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First identified in 1969, komatiites are Earth s oldestknown

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First identified in 1969, komatiites are Earth s oldestknown  [#permalink]

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New post Updated on: 16 Nov 2018, 17:13
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First identified in 1969, komatiites are Earth’s oldest known volcanic rocks and contain three times as much magnesium as do most volcanic rocks. This chemical composition suggests that komatiites formed from the hottest lava known ever to have erupted: a high concentration of magnesium changes the physical properties of lava so that unusually high temperatures would be required for the lava to exist as a liquid.

Komatiites’ discovery was surprising in light of then-current geological theories about magmas, moltenrock that forms in the Earth’s mantle (the layer beneath the crust) and composes volcanic lava eruptions. Prior to 1960, geologists Bowen and Hess disagreed over whether or not the very high temperatures needed to produce magmas rich in magnesium could have existed on Earth. Hess suggested that the presence of water, probably released from minerals decomposing in the Earth’smantle, might have meant that a high-magnesium magma could have existed at a lower temperature. But Bowen showed experimentally that the high temperatures were indeed necessary. By 1960, it was generally accepted that volcanic rocks with such high levels of magnesium could not exist, and thus the discovery of komatiites changed geologists’ assumptions about the characteristics of the Earth’s mantle around the time of the formation of komatiites,between 2.5 and 4 billion years ago.

1. Which of the following most accurately describes the organization of the passage?

A. Two divergent views of a scientific phenomenon are reconciled.
B. A phenomenon is described and its scientific significance is discussed.
C. The discovery of a scientific phenomenon is traced and its implications for further research are suggested.
D. A long-standing scientific theory is examined and recently discovered evidence is shown to support it.
E. The ways in which a particular geological phenomenon is exceptional are detailed and classified.



2. Information in the passage suggests which of the following concerning the Earth’s mantle 2.5 to 4 billion years ago?
A. It contained magmas that were more significantly affected by the decomposition of minerals than are current-day magmas.
B. It contained a lower proportion of water that it contains today.
C. Its characteristics were accurately described by both Bowen and Hess.
D. Its temperature was sufficiently high to produce magmas with high magnesium content.
E. Its total magnesium content then was roughly equivalent to its magnesium content today.



3. Which of the following most accurately states the main point of the passage?

A. Komatiites provide information about rates of volcanic eruption between 2.5 and 4 billion years ago.
B. Komatiites provide information about how the physical properties of lava in the Earth’s past compare with those of current-day lava.
C. Komatiites provide evidence that undermines Bowen’s experimental conclusions regarding the temperatures at which lava exists as a liquid.
D. Komatiites provide evidence that has changed geologists’ ideas about the characteristics of the Earth’s mantle between 2.5 and 4 billion years ago.
E. Komatiites provide evidence that water in the Earth’s mantle may have reduced the temperature required for lava to exist as a liquid.



Originally posted by gmatrant on 13 Dec 2012, 23:31.
Last edited by gmat1393 on 16 Nov 2018, 17:13, edited 2 times in total.
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Re: First identified in 1969, komatiites are Earth s oldestknown  [#permalink]

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New post 14 Dec 2012, 00:16
1
gmatrant wrote:
First identified in 1969, komatiites are Earth’s oldestknown volcanic rocks and contain three times as muchmagnesium as do most volcanic rocks. This chemicalcomposition suggests that komatiites formed from thehottest lava known ever to have erupted: a highconcentration of magnesium changes the physicalproperties of lava so that unusually high temperatureswould be required for the lava to exist as a liquid.

Komatiites’ discovery was surprising in light of then-current geological theories about magmas, moltenrock that forms in the Earth’s mantle (the layerbeneath the crust) and composes volcanic lavaeruptions. Prior to 1960, geologists Bowen and Hessdisagreed over whether or not the very hightemperatures needed to produce magmas rich inmagnesium could have existed on Earth. Hesssuggested that the presence of water, probablyreleased from minerals decomposing in the Earth’smantle, might have meant that a high-magnesiummagma could have existed at a lower temperature. ButBowen showed experimentally that the hightemperatures were indeed necessary. By 1960, it wasgenerally accepted that volcanic rocks with such highlevels of magnesium could not exist, and thus thediscovery of komatiites changed geologists’ assumptions about the characteristics of the Earth’smantle around the time of the formation of komatiites,between 2.5 and 4 billion years ago.

