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GRE阅读题目解析:地幔的结构

2017-03-30 08:39:00来源：新东方在线整理

　　P4

　　1

　　Geologists have long known that the Earth‘s mantle is heterogeneous, but its spatial arrangement remains unresolved — is the mantle essentially layered or irregularly heterogeneous?

　　地理学家早就知道，地幔是由不同物质混杂而成的，但各种成分的空间分布还不清楚 —— 地幔的结构本质上是分层的，抑或完全无规律的混杂?

　　2

　　The best evidence for the layered-mantle thesis is the well-established fact that volcanic rocks found on oceanic islands, islands believed to result from mantle plumes arising from the lower mantle, are composed of material fundamentally different from that of the midocean ridge system, whose source, most geologists contend, is the upper mantle.

　　地幔分层说的最佳证据，在于确实在海岛发现了一些火山岩，这些岛确信由下层地幔升起的地柱形成，岛上的火山岩的构成材料，与构成海洋中部山脊系统的材料完全不同，而后者被多数地理学家认为是上层地幔。

　　(plume 【AHD】地柱，An upwelling of molten material from the earth's mantle.)

　　3

　　Some geologists, however, on the basis of observations concerning mantle xenoliths, argue that the mantle is not layered, but that heterogeneity is created by fluids rich in "incompatible elements" (elements tending toward liquid rather than solid state) percolating upward and transforming portions of the upper mantle irregularly, according to the vagaries of the fluids‘ pathways.

　　然而，一些地理学家基于对地幔中捕虏体的观测，主张地幔不是分层的，而是由含有大量不相容元素(这些元素更倾向于液态而不是固态)的流体组成的多样物质的混合，这些不相容元素向上过滤，并根据流动路径的多变性，不规则地改变上层地幔的成分。

　　(xenolith 【AHD】捕虏体，A rock fragment foreign to the igneous mass in which it occurs. 指在火成岩中形成的外来岩石碎片 )

　　4

　　We believe, perhaps unimaginatively, that this debate can be resolved through further study, and that the underexplored midocean ridge system is the key. (157 words)

　　也许听起来像陈词滥调，我们相信这场争论可以通过进一步研究终结，有待勘测的海洋中部山脊系统则是研究的关键。

　　(underexplored 查不到什么意思，有待勘测的译法是无根据的推测，请勿轻信。)

　　10. According to the passage, it is believed that oceanic islands are formed from

　　(A) the same material as mantle xenoliths

　　(B) the same material as the midocean ridge system

　　(C) volcanic rocks from the upper mantle

　　(D) incompatible elements percolating up from the lower mantle

　　(E) mantle plumes arising from the lower mantle

　　选 E

　　句 2：

　　The best evidence for the layered-mantle thesis is the well-established factthat volcanic rocks found on oceanic islands, islands believed to result from mantle plumes arising from the lower mantle, are composed of material fundamentally different from that of the midocean ridge system, whose source, most geologists contend, is the upper mantle.

　　这是个长句但不算难别怕，蓝色背景为句子主干，绿色部分是选项根据。

　　For the following question, consider each of the choices separately and select all that apply

　　11. It can be inferred from the passage that the supporters of the "layered-mantle" theory believe which of the following?

　　□A The volcanic rocks on oceanic islands are composed of material derived from the lower part of the mantle.

　　□B The materials of which volcanic rocks on oceanic islands and midocean ridges are composed are typical of the layers from which they are thought to originate.

　　□C The differences in composition between volcanic rocks on oceanic islands and the midocean ridges are a result of different concentrations of incompatible elements.

　　选 AB

　　A 在文中可以直接找到根据，句 2 。

　　B composed 之前都是主语，主语的中心词是 materials ，分层说的支持者当然认为两种石头都是所在层次的典型代表，如果他们不相信这一点，理论也就不成立了。

　　C incompatible elements 是乱流说提到的内容，放在分层说题目中，是错误组合的干扰信息。

　　12. In the context of the passage, "unimaginatively" is closest in meaning to

　　(A) pedestrian

　　(B) controversial

　　(C) unrealistic

　　(D) novel

　　(E) paradoxical

　　选 A

　　pedestrian 平淡无奇的，一般的

　　unimaginatively 缺乏想象力地

　　单词题。

　　以上就是新东方在线GER频道为你带来的GRE阅读题目解析:地幔的结构，更多精彩敬请关注新东方在线GRE频道。

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