Isolated from the rest of the world by circumpolar currents and ice

Question

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Passage # 17, Date: 09-Apr-2020
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Isolated from the rest of the world by circumpolar currents and ice fields, the Dry Valleys of Antarctica never see snowfall. They are the coldest, driest places on earth, yet this arid, frigid climate supports several delicate ecosystems. Life in these ecosystems consists of relatively few groups of algae, microorganisms, and invertebrates, as well as plants such as lichen and fungi that live beneath the surface of rocks, where just enough light penetrates for photosynthesis to occur during the short period each year when meltwater is available. This region has proven interesting specifically to scientists researching the possibility of life on Mars because the features of the Dry Valleys are strikingly similar to the Martian landscape.

The Dry Valleys' system of lakes provides a particularly interesting area of research. Lake Hoare boasts a clear ice sun-cover fifteen meters thick that intensifies solar radiation in a way similar to solar panels; summer temperatures in bottom waters can become as high as 25° C, solely from solar heating, and not geothermal heating. This temperature permits huge mats of cyanobacteria to survive and even thrive on the lake floor. Pieces of this mat occasionally break free, floating up to the underside of the icy lake cover to melt through the ice toward the surface. The intense Antarctic winds, sweeping across the lake's surface, cause the ice to sublimate—turn directly from ice into vapor—rapidly. Such continuous sublimation should eventually cause the lake to vanish, but a continuous trickle of water from a nearby glacier—melted by the sun—refreshes the water. With a constant source of water, however small, and the heat generated by the solar radiation and retained by insulation from the thick ice cover, this lake offers an odd paradox: thick ice is responsible for maintaining this lake's liquid state.

The ancient river deltas around the slopes of Lake Fryxell present one feature typical of all river deltas: sediment thick enough to bury fossil life forms. This very thickness, however, makes a formal scientific search for signs of - life impracticable. The floor of Lake Vida, on the other hand, is covered with discrete piles of sediment up to a meter high that have preserved clear signs of life because rocks lying on the lake's surface, heated by sunlight, melt their way through the thick ice cover. Since smaller rocks, with a larger surface-area-tovolume ratio, get warmer and sink lower than larger rocks, pieces of gravel penetrate by as much as a meter, forming cracks in the ice that cause the finest sediment to sink even deeper. When the lake dries seasonally, the refined sediment within the ice drops to the lake floor, leaving a protective layer of gravel on top of the finer sediment. Dried bacteria in Lake Vida sediment have been dated back tens of thousands of years. Some researchers are hoping that exploration of similar terrain on Mars may yield similar results.    1 
 1. According to the passage, thick sediment found in the ancient river deltas of Lake Fryxell

A. forms layers of deposits laden with dried bacteria that are tens of thousands of years old
B. masks life forms by continuously depositing new layers on top of older ones
C. makes it unlikely that scientists will search there for traces of life
D. collects liquid water from nearby glaciers warmed by sunlight during the Antarctic summer
E. is devoid of life due to the impenetrable barrier formed by the sediment

2 
 2. The passage is primarily concerned with

A. the adaptations of microorganisms that allow them to live in the Dry Valleys' hostile environment
B. the relationship between frozen lakes and glaciers which contributes to the availability of fresh water in the Dry Valleys
C. evidence of past and present life forms in the extreme conditions of Antarctica's Dry Valleys
D. the evolutionary histories of ancient lakes and the clues they hold about life in cold, dry ecosystems
E. the differences and similarities between ancient river deltas and ancient lakes

3 
 3. Based on the information in the passage, scientists looking for life on Mars in conditions similar to those in the Dry Valleys would be most likely to find it in which of the following areas?

A. former river deltas
B. circumpolar ice fields
C. larger rocks
D. former glaciers
E. former lakebeds

4 
 4. Based on the information in the passage, mounds of sediment found at the bottom of Lake Vida are refined by

I. Continual sublimation and ice cover
II. Large pieces of rock decomposing on the lake floor
III. Cracks formed in the ice by sinking rocks and gravel

A. I only
B. I and II
C. III only
D. II and III
E. I, II, and III

bM22 · Answer

1. I am still confused b/w B & C, but here is my reasoning.
A. forms layers of deposits laden with dried bacteria that are tens of thousands of years old -  Incorrect  - since this happens in lake Hoare, as mentioned in second para from 2nd line, so this option is out.
B. masks life forms by continuously depositing new layers on top of older ones -  Incorrect - its not mentioned anywhere in the passage for Lake Fryxell.
C. makes it unlikely that scientists will search there for traces of life - Correct  - as its mentioned in para 3 that its makes the search of scientists impracticable, meaning: it its unlikely that scientists would look for life there.
D. collects liquid water from nearby glaciers warmed by sunlight during the Antarctic summer -  Incorrect  - since this is the case with lake Hoare, as mentioned in para 2.
E. is devoid of life due to the impenetrable barrier formed by the sediment - Incorrect  - as its mentioned that this thick enough to bury all fossil life forms, implying that fossils are still present, implying that it is not completely devoid of life.

