QUESTION TEXT: Professor Robinson: A large meteorite impact crater…
QUESTION TYPE: Necessary Assumption – Exception
CONCLUSION: The meteor that made the crater in question didn’t cause the mass extinctions.
REASONING: The crystallized rocks shows that Earth had positive polarity at the time.
ANALYSIS: The professor is assuming that the rocks crystallized when the meteor struck and that they show the earth’s polarity at that time.
Most of the wrong answers show how the rocks could have crystallized from some other cause or at some other time.
___________
- CORRECT. Professor Robinson claims that the crater did not cause the extinctions. So it doesn’t matter if the crater was large enough to have caused the extinctions. (A crater can be big enough to cause extinctions, yet not cause any.)
- If the rocks didn’t re-crystallize soon after they melted then they might not accurately show the polarity of the earth at the time the meteor struck.
- This could mean the rocks re-crystallized some time after the meteor struck. Their polarity wouldn’t be an accurate indication of the Earth’s polarity when the meteor struck.
- If the rocks didn’t melt because of the meteor then they aren’t a good indicator of the polarity at the time the meteor struck.
- If the mass extinction occurred long after the impact then there may have been enough time for Earth’s polarity to change.
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