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 now 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 deep 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).
The author believes that ________.
A意为“板块的移动与地球内部的移动是相对应的”。第一段指 出，地球有100多个地质学家称之为热点的互不相邻的（isolated）火 山活跃区。与地球上多数火山不同的是：它们并非都处在构成地球表 面的巨大漂游板块的连接处，相反，它们多深埋在板块之下（lie deep in the interior of a plate）。这些热点移动缓慢，有时，当板块从 它们上面移动过去时，就会留下死火山痕迹（trails of dead volcanoes）。热点及其火山痕迹标志着板块漂移而过。可见，二者的 移动并没有相对应处。C意为“热点和板块缓慢作反方向移动”。根据 第一段，二者的移动并没有相对应处。D意为“热点的移动证明：大 陆板块正在漂离”。根据第一段最后一句，热点及其火山痕迹证明板 块是移动的。因此D项也不正确。B项意为“关于漂流板的地质理论已 被证明是正确的”。第二段指出，对于板块漂移说目前已不存异议。 因此可知B项为正确答案。
That Africa and South America were once joined can be deduced from the fact that ________.
B项意为“它们有某些共同的地质特征”。第二段指出，对于板 块漂移说目前已不存异议。例如，非洲和南美洲正在漂离，新物质不 断注入二者之间的海底裂痕;虽然有大洋（大西洋）相隔，二者的海 岸线（形状）是互补的，共有某些地质特征，说明它们曾经是连在一 起的。因此可知推断它们曾经连在一起的原因就是“它们具有共同的 地质特征”，因此B项为正确答案。A意为“这两个大陆还在向相反方 向移动”。根据第二段最后一句，通过对热点区域的研究发现，非洲 板块似乎是静止的（stationary），至少3000万年未移动了。因此A项 排除。C意为“非洲板块至少3000万年未移动了”。这也许是事实，但 不是非洲和南美洲曾经是一个板块的证据。D意为“地球有100多个热 点”。这也许是事实，但这也不是非洲和南美洲曾经是一个板块的证据。
The hot-spot theory may prove useful in explaining ________.
D项意为“新的海洋的形成”。最后一段指出，热点说的意义不 限于提供了一个参照点，它看来对推动板块移动的地质物理学过程也 提供了解释。当板块处于热点之上时，底层物质会将板块顶起，形成 巨大的弧线，弧线变高时，板块出现深深的裂痕。当有些地方裂痕迸 裂后，就形成新的海洋。因此可知在解释新的海洋的形成时，热点说 能够发挥作用。因此答案为D。
The passage is mainly about ________.
C项意为“地质物理学中热点说的意义”。这篇文章主要就是在 通过具体的例子阐述热点说的意义。因此C项正确。A意为“火山活动 的特点”。B意为“板块漂移说的重要性”。D意为“火山的形成过程”。 文章有所提及，但都不是主旨。
Which movement of the two continents is not mentioned in the article?
第二段第三句提到了“two continents were once joined”，由此可 知A项在文中是提到了的。第五句提到“one continent is stationary and the other is drifting away from it”，由此可知B项在文中也是提到了 的。第五句同时提到“both continents are moving in opposite directions”，由此可知C项在文中也是提到了的。因此A、B、C三项 均排除。而D选项在文中却没有提到，因此正确答案为D。