabcan’timproveMandarin.
PresidentBarackObama’spicktoheadtheEnvironmentalProtectionAgency(EPA),LisaJackson,hasspent20yearsasanenvironme
DoBritain’sEnergyFirmsServethePublicInterest?[A]Capitalismisthebestandworstofsystems.Lefttoitself,itwillemb
A、Aneffectivetooltohelpformwomen’sfriendship.B、Awaytounderstandandappreciatefriends.C、Anaccessthatawomancan
A、Closebutunequal.B、Friendlybutformal.C、Strainedbutformal.D、Equalandinformal.D本题问的是在美国,父母与子女之间的关系怎样。对话中间,女士询问男士在美国父母
Englishistheleadinginternationallanguage.Indifferentcountriesaroundtheglobe,Englishisacquiredasthemothertongue
A、Ithasmanybigandbeautifulparks.B、Itpossessesmanyhistoricalsites.C、Itisacityofcontrasts.D、Itisanimportanti
RainforestCity[A]Apatchoftropicalrainforesthastwicethenumberofmammalspecies,fivetimesthebatsandbirdsandten
随机试题
(2012年4月,2009年4月)中国人民解放军在1949年4月21日发起的重大战役是________。
下列有关解释程序的叙述正确的是_______。
患者女,尿培养为革兰阴性杆菌,血平板上蔓延生长,硫化氢阳性。对于可能的病原菌,下列叙述错误的是
下列关于牵引的治疗作用不正确的是
患者,女,55岁,丧偶。近1年月经紊乱。现阴道不规则出血1个月余,量时多时少,伴有烘热汗出,心烦不寐。应首选()
成年人在安静平卧时,一次心搏由一侧心室射出的血量约为
公路工程验收的依据包括()。
全国人民代表大会代表或者县级以上地方人民代表大会代表,如果因为是现行犯被拘留,执行拘留的公安机关应当立即向()或者常务委员会报告。
儒家的管理思想贯穿着()的伦理道德精神。
在下面的页面置换算法中,()只是具有理论意义,但是实现起来很困难。
最新回复
(
0
)