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Iridium, a hard, whitish metal similar to platinum, is

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Re: Iridium, a hard, whitish metal similar to platinum, is [#permalink]

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New post 30 Oct 2013, 06:00
I sort of agree with OE.

A is quite opposite of what is stated in the stimulus. Stimulus explicitly states that both volcanic eruptions and meteors are capable producing extremely high concentrations of iridium. A opposes it. Remember we have to accept what is mentioned in the stimulus as a fact and answers negating the fact in stimulus are not good choices. IMHO.

B states that volcanoes erupted frequently 80 million years ago, this implies two scenarios 1) After sometime volcanic eruptions stopped and therefore can not be the reason for dinosaur extinction. 2) The fact the dinosaurs became extinct around 65 million years means that they survived volcanic eruptions that occurred 80 million years ago. With these two one can conclude that dinosaurs continued to exist after volcanic eruptions and there were no volcanic eruptions when dinosaur extinction occurred. This explanation also identifies comet/meteor as the only source of iridium found in rock stratum from 65 million years ago.
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Re: Iridium, a hard, whitish metal similar to platinum, is [#permalink]

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WaterFlowsUp wrote:
Karishma,

Option B comes somewhat closer, but B has flaws:
1. Do we know when for how long dinosaurs existed?
2. 80m years ago meteoric showers were frequent but is that anyhow supports dinosaurs to be killed?


Most of it is an inference/assumption. Usually a GMAT question would be clearer but the intent of this question is clear to us through our general knowledge. Dinosaurs lived in the Mesozoic era (between 230 and 65 million years ago)

We need to strengthen the theory that meteors caused extinction, that is, volcanoes did not. If massive volcanoes were common at that time, they probably did not cause the wipeout.
(A) tells you that very massive volcanoes are rare but it doesn't say they don't occur. Hence it doesn't say that volcanoes probably did not cause the extinction. In fact, if very massive volcanoes are rare, a rare instance could very well have caused the extinction of the species.
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Re: Iridium, a hard, whitish metal similar to platinum, is [#permalink]

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New post 24 Nov 2013, 09:11
I agree with retro, B
B is saying that it is less likely that volcanic activities have led to the extinction because these activities have occurred before the extinction.

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Re: Iridium, a hard, whitish metal similar to platinum, is [#permalink]

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New post 01 Dec 2013, 12:00
B is out. Infact, it is weakening the argument.

Its like , A and B are possible suspects for a murder and the jury has concluded that B is the murderer then suddenly the another lawyer says " no your honor! my client A was also there with the knife. Actually the option B in above case increases uncertainty of the single cause behind the effect and therefore increases the uncertainty of the conclusion hence the argument itself.

Well , yes, between A and C there is an space for debate. First, we have to trust the Experts when they comment as in C case.Second, my preference for A is as because C just repeat the conclusion not adding on to it whereas A add on to the conclusion further. Moreover, as above said, "rare" makes the support variable (from 1% -100%) but here we are providing support not the 100% support.


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Re: Iridium, a hard, whitish metal similar to platinum, is [#permalink]

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New post 06 Aug 2014, 22:01
retro wrote:
Here is the explanation provided by the guide:

Answer: B. This is a strengthen question. Its conclusion and premises are:
Premises: (1) Extremely high concentrations of iridium on Earth result from only two scenarios: massive volcanic eruptions that release iridium from deep within the Earth and meteorites that shower down on Earth from space. (2) Scientists found concentrations of iridium 30 times higher than normal in rock stratum from 65 million years ago.
Conclusion: A massive meteor or comet hit the Earth and caused the mass extinction of the dinosaurs.

According to the premises, there are two possible causes of high iridium levels. But the conclusion states that one of the causes—a meteor— was definitely the culprit. So the assumption must be that there was not a volcanic eruption that caused the extinction. Once again, you have a causal argument, but now you are going to strengthen it. In order to do so, you should look for answers that rule out other possible causes. Choice B strengthens the argument by showing that volcanic eruptions occurred frequently before the extinction, but the dinosaurs continued to live. Thus, it is unlikely that the extinction was caused by a volcano and more likely that a meteor caused it. Choice A doesn’t go far enough. Even if the volcanoes are rare, the extinction could have been caused by just one eruption. Choice C doesn’t strengthen the argument. Other scientists’ support of the hypothesis doesn’t address the connection between the conclusion and the premise. Choice D has nothing to do with the argument, while choice E weakens the argument by indicating that a previous comet strike did not lead to an extinction.



