首页
登录
职称英语
Scattered around the globe are more than 100 small regions of isolated volca
Scattered around the globe are more than 100 small regions of isolated volca
游客
2023-10-31
21
管理
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 ocean is stationary and the other is drifting away from it. Hot spots, anchored in the deeper layer of the earth, provide the measuring instruments needed to resolve the question. From an analysis of the hot-spot population it appears that it has not moved during the 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 layers 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 new ocean. Thus just as earlier theories have explained the mobility of the continents, so hot spots may explain the mobility of the continents, and their mutability(inconstancy). [br] That Africa and South America were once joined can be deduced from the fact that______.
选项
A、the two continents are still moving in opposite directions
B、they have been found to share certain geological features
C、the African plate has been stable for 30 million years
D、over 100 hot spots are scattered all around the globe
答案
B
解析
推理判断题。第二段指出:非洲和南美洲正在漂离对方。大洋两边可以互相填补的海岸线和某些共有的地理特征显示两块大陆曾经相连。故B为答案。A,C,D均无法推测出两大洋曾经相连。
转载请注明原文地址:https://tihaiku.com/zcyy/3145644.html
相关试题推荐
Thefarmerputupironfencesaroundtheflowergarden______neighbor’ssheepsho
Curioustouristsandreportersfromaroundtheglobeare______uponthepeaceful
Thewomanworkedoffthefataroundher______bydoingexerciseeverymorning.A、
Businessschoolsaroundtheglobearefacinga______shortagewithinthenextde
Didyougetyourpoint______totheaudienceinthedebate?A、acrossB、aroundC、
Didyougetyourpoint______totheaudienceinthedebate?A、acrossB、aroundC、
Hewasdeterminedtosailaroundtheworld______hisillnessandoldage.A、give
PeoplearoundFloridastockeduponthefollowingEXCEPT______.[originaltext]
Whatisthenewitemmainlyabout?[br][originaltext]Well,movingaroundt
Whatisthenewitemmainlyabout?[br][originaltext]Authoritiesaroundth
随机试题
Inthe1920s,Gerstmanndescribedasetofproblemsfoundinpeoplewhohave
Asfoodistothebody,soislearningtothemind.Ourbodiesgrowandmuscl
简述农村一二三产业融合发展的方式。
ICP:
实寒证与虚寒证最主要的区别点是A、病程长短 B、病情缓急 C、脉有力无力
医患冲突的化解方式不恰当的是A、不属于医疗事故的医疗纠纷通过医患沟通来化解 B
血涂片瑞氏染色时,红细胞染红色,白细胞核着色不好,缓冲液pH可能为A:5.4B
护理泌尿道感染的患儿正确的做法是A.每日消毒会阴部1~2次 B.尿培养标本在1
村民委员会的负责人由()产生。A.村民推荐 B.村民直接选举 C.乡镇
最新回复
(
0
)