2015年2月GMAT閱讀機經(火山熔漿的形成)

有條不紊的復習才能讓你更好的應對考試。以下是祝福網GMAT考試欄目為大家整理的2015年2月GMAT閱讀機經，供大家參考!

2015年2月GMAT閱讀機經——火山熔漿的形成

【V1】

(關鍵詞: Lava，melting, 希望對考古有幫助)

通篇反正就是在說科學家在研究火山熔漿形成的過程中發生了哪些化學反應(有題問這文章主要講什么，選這個)，然后說了幾個實驗，具體內容不記得，然后第二段說在海底發現的lava sample里面又出現了和第一段相反的情況，然后又說了對于這個情況的兩種解釋，第一種還是有問題，作者認為第二種更靠譜，第二種有提到通過small channels之類的東西在什么之前就完成了化學反應，之后就不會再有反應了(這里有題)

【V2】

還有一篇是lava的，我找的13年7月的，我看到的和這個基本一致，這篇不長，1屏不到

P1講火山爆發來源于Mantle中的Lava，而Lava來源于Melt ，Melt在向地表上升的過程中會與Mantle中的Rock反應并不斷互相交換物質、變化結構，即吸收Orthopyroxene并排出Olivine。越接近closer表面surface，lava的exchange越頻繁

P2一個跟理論不太相符的事情，一種海底里的lava sample，在距離地表45千米突然發現已經停止這種物質交換，Melt的結構不變了。一種假設是那里的Mantle太松散了，使Melt無法與他們接觸并交換物質，但立即被否定了(因為45KM還很深東西都很軟，沒有裂縫)。另一種假設是Melt在之前的上升過程中已經吸收了足夠的Orthopyroxene， 并將能排出的Olivine都排了，無法繼續反應。

最后一篇我連一個關鍵詞都想不起來了，想要考古找內容幫大家也不行啦，大家參考別的狗狗吧~

【考古】

V1 duke3d001 750, wade777, echosweet 700 & yueqianchen

關鍵詞：45KM, Olivine, Orthopyroxene (referenced by gitarrelieber)。這篇文章的題目不難，狗的骨架也很清晰。

第一段講火山爆發來源于Mantle中的Lava，而Lava來源于Melt ，Melt在向地表上升的過程中會與Mantle中的Rock反應并不斷互相交換物質、變化結構，即吸收Orthopyroxene并排出Olivine。

第二段說一個跟理論不太相符的事情，一種海底里的lava sample，在距離地表45千米突然發現已經停止這種物質交換，Melt的結構不變了。一種假設是那里的Mantle太松散了，使Melt無法與他們接觸并交換物質，但立即被否定了(因為45KM還很深東西都很軟，沒有裂縫)。另一種假設是Melt在之前的上升過程中已經吸收了足夠的Orthopyroxene， 并將能排出的Olivine都排了，無法繼續反應。

1 darkchoco 710是什么可以證明這種exchange的存在：熔巖的成分

2 gyz12 740 一道文章最后句定位：Olivine的用完了,exchange就停止了

3 gyz12 740 一道是選chemical composition為特征 sashimiyuki 720 V37 選“lab experiments” indicate 那個melt 的變化的，沒有選chemical composition, 細節題定位后決定的，確認后到現在還沒有深深后悔過

4 tianmo0512 是什么發生反應：選melt

5 feifeizoe 750 V39 文中什么情況下描述了那種正常的exchange：lab experiment中實現了那種現象

6 The author mention “the melt to rise so rapidly” in order to：提出了一種hypothesis，這種hypothesis在后面被反駁

(疑似)原文未縮減 gitarrelieber (sereneys 730 V40 基本確認)

節選自The Origin of the Land under the Sea (Scientific American Magazine @ February 2009)

Author: Peter B. Kelemen

Knowledge of the intense heat and pressure in the mantle led researchers to hypothesize in the late 1960s that ocean crust originates as tiny amounts of liquid rock known as melt—almost as though the solid rocks were “sweating.” Even a minuscule release of pressure (because of material rising from its original position) causes melt to form in microscopic pores deep within the mantle rock. Explaining how the rock sweat gets to the surface was more difficult. Melt is less dense than the mantle rocks in which it forms, so it will constantly try to migrate upward, toward regions of lower pressure. But what laboratory experiments revealed about the chemical composition of melt did not seem to match up with the composition of rock samples collected from the mid-ocean ridges, where eruptedmelt hardens. Using specialized equipment to heat and squeeze crystals from mantle rocks in the laboratory, investigators learned that the chemical composition of melt in the mantle varies depending on the depth at which it forms; the composition is controlled by an exchange of atoms between the melt and the minerals that makeup the solid rock it passes through. The experiments revealed that as melt rises, it dissolves one kind of mineral, orthopyroxene, and precipitates, or leaves behind, another mineral, olivine. Researchers could thus infer that the higher in the mantle melt formed, the more orthopyroxene it would dissolve, and the more olivine it would leave behind.(melt上升時， 溶解Ort產生Oli, 所以melt higher， 溶解的Ort越多，產生的/留在身后的Oli也越多) Comparing these experimental findings with lava samples from the mid-ocean ridges revealed that almost all of them have the composition of melts that formed at depths greater than 45kilometers. This conclusion spurred a lively debate about how meltis able to rise through tens of kilometers of overlying rock while preserving the composition appropriate for a greater depth. If melt rose slowly in smallpores in the rock, as researchers suspected, it would be logical to assume that all melts would reflect the composition of the fashallowest part of the mantle,at 10 kilometers or less. Yet the composition of most mid-ocean ridge lavas amples suggests their source melt migrated through the uppermost 45 kilometers of the mantle without dissolving any orthopyroxene from the surrounding rock. But how? (疑大概為狗狗第一段的背景內容) 精品小說推薦： 昔日落魄少年被逐出家族，福禍相依得神秘老者相助，從此人生路上一片青雲！ 我行我瀟灑，彰顯我性格！ 彆罵小爺拽，媳婦多了用車載！ 妹紙一聲好歐巴，轉手就是摸摸大！ “不要嘛！” 完整內容請點擊辣手仙醫

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