So as per TMH 80 million =65 million. Too oversweeping a generalisation even if we take the large timescales involved and mind you we are not required to have any outside knowledge in GMAT

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Iridium, a hard, whitish metal similar to platinum, is [#permalink]

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retro wrote:
Here is the explanation provided by the guide:

Answer: B. This is a strengthen question. Its conclusion and premises are:
Premises: (1) Extremely high concentrations of iridium on Earth result from only two scenarios: massive volcanic eruptions that release iridium from deep within the Earth and meteorites that shower down on Earth from space. (2) Scientists found concentrations of iridium 30 times higher than normal in rock stratum from 65 million years ago.
Conclusion: A massive meteor or comet hit the Earth and caused the mass extinction of the dinosaurs.

According to the premises, there are two possible causes of high iridium levels. But the conclusion states that one of the causes—a meteor— was definitely the culprit. So the assumption must be that there was not a volcanic eruption that caused the extinction. Once again, you have a causal argument, but now you are going to strengthen it. In order to do so, you should look for answers that rule out other possible causes. Choice B strengthens the argument by showing that volcanic eruptions occurred frequently before the extinction, but the dinosaurs continued to live. Thus, it is unlikely that the extinction was caused by a volcano and more likely that a meteor caused it. Choice A doesn’t go far enough. Even if the volcanoes are rare, the extinction could have been caused by just one eruption. Choice C doesn’t strengthen the argument. Other scientists’ support of the hypothesis doesn’t address the connection between the conclusion and the premise. Choice D has nothing to do with the argument, while choice E weakens the argument by indicating that a previous comet strike did not lead to an extinction.




I think the explanations for Choice A and B contradict each other:

"Choice A doesn’t go far enough. Even if the volcanoes are rare, the extinction could have been caused by just one eruption."By this logic used to eliminate choice A, one can say that although massive volcanoes occurred 80 million years ago without resulting in extinction, one giant unfathomably supernormous volcano did the trick 65 mill yrs ago. Answer choice B leaves equal room for doubt as does choice A. Answer choice C strengthens the argument by adding credibility to the scientist's claim.

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Re: Iridium, a hard, whitish metal similar to platinum, is [#permalink]

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Read Power Score CR Bible those who supports "C".

It clearly says: "Eliminate any alternate cause for the stated fact"

As argument clearly states only meteor or comet (or somewhat about Volcanic eruptions):

[b]"they concluded that a massive meteor or comet hit the Earth and caused the massive extinction of the dinosaurs"


"Cosmic bla bla" is clearly an alternate cause. Though should be eliminated.

As (D) and (E) are already out of scope, so lets get back to (a) & (b):

(a) states "power or strength of eruption" which is clearly out of scope as conclusion is clearly about WHO CAUSED?

Hence, (B) is the choice.

"Work on process on elimination with strong ground to account on, really will give positive results on these types of problems"

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Re: Iridium, a hard, whitish metal similar to platinum, is [#permalink]

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#Top150 CR: Iridium, a hard, whitish metal similar to platinum [#permalink]

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Iridium, a hard, whitish metal similar to platinum, is extremely rare on Earth. Extremely high concentrations of iridium on Earth result from only two scenarios: massive volcanic eruptions that release iridium from deep within the Earth and meteorites that shower down on Earth from space. When scientists found concentrations of iridium 30 times higher than normal in rock stratum from 65 million years ago, they concluded that a massive meteor or comet hit the Earth and caused the massive extinction of the dinosaurs.

Which of the following, if true, most strongly supports the scientist’s conclusion?

A. Volcanoes massive enough to generate high concentrations of iridium are very rare.

B. Massive volcanic eruptions occurred frequently 80 million years ago.

C. Most scientists support the hypothesis that a cosmic impact wiped out the dinosaurs.

D. The massive extinction that occurred 70 million years ago killed not only the dinosaurs but also 70 percent of all life on Earth.

