In 1979, a team of scientists from Berkeley working near Gubbio, Italy

Question

Aristotle

Aristotle RC 99 - Passage 19    
 
  In 1979, a team of scientists from Berkeley working near Gubbio, Italy, discovered a layer of clay that revolutionized theories concerning the disappearance of the dinosaur, which had centred on the assumed gradual climatic change. Beneath the two-centimetre-thick layer lay limestone containing fossil organisms from the late Cretaceous, while above it was limestone with early Cenozoic fossils.

Positionally, then, the Berkeley group could place the clay in a period roughly contemporaneous with the disappearance of the dinosaur approximately 63 million years ago. They found that the clay stratum contained an iridium level thirty times greater than that of clays in adjacent strata. As iridium is distributed fairly evenly over time through micrometeoritic impact, the researchers knew that the anomalous matter in the clay must have originated extra-terrestrially; the high iridium level, moreover, indicated a sudden deposition in an exceptional, catastrophic event.

Scientists are sharply divided on the possible causes of so cataclysmic an event. The possibility that the deposition occurred as an aftereffect of a supernova has been discounted: radioactive isotope Pu-244 was absent from the clay, and neither Ir-191 nor Ir-193 were present in significant proportions.

Those who maintain that the material came from within the solar system contend that the earth must have collided during the late Cretaceous with an astral body large enough to have distributed the iridium-rich material over the globe. An asteroid of the required mass would have been approximately ten kilometres in diameter; a comet would have to have been twice as large, since comets are largely composed of ice water.

Trying to fathom the scale of such an event as this is mind boggling. It is true that from space, an object 10-20 miles across colliding with earth would be akin to something smaller than a grain of sand landing on a basketball, it is also the case that an object twenty miles across that landed on earth would be nearly twice as tall as Mt. Everest (the tallest mountain on Earth) and further across than the length of Manhattan. Furthermore, when the body came crashing to Earth it would have been ablaze in an inferno caused by the friction of entry into our atmosphere. To the argument that there is no geological evidence of the impact of such massive objects, Richard Grieve has replied that the clay layer could have resettled after the impact in the form of fallout. Frank Kyte of UCLA asserts that a comet, if disrupted by the earth‘s gravitational field, would have exposed the surface to a deluge of debris that would not have created major craters. Alternatively, the Berkeley group suggests that an asteroid may have landed in the sea; such a collision would have produced tidal waves eight kilometres high, swamping large areas of the earth.

Whatever the type of body and mode of impact, Walter Alvarez of the Berkeley team argues that the primary effect of the catastrophe was to disrupt the planetary ecology through the suspension of vast clouds of matter in the stratosphere. The effects of the initial impact would have been greatly multiplied, Alvarez argues, as photosynthesis was impeded by the blockage of sunlight; there would then have been a massive disruption at the base of the dinosaur‘s food chain.   1 
The passage discusses a new discovery that may change the way scientists think about one aspect of dinosaurs. It can be inferred that the discovery described in the passage may ―revolutionize‖ (line 4) which aspect of current theories about dinosaurs?
A. The geographical extent of the presumed habitation of the dinosaur
B. The approximate date at which dinosaurs are thought to have become extinct
C. The assumption that dinosaurs became extinct because of a change in their natural environment
D. The rate at which the extinction of the dinosaur is thought to have occurred
E. The notion that dinosaurs became extinct because of the onset of an ice age.

2 
According to the passage, the Berkeley group used which of the following to support their hypothesis on the disappearance of the dinosaur?
I. A comparison of the fossil records of various marine strata
II. A comparison of different clay strata near Gubbio, Italy
III. A comparison of marine strata in several locations
A. I only
B. III only
C. I and II
D. II and III
E. I, II and III

3  
According to the information presented by the author throughout the passage, scientists used the analysis of the isotopes present in the clay to:
A. estimate the age of the stratum more exactly.
B. determine the extent of meteoritic impact upon the earth.
C. derive a hypothesis concerning the effect of the impact of an extraplanetary body on the earth‘s ecology.
D. eliminate a possible theory concerning the enriched clay‘s formation.
E. determine whether dinosaurs were allergic to these

r19 · Answer

nice passage.. 2 correct answer (1 and 3) and took approx 8.5 mins to solve

need help for question 2 , How III is correct ? I cannot correlate it with the passage.
I. A comparison of the fossil records of various marine strata
II. A comparison of different clay strata near Gubbio, Italy
III. A comparison of marine strata in several locations

manoj1115 · Answer

What are the answers of the RC... I found option C for question 1, option D for question 2 and option D again for question 3

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r19 · Answer

answers are 1.D 2.D 3.D. amswer is given with the question

Jimbo1912 · Answer

Hmmm.

