GMAT Question of the Day - Daily to your Mailbox; hard ones only

It is currently 16 Jun 2019, 14:21

Close

GMAT Club Daily Prep

Thank you for using the timer - this advanced tool can estimate your performance and suggest more practice questions. We have subscribed you to Daily Prep Questions via email.

Customized
for You

we will pick new questions that match your level based on your Timer History

Track
Your Progress

every week, we’ll send you an estimated GMAT score based on your performance

Practice
Pays

we will pick new questions that match your level based on your Timer History

Not interested in getting valuable practice questions and articles delivered to your email? No problem, unsubscribe here.

Close

Request Expert Reply

Confirm Cancel

Until the 1980s, most scientists believed that noncatastrophic geologi

  new topic post reply Question banks Downloads My Bookmarks Reviews Important topics  
Author Message
TAGS:

Hide Tags

 
Senior RC Moderator
User avatar
V
Status: Preparing GMAT
Joined: 02 Nov 2016
Posts: 2759
Location: Pakistan
GPA: 3.39
Until the 1980s, most scientists believed that noncatastrophic geologi  [#permalink]

Show Tags

New post 26 Apr 2019, 08:06
1
Question 1
00:00
A
B
C
D
E

based on 49 sessions

90% (03:29) correct 10% (03:02) wrong

HideShow timer Statistics

Question 2
00:00
A
B
C
D
E

based on 62 sessions

81% (00:43) correct 19% (01:04) wrong

HideShow timer Statistics

Question 3
00:00
A
B
C
D
E

based on 55 sessions

36% (01:24) correct 64% (01:50) wrong

HideShow timer Statistics

Question 4
00:00
A
B
C
D
E

based on 55 sessions

85% (00:46) correct 15% (00:56) wrong

HideShow timer Statistics

Question 5
00:00
A
B
C
D
E

based on 53 sessions

64% (01:17) correct 36% (01:45) wrong

HideShow timer Statistics

Question 6
00:00
A
B
C
D
E

based on 47 sessions

77% (01:00) correct 23% (01:20) wrong

HideShow timer Statistics

Question 7
00:00
A
B
C
D
E

based on 43 sessions

60% (01:21) correct 40% (01:31) wrong

HideShow timer Statistics

New Project RC Butler 2019 - Practice 2 RC Passages Everyday
Passage # 170, Date : 26-APR-2019
This post is a part of New Project RC Butler 2019. Click here for Details


Until the 1980s, most scientists believed that noncatastrophic geological processes caused the extinction of dinosaurs that occurred approximately 66 million years ago, at the end of the Cretaceous period. Geologists argued that a dramatic drop in sea level coincided with the extinction of the dinosaurs and could have caused the climatic changes that resulted in this extinction as well as the extinction of many ocean species.

This view was seriously challenged in the 1980s by the discovery of large amounts of iridium in a layer of clay deposited at the end of the Cretaceous period. Because iridium is extremely rare in rocks on the Earth’s surface but common in meteorites, researchers theorized that it was the impact of a large meteorite that dramatically changed the earth’s climate and thus triggered the extinction of the dinosaurs.

Currently available evidence, however, offers more support for a new theory, the volcanic-eruption theory. A vast eruption of lava in India coincided with the extinctions that occurred at the end of the Cretaceous period, and the release of carbon dioxide from this episode of volcanism could have caused the climatic change responsible for the demise of the dinosaurs. Such outpourings of lava are caused by instability in the lowest layer of the Earth’s mantle, located just above the Earth’s core. As the rock that constitutes this layer is heated by the Earth’s core, it becomes less dense and portions of it eventually escape upward as blobs or molten rock, called “diapirs,” that can, under certain circumstances, erupt violently through the Earth’s crust.

Moreover, the volcanic-eruption theory, like the impact theory, accounts for the presence of iridium in sedimentary deposits; it also explains matters that the meteorite-impact theory does not. Although iridium is extremely rare on the Earth’s surface, the lower regions of the Earth’s mantle have roughly the same composition as meteorites and contain large amounts of iridium, which in the case of a diapir eruption would probably be emitted as iridium hexafluoride, a gas that would disperse more uniformly in the atmosphere than the iridium-containing matter thrown out from a meteorite impact. In addition, the volcanic-eruption theory may explain why the end of the Cretaceous period was marked by a gradual change in sea level. Fossil records indicate that for several hundred thousand years prior to the relatively sudden disappearance of the dinosaurs, the level of the sea gradually fell, causing many marine organisms to die out. This change in sea level might well have been the result of a distortion in the Earth’s surface that resulted from the movement of diapirs upward toward the Earth’s crust, and the more cataclysmic extinction of the dinosaurs could have resulted from the explosive volcanism that occurred as material from the diapirs erupted onto the Earth’s surface.
1. The passage suggests that during the 1980s researchers found meteorite impact a convincing explanation for the extinction of dinosaurs, in part because