2.
A. the adaptations of microorganisms that allow them to live in the Dry Valleys' hostile environment -  Incorrect  - The purpose of the passage is clearly mentioned at the end of the 1st para.
B. the relationship between frozen lakes and glaciers  Incorrect  - unrelated to the purpose.
C. evidence of past and present life forms in the extreme conditions of A which contributes to the availability of fresh water in the Dry Valleys -  Incorrect  - completely unrelated to the passage's purpose.ntarctica's Dry Valleys -  Correct  - since the purpose of the passage is to find evidence of life in Dry valleys, since they are have the most similar conditions to Mars.
D. the evolutionary histories of ancient lakes and the clues they hold about life in cold, dry ecosystems -  Incorrect  - this might be the secondary purpose, or the one that we need to compare the terrain of Mars with, but not a direct purpose.
E. the differences and similarities between ancient river deltas and ancient lakes -  Incorrect  - unrelated to the purpose.

3.
A. former river deltas - incorrect, but close one, if we overlook it, this might seem the right answer, but when we look closely, we find that this is incorrect.
B. circumpolar ice fields - incorrect
C. larger rocks - incorrect
D. former glaciers - incorrect, as not mentioned in the passage
E. former lakebeds -  Correct  - as mentioned in the last para, regarding the lake beds of Lake Vida, Dried bacteria in Lake Vida sediment have been dated back tens of thousands of years. Some researchers are hoping that exploration of similar terrain on Mars may yield similar results.

4.
E. I, II, and III - Correct, since all the options are correct.

ksht · Answer

1.) E as life impracticalble term used
2.) D as passage talks about how lakes evolve with life form
3.) E as passage talks about lakes and their formation in all paras, choice related to lakes makes sense for life on moon
4.) E as given in last para

BlueBook · Answer

1)  According to the passage, thick sediment found in the ancient river deltas of Lake Fryxell 
The answer can be found in the 1st line of the 3rd paragraph:  ‘The ancient river deltas around the slopes of Lake Fryxell present one feature typical of all river deltas: sediment thick enough to bury fossil life forms.  This very thickness, however, makes a formal scientific search for signs of - life impracticable. ’  As a result, C) is the answer.

2)  The passage is primarily concerned with
 
A.  the adaptations of microorganisms that allow them to live in the Dry Valleys' hostile environment.    How  microorganisms adapt to live in harsh conditions is not the main focus of the entire passage but only sections of it e.g. sections of the first and second paragraph. However, the 3rd paragraph talks of life forms so we are not sure whether microorganisms are part of these lifeforms or not.

B.  the relationship between frozen lakes and glaciers which contributes to the availability of fresh water in the Dry Valleys.  This has only been covered towards the end of the 2nd paragraph.

C.  evidence of past and present life forms in the extreme conditions of Antarctica's Dry Valleys.  This covers the entire scope of the passage.

D.  the evolutionary histories of ancient lakes and the clues they hold about life in cold, dry ecosystems.  A timeline of how lakes evolve has not been covered in this passage.

E.  the differences and similarities between ancient river deltas and ancient lakes.  This has not been covered anywhere in the passage.

3)   Based on the information in the passage, scientists looking for life on Mars in conditions similar to those in the Dry Valleys would be most likely to find it in which of the following areas?

The answer can be found in the 1st line of the first paragraph. It focuses on the Dry Valleys in the Antarctica and we are told that these valleys are isolated from the rest of the world by circumpolar currents and ice fields so I would go with B) as the answer.

4)  Based on the information in the passage, mounds of sediment found at the bottom of Lake Vida are refined by

I.  Continual sublimation and ice cover.  This has been referenced with regards to Lake Hoare not Lake Vida.
II.  Large pieces of rock decomposing on the lake floor.  From my understanding, smaller rocks sink deeper than larger rocks hence are more likely to be found as sediment at the bottom of Lake Vida.
III.  Cracks formed in the ice by sinking rocks and gravel.  This has been mentioned in the lines  ‘Since smaller rocks, with a larger surface-area-to volume ratio, get warmer and sink lower than larger rocks, pieces of gravel penetrate by as much as a meter, forming cracks in the ice that cause the finest sediment to sink even deeper. When the lake dries seasonally, the refined sediment within the ice drops to the lake floor, leaving a protective layer of gravel on top of the finer sediment.’  C) is the answer.

