2011年考研英语特训：看阅读背单词(6)

　　Scatteredaround the globe are more than 100 small regions of isolated volcanic activity known to geologistsas hot spots. Unlike most of the world’s volcanoes, they are not always found at the boundaries of the great driftingplates that make up the earth’s surface; on the contrary, many of them lie deep in the interiorof 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 milestonesthat 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 remindersof where the two continents were once joined. The relative motion of the plates carrying these continentshas been constructed in detail, but the motion of one plate with respect to another cannot readilybe translated into motion with respect to the earth’s interior. It is not possible to determinewhether 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 significanceof hot spots is not confined to their role as a frameof reference. It now appears that they also have an important influence on the geophysicalprocesses 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 entirelyalong some of these fissures, so that the hot spot initiates the formation of a new ocean. Thus just as earlier theories have explained the mobilityof the continents, so hot spots may explain their mutability(inconstancy).

　　译文

　　地球上散落分布着100多个互不相连的小火山活跃区，地质学家称之为热点。与地球上大多数火山不同的是，它们并不总是在构成地球表面的巨大漂流板块之间的连接处上出现;相反，许多热点处于板块较深的内部。大多数热点移动极为缓慢，有些时候，板块滑过这些热点便留下了死火山的痕迹。热点及其火山痕迹是板块漂移的标志。

　　现在对于板块漂移这一理论是毋庸置疑的。例如，由于有新的物质注入二者之间的海底，非洲和南美洲距离越来越远。即使跨越海洋，但是由于相互吻合的海岸线和某些可乐了海洋类似的地质特征都能使人会想到整个两个大陆曾经是连在一起的。对于这些大陆的板块的相对运动已经能够被详细地解释出来，但是以地球内部为参照物，不能很好地说明一个板块相对于另一个板块的相对运动之间的关系。人们不能确定是两个大陆都朝相反的方向运动漂移而去，还是一个大陆静止不动另一个大陆从他身边漂移而走。处于地球更深层的热点提供了解决该问题的测量仪器。通过对热点区域的研究情况发现，非洲板块似乎是静止不动的，至少在过去的3000万年里没有移动过。

　　热点的重要性不仅只是局限于其作为参照系统所表现的作用。现在看来，热点还对推动板块在地球表面漂移这一地球物理过程有重大影响。当大陆板块漂移到热点上方时，来自地球深层的物质便形成了巨大的拱形隆起物。随着该拱形的增长，板块出现深深的裂缝。至少有些情况下，大陆可能会沿着其中的某些裂缝完全裂开，该热点就引发了一个新的海洋的形成。因此，正如早期的理论解释了大陆的漂移性一样，热点理论或许能够解释大陆板块的易变性。