首页
登录
职称英语
No very satisfactory account of the mechanism that caused the formation of th
No very satisfactory account of the mechanism that caused the formation of th
游客
2023-12-22
55
管理
问题
No very satisfactory account of the mechanism that caused the formation of the ocean basins has yet been given. The traditional view supposes that the upper mantle of the earth behaves as a liquid when it is subjected to small forces for long periods and that differences in temperature under oceans and continents are sufficient to produce convection in the mantle of the earth with rising convection currents under the mid-ocean ridges and sinking currents under the continent. Theoretically, this convection would carry the continental plates along as though they were on a conveyer belt and would provide the forces needed to produce the split that occurs along the ridge.
This view may be correct: it has the advantage that the currents are driven by temperature differences that themselves depend on the position of the continents. On the other hand, the theory is implausible because convection does not normally occur along lines, and it certainly does not occur along lines broken by frequent offsets or changes in direction, as the ridge is.
It has the advantage that the currents are driven by temperature differences that themselves depend on the position of the continents. Such a back-coupling, in which the position of the moving plate has an impact on the forces that move it, could produce complicated and varying motions.
Also it is difficult to see how the theory applies to the plate between the Mid-Atlantic Ridge and the ridge in the Indian Ocean. This plate is growing on both sides, and since there is no intermediate trench, the two ridges must be moving apart. It would be odd if the rising convection currents kept exact pace with them.
An alternative theory is that the sinking part of the plate, which is denser than the hotter surrounding mantle, pulls the rest of the plate after it. Again it is difficult to see how this applies to the ridge in the South Atlantic, where neither the African nor the American plate has a sinking part.
Another possibility is that the sinking plate cools the neighboring mantle and produces convection currents that move the plates. This last theory is attractive because it gives some hope of explaining the enclosed seas, such as the Sea of span. These seas have a typical oceanic floor, except that the floor is overlaid by several kilometers of sediment. Their floors have probably been sinking for long periods.
These seas have a typical oceanic floor, except that the floor is overlaid by several kilometers of sediment. Their floors have probably been sinking for long periods. It seems possible that a sinking current of cooled mantle material on the upper side of the plate might be the cause of such deep basins. The enclosed seas are an important feature of the earth’s surface and seriously require explanation because, in addition to the enclosed seas that are developing at present behind island arcs, there are a number of older ones of possibly similar origin, such as the Gulf of Mexico, the Black Sea, and perhaps the North Sea. [br] According to the passage, which of the following are separated by a plate that is growing on both sides?
选项
A、The Pacific Ocean and the Sea of Japan.
B、The South Atlantic Ridge and the North Sea Ridge.
C、The Gulf of Mexico and the South Atlantic Ridge.
D、The Mid-Atlantic Ridge and the Indian Ocean Ridge.
答案
D
解析
转载请注明原文地址:https://tihaiku.com/zcyy/3296016.html
相关试题推荐
Thisarticleanalysesthenewlaw______ofwhichtheemployersandtheiraccounta
Inthefinancialcrisiswehadto______theirexpenditures,whichcausedasignif
ItisimperativethatalltheaccountsofthePropertyManagementCompanyshould
Informationtheoryisprimarilya________study.A、theoryB、theoreticalC、therapy
Thearrivalofinformationrevolutionmakesenterprisesabsolutelychangetheir
Duringemploymenttheemployeecouldnotuseordisclosethisinformationwithou
Thiscountryisinthesocialtransformationperiodnow,andthesocialtransfor
InorderforpeopletomakethemostoftheInformationSociety,theymusth
ThedefectsoftheBiblemaybecausedby______.[br][originaltext]TheBiblei
ThedefectsoftheBiblemaybecausedby______.[br][originaltext]TheBiblei
随机试题
Insomecountries,studentsareexpectedtobequietand______intheclassroom
按照现代生理学观点,兴奋性为()。A.活的组织或细胞对外界刺激发生反应的能力
下列哪种职能是管理活动的首要职能?()A.计划职能 B.领导职能 C.控制
10岁男孩,出生体重3000g,因臀位剖宫产,出生无青紫窒息史,身材比例匀称,身
参加证券业从业人员资格考试的人员应当满(),具有()学历。A:16周岁高中
医院感染的病原体中最常见的是A.病毒 B.衣原体 C.细菌 D.真菌 E
下列储存物品的火灾危险性属于甲类的是()。A.闪点为20℃的液体 B.爆炸下
下列哪种结清现有互换合约头寸的方式可能产生新的信用风险?( )A.出售现有的互
现货市场与期货市场是两个独立的市场,会受到不同经济因素影响和制约,因而一般情况下
纯粹风险的间接损失包括()。A.营业中断损失 B.破产成本 C.融资成本
最新回复
(
0
)