AnirudhaS · Answer

Answers are in  bold . This is a slightly easier RC to read and solve; if I have to guess it might be a 600 level RC.

1. According to the passage, thick sediment found in the ancient river deltas of Lake Fryxell
A. forms layers of deposits laden with dried bacteria that are tens of thousands of years old
B. masks life forms by continuously depositing new layers on top of older ones
 C. makes it unlikely that scientists will search there for traces of life 
D. collects liquid water from nearby glaciers warmed by sunlight during the Antarctic summer
E. is devoid of life due to the impenetrable barrier formed by the sediment

Explanation of question 1 
Before going to the choices lets summarise what we already know from the passage about Lake Fryxell. In the passage, the reference of Lake Fryxell is given and then the author says that there is thick sedimentation. It is so thick that - a) it might preserve fossils, and b)since it is so thick it would be mighty tough for the scientists to perform searches.
Only 2 choices come close A and C. However, there is a catch in A. A says the thick sediments FORMS layer of deposits laden with life. No, this is not what the passage says. Passage only states that it might preserve.
C is perfect as our second part of the earlier summary says that it would be mighty hard for the scientists to conduct searches, which is exactly what C says.
_________________________________________________________________________________________________________________________________

2. The passage is primarily concerned with
A. the adaptations of microorganisms that allow them to live in the Dry Valleys' hostile environment
B. the relationship between frozen lakes and glaciers which contributes to the availability of fresh water in the Dry Valleys
 C. evidence of past and present life forms in the extreme conditions of Antarctica's Dry Valleys 
D. the evolutionary histories of ancient lakes and the clues they hold about life in cold, dry ecosystems
E. the differences and similarities between ancient river deltas and ancient lakes

Explanation of question 2 
This is pretty easy, as the other options are weak. Let us go through all the options -
A - Adaptations of microorganisms? Really? The passage is not talking about this at all.
B - Too specific
C - Perfect! 
D - Too specific
E - Too specific
_________________________________________________________________________________________________________________________________

3. Based on the information in the passage, scientists looking for life on Mars in conditions similar to those in the Dry Valleys would be most likely to find it in which of the following areas?
A. former river deltas
B. circumpolar ice fields
C. larger rocks
D. former glaciers
 E. former lakebeds

Explanation of question 3 
It is stated in the passage, in the third paragraph -"Dried bacteria in  Lake Vida sediment  have been dated back tens of thousands of years. Some researchers are hoping that  exploration of similar terrain  on Mars may yield similar results."
This explicitly mentions that LAKE vida is similar to Mars. Answer is E.
_________________________________________________________________________________________________________________________________

4. Based on the information in the passage, mounds of sediment found at the bottom of Lake Vida are refined by
I. Continual sublimation and ice cover
II. Large pieces of rock decomposing on the lake floor
III. Cracks formed in the ice by sinking rocks and gravel
A. I only
B. I and II
 C. III only 
D. II and III
E. I, II, and III

Explanation of question 4 
I -  continual sublimation is affecting the lake. Eventually the lake would vanish due to constant sublimation. This in no way is related to sedimentation in Lake Vida.  
II -  rock decomposing? Not mentioned in the passage. 
III -  Yes, actually this is stated in the passage. the small cracks enable the fine sediments to fall through. Only III is correct. 
Answer: C

Sakshikothari · Answer

1) C because in para 3 it is clearly written that due to thickness of these sediments makes research on life .

2) D because in all the paragraphs the writer has said about the life on these lakes.

3) B because in first para it is mentioned about it.

4) C - it is clearly in the last para.

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SiffyB · Answer

1. According to the passage, thick sediment found in the ancient river deltas of Lake Fryxell
 
A. forms layers of deposits laden with dried bacteria that are tens of thousands of years old
B. masks life forms by continuously depositing new layers on top of older ones
  C. makes it unlikely that scientists will search there for traces of life 
 D. collects liquid water from nearby glaciers warmed by sunlight during the Antarctic summer
E. is devoid of life due to the impenetrable barrier formed by the sediment

The third paragraph states that deltas around the Lake Fryxell have ancient sediements that are so thick that they point towards the uncertainity of the existance of any life form there. Thus, the scientists will probably not search these areas for traces of life. Option (C) fits our thinking and is the correct option.

