LSAT 111 – Section 1 – Question 17

LSAT 111 - Section 1 - Question 17

October 2001

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Question
QuickView		 Type Tags Answer
Choices		 Curve Question
Difficulty		 Psg/Game/S
Difficulty		 Explanation
PT111 S1 Q17
+LR
Flaw or descriptive weakening +Flaw
Causal Reasoning +CausR
Eliminating Options +ElimOpt
A
3%
160
B
8%
159
C
25%
163
D
7%
161
E
56%
167
148
162
175
 +Hardest 147.471 +SubsectionMedium

On the basis of the available evidence, Antarctica has generally been thought to have been covered by ice for at least the past 14 million years. Recently, however, three-million-year-old fossils of a kind previously found only in ocean-floor sediments were discovered under the ice sheet covering central Antarctica. About three million years ago, therefore, the Antarctic ice sheet must temporarily have melted. After all, either severe climatic warming or volcanic activity in Antarctica’s mountains could have melted the ice sheet, thus raising sea levels and submerging the continent.

Summarize Argument: Phenomenon-Hypothesis
The author hypothesizes that about 3 million years ago, the Antarctic ice sheet must temporarily have melted. This is based on the fact that we recently discovered 3-million-year-old fossils under the ice sheet of Antarctica. These fossils are of a kind that have only been found in ocean-floor sediments. In addition, severe climatic warming or volcanic activity in Antarctica’s mountains could have melted the ice sheet, which would have produced liquid water that submerged the area.

Identify and Describe Flaw
The author assumes there’s no way for the fossils to be found under the ice sheet unless the ice sheet was melted. This overlooks other explanations for the presence of the fossils. Perhaps, for example, the floor has shifted underneath the ice sheet, which allowed the fossils to move underneath when they were originally not underneath the ice sheet.

A
That a given position is widely believed to be true is taken to show that the position in question must, in fact, be true.
The author’s conclusion that the ice sheet must have melted is not based on the idea that this view is widely believed to be true. We don’t know whether other people besides the author believe the ice sheet melted.
B
That either of two things could independently have produced a given effect is taken to show that those two things could not have operated in conjunction to produce that effect.
The author does not assume that the melting of the ice sheet could not have been produced by a combination of climatic warming and volcanic activity. The author presents those two things as potential causes for the melting, but never suggests they were mutually exclusive.
C
Establishing that a certain event occurred is confused with having established the cause of that event.
The author’s conclusion is that a certain event occurred — the ice sheet melted. The flaw relates to the author’s failure to prove that this event happened. The author did not establish this event occurred, and does not try to reach a conclusion about the cause of this event.
D
A claim that has a very general application is based entirely on evidence from a narrowly restricted range of cases.
The claim that the ice sheet must have temporarily melted does not have “general application.” It is a claim about a particular ice sheet and that it must have melted around 3 million years ago. This does not apply to other ice sheets or other time periods.
E
An inconsistency that, as presented, has more than one possible resolution is treated as though only one resolution is possible.
The inconsistency is that we found 3-million-year-old fossils under the ice sheet, even though this kind of fossil has previously been found only in the ocean floor. The author thinks this must be because the ice sheet melted. This overlooks other explanations.

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LSAT PrepTest 111 Explanations

Section 1 - Logical Reasoning

Section 2 - Reading Comprehension

Section 3 - Logical Reasoning

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