E. A comet struck the earth some 120 million years ago, but no widespread extinction occurred.
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Re: #Top150 CR: Iridium, a hard, whitish metal similar to platinum [#permalink]

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New post 11 Oct 2015, 05:04
Iridium, a hard, whitish metal similar to platinum, is extremely rare on Earth. Extremely high concentrations of iridium on Earth result from only two scenarios: massive volcanic eruptions that release iridium from deep within the Earth and meteorites that shower down on Earth from space. When scientists found concentrations of iridium 30 times higher than normal in rock stratum from 65 million years ago, they concluded that a massive meteor or comet hit the Earth and caused the massive extinction of the dinosaurs.

Which of the following, if true, most strongly supports the scientist’s conclusion?

A. Volcanoes massive enough to generate high concentrations of iridium are very rare.
not impossible and we are not sure it cannot be a possibility at 65 million years.

C. Most scientists support the hypothesis that a cosmic impact wiped out the dinosaurs.
(most scientists supporting a theory does not validate it.)

E. A comet struck the earth some 120 million years ago, but no widespread extinction occurred.
(no extinction and 120 years ago does not help our conclusion.)

Between B and D,

B. Massive volcanic eruptions occurred frequently 80 million years ago.
(This explains the scenario 80 million years ago but what about 15 million years later.)
D. The massive extinction that occurred 70 million years ago killed not only the dinosaurs but also 70 percent of all life on Earth.
(this just says extinction but it does not say what might be the cause for it. Is it volcano or comet)
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Re: #Top150 CR: Iridium, a hard, whitish metal similar to platinum [#permalink]

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New post 29 Feb 2016, 07:28
The question is why experts concluded that dinosaurs went extinct due to comet strike rather than volcano.
A. Volcanoes massive enough to generate high concentrations of iridium are very rare.
Maybe they are rare now. But once in 65 mil years is rare too. So, this cannot say why the extinction should not have been caused by volcano.

B. Massive volcanic eruptions occurred frequently 80 million years ago.
Correct. Massive volcanic eruption was common around 80 million years ago. So dinosaurs had evolved to survive such eruptions.

C. Most scientists support the hypothesis that a cosmic impact wiped out the dinosaurs.
Doesn't explain why eruption was ruled out or cosmic impact explanation was picked to be the cause.

D. The massive extinction that occurred 70 million years ago killed not only the dinosaurs but also 70 percent of all life on Earth.
Unhelpful

E. A comet struck the earth some 120 million years ago, but no widespread extinction occurred.
Undermines the conclusion.

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Re: Iridium, a hard, whitish metal similar to platinum, is [#permalink]

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New post 08 Jul 2016, 00:48
retro wrote:
Here is the explanation provided by the guide:

Answer: B. This is a strengthen question. Its conclusion and premises are:
Premises: (1) Extremely high concentrations of iridium on Earth result from only two scenarios: massive volcanic eruptions that release iridium from deep within the Earth and meteorites that shower down on Earth from space. (2) Scientists found concentrations of iridium 30 times higher than normal in rock stratum from 65 million years ago.
Conclusion: A massive meteor or comet hit the Earth and caused the mass extinction of the dinosaurs.

According to the premises, there are two possible causes of high iridium levels. But the conclusion states that one of the causes—a meteor— was definitely the culprit. So the assumption must be that there was not a volcanic eruption that caused the extinction. Once again, you have a causal argument, but now you are going to strengthen it. In order to do so, you should look for answers that rule out other possible causes. Choice B strengthens the argument by showing that volcanic eruptions occurred frequently before the extinction, but the dinosaurs continued to live. Thus, it is unlikely that the extinction was caused by a volcano and more likely that a meteor caused it. Choice A doesn’t go far enough. Even if the volcanoes are rare, the extinction could have been caused by just one eruption. Choice C doesn’t strengthen the argument. Other scientists’ support of the hypothesis doesn’t address the connection between the conclusion and the premise. Choice D has nothing to do with the argument, while choice E weakens the argument by indicating that a previous comet strike did not lead to an extinction.



It is not mentioned that Dinosaurs continued to live after Massive volcanic eruptions that occurred frequently 80 million years ago. The rock stratum is from 65 million years ago. And what if the Iridium resulted from the massive volcano eruptions. I agree that A doesn't go far enough, but B also doesn't seem to be convincing.

