2. 外语
  3. Scattered around the globe are more than 100 small regions of isolated volcanic activity known to geologists as hot spots. Unlik

Scattered around the globe are more than 100 small regions of isolated volcanic activity known to geologists as hot spots. Unlik

admin2017-07-31  34
问题     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 eath 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(inconstant).
The author believes that______.
选项 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
答案B
解析 从文章第1段的内容可知，地球上散布着一百多个热点；大部分热点区移动极其缓慢，某些情况下，板块滑过这些热点区，便留下死火山的痕迹；热点区及其火山痕迹是板块移动的象征。从文章第2段的内容可知，如今，板块漂移学说已是无须质疑的了；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易变性。据此可知，作者认为有关大陆移动的理论是正确的。B项与文章的意思相符，因此B项为正确答案。
转载请注明原文地址:https://jikaoti.com/ti/jjmYFFFM
0

考博英语

相关试题推荐
随机试题
最新回复(0)