Which of the following most accurately describes theorganization of the passage?
A. Two divergent views of a scientific phenomenon arereconciled.
B. A phenomenon is described and its scientificsignificance is discussed.
C. The discovery of a scientific phenomenon is tracedand its implications for further research are suggested.
D. A long-standing scientific theory is examined andrecently discovered evidence is shown to support it.
E. The ways in which a particular geologicalphenomenon is exceptional are detailed and classified

OA is B. Can you please tell me why D is not correct?


Hii GMATRANT.
The passage discusses the discovery of Komatites or whatever, which is rich in Mg.
Then the passage goes on to tell that two scientists Hess and Bowen examined the formation of molten rocks with high Mg, at certain temperatures.
Hess suggested in favour i.e. rocks rich in Mg can be formed at lower temperature whereas Bowen countered by saying that high temperature is necessary.
Later it was proved that such volcanic rocks with high Mg could not exist.

D suggests "A long-standing scientific theory is examined and recently discovered evidence is shown to support it". We can't say whether a theory if persists for 9 years can be proclaimed as long standing theory. Moreover The discovery of Komatites did not support the view but rather changed the previous perception and proved that such rocks, which have high Mg content can exist.

B is correct since it is the best among the choices. However, I am not very convinced about the first part of B; second part looks perfect.

Please mention the source of the question while posting the questions.

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Re: First identified in 1969, komatiites are Earth s oldestknown  [#permalink]

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New post 16 Dec 2012, 23:13
(B) it is.

Discovery of "K" - in 1969 => Require hottest LAVA(which can be formed only in high temperatures).
k = 3(Mg than general Lava) and High MG requires High Temperatures.

So "K" was discovered => there existed LAVA rich in MG and HIGH Temp.

1960 - view was molten magma and blah blah.Two scientist checked for the existence of high MG with low temperature and thereby one of the SCI testified that HIGH Temp is req => HIGH MG.

So the Discovery of "k" changed assumptions of many scientists .(Significance of the discovery).
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Re: First identified in 1969, komatiites are Earth s oldestknown  [#permalink]

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New post 01 Jan 2015, 01:10
2
Information in the passage suggests which of the following concerning the Earth’s mantle 2.5 to 4
billion years ago?
A. It contained magmas that were more significantly affected by the decomposition of minerals than
are current-day magmas.
B. It contained a lower proportion of water that it contains today.
C. Its characteristics were accurately described by both Bowen and Hess.
D. Its temperature was sufficiently high to produce magmas with high magnesium content.
E. Its total magnesium content then was roughly equivalent to its magnesium content today.

Which of the following most accurately states the main point of the passage?
A. Komatiites provide information about rates of volcanic eruption between 2.5 and 4 billion years
ago.
B. Komatiites provide information about how the physical properties of lava in the Earth’s past
compare with those of current-day lava.
C. Komatiites provide evidence that undermines Bowen’s experimental conclusions regarding the
temperatures at which lava exists as a liquid.
D. Komatiites provide evidence that has changed geologists’ ideas about the characteristics of the
Earth’s mantle between 2.5 and 4 billion years ago.
E. Komatiites provide evidence that water in the Earth’s mantle may have reduced the temperature
required for lava to exist as a liquid.
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Re: First identified in 1969, komatiites are Earth s oldestknown  [#permalink]

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New post 01 Jan 2015, 01:11
Difficulty level Medium
Time taken :- 9:30
All correct
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Re: First identified in 1969, komatiites are Earth s oldestknown  [#permalink]

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New post 08 Feb 2015, 11:18
WaterFlowsUp wrote:
Information in the passage suggests which of the following concerning the Earth’s mantle 2.5 to 4
billion years ago?
A. It contained magmas that were more significantly affected by the decomposition of minerals than
are current-day magmas.
B. It contained a lower proportion of water that it contains today.
C. Its characteristics were accurately described by both Bowen and Hess.
D. Its temperature was sufficiently high to produce magmas with high magnesium content.
E. Its total magnesium content then was roughly equivalent to its magnesium content today.

