The extinction of the dinosaurs – thought to be caused by an asteroid

Question

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Passage # 122, Date: 31-May-2020
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The extinction of the dinosaurs – thought to be caused by an asteroid impact some 65 million years ago – was more likely to have been caused by a 'mantle plume' – a huge volcanic eruption from deep within the earth's mantle, the region between the crust and the core of the earth. This theory, already supported by a significant body of geologists and palaeontologists, is strengthened by new evidence.

Research by an American earth scientist, Professor Gerta Keller and her team, suggests that a similar eruption under the Indian Ocean several million years before the extinction of the dinosaurs had a similarly devastating impact on the environment. However, at this earlier time there is no evidence of any asteroid impact. Her findings are based on analysis of microfossil assemblages, which were found inside cores that had been drilled deep into sediments on the ocean floor.

The eruptions that were responsible for these two extinction events were as a result of mantle plumes – a phenomenon caused by the hot mantle rising from deep within the earth. Likened to the actions of a lava lamp, the mantle's heat causes it to rise and mushroom out; it then flattens causing the mantle to melt and spew magma over the earth's surface and across an area of some 1,000 kilometres diameter. These eruptions last between one and two million years and more than one million cubic kilometres of lava can be erupted in that time. Today, we can witness seven huge remnants of such mantle plume activity. These are also known as 'hotspots' and are responsible for the volcanic activity on Iceland, the islands of Hawaii, Easter, Reunion, Tristan and Louisville as well as volcanism in the Afar region of Ethopia.

According to Dr. Andrew Kerr of Cardiff University's School of Earth, Ocean and Planetary Sciences, mantle plumes are a catalyst for the formation of ocean basins and the fundamental reshaping of the earth's surfaces. The massive outpouring of lava, ashes, and gas can have significant effects on climate and have the potential to dictate the course of evolution. Kerr says that it is likely that were it not for mantle plumes, mammals would not have become predominant, and humankind would not be here today. Bizarrely, however, there is a vocal minority of earth scientists who do not believe that mantle plumes exist.
   1 
 D 
 1. What is the central theme of the passage?

A. The role of mantle plumes in the extinction of dinosaurs
B. Unanticipated effects of mantle plume activity
C. Earth science theories that explain the extinction of dinosaurs
D. The formation and consequences of mantle plumes
E. Contrasting views of earth scientists on the mantle plume phenomenon

2 
 E 
 2. The author mentions ‘two extinction events’ in line 11 most probably in order to

A. support Dr. Kerr’s view that mantle plumes have a significant effect on the course of evolution, especially the predominance of mammals and the origin of humankind
B. undermine the evidence offered by Professor Keller’s study of mantle plume eruptions
C. highlight the devastating effects that mantle plume activities can have on the earth’s environment
D. question the assertion that mantle plumes were responsible for the eruptions that caused devastating environmental impact
E. strengthen the theory that asteroid impact was not the primary reason for the extinction of species in the past

3 
 C 
 3. According to the passage, each of the following statements about mantle plume activity is true, EXCEPT:

A. It is caused due to the heat from the earth’s mantle bubbling up, similar to the functioning of a lava lamp
B. During mantle plume eruptions, magma is spewed over hundreds of kilometres on the earth’s surface
C. Several ‘hotspots’ of volcanic activity across the globe give rise to mantle plume eruptions
D. It is an eruption that originates between the earth’s crust and its core and lasts for one or two million years
E. The massive deluge of lava, ashes, and gas during mantle plume eruptions can have significant effects on climate and evolution

4 
 A 
 4. It can be inferred from the passage that Professor Keller and team would be most likely to agree that which of the following is a possible outcome of mantle plume activity

A. The extinction of a species other than dinosaurs
B. The asteroid impact that happened 65 million years ago
C. The formation of microfossil assemblages on the ocean floor
D. The fundamental reshaping of the earth’s surface
E. The recent bouts of volcanic activity that the earth’s ‘hotspots’ have seen

globaldesi · Accepted Answer

Official answers:
1.OA: D
The focus is on mantle plumes and not on dinosaurs – dinosaur extinction is only one of the several outcomes of mantle plumes. So, A and C are incorrect. The central theme is not the diverse views of earth scientists – for one, both views expressed (Kerr and Keller) are similar, not contrasting; there is only a mention that a different set of views exist. So E is also incorrect. Option B mentions 'unanticipated' – the passage makes no mention of whether the outcomes were surprising – so B is also incorrect.

