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
2018-06-06
40
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.
The author refers to a "conveyer belt"(Para. 1)in order to______.
选项
A、illustrate the effects of convection in the mantle
B、show how temperature differences depend on the positions of the continents
C、demonstrate the linear nature of the Mid-Atlantic Ridge
D、describe the complicated motions made possible by back-coupling
答案
A
解析
转载请注明原文地址:https://jikaoti.com/ti/C8CYFFFM
本试题收录于:
NAETI中级口译笔试题库外语翻译证书(NAETI)分类
0
NAETI中级口译笔试
外语翻译证书(NAETI)
相关试题推荐
DemonstratorsrallyatLosAngelesCityHallduringthefirstWomen’sMarch,heldonJan.21,2017,onedayafterPresidentTrum
Consumers______thecompetitiveresultofyourspecialopponentbutnotyourproduct,becauseitishardtoknowyourproduct’sq
Inthepopularmind,theInternetistherealizationoftheglobalvillage,wheretheflowofinformationandideasisunimpeded
Inthepopularmind,theInternetistherealizationoftheglobalvillage,wheretheflowofinformationandideasisunimpeded
Theresearchteamcanhandle________needstobehandled.
中国的改革开放已经走过了26个年头。26年来,中国发生了翻天覆地的变化。中国经济持续快速增长,国内生产总值从不到1500亿美元增长到1.65万亿美元。进出口总额从206亿美元增长到1.15万亿美元。中国经济在世界经济总量中的比重从1%左右提高到
《北京2008》和大家见面了!在对这份精美的杂志表示衷心祝贺的同时,希望它更好地反映2008年北京奥运会的筹备情况,展示北京东方文明故都的城市风貌、厚重的历史、灿烂的文化和充满生机的现代气息,使这份刊物成为增强我们同国际奥林匹克大家庭之间联系的桥梁和纽带。
A、DidyoubuyanewsweateronSunday?B、Hasn’ttheweatherbeenstrangethissummer?C、It’sbeenveryquietthissummer,hasn’t
随机试题
体现医患之间契约关系的有下列做法,但不包括
崩解剂的加入方法影响崩解和溶出的速度,崩解较快的方法是
芒硝是一种硫酸盐经加工精制而成的结晶体。属于泻下药,具有软坚散结、泻下通便、回乳的功效。适用于燥屎坚硬难下等症。在炮制过程中,能够使芒硝结晶析出,且与杂质分离的方法是
房地产经纪人为买房客户提供多套房源供其选择,这表明房源具有()的特征。
盾构是用来开挖土砂类围岩的隧道机械,由()组成。
()不属于旅游饭店的权利。
城市总体规划的期限一般为()。
欧盟《传统植物药注册程序指令》大限将至,中药出口欧洲遭遇严冬,人们不禁对中药_________产生了不小的怀疑。这其中确有中药自身种植、生产加工不统一的原因,致使药效和安全性能受到国际市场_________,但究其深层原因,则与国际中药市场暗藏的利益争夺不
已知a2+4a+1=0,且,则m=().
WhenthegiantIndiantechnology-servicesfirmInfosysannouncedlastNovemberthatitwouldopenadesignandinnovationhubin
最新回复
(
0
)