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　　关于一篇托福阅览文章，考生该怎样充分利用才算是将这篇文章真实“吃透”了呢?相信许多考生都会有这样的疑问，今日辛达代报就以一篇阅览文章为例，教给考生提取它的难词，难句，杂乱的文章结构，我们可以在备考托福阅览的时候，都用这种方式进行操练，有助于咱们在托福阅览考试中挥洒自如，进步托福写作能力。

　　原文：

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

　　一、难词

　　spatial: a.1.空间的，太空的;2.存在(或许发作)于宇宙空间的

　　plume: n.1.羽状物2.柱，地柱

　　xenolith:俘虏岩

　　percolate:v.1.浸透2.分散到，充满于

　　portions: n.一部分

　　二、难句

　　1.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 mid-ocean ridge system， whose source，most geologists contend，is the upper mantle.

　　关于地幔分层观点来说，最好的根据乃这样一个承认的事实，即在那些海洋岛屿——这些岛屿据信是源于由基层地幔升上来的地幔柱状溶岩流(mantle plume)——上发现的火山岩石，是由与海洋中部山脊体系的物质底子不同的物质构成的，而这一海洋中部山脊体系的成因，大多数地质学家论辩道，为上部地幔。

　　难句类型：杂乱润饰、插入语

　　解说：本句前面的骨干并不算难，即the evidence is the fact that,难就难在fact之后阐明fact 的同位语从句。此从句中既有大段插入语，又有从句，较为难读。同位语从句的主语是volcanic rocks，主语后边的found on oceanic islands是分词润饰volcanic rocks的;islands后边又有一个阐明islands的同位语islands believed to result from mantle plumes arising from the lower mantle,此同位语实践起到一个分隔主谓的同位语的效果。这以后是谓语动词are composed/of fundamentally different from that of the midocean ridge system, whose source, most geologists contend, is the upper mantle。

　　句中有一些专有词汇。如果抛开文章不说，单看这一个语句，则句首的layered mantle thesis就难以了解。可是如果读者可以读懂语句的大致意思，看到layered mantle thesisr最有力根据就是其资料fundamentally different from… the upper mantle,这应该可以推测出，既然不同于上层地幔，则这个理论一定是在说地幔有不同的层面。

　　2. 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. (4+)

　　可是，某些地质学家，以对地幔捕虏岩体(xenolith)所作的观察为根据，指出地幔并非是分层摆放的，相反，地幔的异质性是由那些富含“不相容成分”的流质构成的，这些成分趋向于流体而非固体的状况，自下而上浸透分散，并按照这些流质流向的任意性，不规则地将上部地幔的某些部分予以改动。

　　难句类型：杂乱润饰、插入语

　　解说：本句的主句中有一个长插入语however, on the basis of observations concerning mantle xenoliths,割裂了主谓，但语句的首要难度还是在that引导的宾语从句中，从句中有由but 所衔接的两个语句，一同延续到句末。首选是rich in incompatible elements润饰fluids;后边又有一个同位语和一个分词结构，都是润饰incompatible elements的，最终还有一个状语来润饰那个分词结构，层层润饰，比较杂乱。

　　三、文章结构

　　Ts是文章的榜首句，因而这一篇短文章是定论解说型。文章开端说出了地幔是heterogeneous,然后又指出了他的spatial arrangement remains unresolved,然后提出了两种理论，一是layered-mantle thesis,另外一个是irregularly heterogeneous.然后分别对这两种理论进行describe.最终作者指出，We believe, perhaps unimaginatively, that this debate can be resolved through further study, and that the underexplored midocean ridge system is the key.

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