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Information and IdeasEasySelecting evidence of rapid change in a record

Information and Ideas practice question

Glaciologist Ana Sorensen and her team drilled a 400-meter ice core from the Kalvard Ice Cap. Describing the record the core preserves, Sorensen writes that "the upper ice contains annual layers, each thin band representing one year of snowfall." She reports that "between the layers dated to 11,700 and 11,640 years ago, chemical markers of temperature climb by an amount that elsewhere in the core takes several thousand years to accumulate." Sorensen also notes that "the deepest ice is too compressed for individual years to be counted" and that "the dust content of the core varies with the strength of regional winds."

Which quotation from the text best supports the claim that the Kalvard core records an episode of unusually fast warming?

  1. A. "the upper ice contains annual layers, each thin band representing one year of snowfall"
  2. B. "between the layers dated to 11,700 and 11,640 years ago, chemical markers of temperature climb by an amount that elsewhere in the core takes several thousand years to accumulate"Correct
  3. C. "the deepest ice is too compressed for individual years to be counted"
  4. D. "the dust content of the core varies with the strength of regional winds"

Answer: B. "between the layers dated to 11,700 and 11,640 years ago, chemical markers of temperature climb by an amount that elsewhere in the core takes several thousand years to accumulate"

B pairs a large temperature rise with a very short span of layers (about 60 years) and contrasts it with the thousands of years such a rise usually requires, which is exactly the claim of unusually fast warming. A explains how the core is dated but reports no temperature change. C is a limitation of the record, not evidence about the speed of warming. D concerns wind-driven dust, a different variable altogether.

Why the other answers are wrong

A. "the upper ice contains annual layers, each thin band representing one year of snowfall"
This quotation explains how the core is dated year by year, but it reports no temperature change at all — you need a quotation about warming, not about counting layers.
C. "the deepest ice is too compressed for individual years to be counted"
This describes a limit on what the deepest ice can tell us; a gap in the record isn't evidence that warming happened quickly.
D. "the dust content of the core varies with the strength of regional winds"
Dust and wind strength are a different variable entirely — the claim is about temperature rising fast, which this quotation never addresses.

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