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Re: Iridium, a hard, whitish metal similar to platinum, is [#permalink]

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New post 18 Aug 2017, 03:01
B is correct only if it is known that massive volcanic eruptions could cause the extinction of dinosaurs. I think the passage is not focused and the conclusion is not well developed.
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Re: Iridium, a hard, whitish metal similar to platinum, is [#permalink]

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New post 21 Aug 2017, 08:01
Merged topics. Please, search before posting questions!
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Re: Iridium, a hard, whitish metal similar to platinum, is [#permalink]

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New post 24 Aug 2017, 11:10
This is a substandard question.
A and B both talk about the rarity of a massive volcanic eruption. However there was a need of only one massive volcanic eruption anyways.

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Re: Iridium, a hard, whitish metal similar to platinum, is [#permalink]

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New post 30 Sep 2017, 05:11
Got this explanation below:-

Answer: B. This is a strengthen question. Its conclusion and premises are:
Premises: (1) Extremely high concentrations of iridium on Earth result from only two scenarios: massive volcanic eruptions that release iridium from deep within the Earth and meteorites that shower down on Earth from space. (2) Scientists found concentrations of iridium 30 times higher than normal in rock stratum from 65 million years ago.
Conclusion: A massive meteor or comet hit the Earth and caused the mass extinction of the dinosaurs.

According to the premises, there are two possible causes of high iridium levels. But the conclusion states that one of the causes???a meteor??? was definitely the culprit. So the assumption must be that there was not a volcanic eruption that caused the extinction. Once again, you have a causal argument, but now you are going to strengthen it. In order to do so, you should look for answers that rule out other possible causes. Choice B strengthens the argument by showing that volcanic eruptions occurred frequently before the extinction, but the dinosaurs continued to live. Thus, it is unlikely that the extinction was caused by a volcano and more likely that a meteor caused it. Choice A doesn???t go far enough. Even if the volcanoes are rare, the extinction could have been caused by just one eruption. Choice C doesn???t strengthen the argument. Other scientists??? support of the hypothesis doesn???t address the connection between the conclusion and the premise. Choice D has nothing to do with the argument, while choice E weakens the argument by indicating that a previous comet strike did not lead to an extinction.

In this explanation we are assuming that there are only two possibilities for the extinction of dinosaur what if there are other possibility (other than volcano & Meteorite)
If volcano didnt lead to extinction then there can be other possibilities as well.
Consider This:-
Iridium found in excess quantity is a result of volcano, and dinosaur extinction was a result of extremely low temp 65 milion year ago.

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Re: Iridium, a hard, whitish metal similar to platinum, is [#permalink]

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New post 07 Oct 2017, 06:28
VeritasPrepKarishma wrote:
targetgmatchotu wrote:
P1: Two causes

1. Volcanoes
2. Meteorites/Comets = > Iridium

P2: -65 million yrs , iridium was 30 times the normal

C: M/C => Dinosaurs extinction

Now B Says ,Massive volcanic eruptions occurred frequently 80 million years ago.Moreover,nowhere it is mentioned that they were infrequent (-65) million years.

A. Volcanoes massive enough to generate high concentrations of iridium are very rare.
B. Massive volcanic eruptions occurred frequently 80 million years ago.
C. Most scientists support the hypothesis that a cosmic impact wiped out the dinosaurs.
D. The massive extinction that occurred 70 million years ago killed not only the dinosaurs but also 70 percent of all life on Earth.
E. A comet struck the earth some 120 million years ago, but no widespread extinction occurred.

Poorly framed question

Plz Advice !!


The OA is a little debatable but not very much.
(C) is certainly not in the running. Just because other people say it, something doesn't become true. You need facts. Most scientists supporting the hypothesis is not a fact that will help me believe the hypothesis. The reason why most scientists support it, might.
(D) and (E) are irrelevant.

So it comes down to:
A. Volcanoes massive enough to generate high concentrations of iridium are very rare.
B. Massive volcanic eruptions occurred frequently 80 million years ago.