(A) earlier theories had failed to account for the gradual extinction of many ocean species at the end of the Cretaceous period
(B) geologists had, up until that time, underestimated the amount of carbon dioxide that would be released during an episode of explosive volcanism
(C) a meteorite could have served as a source of the iridium found in a layer of clay deposited at the end of the Cretaceous period
(D) no theory relying on purely geological processes had, up until that time, explained the cause of the precipitous drop in sea level that occurred at the end of the Cretaceous period
(E) the impact of a large meteorite could have resulted in the release of enough carbon dioxide to cause global climatic change



2. According to the passage, the lower regions of the Earth’s mantle are characterized by

(A) a composition similar to that of meteorites
(B) the absence of elements found in rocks on the Earth’s crust
(C) a greater stability than that of the upper regions
(D) the presence of large amounts of carbon dioxide
(E) a uniformly lower density than that of the upper regions



3. It can be inferred from the passage that which one of the following was true of the lava that erupted in India at the end of the Cretaceous period?

(A) It contained less carbon dioxide than did the meteorites that were striking the Earth’s surface during that period.
(B) It was more dense than the molten rock, located just above the Earth’s core.
(C) It released enough iridium hexafluoride into the atmosphere to change the Earth’s climate dramatically.
(D) It was richer in iridium than rocks usually found on the Earth’s surface.
(E) It was richer in iridium than were the meteorites that were striking the Earth’s surface during that period.



4. In the passage, the author is primarily concerned with doing which one of the following?

(A) describing three theories and explaining why the latest of these appears to be the best of the three
(B) attacking the assumptions inherent in theories that until the 1980s had been largely accepted by geologists
(C) outlining the inadequacies of three different explanations of the same phenomenon
(D) providing concrete examples in support of the more general assertion that theories must often be revised in light of new evidence
(E) citing evidence that appears to confirm the skepticism of geologists regarding a view held prior to the 1980s



5. The author implies that if the theory described in the third paragraph is true, which one of the following would have been true of iridium in the atmosphere at the end of the Cretaceous period?

(A) Its level of concentration in the Earth’s atmosphere would have been high due to a slow but steady increase in the atmospheric iridium that began in the early Cretaceous period.
(B) Its concentration in the Earth’s atmosphere would have increased due to the dramatic decrease in sea level that occurred during the Cretaceous period.
(C) It would have been directly responsible for the extinction of many ocean species.
(D) It would have been more uniformly dispersed than iridium whose source had been the impact of a meteorite on the Earth’s surface.
(E) It would have been more uniformly dispersed than indium released into the atmosphere as a result of normal geological processes that occur on Earth.



6. The passage supports which one of the following claims about the volcanic-eruption theory?

(A) It does not rely on assumptions concerning the temperature of molten rock at the lowest pan of the Earth’s mantle.
(B) It may explain what caused the gradual fall in sea level that occurred for hundreds of thousands of years prior to the more sudden disappearance of the dinosaurs.
(C) It bases its explanation on the occurrence of periods of increased volcanic activity similar to those shown to have caused earlier mass extinctions.
(D) It may explain the relative scarcity of iridium in rocks on the Earth’s surface compared to its abundance in meteorites.
(E) It accounts for the relatively uneven distribution of iridium in the layer of clay deposited at the end of the Cretaceous period.



7. Which one of the following, if true, would cast the most doubt on the theory described in the last paragraph of the passage?

(A) Fragments of meteorites that have struck the Earth are examined and found to have only minuscule amounts of iridium hexafluoride trapped inside of them.
(B) Most diapir eruptions in the geological history of the Earth have been similar in size to the one that occurred in India at the end of the Cretaceous period and have not been succeeded by periods of climatic change.
(C) There have been several periods in the geological history of the Earth, before and after the Cretaceous period, during which large numbers of marine species have perished.
(D) The frequency with which meteorites struck the Earth was higher at the end of the Cretaceous period than at the beginning of the period.
(E) Marine species tend to be much more vulnerable to extinction when exposed to a dramatic and relatively sudden change in sea level than when they are exposed to a gradual change in sea level similar to the one that preceded the extinction of the dinosaurs.




  • Source: LSAT Official PrepTest 15 (June 1995)
  • Difficulty Level: 650

_________________
New Project RC Butler 2019 - Practice 2 RC Passages Everyday
Final days of the GMAT Exam? => All GMAT Flashcards.
This Post Helps = Press +1 Kudos
Best of Luck on the GMAT!!
Verbal Forum Moderator
User avatar
V
Status: Greatness begins beyond your comfort zone
Joined: 08 Dec 2013
Posts: 2301
Location: India
Concentration: General Management, Strategy
Schools: Kelley '20, ISB '19
GPA: 3.2
WE: Information Technology (Consulting)
GMAT ToolKit User Reviews Badge CAT Tests
Re: Until the 1980s, most scientists believed that noncatastrophic geologi  [#permalink]

Show Tags

New post 26 Apr 2019, 23:53
1
All correct in 12 mins 20 seconds, including almost 4 mins to read

Para 1- Theory 1- noncatastrophic geological processes caused the extinction of dinosaurs
Para 2- meteorite impact theory- iridium presence
Para 3- volcanic-eruption theory
Para 4- Why volcanic-eruption theory is the best among the three?