2.OA: E
According to the passage, there were 2 extinction events. In the first case, there was no evidence of asteroid impact. The second is thought to be caused by asteroid impact. But the effects of both were similar. Dr. Kerr identifies that the cause of both was mantle plume activity and not asteroid impact. Thus, the author mentions this fact to support Professor Keller's finding – i.e. asteroid impact was probably not the primary reason for extinction of dinosaurs. Option A is wrong as it refers to Dr. Kerr – no relation. B is wrong as the author does not undermine Keller's study. Option C is wrong as this fact does not really help to highlight the devastating effects of mantle plumes – it just tells us that 2 events happened; nothing about their impact or intensity. Option D is incorrect as the author never questions the theory that mantle plumes caused the eruptions.

3.OA: C
This is an EXCEPT question. So we need to eliminate every answer choice that is mentioned in the passage. Option A (lines 12-13), B (lines 14-15), D (line 3 and line 15) and E (lines 22-23). However, the opposite of option C is mentioned in lines 16 to 18 – mantle plume activity is responsible for volcanic hotspots and vice versa.

4.OA: A
Since two extinction events with similar devastating effects are mentioned (lines 6 to 8), we can infer that a species apart from dinosaurs could have become extinct in the first eruption that occurred several million years before the extinction of dinosaurs. This is why option A is right. In option B, we DKCS anything about what caused the asteroid impact. In option C, the microfossil assemblages were studied by Prof Keller – but we DKCS if mantle plume activity caused the formation of these. Option D mentions a viewpoint of Dr. Kerr – we DKCS if Prof Keller would agree with this. Option E mentions 'recent volcanic activity' – we DKCS whether mantle plume activity caused this.

GDT · Answer

SajjadAhmad

Pls post OE for Q4

Codebug4it · Answer

1. What is the central theme of the passage?

A. The role of mantle plumes in the extinction of dinosaurs
 => It is only discussed in one of the paras, not the passage as a whole

B. Unanticipated effects of mantle plume activity
 => It was not unanticipated, the scientists did some thorough research.

C. Earth science theories that explain the extinction of dinosaurs
 =>Same as A

D. The formation and consequences of mantle plumes
 =>CORRECT. The passage discusses its formation, eruptions, and effects over the surroundings and earth

E. Contrasting views of earth scientists on the mantle plume phenomenon
 => The views are not contrasting. The contrast is nowhere discussed.

------------------------------------------------------------------------------------------------------------------------------------------------------------

2. The author mentions ‘two extinction events’ in line 11 most probably in order to

A. support Dr. Kerr’s view that mantle plumes have a significant effect on the course of evolution, especially the predominance of mammals and the origin of humankind
 => No, the events are mentioned to show the cause of Extinctions but Dr. Kerr's view talks about evolution. Doesn't support each other

B. undermine the evidence offered by Professor Keller’s study of mantle plume eruptions
 =>Doesn't undermine, instead the study has been used to conclude the statement of two extinction events

C. highlight the devastating effects that mantle plume activities can have on the earth’s environment
 => It is a devastating effect of the mantle plume activity but not the most probable reason for mentioning it there because Extinction has already been mentioned in the one para back to this.

D. question the assertion that mantle plumes were responsible for the eruptions that caused devastating environmental impact
 => It doesn't question, it supports.

E. strengthen the theory that asteroid impact was not the primary reason for the extinction of species in the past
 => CORRECT. Yes, if Mantle plume activity was the reason for the 2 two extinction events, then it means asteroid impact was not. Hence it correctly strengthens the theory.

------------------------------------------------------------------------------------------------------------------------------------------------------------

3. According to the passage, each of the following statements about mantle plume activity is true, EXCEPT:

A. It is caused due to the heat from the earth’s mantle bubbling up, similar to the functioning of a lava lamp
 => "Likened to the actions of a lava lamp, the mantle's heat causes it" - mentioned here

B. During mantle plume eruptions, magma is spewed over hundreds of kilometres on the earth’s surface
=> => "spew magma over the earth's surface and across an area of some 1,000 kilometres diameter." - mentioned here

C. Several ‘hotspots’ of volcanic activity across the globe give rise to mantle plume eruptions
 => CORRECT. The passage says that "hotspots" are the remnant of the Mantle plume eruptions, not caused by it.

D. It is an eruption that originates between the earth’s crust and its core and lasts for one or two million years
=> => "'mantle plume' – a huge volcanic eruption from deep within the earth's mantle, the region between the crust and the core of the earth" - mentioned here

E. The massive deluge of lava, ashes, and gas during mantle plume eruptions can have significant effects on climate and evolution
=> => "The massive outpouring of lava, ashes, and gas can have significant effects on climate and have the potential to dictate the course of evolution" - mentioned here

------------------------------------------------------------------------------------------------------------------------------------------------------------

4. It can be inferred from the passage that Professor Keller and team would be most likely to agree that which of the following is a possible outcome of mantle plume activity

A. The extinction of a species other than dinosaurs
 => CORRECT. "a similar eruption under the Indian Ocean several million years before the extinction of the dinosaurs had a similarly devastating impact on the environment" - This states that mantle plume activity could be the cause for other species' extinction as well as because of similar devastating impact

B. The asteroid impact that happened 65 million years ago
 => No, they researched on mantle plume activity but didn't find any evidence on asteroid impact

C. The formation of microfossil assemblages on the ocean floor
 => Keller's findings are based on microfossil assemblages but no info on if they were an outcome of mantle plume activity. They could have always there but had traces of plumes when eruptions occurred and passed over them.

