GWD-7-Q25 知道定位点，但不知为何是此处定位~？

miss绿光

Earth’s surface consists of rigid plates that are constantly shifting and jostling one another.Plate movements are the surface expressions of motions in the mantle—the thick shell of rock that lies between Earth’s crust and its metallic core.Although the hot rock of the mantle is a solid, under the tremendous pressure of the crust and overlying rock of the mantle, it flows like a viscous liquid.The mantle’s motions, analogous to those in a pot of boiling water, cool the mantle by carrying hot material to the surface and returning cooler material to the depths.When the edge of one plate bends under another and its cooler material is consumed in the mantle, volcanic activity occurs as molten lava rises from the downgoing plate and erupts through the overlying one.

Most volcanoes occur at plate boundaries.However, certain “misplaced” volcanoes far from plate edges result from a second, independent mechanism that cools the deep interior of Earth.Because of its proximity to Earth’s core, the rock at the base of the mantle is much hotter than rock in the upper mantle.The hotter the mantle rock is, the less it resists flowing.Reservoirs of this hot rock collect in the base of the mantle.When a reservoir is sufficiently large, a sphere of this hot rock forces its way up through the upper mantle to Earth’s surface, creating a broad bulge in the topography.The “mantle plume” thus formed, once established, continues to channel hot material from the mantle base until the reservoir is emptied. The surface mark of an established plume is a hot spot—an isolated region of volcanoes and uplifted terrain located far from the edge of a surface plate.Because the source of a hot spot remains fixed while a surface plate moves over it, over a long period of time an active plume creates a chain of volcanoes or volcanic islands, a track marking the position of the plume relative to the moving plate.The natural history of the Hawaiian island chain clearly shows the movement of the Pacific plate over a fixed plume.
According to the passage, a hot spot on Earth’s surface is an indication of which of the following?

A.An untapped reservoir of hot rock in the base of the mantle

B.Volcanic activity at the edge of a plate

C.Solid mantle rock under tremendous pressure

D.The occurrence of a phenomenon unique to the Pacific plate

E.A plume of hot mantle rock originating near Earth’s core


根据以上两处定位得答案E。

不明白为何定位那两处，也不明白为什么由这两处得出E。

求大家帮助。

抓抓sandra

定位首先先看题目,题目里头可以提取出keywords: "hot spot" "indication",由此可知问题和hot spot的含义有关.

找到keyword以后,回到原位去定位,就会发现hot spot出现在第二段你highlight的第二个句子. 同时根据读题知道题目问的是hot spot的含义是什么,所以在原文定位上下文找描述hot spot的意义的句子.  第二处highlight是提示你这段话介绍的hot spot和第一段介绍的边缘板块理论不同的特殊之处,就在于its proximity to Earth’s core
"The surface mark of an established plume is a hot spot."这句话本身已经提示hot spot MARKs an established plume,基本上已经是E的同义改写了

不放心的话,再往后读一句: 后一句说到了hot spot如何留下a chain of volcanoes or volcano islands,更重要的是同位语解释了这个chain的作用——a track marking the position of the plume relative to the moving plate.
到这里已经可以非常确定选E了.
A.无关,提到reservoir的前文目的是介绍hot spot的形成过程,问的是hot spot的indication
B.无关,volcano activity at the edge是第一段的内容,第二段开头明确提出要介绍的是完全不同的一种火山活动
C.无关,同样也是第一段的内容,看文章第二行
D.无端猜测. pacific plate确实出现了这种hot spot,但是文章没有说是unique的
E选项就是这个同位语的同义改写

月上柳梢头

抓抓sandra 发表于 2011-10-4 16:00
定位首先先看题目,题目里头可以提取出keywords: "hot spot" "indication",由此可知问题和hot spot的含义有 ...

同意！