Both support the conclusion to an extent.
In (A), volcanoes massive enough to generate high concentrations of iridium are rare, not impossible. There could have been one 65 million yrs ago. Hence, it doesn't strengthen our belief in a comet/meteor much.
In (B), massive volcanic eruptions occuring frequently through Earth's history while dinosaurs lived doesn't imply that there couldn't have been an especially huge one which wiped out the dinosaurs. But it does make comet/meteor theory more probable.

Look at the argument again - two things cause concentration of iridium - volcanoes and meteors
Volcanoes occured frequently while dinosaurs lived on Earth. Chances are that an activity which was not usual wiped out dinosaurs. Since dinosaurs were wiped out 65 million yrs ago and there was iridium concentration in rocks which are from 65 million yrs ago, it makes it more likely that a meteor wiped out dinosaurs.


Hi Karishma,
I initially chose A over B.
I have one query.
office explanation says for B, massive valcanoes eruption happened 80 milliions years ago and [dinosaurs did survive], which means massive valcanoes are not enough to extinct dinosaurs. so only cause to extinction is comet.

But that highlighted portion in red is not mentioned in the passage. It is rather assumption on which official explanation for choice B lies. But this assumption need not be true, maybe, comet did strike 65 milliions years ago but before that a single massive massive valcano could have extincted all dinosaurs.

am i thinking correct?

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Re: Iridium, a hard, whitish metal similar to platinum, is [#permalink]

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New post 12 Oct 2017, 00:02
hellosanthosh2k2 wrote:
VeritasPrepKarishma wrote:
targetgmatchotu wrote:
P1: Two causes

1. Volcanoes
2. Meteorites/Comets = > Iridium

P2: -65 million yrs , iridium was 30 times the normal

C: M/C => Dinosaurs extinction

Now B Says ,Massive volcanic eruptions occurred frequently 80 million years ago.Moreover,nowhere it is mentioned that they were infrequent (-65) million years.

A. Volcanoes massive enough to generate high concentrations of iridium are very rare.
B. Massive volcanic eruptions occurred frequently 80 million years ago.
C. Most scientists support the hypothesis that a cosmic impact wiped out the dinosaurs.
D. The massive extinction that occurred 70 million years ago killed not only the dinosaurs but also 70 percent of all life on Earth.
E. A comet struck the earth some 120 million years ago, but no widespread extinction occurred.

Poorly framed question

Plz Advice !!


The OA is a little debatable but not very much.
(C) is certainly not in the running. Just because other people say it, something doesn't become true. You need facts. Most scientists supporting the hypothesis is not a fact that will help me believe the hypothesis. The reason why most scientists support it, might.
(D) and (E) are irrelevant.

So it comes down to:
A. Volcanoes massive enough to generate high concentrations of iridium are very rare.
B. Massive volcanic eruptions occurred frequently 80 million years ago.

Both support the conclusion to an extent.
In (A), volcanoes massive enough to generate high concentrations of iridium are rare, not impossible. There could have been one 65 million yrs ago. Hence, it doesn't strengthen our belief in a comet/meteor much.
In (B), massive volcanic eruptions occuring frequently through Earth's history while dinosaurs lived doesn't imply that there couldn't have been an especially huge one which wiped out the dinosaurs. But it does make comet/meteor theory more probable.

Look at the argument again - two things cause concentration of iridium - volcanoes and meteors
Volcanoes occured frequently while dinosaurs lived on Earth. Chances are that an activity which was not usual wiped out dinosaurs. Since dinosaurs were wiped out 65 million yrs ago and there was iridium concentration in rocks which are from 65 million yrs ago, it makes it more likely that a meteor wiped out dinosaurs.


Hi Karishma,
I initially chose A over B.
I have one query.
office explanation says for B, massive valcanoes eruption happened 80 milliions years ago and [dinosaurs did survive], which means massive valcanoes are not enough to extinct dinosaurs. so only cause to extinction is comet.

But that highlighted portion in red is not mentioned in the passage. It is rather assumption on which official explanation for choice B lies. But this assumption need not be true, maybe, comet did strike 65 milliions years ago but before that a single massive massive valcano could have extincted all dinosaurs.

am i thinking correct?


Dinosaurs became extinct 65 million years ago. That is why the hypothesis links high level of iridium found 65 million years ago with dinosaur extinction. They could not have become extinct 80 million years ago.
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