D. The fundamental reshaping of the earth’s surface
 => This is Dr. Kerr's views, not Keller's views

E. The recent bouts of volcanic activity that the earth’s ‘hotspots’ have seen
 => Not relevant to Keller's research

Sajjad1994 · Answer

Official Explanation

4. It can be inferred from the passage that Professor Keller and team would be most likely to agree that which of the following is a possible outcome of mantle plume activity

Difficulty Level:   700

Explanation

A  - Since two extinction events with similar devastating effects are mentioned in the  para 1 , we can infer that a species apart from dinosaurs could have become extinct in the first eruption that occurred several million years before the extinction of dinosaurs. This is why option  A  is right.

B  - We don't know anything about what caused the asteroid impact.

C  - The microfossil assemblages were studied by Prof Keller – but we don‖t know if mantle plume activity caused the formation of these.

D  –It mentions a viewpoint of Dr. Kerr – we don‖t know if Prof Keller would agree with this.

E  - It mentions ―recent volcanic activity‖ – we don‖t know whether mantle plume activity caused this.

Answer: A

PS: All OEs are already posted above.

SergioGG · Answer

Hello, I would like to pose a question that maybe, just maybe, may seem stupid, but a thoughtful and serious answer might not seem so stupid. I am aware that under the premise that it should be impossible, or perhaps not, a planet cannot in a short space of time increase its "gravity" due to an external event (I could have a hypothesis in this regard, of course not verified , but very interesting). So, I throw the following question; -
 What could have happened, if life on earth 80-65 million years ago had faced a temporary increase (1 year, 10 million years ...?) In gravity of 0.3 / 0.4g?

I apologize for my English
Regards.

richirish · Answer

4 mins all correct, moderate passage imo, 650 level, happy to help if needed !

sssanskaar · Answer

Answering this question just for the sake of fun and also because I am happy today since I did well in this 700 lvl RC after many days of effort

What could have happened, if life on earth 80-65 million years ago had faced a temporary increase (1 year, 10 million years ...?) In gravity of 0.3 / 0.4g? I am not an expert but I do have a deep interest in physics. From my humble understanding, I believe the if and when the earth would have had suddenly experienced a gravity increase of 0.3/0.4g - we are talking about 30% to 40% increase here btw - the first and very important evolutionary changes that we would have seen, IF WE ARE TALKING ABOUT A CHANCE WHERE MAMMALS STILL SURVIVE THIS CHANGE, would be the changes in the bone density of the vertebrates. The bone density would be higher than what it is now. Also, our circulatory system would have been stronger because our heart and blood vessels would have required way more effort to counter gravity so as to flow the blood throughout the body. In terms of architecture, our whole engineering and hydraulic systems would have had developed in a whole new concept because the early humans would have to find way stronger materials to build a strong enough bridge to sustain the bare minimum weight of the vehicles or even to build a simple house. Finding such rare and stronger materials would have had big implications on the world trade and economy and everything related to geo-politics and balance of power that we see today would have had been very different from what we can imagine. Another thing to take into consideration is that our atmosphere would have been way denser, which can be good in some ways. However, the pollution caused by us would have impacted us in a way stronger manner than the manner in which we are facing today. For this reason, either our lungs would have had given up and we would have been on the verge of extinction or we would have adapted an evolutionary change in terms of respiration. (of course, if this gravity increase event happens for a longer time). This event would have taken a huge toll on floods and devastation as well. The moon would be much closer due to an increase in the gravity of the earth and this change would have initiated a sudden change in tidal waves, making them much stronger and fearsome. Lots of regions would have faced sudden floods and tsunamis. There would be a total collapse of ecological systems and the earth would have seen unprecedented chaos of devastation. These are some of the obvious effects that the earth would have had to encounter if it would have faced the scenario mentioned in your question. In short, everything is in perfect balance and in the perfect numerical amount on our planet so as to sustain life. Tip anything towards the extremes and life will cease to exist in the way it is existing now. I hope I have satiated your hunger for the answer

VerbalBot · Answer

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The extinction of the dinosaurs – thought to be caused by an asteroid

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The extinction of the dinosaurs – thought to be caused by an asteroid

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