2. The passage is primarily concerned with
 
A. the adaptations of microorganisms that allow them to live in the Dry Valleys' hostile environment
B. the relationship between frozen lakes and glaciers which contributes to the availability of fresh water in the Dry Valleys
C. evidence of past and present life forms in the extreme conditions of Antarctica's Dry Valleys
  D. the evolutionary histories of ancient lakes and the clues they hold about life in cold, dry ecosystems  
E. the differences and similarities between ancient river deltas and ancient lakes

In such questions, we must summarize each paragraph and collate their summaries to determine the primary concern of the passage. 
Option (A) is out because while the passage does talk about the adaptations of microorganisms, it is referenced only in passage two. This choice is not the correct option becasue of partial scope.
(B) is out because availability of fresh water is not the concern of the passage as whole.
(C) talks about evidence which is correct but that is not the main purpose. The main intention behind writing this passage is to study the Dry Valley and determine clues they hold about life so as to gain insight about life on Mars.
(D) is our correct option.
(E) is out because its scope is limited to the third paragraph.

3. Based on the information in the passage, scientists looking for life on Mars in conditions similar to those in the Dry Valleys would be most likely to find it in which of the following areas?
 
A. former river deltas
B. circumpolar ice fields
C. larger rocks
D. former glaciers
  E. former lakebeds

Pay attention to the third paragraph last few sentences. Thye state that- 
"Dried bacteria in Lake Vida sediment have been dated back tens of thousands of years. Some researchers are hoping that exploration of similar terrain on Mars may yield similar results."
The lakebed of Lake Vida is talked about in this context. Thus, our correct option ahs to be (E).

4. Based on the information in the passage, mounds of sediment found at the bottom of Lake Vida are refined by
 
I. Continual sublimation and ice cover
II. Large pieces of rock decomposing on the lake floor
III. Cracks formed in the ice by sinking rocks and gravel

A. I only
B. I and II
  C. III only  
D. II and III
E. I, II, and III

I is definitely out because it is referenced in paragraph two where we talk about Lake Fryell. Thus, we can elimiate options (A), (B) and (E).
III is definitely correct as is vividly stated in paragraph three. 
I'm confused about whether II is correct because while the text does reference large rocks (it says smaller rocks, which means there have to larger ones out there!). Howveer, those larger rocks are on the lake's surface and not on the lake's floor. Thus, we can conclude that only the cracks formed in ice by sinking rocks and gravel refine the mounds of sediment. Thus, option (C) is correct!

SSandy066 · Answer

1. According to the passage, thick sediment found in the ancient river deltas of Lake Fryxell

A. forms layers of deposits laden with dried bacteria that are tens of thousands of years old
B. masks life forms by continuously depositing new layers on top of older ones.
 C. makes it unlikely that scientists will search there for traces of life- >Correct 
 Explanation: para 3-“The ancient river deltas around the slopes of Lake Fryxell present one feature typical of all river deltas: sediment thick enough to bury fossil life forms. This very thickness, however, makes a formal scientific search for signs of - life impracticable” 
D. collects liquid water from nearby glaciers warmed by sunlight during the Antarctic summer
E. is devoid of life due to the impenetrable barrier formed by the sediment.

2. The passage is primarily concerned with
A. the adaptations of microorganisms that allow them to live in the Dry Valleys' hostile environment -.  Out of scope  
B. the relationship between frozen lakes and glaciers which contributes to the availability of fresh water in the Dry Valleys-   Only related to para2-Wrong choices  
 C. evidence of past and present life forms in the extreme conditions of Antarctica's Dry Valleys.-> Correct 
 E xplanation:
Para-1: about Antarctica’s Dry valley environment and present life.
 Para -2: about importance of research of Dry valley lakes.
 Para-3: example of delta & lakebed about past life form.  
D. the evolutionary histories of ancient lakes and the clues they hold about life in cold, dry ecosystems.  Not about evolutionary histories about ancient lake, Wrong Choices 
E. the differences and similarities between ancient river deltas and ancient lakes.  Only related to para 3. Wrong choice

3. Based on the information in the passage, scientists looking for life on Mars in conditions similar to those in the Dry Valleys would be most likely to find it in which of the following areas?

