Earths surface consists of rigid plates that are constantly shifting

Question

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.   1 
 1. The passage is primarily concerned with discussing

(A) the composition of Earth’s mantle
(B) how the Hawaiian Islands were created
(C) what causes Earth’s surface plates to move
(D) two different mechanisms by which volcanoes are formed
(E) why most volcanoes occur at plate boundaries

2 
 2. 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

3 
 3. 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

4 
 4. 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

anairamitch1804 · Accepted Answer

Earth - plates moving around, showing motions deeper down 
like boiling water - hot stuff comes to the top and cooler stuff goes down 
can cause volcanoes (usually at plate boundaries) 
BUT there's another way to get volcanoes: 
hotter rock = flows more easily 
this hot rock collects deep down 
when you get enough, it pushes up to make a bulge (volcano) even though it's not at a plate boundary 
this kind can create chains or islands of volcanoes - eg Hawaii 
Then I'd go back and label my first three lines "1 way" and the rest "the other way" (meaning the passage is split into two different ways to make a volcano)

1)The answer here is D, because the text has two distinctive sections, discussing two different processes: 
- volcanic activity molten lava rises from the down going plate and erupts through the overlying one 
- volcanoes that appear far away from plate intersections, in the "mantle plume" situation 
A is incorrect because the composition of the mantle is not discussed, rather its movements. B is also incorrect because the islands are only mentioned once as an example C is wrong because these surface plates are only discussed in the first part of the text. The second concerns that mantle plume situation, which is not a part of the "surface plates" topic. The last answer choice is similarly wrong, because this is only mentioned in the first part of the text.
or
Q1 Main idea 
a couple of different ways to make volcanoes (can get this from my notes above). Answer D says almost exactly that. 
Q2 inference - chain of volcanoes - I remember that's from towards the end of my notes, so I go scan the passage again.
"over a long period of time an active plume creates a chain of volcanoes" 
So, if it takes place over a long period of time, those volcanoes must be different in age relative to each other. A is tempting because I remember seeing maps of volcano chains... but that's not in the passage. C is contradicted by the passage. D and E aren't discussed - I have no idea (so, therefore, I can't infer the info). 
Hence B. 
Q3 why does the author refer to Hawaii 
From my notes - Hawaii is an example of the chain thing 
A is fine until we get to "does not occur elsewhere" - this is one of the major two ways of making volcanoes 
scanning down... E matches my original idea (which I developed before looking at the choices) - it's an example of how this alternate way works 
Q4 specific detail - a "hot spot" is an example of what? 
That's about the "hotter rock" which was also talked about in the second way (chains), so scanning the passage...
"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." 
So, not B. Not D - says nothing about being unique to Pacific. Need a little more info - back to the passage. So the "hot spot" is this "established plume" thing and a "plume" is the result of a reservoir of very hot rock from the mantle. 
A says the reservoir is "untapped" - but if it's coming up to the surface, then we can't call it "untapped." C says the rock is under enormous pressure - and I generally believe that, but I'm not finding a place in the passage where it specifically says that. 
E calls it a plume, which the passage does say, and also says it's mantle rock, which is true according to the passage. And E says that this mantle rock comes from near the core and the passage does say that this stuff comes from the "base" of the mantle and describes it as having "proximity to Earth's core." So this one looks right!

BrentGMATPrepNow · Answer

As we read the passage, we should note the following:
- summary of each paragraph (4 to 8 words)
- Two (or more) points of view (4 to 8 words)
- main idea (4 to 8 words)

Paragraph 1 summary: Moving plates cause volcanoes at edges
Paragraph 2 summary: Non-edge volcanoes from rising hot mantle bulge
Two points of view: 2 ways volcanoes form
Main idea: 2 ways volcanoes form

1. The passage is primarily concerned with discussing
(A) the composition of Earth’s mantle
(B) how the Hawaiian Islands were created
(C) what causes Earth’s surface plates to move
 (D) two different mechanisms by which volcanoes are formed 
(E) why most volcanoes occur at plate boundaries