Which of the following most accurately states the main point of the passage?
A. Komatiites provide information about rates of volcanic eruption between 2.5 and 4 billion years
ago.
B. Komatiites provide information about how the physical properties of lava in the Earth’s past
compare with those of current-day lava.
C. Komatiites provide evidence that undermines Bowen’s experimental conclusions regarding the
temperatures at which lava exists as a liquid.
D. Komatiites provide evidence that has changed geologists’ ideas about the characteristics of the
Earth’s mantle between 2.5 and 4 billion years ago.
E. Komatiites provide evidence that water in the Earth’s mantle may have reduced the temperature
required for lava to exist as a liquid.


so whats the answer to the two questions...
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Re: First identified in 1969, komatiites are Earth s oldestknown  [#permalink]

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New post 08 Feb 2015, 21:04
Time Taken 6:24. All Correct.

Information in the passage suggests which of the following concerning the Earth’s mantle 2.5 to 4 billion years ago?
A. It contained magmas that were more significantly affected by the decomposition of minerals than are current-day magmas.
B. It contained a lower proportion of water that it contains today.
C. Its characteristics were accurately described by both Bowen and Hess.

D. Its temperature was sufficiently high to produce magmas with high magnesium content.

ButBowen showed experimentally that the hightemperatures were indeed necessary. By 1960, it was generally accepted that volcanic rocks with such high levels of magnesium could not exist, and thus the discovery of komatiites changed geologists’ assumptions about the characteristics of the Earth’s mantle around the time of the formation of komatiites,between 2.5 and 4 billion years ago.

E. Its total magnesium content then was roughly equivalent to its magnesium content today.

Which of the following most accurately states the main point of the passage?
A. Komatiites provide information about rates of volcanic eruption between 2.5 and 4 billion years ago.
B. Komatiites provide information about how the physical properties of lava in the Earth’s past compare with those of current-day lava.
C. Komatiites provide evidence that undermines Bowen’s experimental conclusions regarding the temperatures at which lava exists as a liquid.
D. Komatiites provide evidence that has changed geologists’ ideas about the characteristics of the Earth’s mantle between 2.5 and 4 billion years ago.
Thats is pretty much covered in the starting and end of second para.
E. Komatiites provide evidence that water in the Earth’s mantle may have reduced the temperature required for lava to exist as a liquid.
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Re: First identified in 1969, komatiites are Earth s oldestknown  [#permalink]

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New post 11 Aug 2016, 04:00
1
Interesting passage . Took 7 mins 30 seconds :roll: , including 2 mins 30 seconds to read .

-The author describes a certain phenomenon that was first identified in 1969
-The author then discusses the significance of that phenomenon

1. B

2.“By 1960, it was generally accepted that volcanic rocks with such high levels of magnesium could not exist, and thus the discovery of komatiites changed geologists’ assumptions about the characteristics of the Earth’s mantle around the time of the formation of komatiites, between 2.5 and 4 billion years ago."
Since geologists assumed that temperatures weren’t high enough to produce magmas with sufficient magnesium content, the information in the passage changed those assumptions leading to option (D) as the right answer choice.

3.
“By 1960, it was generally accepted that volcanic rocks with such high levels of magnesium could not exist, and thus the discovery of komatiites changed geologists’ assumptions about the characteristics of the Earth’s mantle around the time of the formation of komatiites, between 2.5 and 4 billion years ago."
Option (D) is a clear word justification of the above and is hence correct.
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Re: First identified in 1969, komatiites are Earth s oldestknown  [#permalink]

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New post 06 Oct 2017, 21:04
All correct. 6:20 minute taken.
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Re: First identified in 1969, komatiites are Earth s oldestknown  [#permalink]

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New post 20 Sep 2018, 23:22
1
Took 7 minutes
2 correct and 1 wrong :P
An issue with question 1 is - nowhere in the paragraph 'scientific significance is discussed'. Please provide an explanation for this.
AT the last of the paragraph, only a sentence is written but it cannot be called discussed.
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Re: First identified in 1969, komatiites are Earth s oldestknown  [#permalink]

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New post 30 Oct 2018, 13:35
Took 7 minutes
2 correct and 1 wrong :P
An issue with question 1 is - nowhere in the paragraph 'scientific significance is discussed'. Please provide an explanation for this.
AT the last of the paragraph, only a sentence is written but it cannot be called discussed.
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Re: First identified in 1969, komatiites are Earth s oldestknown &nbs [#permalink] 30 Oct 2018, 13:35
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First identified in 1969, komatiites are Earth s oldestknown

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