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The Earth s rivers constantly carry dissolved salts into its

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Re: CR: Ocean salinity [#permalink] New post 20 Jul 2011, 01:38
bupbebeo wrote:
I believe E is correct answer

let's consider one thing in the stimulus. it says that we can calculate maximum age of the Earth's oceans, not age alone.

so, even A is true, we can still calculate maximum age of oceans because we still have the data of the salt in the ocean, which originates from rivers. In other words, the amount the rivers carry now in the oceans

but in E, it is very different, if we don't have data from the use of salts from biological activity in the oceans, so we don't know whether the amount rivers carry is all in the ocean. So how we can calculate the MAXIMUM AGE.


good point...very confused between A&E.....need an official explaination for this question...
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Re: CR: Ocean salinity [#permalink] New post 20 Jul 2011, 21:07
My original prediction before seeing the answers was that the rate by which salt was deposited in the last century must be representative of the centuries since the dawn of Earth.

But, since I'm still a careless noob at this point, I broke from my strategy and chose E.

Quote:
E. None of the salts carried into the Earth’s oceans by rivers are used up by biological activity in the oceans.


Remember, though, that we're looking only for an accurate estimate. So we don't need to be so bold (well, extreme) and assume none of the salts are used up by biological activity. They can. This is an estimate after all, right?

Quote:
A. The quantities of dissolved salts deposited by rivers in the Earth’s oceans have not been unusually large during the past hundred years.


Reading A again, I should have stuck with my prediction. For this argument, we must assume that the salt deposited wasn't unusually large during the last century. Else, we'd undershoot the age of the Earth -- certainly more than by a variance in our estimate of age due to biological activity. A is the correct answer IMO.
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Re: CR: Ocean salinity [#permalink] New post 22 Jul 2011, 11:10
IMO A. Biological processes can be considered to have been taking place since the very beginning. Hence, the effect of bio act can be considered constant and thus it doesn't effect our calculation of Earth's age by the method suggested.
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Re: CR: Ocean salinity [#permalink] New post 26 Jul 2011, 10:02
+1 A
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Re: CR: Ocean salinity [#permalink] New post 27 Jul 2011, 07:44
A For me

The method of estimating talks about prorating the salt increase in the last 100 years to an initial zero state.

If this method should work the value should be more or less closer to a constant increase over time.

Otherwise we would be over under-estimating the age of the earth.

A) says this is not the case and in the last century it is unusually high. Directly points out to a flaw in the method.
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Re: CR: Ocean salinity [#permalink] New post 07 Aug 2011, 02:16
"E" for me
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Re: The Earth s rivers constantly carry dissolved salts into its [#permalink] New post 19 Nov 2013, 03:55
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Re: The Earth s rivers constantly carry dissolved salts into its [#permalink] New post 20 Nov 2013, 01:17
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A will be the correct answer .

E states that the salt is not being used by any biological activity . But , if we are to measure the age of the oceans this will not hamper that measurement as the quantity of salt, if being used by any biological activity would have been constant since the beginning . So , that constant will not affect the measurement .

A assumes that the quantity of salts deposited in recent hundred years is larger than other hundreds of years , thus the experiment will give an inconsistent answer .

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Re: The Earth s rivers constantly carry dissolved salts into its [#permalink] New post 25 Apr 2014, 10:53
lexis wrote:
The Earth’s rivers constantly carry dissolved salts into its oceans. Clearly, therefore, by taking the resulting increase in salt levels in the oceans over the past hundred years and then determining how many centuries of such increases it would have taken the oceans to reach current salt levels from a hypothetical initial salt-free state, the maximum age of the Earth’s oceans can be accurately estimated.

Which of the following is an assumption on which the argument depends?

A. The quantities of dissolved salts deposited by rivers in the Earth’s oceans have not been unusually large during the past hundred years.
B. At any given time, all the Earth’s rivers have about the same salt levels.
C. There are salts that leach into the Earth’s oceans directly from the ocean floor.
D. There is no method superior to that based on salt levels for estimating the maximum age of the Earth’s oceans.
E. None of the salts carried into the Earth’s oceans by rivers are used up by biological activity in the oceans.


Conclusion : By measuring the increase in salt over the past hundred years and by extrapolating the results, we can determine the maximum age of the Earth's Ocean.

Option A) Negation :
The quantities of dissolved salts deposited by rivers in the Earth’s oceans have been unusually large during the past hundred years.
More quantities of salt is added in the past 100 years, So if we extrapolate it over thousand of years, the years required will be lesser as compared to the actual age. That can impact the Maximum age calculation. Hence an assumption.

Option B) Doesn't matter as argument talks about the cumulative salt in the ocean.
Option C) Salt leach into the Earth's ocean from the floor. This would be captured the data for the last 100 years and it will be constant over the years. Hence it doesn't affect.
Option D) Out of scope.
Option E) Negation.
Some of the salts carried into the Earth’s oceans by rivers are used up by biological activity in the oceans.
In that case, this would be factored in the measurement done for the past 100 years and can be extrapolated over the thousands of years.

hence A)

BTW : It is from GMATPrep Question Pack 1.
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Re: The Earth s rivers constantly carry dissolved salts into its   [#permalink] 25 Apr 2014, 10:53
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