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

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In 1979, a team of scientists from Berkeley working near Gubbio, Italy  [#permalink]

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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.

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.


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


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


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In 1979, a team of scientists from Berkeley working near Gubbio, Italy  [#permalink]

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New post 20 Aug 2017, 09:25
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
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Re: In 1979, a team of scientists from Berkeley working near Gubbio, Italy  [#permalink]

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New post 20 Aug 2017, 09:52
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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In 1979, a team of scientists from Berkeley working near Gubbio, Italy  [#permalink]

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New post 20 Aug 2017, 10:46
manoj1115 wrote:
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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answers are 1.D 2.D 3.D. amswer is given with the question
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Re: In 1979, a team of scientists from Berkeley working near Gubbio, Italy  [#permalink]

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New post 23 Aug 2017, 11:00
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?
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Re: In 1979, a team of scientists from Berkeley working near Gubbio, Italy  [#permalink]

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New post 28 Aug 2017, 14:18
Gnpth wrote:
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.

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.


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


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


Gnpth,
Please check the answer choices in Q2. I cannot find anything in the passage that talks about marine data.
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Re: In 1979, a team of scientists from Berkeley working near Gubbio, Italy  [#permalink]

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New post 30 Aug 2017, 03:39
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?
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Re: In 1979, a team of scientists from Berkeley working near Gubbio, Italy  [#permalink]

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New post 26 Oct 2018, 01:16

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.
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Re: In 1979, a team of scientists from Berkeley working near Gubbio, Italy  [#permalink]

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New post 26 Oct 2018, 01:19

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
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Re: In 1979, a team of scientists from Berkeley working near Gubbio, Italy &nbs [#permalink] 26 Oct 2018, 01:19
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