TN-5-Q24+Q25常做常错

fatmoe

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 likea 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.

Q23:

It can be inferred from the passage that a chain of volcanoes created by a mantle plume would most likely be characterized by

A.a curved outline

B.constituent volcanoes that differ from each other in age

C.occurrence near a plate boundary where one plate bends under another

D.appearance near many other volcanic chains

E.rocks with a wide range of chemical composition

答案是B。求定位……

Q24:

The author’s reference to the Hawaiian Islands serves primarily to

A.provide an example of a type of volcanic activity that does not occur elsewhere

B.identify the evidence initially used to establish that the Pacific plate moves

C.call into question a theory about the source of the volcanoes that created the Hawaiian Islands


D.illustrate the distance from plate edges at which volcanoes typically appear

E.provide an example of how mantle plumes manifest themselves on Earth’s surface

答案是E，求解释……

Q23已经把文章读了两遍了，但是就是找不到。最近做RC经常错细节题，不知道是不是年纪大了，眼神不好了……Q24也是我经常错的类型。觉得答案说的意思都很接近。求NN解释~~万分感谢~~
今天做的这套题错误率出奇的反弹了，所以很想究一究为甚！拜谢！！

xuganwilliam

虽然已经考完GMAT半年了，看MM这么执着就来掺和一下。
Q23要理解为何选B关键是理解这一句话：
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.
hot spot保持不动，但是上面的surface plate一直在移动。因此每隔一段时间发飙的active plume会在surface plate上每隔一段距离打出一个印记，每个印记就是一个volcano。经过很长时间后，这些印记会形成一条链状结构。从上面也可以推导出，这条链上的印记会是从老到新排列。即选项B的含义。

可以做一个电影里的场景做类比，坏蛋拿着冲锋枪对着正在关闭的电梯门扫射，电梯门会由于自身的移动而产生一列整齐的凹坑，第一个凹坑的年纪最大，之后逐渐变新。

xuganwilliam

我对Q24的解释跟Q23中的是一样的，所以就不重复了。如果不理解可以继续问。

chenlencu

稍微明白了点。。

sabineceng

当时直接没读懂，选了A……

findjuhl

同求24题的答案解析，为什么不是A呢？