I agree with Qs 1 and 3. I'm having trouble justifying the OA to question 2? Where in the passage does it discuss marine strata?

shakun · Answer

Gnpth ,
Please check the answer choices in Q2. I cannot find anything in the passage that talks about marine data.

IIMC · Answer

Where as mentioned in Q2 answer has the author mentioned that the scientists compared the marine strata and how for Q3 can we deduce that D is correct answer?

Gmatsaiyan · Answer

Topic and Scope - The iridium layer‘s impact on theories of dinosaur extinction
 Mapping the Passage 
¶s 1 and 2 describe the Berkeley group's discovery of the iridium layer and its significance to dinosaur extinction.
¶3 discusses conflicting theories for the cause of iridium deposition.
¶s4 and 5 elaborate on various theories that an asteroid or comet was responsible for the iridium layer.
¶6 presents Alvarez‘s mechanism for extinction: debris from impact blocked sunlight, impeded photosynthesis, and harmed the dinosaurs‘ food chain.

Gmatsaiyan · Answer

Answers and Explanations OE 
 1) Read the phrase in context. The author argues that the discovery of the iridium layer revolutionized theories about dinosaur extinction. What is true about these theories? Immediately afterwards the author says that they ―had centred on the assumed gradual climatic change.‖ The implication is that the iridium layer suggests a fast climatic change. (D) is therefore correct: it‘s likely that the discovery will change the time frame that scientists had used.
(A): Out of Scope. The author doesn‘t discuss any geographic angles of the theories.
(B): Distortion. Though theories about the length of time over which the extinction occurred may have changed, the author notes that the iridium layer was found in ―a period roughly contemporaneous with the disappearance of the dinosaur,‖ which suggests that the date of extinction was already well-established.
(C): Out of Scope. The author doesn‘t suggest that this is an assumption of traditional theories, and if it was, it wouldn‘t change: the impact theory, at least as described by Alvarez, says the same thing.
(D): The correct answer
(E): Ice age is not within the scope of the passage.
 2)  A detail question. Review the Berkeley groups‘ hypothesis: lots of material was deposited in a very short span of time, suggesting a quick extinction. Any support that they have must be in the form of the iridium evidence listed in the first two paragraphs. RN I doesn‘t pass the test: fossils are mentioned in ¶1, but not in the context of marine strata. RN II, however, repeats the fact that the group compared the iridium strata with the nearby strata from the late Cretaceous and early Cenozoic. Only (D) remains as an answer choice, and there‘s no need to look at RN
III. RN III has to be true from the information in the passage: the Berkeley group compared their findings with marine rocks from various other locations.
(A): Opposite. As described above.
(B): Opposite. As above.
(C): Opposite. As above.
(D): The correct answer
(E): Opposite. As above.
 3)  Review ¶3: Why are isotopes important? Predict: They rule out the possibility that the iridium deposits were caused by a supernova. (D) says the same in slightly vaguer terms.
(A): Out of Scope. The passage doesn‘t discuss any such attempt to estimate the age of the iridium layer.
(B): Out of Scope. The isotopic information is useful only to determine that the iridium wasn‘t extrasolar, not to determine what type of object from within the solar system hit or how extensive the damage was.
(C): Faulty Use of Detail. Alvarez has a hypothesis that does this, but it doesn‘t rely at all on the isotopic data.
(D): The correct answer
(E): ‗Allergy‘ is outside the scope of the passage

ssaamm · Answer

can anyone explain this passage.i am not getting its oa to be correct.ques 1 and 2nd is hard to solve

Sajjad1994 · Answer

Hi

Question number 2 is off the passage in my point of view, Official Explanation didn't support the question to be a perfect one, Three options in the question are flawed. I have selected C as the answer based on my guess and i was not confident about that even.  generis  your views on question number 2 may prove helpful.

