提出问题No very satisfactory account of the mechanism that caused the formation of the ocean basins has yet been given. The traditional view*1*4*6（-） 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*1E under oceans and continents are sufficient to produce convection in the mantle of the earth with rising 理论一convection currents under the mid-ocean ridges and sinking currents under the continents. Theoretically, this convection would carry the continental plates along as though they were on a conveyor belt*3*7A（比喻） (conveyor belt: n. 传送带) and would provide the forces needed to produce the split that occurs along the ridge. This view may be correct（小+）: it has the advantage that the currents are driven by temperature differences that themselves depend on the position of the continents. Such a 优点back-coupling互相挂钩，互为因果, in which the position of the moving plate has an impact on the forces that move it, could produce complicated and varying motions.
On the other hand, the theory is implausible（大-） because（原因） convection does not normally occur along 缺点一lines*6A, and it certainly does not occur along lines broken by frequent offsets (an abrupt bend in an object by which one part is turned aside out of line) or changes in direction, as the ridge is. 缺点二：不能适用于某个板块Also（第二个原因） it is difficult to see how the theory applies to the plate between the Mid-Atlantic Ridge and the ridge in the Indian Ocean*5D. This plate is growing on both sides*5, and since there is no intermediate trench, the two ridges must be moving apart. It would be odd if（欲擒故纵的反证法） the rising convection currents kept exact pace with them. An alternative theory is that the 理论二sinking part of the plate, which is denser than the hotter surrounding mantle, pulls the rest of the plate after it. 缺点：不能适用于另一个板块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 理论三sinking plate cools the neighboring mantle and produces convection currents that move the plates. This last theory is attractive（+） because（原因） it gives some hope of explaining the enclosed seas, such as the Sea of Japan. These seas have a typical oceanic floor, except that the floor is overlaid by several kilometers of sediment*2*7B. 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（问题解决了） 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*2B*7, and perhaps the North Sea.（跑题的延伸性内容）
1. According to the traditional view*1（第一个观点） of the origin of the ocean basins, which of the following is sufficient to move the continental plates?直接事实题
(A) Increases in sedimentation on ocean floors
(B) Spreading of ocean trenches
(C) Movement of mid-ocean ridges
(D) Sinking of ocean basins（E）
(E) Differences in temperature*1E under oceans and continents
2. It can be inferred from the passage that, of the following, the deepest sediments*2（最后一段） would be found in the
(A) Indian Ocean
(B) Black Sea*2B
(C) Mid-Atlantic
(D) South Atlantic（B）
(E) Pacific
3. The author refers to a “conveyor belt*3” in line 13 in order to举例作用题（备选选项：illustrate和give an example of开头的选项）
(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
(E) account for the rising currents under certain mid-ocean ridges
4. The author regards the traditional view*4（大-小+） of the origin of the oceans with态度题（混合评价的表达方法：由but和and连接的两个不同方向的评价词；由修饰词限定的评价词——本题）
(A) slight apprehension恐惧（极端）
(B) absolute indifference（过于中庸）
(C) indignant anger愤慨的愤怒（人身攻击）
(D) complete（程度过强） disbelief
(E) guarded skepticism
5. According to the passage, which of the following are separated by a plate that is growing on both sides*5?直接事实题（细节，极难定位，没时间可舍）
(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*5D
(E) The Black Sea and the Sea of Japan
6. Which of the following, if it could be demonstrated, would most support the traditional view*6 of ocean formation?改善题（找理论一的缺点，取非）
(A) Convection usually occurs along lines*6A.
(B) The upper mantle behaves as a dense solid.
(C) Sedimentation occurs at a constant rate.
(D) Sinking plates cool the mantle.
(E) Island arcs surround enclosed seas.
7. According to the passage, the floor of the Black Sea*7（最后一段） can best be compared to a信息题（有定位）ACDE无
(A) rapidly moving conveyor belt*7A（第一段）
(B) slowly settling foundation（Sediment*7B）
(C) rapidly expanding balloon
(D) violently erupting volcano
(E) slowly eroding mountain
8. Which of the following titles would best describe the content of the passage?主题题（内容性，三出现做法：重要关键词必须出现，细节和新内容不能出现）
(A) A Description of the Oceans of the World（范围过大）
(B) Several Theories of Ocean Basin Formation
(C) The Traditional View of the Oceans（细节）
(D) Convection and Ocean Currents（细节）（B）
(E) Temperature Differences among the Oceans of the World（细节）
责任编辑：虫虫
