GRE閱讀｜Geologists have long known that the Earth‘s mantle is heterogeneous, but its spatial arrangement remains unresolved－熱血背包客莊ㄟ

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.

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

(D) incompatible elements percolating up from the lower mantle

(E) mantle plumes arising from the lower mantle

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.

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

(A) pedestrian

(B) controversial

(D) novel

(E) paradoxical

結構分析：

老樣子第一句出發，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?

這句我關心的重點是那個but，句內轉折句，but後方才是重點，有看過game of thrones，對於那位臨冬城的老爸豪爾史塔克，哈哈不對，應該是奈德史塔克講的那句話可能還記憶猶新：everything before the word "BUT" is bullshit.既然母語人士都這麼說了，那我們關心後方即可，可是後面只有提到unresolved，這充其量只能表示？？沒有提供內容出來，但是破折號有提供另外的資訊，所以繼續往下看，這裡假設破折號之前已經知道文章方向的話就別看了，但此文章是必須透過破折號後方的內容才知道作者要放啥屁。所以is the mantle essentially layered or irregularly heterogeneous?這裡點出重點了，剛剛文章前面說到unresolved，然後後面再接layered or heterogeneous?這就所以大概可以知道等等作者會針對誰是贊成layered跟誰是贊成heterogenous來討論，因為你看剛剛我們刻意忽略的句子他的主詞是Geologists，所以有人，有觀點，那表示文章在探討觀點對立是很高的可能的，沒關係如果猜錯等等在修正就好，只是在做題目之前，一定要問自己：這一句話到底在幹媽用的？？

理由二：有沒有覺得著一句話的結構很眼熟is the mantle essentially layered or irregularly heterogeneous?

我如果再加上幾個字上去，你可能就會想起來is the mantle essentially layered or irregularly heterogeneous? Use specific reasons and examples to support your opinion.這不就是托福獨立寫作題嗎？那一般寫作的模板都會告訴你：先寫某某人認為怎樣怎樣，誰誰誰認為又是另外怎樣怎樣，轉折打槍前面的人所有論述，最後我認為怎樣怎樣。這都是事前猜測，繼續往下看。

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.

這句話可麻煩了，一堆關係代名詞和插入句糾結在一起，所以要想辦法抓主幹出來，老樣子：修飾詞亂我主幹者，必～殺～之！！

The best evidence for the layered-mantle thesis is the well-established fact that volcanic rocks found on oceanic islands（這是關係代名詞限定用法修飾前面的火山岩）, islands believed to result from mantle plumes arising from the lower mantle,（這是同位語修飾前面的那個島，是什麼島是高橋名人的冒險島還是葡萄牙人說的福爾摩沙島）are composed of material fundamentally different from that of the midocean ridge system（比較詞去跟前方的material對比，比較只是要讓目標更明確，所以也屬修飾詞一環）, whose source, most geologists contend,（關係代名詞非限定用法修飾前面的source） is the upper mantle.

最後整理一下會發現如沐春風啊～～

The best evidence for the layered-mantle thesis is the well-established fact that volcanic rocks are composed of material fundamentally看到這裡就好了，後面那個whose....這個關係所有個也是修飾詞的一種，跟關係代名詞同類。因此簡單總結就是，有evidence，然後是火山物質來的。所以由此大概就知道有人支持layer說，然後證據來自於火山岩的物質。

接著往下看下一段。

這開頭也怪噁心的，不過沒關係，有沒有感覺到這個托福寫作的模板，有出現轉折however，然後有出現另外一組人馬Some geologists，所以未看先猜他一定在講剛剛那個問題的另外一個支持方：irregularly heterogeneous。一定如此沒錯，不然那個however會沒意義。然後往下看到最後一句話

We believe, perhaps unimaginatively, that this debate can be resolved through further study, and that the underexplored midocean ridge system is the key. 哈哈I got you!! I got you!! I got you!! 這根本就是模板啊，可以把它抄下來當作托福寫作的第一段來處理，看到we不是憤怒鳥～～是因為we表示作者要講他自己的觀點了，那假設等等如果有考作者態度題，那這句話絕對是關鍵，特別是這個 midocean ridge system is the key。每次看到we都會想到法國人we來we去，法文的『沒錯』『對』就是wee!!! hahaha~~wee!!!

