Rock varnish is typically rich in iron and manganese, with the presenc

Question

Rock varnish is typically rich in iron and manganese
Manganese is present because of bacteria on the surface of the rock.
Bacteria would not survive on the surface of rocks in the colder, continuously frozen, reaches of Antarctica.
Scientists found rock varnish in Antarctica consists only a form of iron (makes sense since manganese wouldn't be found in continuously frozen places).
This iron had penetrated from the surfaces of the rocks into the cracks.
However, although moisture is essential to the movement of this iron, snow has not melted in the Thiel Mountains in recent times.

Indicate which statement in the given information most strongly suggests is true, and the statement that the given information most strongly suggests is false. Make only two selections, one in each column.

Sajjad1994 · Accepted Answer

Official Explanation

The passage strongly suggests that liquid water is necessary for the formation of rock varnish containing manganese, and for the movement of limonite (and rock varnish consisting only of limonite). The frozenness of the Thiel Mountains is suggested as an explanation of the absence of manganese in the rock varnish there, suggesting that temperatures on the rocks are also below freezing.

The passage states that limonite had penetrated the cracks. This suggests that the limonite had moved from the surface of the rock, which in turn very strongly suggests (with the above) that temperatures on the rocks have been above freezing at some point. Because the rocks are continuously frozen at present, it can be inferred that temperatures on the rocks must have been above freezing at some point in the past (the sixth option).

Although the passage as a whole rather strongly suggests that rock varnish in continuously frozen areas tends to be especially rich in iron, any suggestion that rock varnish especially rich in iron tends not to exist outside of extremely cold areas is at best very weak. It would therefore be a mistake to choose the fourth option as a key (over the sixth option).

Because the second option is the negation of the first option, it may seem likely that one or the other is true. And indeed, the passage cites an absence of moisture as an explanation for an absence of manganese in certain places. However, not enough information is given to infer whether or not moisture is required for the presence of significant amounts of manganese in the environment.

The correct answer is Temperatures on rocks in the Thiel Mountains were above freezing at some point in the past.

Given the strong suggestion, with the correct answer above, that temperatures on rocks in the Thiel Mountains were above freezing at some point the past, together with the statement that rock varnish in the Thiel Mountains (including rock varnish in the cracks of rocks) consists only of limonite, we find a suggestion that manganese need not begin to penetrate cracks in rocks in every case in which temperatures in a continuously frozen location increase to above freezing. This suggests that the third option may be false. This suggestion is much stronger than any such suggestion with respect to the other statements.

The correct answer is When temperatures in a continuously frozen location increase to above freezing, cracks in rocks there begin to take in rock varnish containing significant amounts of manganese.

Apt0810 · Answer

True: Temperatures on rocks in the Thiel Mountains were above freezing at some point in the past.

Since bacteria could not survive the rocks of colder surfaces,but still Thiel mountains had rock varnish that means in past the temperature was greater than freezing point in past
False: When temperatures in a continuously frozen location increase to above freezing, cracks in rocks there begin to take in rock varnish containing significant amounts of manganese.
This is not possible since without moisture limonite can't move down so varnish can't be there

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mSKR · Answer

Rock varnish ( iron and Mg)  due to bacteria 
If cold, no bacteria

Cold Antartica : only of limonite, a form of oxidized iron  penetrated in cracks
Snow not melted and limonite needs water to move to move

Option: Moisture is required for the presence of significant amounts of manganese in the environment.
>> not mentioned

Option: Moisture is not required for the presence of significant amounts of manganese in the environment.
>> not mentioned

Option: When temperatures in a continuously frozen location increase to above freezing, cracks in rocks there begin to take in rock varnish containing significant amounts of manganese.
 >> opposite mentioned: containing significant amounts of limonite-FALSE.

Option: Rock varnish that is especially rich in iron is mostly found in extreme cold.
>>not mentioned

Option: Manganese i s unable to penetrate into cracks in significant amounts.
>>not mentioned

Option: Temperatures on rocks in the Thiel Mountains were above freezing at some point in the past.
 >>yes due to snow not stop yet-TRUE

robu1 · Answer

FALSE:  When temperatures in a continuously frozen location increase to above freezing, cracks in rocks there begin to take in rock varnish containing significant amounts of manganese.- In the colder area, bacteria are absent , therefore manganese is absent hence no possibility of manganese in crack.

