Text 16
Scattered around the globe are more than 100 small regions of isolated volcanic activity known to geologists as hot spots. Unlike most of the world's volcanoes, they are not always found at the boundaries of the great drifting plates that make up the earth's surface. On the contrary, many of them lie deep in the interior of a plate. Most of the hot spots move only slowly, and in some cases the movement of the plates past them has left trails of dead volcanoes. The hot spots and their volcanic trails are milestones that mark the passage of the plates.
That the plates are moving is not beyond dispute. Africa and South America, for example, are moving away from each other as new material is injected into the sea floor between them. The complementary coastlines and certain geological features that seem to span the ocean are reminders of where the two continents were once joined. The relative motion of the plates carrying these continents has been constructed in detail, but the motion of one plate with respect to another cannot readily be translated into motion with respect to the earth's interior. It is not possible to determine whether both continents are moving in opposite directions or whether one continent is stationary and the other is drifting away from it. Hot spots, anchored in the deeper layers of the earth, provide the measuring instruments needed to resolve the question. From an analysis of the hot spot population it appears that the African plate is stationary and that it has not moved during the past 30 million years.
The significance of hot spots is not confined to their role as a frame of reference. It now appears that they also have an important influence on the geophysical processes that propel the plates across the globe. When a continental plate come to rest over a hot spot, the material rising from deeper layer creates a broad dome. As the dome grows, it develops seed fissures (cracks); in at least a few cases the continent may break entirely along some of these fissures, so that the hot spot initiates the formation of a new ocean. Thus just as earlier theories have explained the mobility of the continents, so hot spots may explain their mutability (inconstancy).
1.The author believes that_______.
A.the motion of the plates corresponds to that of the earth's interior
B.the geological theory about drifting plates has been proved to be true
C.the hot spots and the plates move slowly in opposite directions
D.the movement of hot spots proves the continents are moving apart
2.That Africa and South America were once joined can be deduced from the fact that_______.
A.the two continents are still moving in opposite directions
B.they have been found to share certain geological features
C.the African plates has been stable for 30 million years
D.over 100 hot spots are scattered all around the globe
3.The hot spot theory may prove useful in explaining_______.
A.the structure of the African plates B.the revival of dead volcanoes
C.the mobility of the continents D.the formation of new oceans