第一題：

這個就是細節題而已所以就很呆板的看關鍵字，找文章內容，最後對應選項。我們由oceanic islands找到文章第二句話。

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.

是剛剛那個先跳過的超複雜句，不過知道他是同位語的話 islands believed to result from mantle plumes arising from the lower mantle,就可以秒選了，同位語就是補充說明的意思，也就是等於『＝』，因此這裡 oceanic islands＝ mantle plumes arising from the lower mantle，直接秒殺（Ｅ），

那如何判斷他是同位語呢，我們拿這個來說明 ,islands believed to result from mantle plumes arising from the lower mantle,這裡其實只有islands單一名詞而已，其他像是believed to result from mantle plumes arising from the lower mantle全都是修飾詞，首先看到believed這個不是一般動詞的過去式，他是一個過去分詞，假設你還原的話他就是一個關係代名詞了 islands （which were）believed to，所以它是修飾前面島嶼的修飾詞，它不是用來跟島嶼組成句子的動詞跟名詞。

再來 to result from mantle plumes這個是不定詞的結構，這不多贅述，這大家很熟了，不定詞的to＋ＶＲ是有表示目的含義的，那這麼一來也是去服務修飾前方的動詞或名詞的，感覺上就是：某某某做了這件事，『是為了...』，這裡如果只接把某某某做某件事講完就可以了，後面的東西都是為了讓內容更清楚而已。最後又是一個關係代名詞限定用法的結構省略法，mantle plumes arising from the lower mantle，從which arise來的，這就不用說了就是修飾前方的mantle plumes，從較低的地幔升起來的擎天柱。好拉所以再看一下這句逗點和逗點之間的句子 ,islands believed to result from mantle plumes arising from the lower mantle,這句子只有一個名詞存在，他沒有『真正』的動詞，也沒有連接詞，所以單存留下一個名詞，所以才會被稱作同位語。那為什麼同位語就要修飾前方的名詞呢？由剛剛的省略結構客官們應該可以推得出來，那就是這句話其實是關係代名詞的省略，oceanic islands, which were islands believed to result from mantle plumes arising from the lower mantle,所以在此在下一個結論：同位語可以當作是由關係代名詞變化過來的東西，既然是從那變過來的，那也會攜帶相同的屬性，就是：修飾前方的先行詞，而這個先行詞是名詞，既然是修飾詞，所以不是主幹，可視情況忽略。那本題就是根據他是修飾前方名詞的依據來解題的，其他像是(A) xenoliths(D) incompatible elements這都是在第二段的內容，由於however已經把兩份內容隔開了，前後兩段是兩碼的事，不能混為一談，基本上有第二段內容不刪掉對不起自己。

第二題：

又考一次第一段的內容"layered-mantle" theory，沒辦法他是複選題所以要一個一個看確保拿到分數。

(A) The volcanic rocks on oceanic islands are composed of material derived from the lower part of the mantle.這跟第一題一模一樣，我就要過了。

(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.

稍微去蕪存菁一下：volcanic rocks and midocean ridges are typical of the layers，是的都是在layered學說裡面出現的，要選

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

incompatible elements.出現在第二段直接刪除。不用管他們不同在哪了，兩派學說的內容是不能corssover的，這不是汽車。但是如果要知道真正的『不同』是在這裡are composed of material fundamentally different from that of the midocean ridge system, whose source, most geologists contend,is the upper mantle.這裡有說道確實兩者不同，火山岩是由身上來的擎天柱生成的，庵昇天拉～～然後ＭＲＳ是由上地慢組成。ＶＲ＝擎天柱，ＭＲＳ＝upper mantle。最後這題真正的錯因是a result of，文章只有講到兩者不同之去，但是並沒有講到兩者不同處的原因，並且文章內容只能找第一段，因為題目問的supporters of the "layered-mantle" theory逼你只能看第一段。

選（Ａ）（Ｂ）

第三題：

（Ｂ）和（Ｅ）有同意概念，因此他先掰掰。而題目unimaginatively沒有想像的，那就表示（Ｃ）絕對錯，所以要往普通，一般般，平凡，等等沒有特別之處的單字，選（Ａ）

以上個人筆記希望有幫助到大家，有誤再請指教!!