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
No very satisfactory account of the mechanism that caused the formation of the ocean basins has yet been given. The traditional
No very satisfactory account of the mechanism that caused the formation of the ocean basins has yet been given. The traditional
admin
2010-07-14
30
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 layer of the earth behaves as a liquid when it is subjected to small focus for long periods and that differences in temperature under oceans and continents are sufficient to produce movements in the upper layer of the earth with rising currents under the mid- ocean ridges (山脊) and sinking currents under the continents. Theoretically, these movements would carry the continental plates along as though they were on a conveyor belt and would provide the forces needed to produce the split that occur 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 unconvincing because the movements do not normally occur along lines, and it certainly does not occur along lines broken by frequent changes in direction, as the ridge is. 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. An alternative theory is that the sinking part of the plate, which is denser than the hotter surroundings, pulls the rest of 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 (地幔) and produces motion currents that move the plates. This last theory is attractive because it gives some hope of explaining the neighboring mantle and produces motion currents that move the plates. This last theory is attractive because it gives some hope of explaining the enclosed seas. These seas have a typical oceanic floor, except that the floor is overlaid by several kilometers of sediment (沉积物). Their floors have probably been sinking for long periods. It seems possible that a sinking current of cooled material on the upper side of the might be the cause of such deep basins. The enclosed seas are an important feature of the earth’s surface and seriously require explanation.
According to the traditional view of the origin of the ocean basins, which of the following is sufficient to move the continental plates?
选项
A、Spreading of ocean trenches.
B、Movements of min-ocean ridges.
C、Sinking of ocean basins.
D、Differences in temperature under oceans and continents.
答案
D
解析
见短文第一段的最后两句话,“This view may be correct.Is has the advantage that the currents are driven by temperature differences that themselves depend on the position of the continents."作者告诉我们真正的动力是大洋与陆地的温度差。
转载请注明原文地址:https://jikaoti.com/ti/H7MMFFFM
0
大学英语六级
相关试题推荐
Whataccountsfortheincreasingnumberofbackpainsufferersinmodernlifeisanumberoffactorssuchasoverweight,lackof
Theoldestandsimplestmethod,then,ofdescribingdifferencesinpersonalitywasto【B1】______peopleaccordingto【B2】______.
Directions:Forthispart,youareallowedthirtyminutestowriteashortessayentitledGoodMannersYoushouldwriteatleast
HowAmerica’sMostSuccessfulExecutivesAccomplishSoMuchinSoLittleTimeTheyheadthenation’sbiggest,fastest-grow
A、Consulthimoutsideofclass.B、Lookforhimintheoffice.C、Talktohimduringclassroomhours.D、Makeanappointmentwithh
A、Cathyisnotsobrilliant.B、Cathythinkshermotherisverykind.C、ShewenttoFrancewiththeschoolchoirlastyear.D、The
Thenewresidentialblockswereskillfullyintegrated_________________________(和大学的其它部分形成一个整体)
AllEskimoslivemostoftheirlivesclosetosaltorfreshwater.Theymayfollowgameinlandforseveralhundredmiles,butth
A、Indifferent.B、Surprised.C、Worried.D、Confident.C
随机试题
Whyaresomanypeoplesoafraidoffailure?Quitesimplybecausenoonetellsushowtofailsothatfailurebecomesanexperie
女性。ITP患者。血小板20×109/L,骨髓增生活跃,巨核细胞200个/片,产板巨核细胞减少。以下治疗不适宜的是
高滴度的抗RNP抗体为下列哪种疾病所特有
根据《中华人民共和国行政处罚法》的规定,行政处罚决定中听证程序包括()
A.进口药品申请B.补充申请C.已有国家标准药品的申请D.改变剂型和给药途径的已上市的药品申请E.药品注册管理工作
代理人根据人民法院或者指定机关的指定而进行的代理是()。
分析下述论证中存在的缺陷和漏洞,写一篇600字左右的文章,对该论证的有效性进行分析和评论。公司收入下降的同时伴随着生产的迟滞。接下来,这种生产上的迟滞在很大程度上归因于在购买金属原材料上的计划不当。进一步考虑的话,公司负责购买金属原材料的部门经理在
Forgetmilkydrinks,hotwaterbottlesorcurlingupwithagoodbook.Therealsecrettoagoodnight’ssleepmaybewhereyou
Pollutionisa"dirty"word.Topollutemeanstocontaminate—topsoilorsomethingbyintroducingimpuritieswhichmake(31)unfi
Malariaisworld’ssecondmostcommondiseasecausingover【C1】______infectionsandonemilliondeathseveryyear.【C2】______itis
最新回复
(
0
)