Answer choice D matches our summary. 
---------------------------------------------------------------------
2. 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

The passage tells us that " 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. "
So, as the plates travel over the fixed hot spot, new volcanoes are formed and those volcanoes are transported away from the hot spot via plate movement. This allows for the formation of another volcano over that fixed hot spot. And another. etc
So, the resulting chain of volcanoes will be of various ages. 
Answer: B
---------------------------------------------------------------------
3. 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 
By the process of elimination, we are left with answer choice E
---------------------------------------------------------------------
4) 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

The passage says  The surface mark of an established plume is a hot spot 
Answer: E

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Nightfury14 · Answer

Timer - 9min: 32sec

1) The passage is primarily concerned with discussing 
A. the composition of Earth’s mantle
B. how the Hawaiian Islands were created
C. what causes Earth’s surface plates to move
 D. two different mechanisms by which volcanoes are formed 
E. why most volcanoes occur at plate boundaries

2) 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  Correct, Because the source of a hot spot remains fixed while a surface plate moves over it,  over a long period of time  
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

3)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 Correct -  the natural history of the Hawaiian island chain clearly shows the movement of the Pacific plate over a fixed plume.

4) 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  Correct, B ecause of its proximity to Earth’s core, the rock at the base of the mantle is much hotter than rock in the upper mantle.

Good luck

Will2020 · Answer

BrentGMATPrepNow BrightOutlookJenn GMATNinja What is your thought process for question 2 (inference)? How would you solve it?! How can I do it faster? Tks!

BrightOutlookJenn · Answer

Hi  Will2020

Thanks for the tag.

You asked:

The heavy lifting on this question is actually done when reading the passage.  Reading this passage effectively requires  a lot of visualization . My thought process: as soon as I hit the second sentence of the first paragraph, I paused and took a moment to try to visualize these layers (crust/mantle/core) that are being described. With every new detail, I really tried to visualize it in my mind, in as much detail as is described. Some candidates will find it helpful to sketch a quick diagram.

If you don't have clear images in your mind of what the passage is describing, you are dead in the water on this , because the second paragraph goes on with new details that build on your understanding of the general layout (crust/mantle/core) initially mentioned in the first paragraph.

To get into my thought process while reading the second paragraph ... as soon as it starts with   Most  blah blah blah do X , you know you're going to get a  But SOME WEIRD OTHER ones do Y . Here we get it with these weirdo volcanoes in the middle of nowhere relative to plate boundaries. My thought - "how the heck did they get there? That's WEIRD." So now I'm keen to know about what created these middle-of-nowhere volcanoes. As I read about the plumes, I visualize as much as possible, and then they helpfully include the Hawaiian islands as a concrete example. I'm clearly envisioning the crust moving over the same hot spot and these volcanoes popping up, one after the other, creating Hawaii.

My understanding of this is really clear after my first reading of the passage, so question 2 then becomes relatively straightforward. C is hardcore wrong (describes the paragraph 1 kind of volcanoes) and E is completely out of scope, so I eliminate these right away. Then I go back to the paragraph, and look for where they actually talk about the volcanoes created by this process. It's in the last two sentences of the paragraph. There's no clear evidence in these sentences for a curved outline or the presence of other volcanic chains, but the way they describe Hawaii means that one volcano was created first, then the crust moved a bit, and a new volcano was created, crust moved more, a third volcano, and so on ... and this matches well with the description in B, that the volcanoes differ in age. (Since there was a first one, second one, third one, etc, thus they weren't all created at the same time, they have to have different ages.)

So the way to  do this question faster  is probably to  read the passage more slowly , to  really visualize  and understand what they are describing. That allows you to make short work of the question itself, as you eliminate clearly wrong answers (C and E) and know where to go back to find the evidence you need to narrow down the rest.

Does this help? Please let us know.

mSKR · Answer

Matching Text:
 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.

