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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] New post 30 Oct 2013, 05:00
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] New post 30 Oct 2013, 18:58
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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] New post 24 Nov 2013, 08:11
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] New post 01 Dec 2013, 11:00
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] New post 06 Aug 2014, 21:01
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] New post 10 Aug 2014, 09:50
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] New post 14 Aug 2014, 10:53
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"
Re: Iridium, a hard, whitish metal similar to platinum, is   [#permalink] 14 Aug 2014, 10:53
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