4.The passage is mainly about_______.
A.the features of volcanic activities
B.the importance of the theory about drifting plates
C.the significance of hot spots in geophysical studies
D.the process of the formation of volcanoes
5.Which movement of the two continents is NOT mentioned in the article?
A.Two continents were joined.
B.One continent is stationary while other drifting.
C.Two continents move in reverse direction.
D.Two continents move in the same direction.
长难例句分析
［长难例句］Unlike most of the world's volcanoes, they are not always found at the boundaries of the great drifting plates that make up the earth's surface; on the contrary, many of them lie deep in the interior of a plate.
［结构分析］本句话中，主干是they are not found... on the contrary... many of them lie。unlike引导的是状语，由that引导的主语从句修饰the great drifting plates。on the contrary为连接词，把两个句子连接在一起。
［参考译文］和大多数火山不同，它们都不位于形成地球表面的巨大漂移板块的连接点，反而有很多藏于板块的深处。
全文参考译文
地球上零碎分布着一百多个相互独立并且面积不大的火山活动区，地质学家称之为“热点区”。和大多数火山不同，它们都不位于形成地球表面的巨大漂移板块的连接点，反而有很多藏于板块的深处。大部分热点区移动极其缓慢，有时候，板块滑过这些热点区，便留下死火山的痕迹。热点区加上其火山痕迹是板块移动的象征。
板块漂移学说如今已是无需质疑的了。例如非洲和南美洲，因为有新物质深入洋底，两个大陆距离愈来愈远。即使远隔大洋，可相互吻合的海岸线和似乎好像跨越过海的地质特征，均会让人想到这两个大陆曾是相连的。带着两个大陆漂移的板块做相对运动，这已得到具体解释，但不能把一个板块相对于另一板块的运动简单地解释为板块与地球内部之间的运动。由于人们还没法肯定两个大陆是否在朝相反的方向运动，也没法肯定是否是一个大陆原地不动，而另一个大陆正在远离它而去。因而位于地壳深处的热点区提供了解决这一问题的测量仪。从热点区的人口情况分析显示，好像非洲板块是不动的，3000万年过去了也没见移动。
热点区的重要意义并不仅仅只是它们所起到的参照物的作用。如今它们还对推动板块在地球表面漂移这一地球物理进程有重要作用。当大陆板块漂移到热点区上方时，由地壳深处涌出的物质便会使板块凸起，形成巨大圆盖。圆盖不断裂大，板块出现深深的裂痕。至少有几次，大陆差点顺着这些裂痕完全分开。因而，热点区理论解释了新海洋的起因。这样一来，就像早些时候的一些理论已经解释了大陆的流动性一样，热点区理论或许能对大陆板块的不稳定性加以说明。
题目答案与解析
1.作者相信，________。
A.板块的运动与地球内部的运动相似
B.有关板块漂移的地质理论已经被证实是正确的
C.热点与板块向相反的方向缓慢移动
D.热点的运动证明大陆正在逐渐分离
【答案】B
【解析】从文章第一段的内容可知，地球上散布着一百多个热点；大多数的热点独自缓慢运动，某些情况下，经过这些热点的板块运动留下死火山的痕迹；热点及其火山痕迹是标志板块迁移的符号；从文章第二段的内容可知，如今，有关板块在运动的理论已经无可争辩；然后举例进一步说明；从文章最后一段的内容可知，热点的重要性并不仅限于作为参照体系这一作用上；现在看来，它们对推动板块在地球上移动的地球物理学的过程也产生了重大影响；因此，正如早期的理论解释了大陆的移动那样，热点或许可以解释大陆的不稳定性。据此可知，作者认为有关大陆移动的理论是正确的。B项文中的意思相符，因此为正确答案。
2.推论出非洲和南美洲曾经连在一起，可以依据________。
A.这两个洲仍然在向相反的方向移动 B.人们发现，这两个洲具有引人注目的地质特征
C.非洲板块已经稳定了3000万年 D.地球各地散布着一百多个热点
【答案】B
【解析】本题可参照文章的第二段。从中可知，由于新物质被增添进非洲和南美洲之间的海底，因此这两个洲正在逐渐分离；相吻合的海岸线以及似乎横跨海洋的地质特征提示人们——这两块大陆曾经连接在一起。据此可知，人们之所以认为非洲和南美洲曾经连在一起，是因为它们的某些地质特征相似。B项与文中的意思相符，因此为正确答案。
3.热点理论在解释_______时可能被证实有用。
A.非洲板块的结构 B.死火山的复活
C.大陆的漂移 D.新海洋的形成
【答案】D
【解析】本题可参照文章的第三段。从中可知，热点的重要性并不仅限于作为参照体系这一作用上；现在看来，它们对推动板块在地球上移动的地球物理学的过程也产生了重大影响；当一个大陆性板块在一个热点上停止移动时，从地球更深层涌出的物质会形成一个巨大的圆丘；随着圆丘不断增长，它会出现深深的裂沟；在某些情况下，大陆至少可能会沿着这样的一些裂缝完全分裂，于是，该热点便开始形成一个新海洋；因此，正如早期的理论解释了大陆的移动那样，热点或许可以解释大陆的不稳定性。据此可知，热点理论可以用于解释大陆的不稳定性，即热点可以促使形成新海洋。D项与文章的意思相符，因此为正确答案。
4.本篇文章主要是关于________。
A.火山运动的特点 B.有关板块漂移理论的重要性
C.地质物理研究中热点的重要性 D.火山形成的过程
【答案】C
【解析】从文章第一段的内容可知，地球上散布着一百多个与外部隔绝的火山活动小区域，地质学家称之为热点；随后说明了热点的特点；文章第二段说明了板块漂移理论，最后一句话指出：根据热点密度的分析可以看出——非洲板块静止不动了3000万年；从文章第三段的内容可知，热点的重要性并不仅限于作为参照体系这一作用上，它们对推动板块地球上移动的地质物理过程也产生了重大影响；然后具体说明了热点如何促使形成了新海洋；从文章的最后一句话可知，正如早期的理论解释了大陆的移动那样，热点理论或许可以解释大陆的易变性。据此可知，本文主要讲的是热点理论在地质物理研究中的重要作用。C项与文章的意思相符，因此为正确答案。
5.对于两个大陆之间的运动关系，文中没有提及是哪一个？
A.两个大陆连接起来。 B.一个大陆固定不动，另一个大陆在漂移。
C.两个大陆背向漂移。 D.两个大陆相向漂移。
【答案】D
【解析】本题考查对细节的理解。全文中没有提到大陆板块相撞的话题。
