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# Earth’s surface consists of rigid plates that are constantly shifting

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Re: Earth’s surface consists of rigid plates that are constantly shifting [#permalink]
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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 surfaceCorrect - 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, 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.

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Re: Earth’s surface consists of rigid plates that are constantly shifting [#permalink]
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Hi Experts - could you please provide some tips on tackling such RCs. I usually get a bit confused in RCs that discuss rocks, topography etc. maybe because they have technical information. Would it help if I skip the technical part? (I got 2/4 correct on this one.)
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Re: Earth’s surface consists of rigid plates that are constantly shifting [#permalink]
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Hi Experts - could you please provide some tips on tackling such RCs. I usually get a bit confused in RCs that discuss rocks, topography etc. maybe because they have technical information. Would it help if I skip the technical part? (I got 2/4 correct on this one.)

You have no option! You should fall in love the topic you are reading if you want to be successful in RC.
Start from reading more scientific articles in Scientific American or similar, watch more National Geographic.
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Re: Earth’s surface consists of rigid plates that are constantly shifting [#permalink]
2. It can be inferred from the passage that a chain of volcanoes created by a mantle plume would most likely be characterized by

Quote:
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.

(A) a curved outline. The passage says that a track is created. We cannot say if the track is straight or curved from the passage.
(B) constituent volcanoes that differ from each other in age. From the italacized part of the quoted text we can infer this.
(C) occurrence near a plate boundary where one plate bends under another. This is in the context of how volcanic activity occurs. Not in the context of chain of volcanoes.
(D) appearance near many other volcanic chains. Nothing as such is mentioned in the passage.
(E) rocks with a wide range of chemical composition. Nothing as such is mentioned in the passage.

4) According to the passage, a hot spot on Earth’s surface is an indication of which of the following?

Quote:
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.

A. An untapped reservoir of hot rock in the base of the mantle. We can't say anything about the reservoir being tapped or untapped from the passage. Moreover, a hot spot on the surface represents hot material(liquid form) at the mantle base, not hot rock(solid form).
B. Volcanic activity at the edge of a plate. This choice is exact opposite. A hot spot is volcanic activity far from the edge of a surface plate.
C. Solid mantle rock under tremendous pressure.
Quote:
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
.[color=#ff0000]A sphere forcing its way up does not necessarily mean solid mantle rock is under tremendous pressure.

D. The occurrence of a phenomenon unique to the Pacific plate. Nothing as such is mentioned in the passage.
E. A plume of hot mantle rock originating near Earth’s core. Correct
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Re: Earth’s surface consists of rigid plates that are constantly shifting [#permalink]
I am still confused about second question. The passage says "... forces its way up through the upper mantle to Earth’s surface, creating a broad bulge in the topography...". Does it not mean that it is a curved outline?
anairamitch1804
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!
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Re: Earth’s surface consists of rigid plates that are constantly shifting [#permalink]
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5min 50 Sec to Read and solve the questions

1. The passage is primarily concerned with discussing

The first para talks about how volcanoes are formed generally (at the edge of the plates), whereas the second Para talks about how volcanoes can form in a different way from the one mentioned previously.

(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 > Fits the bill
(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

Refer to 2nd para, last but 5-6th line " 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," this indicates that volcanoes in the chain differ across age over a broad range

(A) a curved outline
(B) constituent volcanoes that differ from each other in age > Fits the bill
(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 > this was never stated explicitly in the passage
(B) identify the evidence initially used to establish that the Pacific plate moves >the example tells that volcanic eruption can occur due to reason different mentioned in the first para
(C) call into question a theory about the source of the volcanoes that created the Hawaiian Islands >Authors gives an example of the 2nd mechanism, he does not contradict the 1st mechanism mentioned in the first para
(D) illustrate the distance from plate edges at which volcanoes typically appear >Irrelavent information
(E) provide an example of how mantle plumes manifest themselves on Earth’s surface >Correct

4) According to the passage, a hot spot on Earth’s surface is an indication of which of the following?

Based on the below lines from 2nd para

"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. "
"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,"
"The surface mark of an established plume is a hot spot"

We can conclude hotspot refers to plume of the upper mantle from the earth center.core

(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
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Earth’s surface consists of rigid plates that are constantly shifting [#permalink]
BrentGMATPrepNow
souvik101990
New GMAT Prep RC Project: 1 RC Every day. Don't forget to time yourself with the stopwatch below to earn kudos.

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. 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
(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

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

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.
---------------------------------------------------------------------
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

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BrentGMATPrepNow BrightOutlookJenn GMATNinja What is your thought process for question 2 (inference)? How would you solve it?! How can I do it faster? Tks!
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Re: Earth’s surface consists of rigid plates that are constantly shifting [#permalink]
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Hi Will2020

Thanks for the tag.

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

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.
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Re: Earth’s surface consists of rigid plates that are constantly shifting [#permalink]
Quote:
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

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?

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Re: Earth’s surface consists of rigid plates that are constantly shifting [#permalink]
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Quote:
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

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?

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.

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Re: Earth’s surface consists of rigid plates that are constantly shifting [#permalink]

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,
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Re: Earth’s surface consists of rigid plates that are constantly shifting [#permalink]
PanpaliaAnshul

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

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.
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Re: Earth’s surface consists of rigid plates that are constantly shifting [#permalink]
still really dont understand why it's E over A for the question on the hot spot. I guess "untapped" is the dealbreaker here (if so sheesh GMAT, being so harsh with intricacies)? What an intricate detail, as hot rock clearly is not the reason as someone said above (even though it flows like a liquid, it is still a hot rock technically, is what I'm reading at least).
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Re: Earths surface consists of rigid plates that are constantly shifting [#permalink]

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.
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Re: Earths surface consists of rigid plates that are constantly shifting [#permalink]
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.
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Re: Earths surface consists of rigid plates that are constantly shifting [#permalink]
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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.
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Re: Earths surface consists of rigid plates that are constantly shifting [#permalink]
For question 4 - option A, if it's untapped, then we don't have the hot spot in the first place. We have the spot because the reservoir has been tapped thus creating the hot-spot. Option C described the mantle in general, as explained in the 1st para. Only option E is left which is a bit weird but is true per the passage.

For Question 3 - in option A "elsewhere" is extreme and Huwaii is one example of this type of volcano. E is only correct per the passage.
Re: Earths surface consists of rigid plates that are constantly shifting [#permalink]
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