TRUE:  Temperatures on rocks in the Thiel Mountains were above freezing at some point in the past , leading to the movement of limonite in the crack.

cheshire · Answer

Hope this helps!

Understanding the Passage 
Key points:
 
 Rock varnish is usually rich in both  iron and manganese.  
  Manganese is deposited by bacteria, which cannot survive in cold , continuously frozen environments like Antarctica. 
 In the Thiel Mountains, scientists did not find manganese —  only limonite (oxidized iron) . 
  Limonite   was found  inside cracks,  having penetrated from the surface.  
  Moisture is needed for limonite to move . 
 However, no snow has melted recently, so  moisture hasn't been present in recent times.

Correct “True” Statement: 
 “Temperatures on rocks in the Thiel Mountains were above freezing at some point in the past.” 
 
 Why? Because moisture is needed for limonite to move into cracks. 
 And since limonite was found inside the cracks, moisture must have been present at some point. 
 But the passage says there has been no snowmelt in recent times, so that moisture must have come from older, warmer conditions — i.e., temperatures were above freezing in the past.

Correct “False” Statement: 
 “When temperatures in a continuously frozen location increase to above freezing, cracks in rocks there begin to take in rock varnish containing significant amounts of manganese.” 
 
 The passage tells us manganese comes from bacteria, and these cannot survive in the cold Antarctic environment. 
 Even if temperatures rise above freezing, unless bacteria are present, no manganese will be deposited. 
 So, just increasing the temperature is not sufficient for manganese-containing rock varnish to penetrate cracks. 
 Thus, this causal claim is not supported and is false.

Tucky · Answer

KarishmaB MartyMurray ChiranjeevSingh DmitryFarber

I found this slightly confusing and wanted to verify that my thought process aligns with yours:

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KarishmaB · Answer

Given:
 Rock varnish is typically rich in iron and manganese
Manganese is present because of bacteria on the surface of the rock. 
Bacteria would not survive on the surface of rocks in the colder, continuously frozen, reaches of Antarctica.
Scientists found rock varnish in Antarctica consists only a form of iron (makes sense since manganese wouldn't be found in continuously frozen places). 
This iron had penetrated from the surfaces of the rocks into the cracks. 
However, although moisture is essential to the movement of this iron, snow has not melted in the Thiel Mountains in recent times.

What this tells us is that iron had seeped into cracks and moisture (liquid water) is necessary for it. But in recent times snow has not melted so no liquid water. It means in the past snow must have melted into liquid water to make the iron seep into cracks. So temp must have been above freezing at that point. 
Hence (F) is supported to be True. 
  (F) Temperatures on rocks in the Thiel Mountains were above freezing at some point in the past.

(C) When temperatures in a continuously frozen location increase to above freezing, cracks in rocks there begin to take in rock varnish containing significant amounts of manganese.  
Also (C) is false because  temperatures in a continuously frozen location do not allow manganese to be present (because they do not allow bacteria). So they cannot take in rock varnish containing significant amounts of manganese.
 Hence (C) is supported to be False.

(D) Rock varnish that is especially rich in iron is mostly found in extreme cold.

Can't say. It could also be found in extremely hot, extremely rainy, extremely clean air places etc. Also, are we given that Antarctica has expecially rich in iron rock varnish? Not sure. We are given that it has only iron and no manganese, but is it especially rich in iron (more than usual), don't know.

(E) Manganese is unable to penetrate into cracks in significant amounts
  
Argument tells us nothing about whether manganese can penetrate rocks. We only know that limonite, a form of iron can.

Rock varnish is typically rich in iron and manganese, with the presenc

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True	False	Statements
		Moisture is required for the presence of significant amounts of manganese in the environment.
		Moisture is not required for the presence of significant amounts of manganese in the environment.
		When temperatures in a continuously frozen location increase to above freezing, cracks in rocks there begin to take in rock varnish containing significant amounts of manganese.
		Rock varnish that is especially rich in iron is mostly found in extreme cold.
		Manganese is unable to penetrate into cracks in significant amounts.
		Temperatures on rocks in the Thiel Mountains were above freezing at some point in the past.

GMAT Two-part Analysis (TPA) Questions

Rock varnish is typically rich in iron and manganese, with the presenc

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