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

I don't doubt that how B is the correct answer. But I find A is hard to reject . 
A curved outlines indicates at the bold lines that I have marked. Please suggest how to reject A option.

I was also not easy in rejecting D but A and B are definitely better than D ( creates a chain of volcanoes or volcanic islands  - this text doesn't necessarily represent that many other volcanic chains necessarily need to be each other ). Am i right?

Please suggest  AndrewN   GMATNinja

AndrewN · Answer

Hello,  mSKR . I think  BrightOutlookJenn  in the post above yours outlines how to steer clear of a trap answer like (A). You cannot pick and choose which keywords to stitch together to create a valid answer. Here, the question refers to  a chain of volcanoes created by a mantle plume . The first snippet of text you quoted above contains the keywords  plume ,  creates , and, of course,  a chain of volcanoes . The only missing word is  mantle . Meanwhile, the second contains the missing  mantle , and it does say  creating , but what is being created? A chain of volcanoes? I cannot say that  a broad bulge  is necessarily synonymous with  a chain of volcanoes  from the question stem. (Since when would I describe volcanoes as a broad bulge in the topography?) (A) is unclear and takes a little logical finagling to justify; (B) has direct textual evidence. Finally, (D) is saying that one volcanic chain appears near other—entirely different—volcanic chains (not individual volcanoes). You have to read carefully, but this is an easier elimination than (A).

I hope that helps.

- Andrew

anshul0130 · Answer

VeritasKarishma  - Please review below understanding on question 2 option D and advise if it's correct.

An active plume creates a chain of volcanoes i.e. new individual volcanoes are added to old ones, and not new volcano chains appear near to other existing volcano chain.

If my understanding is not apt, please share your understanding for knocking off option D.

Thanks,
Anshul

KarishmaB · Answer

Yes, the plume creates more and volcanoes over time and hence you get a volcanic chain.

We are given that "plumes create a hot spot - an isolated region of volcanoes". So you wouldn't see other volcanic chains nearby. Most volcanoes occur at plate boundaries. However, certain “misplaced” volcanoes far from plate edges result from plumes.

Rickooreo · Answer

KarishmaB  can you please help me with Q2 and Q3 of this RC

In Q2, I understand that B is correct, however, I am unable to eliminate D because of the following para from the passage :
Option D : appearance near many other volcanic chains

"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. "

Chain of volcanoes means there will be other volcanoes around, D mentions the same. Is it that I am missing something ?

Q3 The author’s reference to the Hawaiian Islands serves primarily to
(B) identify the evidence initially used to establish that the Pacific plate moves
The passage mentions : 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.

Because of the bold part I selected option B.

Rickooreo · Answer

In Q2, I understand that B is correct, however, I am unable to eliminate D because of the following para from the passage :
Option D : appearance near many other volcanic chains

"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. "

Chain of volcanoes means there will be other volcanoes around, D mentions the same. Is it that I am missing something ?

Q3 The author???s reference to the Hawaiian Islands serves primarily to
(B) identify the evidence initially used to establish that the Pacific plate moves
The passage mentions : 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.

Because of the bold part I selected option B.

RonTargetTestPrep · Answer

Choice D doesn't just refer to  a group of volcanoes —it actually refers to a group  OF GROUPS of volcanoes .

You've already realized that "a  chain  of volcanoes" is a  group  of them (formed over one hot spot, as one of Earth's plates moves over that spot).

Choice D, however, talks about "many  OTHER  volcanic  chains "—in other words, other clusters or groups of the same type.
That's directly contradicted by the passage text, which says that an established mantle plume will create "an  isolated  region of volcanoes"—and, a couple lines later, clarifies that this isolated region will contain " a chain  of volcanoes or volcanic islands", i.e., only ONE chain = ONE group.

Since that chain/group of volcanoes is ISOLATED—i.e., nowhere near any other such group—choice D states the opposite of the truth.

Earths surface consists of rigid plates that are constantly shifting

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GMAT Reading Comprehension (RC) Questions

Earths surface consists of rigid plates that are constantly shifting

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