Geographer: "Sorted circles" are patterned geological formations consisting of a circular border of stones around a center of finer material....
GMAT Critical Reasoning : (CR) Questions
Geographer: "Sorted circles" are patterned geological formations consisting of a circular border of stones around a center of finer material. They are found mainly in or near the Arctic and Antarctic. In attempts to explain how they were formed, two hypotheses are currently most commonly debated: one proposes frost, the other heat. But frost cannot be the complete explanation for the uniformity in size of the circles on Marion Island, located in the maritime Subantarctic. Therefore, heat, either in water or in saturated soil, was likely involved in the formation of the circles.
Which of the following would, if true, most weaken the geographer's argument?
Passage Analysis:
| Text from Passage | Analysis |
| "Sorted circles" are patterned geological formations consisting of a circular border of stones around a center of finer material. |
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| They are found mainly in or near the Arctic and Antarctic. |
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| In attempts to explain how they were formed, two hypotheses are currently most commonly debated: one proposes frost, the other heat. |
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| But frost cannot be the complete explanation for the uniformity in size of the circles on Marion Island, located in the maritime Subantarctic. |
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| Therefore, heat, either in water or in saturated soil, was likely involved in the formation of the circles. |
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Argument Flow:
The geographer starts by defining sorted circles and noting two competing theories (frost vs heat). Then uses specific evidence from Marion Island - where circles show uniform sizing - to argue against the frost theory. Based on this elimination, concludes that heat must be involved.
Main Conclusion:
Heat, either in water or in saturated soil, was likely involved in forming the sorted circles.
Logical Structure:
This is an elimination argument: if frost can't explain the uniform sizing on Marion Island, then the other main theory (heat) must be correct. The logic relies on there being only two viable explanations and successfully ruling out one of them.
Prethinking:
Question type:
Weaken - We need to find information that would reduce belief in the geographer's conclusion that heat was likely involved in forming the circles on Marion Island
Precision of Claims
The key claim is specific: heat (in water or saturated soil) was likely involved because frost cannot completely explain the uniformity in size of circles on Marion Island specifically
Strategy
To weaken this argument, we need to either show that frost CAN actually explain the uniformity in size on Marion Island, or provide an alternative explanation that doesn't require heat. We can also attack the logic by showing the geographer jumped to conclusions or missed other possibilities
Field experiments show there is currently frost at all sorted-circle sites on Marion Island. This choice actually supports rather than weakens the argument. The geographer isn't claiming that there's no frost on Marion Island - they're saying frost alone cannot explain the uniform sizing of the circles. The presence of frost doesn't contradict the geographer's position that additional factors (heat) were needed to create the observed uniformity.
The two hypotheses do not exhaust the possibilities regarding formation processes for sorted circles. This directly attacks the core logic of the geographer's argument. The geographer uses elimination reasoning: since frost can't completely explain the uniform sizing, heat must be involved. But this logic only works if frost and heat are the only two possibilities. If there are other potential explanations beyond these two hypotheses, then ruling out frost doesn't automatically support the heat theory. This fundamentally undermines the geographer's reasoning process.
The definition given for sorted circles excludes many land features that may be caused by frost or heat. This choice discusses definitional issues but doesn't weaken the specific argument about Marion Island's circles. Whether other land features are excluded from the definition doesn't affect the geographer's reasoning about the circles that are included in the study. The argument is about explaining the formation of actual sorted circles, not about definitional boundaries.
The sorted circles on Marion Island were probably not all formed at the same time. This doesn't weaken the argument about what caused their formation. Even if the circles formed at different times, the geographer's point about uniform sizing requiring heat involvement could still be valid. The timing of formation doesn't address whether frost alone can explain the uniform sizing that the geographer observes.
Neither of the two hypotheses explains how stones and finer material came to be on Marion Island in the first place. This addresses the availability of raw materials rather than the formation process of the circles themselves. The geographer's argument assumes the materials are already present and focuses on what shaped them into uniform-sized circles. The origin of the materials doesn't affect whether heat was needed to create the observed uniformity in circle size.