首页
登录
职称英语
No very satisfactory account of the mechanism that caused the formation of
No very satisfactory account of the mechanism that caused the formation of
游客
2023-09-11
49
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 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. [br] The author refers to a "conveyor belt"(L. 6, Para. 1) in order to ______.
选项
A、illustrate the effects of movements in the upper layer of the earth
B、show how temperature differences depend on the positions of the continents
C、describe the complicated motions made possible by the ocean currents
D、account for the rising currents under min-ocean ridges
答案
A
解析
在此句之前一直在讲深层地壳运动的影响,“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.”而本句的主语为“这些运动”,所以正确答案是A。
转载请注明原文地址:https://tihaiku.com/zcyy/3004914.html
相关试题推荐
Aftermorethan40yearsofparalleldevelopment,theinformationandlife
Aftermorethan40yearsofparalleldevelopment,theinformationandlife
Aftermorethan40yearsofparalleldevelopment,theinformationandlife
Aftermorethan40yearsofparalleldevelopment,theinformationandlife
Aftermorethan40yearsofparalleldevelopment,theinformationandlife
Themechanism_____________________________hasnotbeendearlyunderstood.(大脑细胞储
[originaltext]M:Whatdoyouthink?AmIOK?W:Well,thereissomeinformation
[originaltext]M:Whatdoyouthink?AmIOK?W:Well,thereissomeinformation
[originaltext]M:Whatdoyouthink?AmIOK?W:Well,thereissomeinformation
[originaltext]M:Whatdoyouthink?AmIOK?W:Well,thereissomeinformation
随机试题
WeliveinsouthernCaliforniagrowinggrapes,afirstgenerationofvintner
1.题目:八年级《苏州园林》片段教学 2.内容: 我国的建筑,从古代的宫殿到
我国高等教育层次结构调整的基本途径包括()。A.停止高等教育大众化 B.继续
根据公文的来源,在一个机关内可将公文分为()。A.收文、发文 B.上行文、平行
半夏泻心汤的组成药物中,除半夏、人参、甘草、生姜、大枣外,还有()A.黄连
2017年我国成年国民图书阅读率为59.1%,比上年增加0.3个百分点;报纸阅读
某地区三种农副产品的收购资料如表7-2所示。 表7-2 请根据上述
平衡计分卡是一个有效的战略执行系统,通过引入程序可以使得管理者能够把长期行为与短
张某兴办甲个人独资企业,2016年相关财务资料如下: (1)向非金融企业借
刺激小肠粘膜释放缩胆囊素作用最强的物质是A、盐酸 B、蛋白质分解产物 C、脂
最新回复
(
0
)