A. former river deltas
B. circumpolar ice fields
C. larger rocks
D. former glaciers
 E. former lakebeds -Correct 
 Explanation: Para 3 “The floor of Lake Vida, on the other hand, is covered with discrete piles of sediment up to a meter high that have preserved clear signs of life……….. Lake Vida sediment have been dated back tens of thousands of years. Some researchers are hoping that exploration of similar terrain on Mars may yield similar results”

4. Based on the information in the passage, mounds of sediment found at the bottom of Lake Vida are refined by

I. Continual sublimation and ice cover
II. Large pieces of rock decomposing on the lake floor
III. Cracks formed in the ice by sinking rocks and gravel

A. I only
B. I and II
C. III only
 D. II and III  ->Correct  
E. I, II, and III
 Explanation: Para 3 “The floor of Lake Vida, on the other hand, is covered with discrete piles of sediment ………. because rocks lying on the lake's surface, ….smaller rocks, with a larger surface-area-to volume ratio, get warmer and sink lower than larger rocks, pieces of gravel penetrate by as much as a meter, forming cracks in the ice that cause the finest sediment to sink even deeper. When the lake dries seasonally, ……… leaving a protective layer of gravel on top of the finer Sediment”

GDT · Answer

1. According to the passage, thick sediment found in the ancient river deltas of Lake Fryxell

A. forms layers of deposits laden with dried bacteria that are tens of thousands of years old - mentioned w.r.t Lake Vida not ancient river deltas
B. masks life forms by continuously depositing new layers on top of older ones - mentioned w.r.t Lake Vida not ancient river deltas
C. makes it unlikely that scientists will search there for traces of life -   Correct   as can be inferred from the quoted
D. collects liquid water from nearby glaciers warmed by sunlight during the Antarctic summer - Not mentioned in this context, mentioned w.r.t Lake Hoare
E. is devoid of life due to the impenetrable barrier formed by the sediment - a good contender, but just because it is difficult to penetrate doesn't means life doesn't exist at all

2. The passage is primarily concerned with

A. the adaptations of microorganisms that allow them to live in the Dry Valleys' hostile environment - not discussed
B. the relationship between frozen lakes and glaciers which contributes to the availability of fresh water in the Dry Valleys - discussed but not main point
C. evidence of past and present life forms in the extreme conditions of Antarctica's Dry Valleys - the passage intends to say much more than that, through these examples it hypothesizes about possibility of life on Mars
D. the evolutionary histories of ancient lakes and the clues they hold about life in cold, dry ecosystems -  Correct.   can be inferred from the 1st & last para, the middle para contributes to the findings of life given in the last para
E. the differences and similarities between ancient river deltas and ancient lakes - though discussed, it is not the main point

3. Based on the information in the passage, scientists looking for life on Mars in conditions similar to those in the Dry Valleys would be most likely to find it in which of the following areas?

A. former river deltas
B. circumpolar ice fields
C. larger rocks
D. former glaciers
E. former lakebeds -   correct   mentioned in the last para

4. Based on the information in the passage, mounds of sediment found at the bottom of Lake Vida are refined by

I. Continual sublimation and ice cover
II. Large pieces of rock decomposing on the lake floor
III. Cracks formed in the ice by sinking rocks and gravel

A. I only
B. I and II
C. III only  Correct  
D. II and III
E. I, II, and III

Sajjad1994 · Answer

OAs of this RC posted now, if anyone have any question kindly let me know.

1. C
2. C
3. E
4. C

Will share my thoughts shortly.

Sajjad1994 · Answer

This is a very hard science passage, Excellent to those who got 4/4, very good job who got 3/4, 2/4 is also not bad at all.

Explanation ranks as follow.

1. AnirudhaS
2. SSandy066
=2. abcdddddd
4. BlueBook 
5. GDT

Good Luck

Pranjal3107 · Answer

Can you please provide OE for Q2 ? I'm unable to pick one b/w C and D.

Sajjad1994 · Answer

Official Explanation

2. The passage is primarily concerned with

Difficulty Level:   700

Explanation

Based on our Passage Map this Global question would be something like  “describing Dry Valley lakes’ ecosystems and how they preserve signs of life.”  That's a great match with  (C).

(A)  is out of scope: adaptations of organisms are never considered.

(B)  is too narrow, since it refers to material mentioned only at the end of  Paragraph 2.

(D)  is out of scope;  evolutionary histories are never discussed, and the clues about life in cold, dry ecosystems  is a trap for those who thought the passage focused on parallels with Mars.

The details referenced in  (E)  are mentioned only briefly—if you read for structure, you may not even have noticed them!

Answer: C

Hope it help.

richirish · Answer

6 mins all correct, good passage. Happy to help folks if needed !

dhruva09 · Answer

Sajjad1994  Please help with OA explanation of Q3.

Isolated from the rest of the world by circumpolar currents and ice

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Isolated from the rest of the world by circumpolar currents and ice

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