Thanks

generis · Answer

SajjadAhmad  , either this author went off the deep end or the passage was changed but the questions were not.

Question 2 is flawed. I would delete it.

Only option II has textual support.
No textual support exists for I or III.

• support for II

The Berkeley people DID use
  II. A comparison of different clay strata near Gubbio, Italy  
to support their hypothesis about dinosaur extinction.

The Berkeley group's hypotheses about the disappearance of the dinosaur, roughly, is
(1) conclusion: the dinosaur disappeared quickly, not gradually

(2) that quick disappearance was caused by a catastrophic event: a large extra-terrestrial body hit somewhere on earth (probably the sea), sending vast clouds of matter into the stratosphere that blocked out the sun

(3) No sun = no photosynthesis = no plants. Plant-eating dinosaurs perish. Meat-eating dinosaurs that eat plant-eating dinosaurs perish.

What did the Berkeley group use to  support  its hypothesis?

1. The date of the clay (coincides with time period during which dinosaurs perished)

Paragraph 1: Two layers of limestone sandwiched a layer of clay.
Berkeley scientists knew the dates of the eras during which the limestone formed. 
The clay lay in between the end of one era and the beginning of the other.
The "between two eras" allowed scientists to 
"place the clay in a period roughly contemporaneous with the disappearance of the dinosaur approximately 63 million years ago."

2. Unearthly levels of iridium in that layer of clay compared to iridium in other layers of clay indicated that the iridium was deposited by an extra-terrestrial body that caused a catastrophic event.
Paragraph 2: ( They found that the clay stratum contained an iridium level thirty times greater than that of clays in adjacent strata.  )
During the same time period that dinosaurs became extinct, a celestial body hit the earth.

3. Effect? Matter flooded the stratosphere, blocked out the sun, and prevented photosynthesis. 
Plants, plant-eating dinosaurs, and meat-eating dinosaurs perished quickly. (Last paragraph.)

Option II has support.

Both I and III depend on the presence of marine strata. 
If Option III has no support, then Option I has none, either.
Start with Option III

Can we find any hint that the Berkeley people examined marine strata? 
-- Marine strata = Ocean or sea layers. ( Marine  refers to seas.)

• Option III (and I): are not supported by the passage.

The passage does not mention marine strata (sea or ocean layers).

One reference to the sea exists: The earth  may  have been flooded by sea water.

I wondered whether I could reason this way:

1) Berkeley people believe that object MAY have landed in the sea, a landing that caused large areas of flooding 
-- (Paragraph 5:  Alternatively, the Berkeley group suggests that an asteroid  may  have landed in the sea; such a collision would have produced tidal waves eight kilometres high, swamping large areas of the earth. )

2) Two different limestone layers are mentioned. 
(Paragraph 1 -  The limestone layer beneath the clay contain  fossil organisms from the late Cretaceous, while above   was limestone with early Cenozoic fossils. )

3) Maybe the text would connect limestone to water, the sea, or flooding?  No. 
Clay is not connected to sea water, either.

No mention of marine strata. 
No connection of mentioned limestone and clay strata to sea water.
No mention of "various places."
The Berkeley people did not use anything from Options I or III to support their hypothesis.

Logically, it is not possible to jump from "a possible impact in ocean that created tidal waves, swampinglarge areas of earth" 
to "
a comparison of   marine strata in several locations ."

GAh. Bad questions are the hardest to explain. This question is so awful that I suspect an editing mistake.

Your instincts are correct.
Hope that helps.

UdivyaS · Answer

I didnt understand qn 1...How does gradual climatic change translate to rate of extinction?

maximequi · Answer

what was the GMAT score level of this RC if we don't consider the 2nd question?

Sajjad1994 · Answer

Hi

All three questions in this RC are very hard hence removing question 2 won't change its class of difficulty. It will remain (805+ level) as the difficulty-level tag suggests.

Thank you!

suscipitfugit · Answer

I think option c is correct for question 2. I have verified it from multiple AI like chatgpt and gemini as well. Waiting for your opionion

Bunuel · Answer

The question has flaws. Archiving it.

In 1979, a team of scientists from Berkeley working near Gubbio, Italy

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