1. The passage suggests that during the 1980s researchers found meteorite impact a convincing explanation for the extinction of dinosaurs, in part because
(C) a meteorite could have served as a source of the iridium found in a layer of clay deposited at the end of the Cretaceous period - Correct, refer to 2nd para

2. According to the passage, the lower regions of the Earth’s mantle are characterized by
(A) a composition similar to that of meteorites

Although iridium is extremely rare on the Earth’s surface, the lower regions of the Earth’s mantle have roughly the same composition as meteorites and contain large amounts of iridium

3. It can be inferred from the passage that which one of the following was true of the lava that erupted in India at the end of the Cretaceous period?
(C) It released enough iridium hexafluoride into the atmosphere to change the Earth’s climate dramatically.- incorrect, iridium hexafluoride did not cause climate change but carbon dioxide did
(D) It was richer in iridium than rocks usually found on the Earth’s surface.- Correct

Although iridium is extremely rare on the Earth’s surface, the lower regions of the Earth’s mantle have roughly the same composition as meteorites and contain large amounts of iridium

4. In the passage, the author is primarily concerned with doing which one of the following?
(A) describing three theories and explaining why the latest of these appears to be the best of the three- Correct,

Moreover, the volcanic-eruption theory, like the impact theory, accounts for the presence of iridium in sedimentary deposits

In addition, the volcanic-eruption theory may explain why the end of the Cretaceous period was marked by a gradual change in sea level.

5. The author implies that if the theory described in the third paragraph is true, which one of the following would have been true of iridium in the atmosphere at the end of the Cretaceous period?
(D) It would have been more uniformly dispersed than iridium whose source had been the impact of a meteorite on the Earth’s surface.

Although iridium is extremely rare on the Earth’s surface, the lower regions of the Earth’s mantle have roughly the same composition as meteorites and contain large amounts of iridium, which in the case of a diapir eruption would probably be emitted as iridium hexafluoride, a gas that would disperse more uniformly in the atmosphere than the iridium-containing matter thrown out from a meteorite impact.

6. The passage supports which one of the following claims about the volcanic-eruption theory?
(B) It may explain what caused the gradual fall in sea level that occurred for hundreds of thousands of years prior to the more sudden disappearance of the dinosaurs

In addition, the volcanic-eruption theory may explain why the end of the Cretaceous period was marked by a gradual change in sea level. Fossil records indicate that for several hundred thousand years prior to the relatively sudden disappearance of the dinosaurs, the level of the sea gradually fell, causing many marine organisms to die out. This change in sea level might well have been the result of a distortion in the Earth’s surface that resulted from the movement of diapirs upward toward the Earth’s crust

7. Which one of the following, if true, would cast the most doubt on the theory described in the last paragraph of the passage?
(B) Most diapir eruptions in the geological history of the Earth have been similar in size to the one that occurred in India at the end of the Cretaceous period and have not been succeeded by periods of climatic change.-- Correct, cause(diapir eruptions) is present but effect(periods of climatic change) is not
_________________
When everything seems to be going against you, remember that the airplane takes off against the wind, not with it. - Henry Ford
The Moment You Think About Giving Up, Think Of The Reason Why You Held On So Long
+1 Kudos if you find this post helpful
Senior Manager
Senior Manager
avatar
G
Joined: 11 Feb 2018
Posts: 280
Location: India
Concentration: General Management, Finance
GMAT 1: 690 Q47 V37
GMAT 2: 710 Q50 V36
GMAT 3: 750 Q50 V42
Re: Until the 1980s, most scientists believed that noncatastrophic geologi  [#permalink]

Show Tags

New post 12 May 2019, 06:41
All correct...8 mins 37secs(including reading which took about 2mins, maybe because I am a science student)

For Q3)

Iri Hex is mentioned only in the last para.Going there we get that iri hex was released and it acted as a source of iridium.Climate change is not touched upon AT ALL in this para.

as skywalker rightly said it is carbon dioxide, but I dint use that information to eliminate C...

D though is clearly mentioned from the third line onwards..

For Q5)

D is very clearly mentioned in the same 4th para.There is no other competition for option D) I believe..

Cheerio..
GMAT Club Bot
Re: Until the 1980s, most scientists believed that noncatastrophic geologi   [#permalink] 12 May 2019, 06:41
Display posts from previous: Sort by

Until the 1980s, most scientists believed that noncatastrophic geologi

  new topic post reply Question banks Downloads My Bookmarks Reviews Important topics  


Powered by phpBB © phpBB Group | Emoji artwork provided by EmojiOne