Icebergs generally appear to be mostly white or blue, depending on how the ice reflects sunlight. Ice with air bubbles...
GMAT Information and Ideas : (Ideas) Questions
Icebergs generally appear to be mostly white or blue, depending on how the ice reflects sunlight. Ice with air bubbles trapped in it looks white because much of the light reflects off the bubbles. Ice without air bubbles usually looks blue because the light travels deep into the ice and only a little of it is reflected. However, some icebergs in the sea around Antarctica appear to be green. One team of scientists hypothesized that this phenomenon is the result of yellow-tinted dissolved organic carbon in Antarctic waters mixing with blue ice to produce the color green.
Which finding, if true, would most directly weaken the team's hypothesis?
White ice doesn't change color when mixed with dissolved organic carbon due to the air bubbles in the ice.
Dissolved organic carbon has a stronger yellow color in Antarctic waters than it does in other places.
Blue icebergs and green icebergs are rarely found near each other.
Blue icebergs and green icebergs contain similarly small traces of dissolved organic carbon.
Step 1: Decode and Map the Passage
Passage Analysis Table
| Text from Passage | Analysis |
|---|---|
| 'Icebergs generally appear to be mostly white or blue, depending on how the ice reflects sunlight.' |
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| 'Ice with air bubbles trapped in it looks white because much of the light reflects off the bubbles.' |
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| 'Ice without air bubbles usually looks blue because the light travels deep into the ice and only a little of it is reflected.' |
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| 'However, some icebergs in the sea around Antarctica appear to be green.' |
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| 'One team of scientists hypothesized that this phenomenon is the result of yellow-tinted dissolved organic carbon in Antarctic waters mixing with blue ice to produce the color green.' |
|
Passage Architecture & Core Elements
Main Point: Scientists have proposed that green icebergs result from yellow dissolved organic carbon mixing with blue ice, offering an explanation for this color anomaly.
Argument Flow: The passage establishes normal iceberg coloring (white from air bubbles, blue from deep light penetration), introduces the puzzle of green Antarctic icebergs, then presents a hypothesis explaining this phenomenon through chemical mixing.
Step 2: Interpret the Question Precisely
What's being asked? Which finding would most directly weaken the scientists' hypothesis about green icebergs
What type of answer do we need? Evidence that would undermine or contradict their explanation
Any limiting keywords? 'Most directly' tells us we want the clearest, most relevant challenge to their hypothesis
Step 3: Prethink the Answer
- The scientists claim that green icebergs form when yellow dissolved organic carbon mixes with blue ice
- To weaken this hypothesis, we'd need evidence showing that:
- This mixing doesn't actually produce green color, OR
- Green icebergs don't actually contain more dissolved organic carbon than blue ones, OR
- There's some other factor that better explains the green color
- The right answer should provide evidence that challenges the core assumption that dissolved organic carbon is what differentiates green icebergs from blue ones
White ice doesn't change color when mixed with dissolved organic carbon due to the air bubbles in the ice.
✗ Incorrect
- This discusses white ice, but the hypothesis is specifically about blue ice turning green
- The presence of air bubbles in white ice doesn't affect the blue-to-green transformation being proposed
Dissolved organic carbon has a stronger yellow color in Antarctic waters than it does in other places.
✗ Incorrect
- This would actually strengthen the hypothesis by showing that Antarctic waters have more yellow tinting
- If the dissolved organic carbon is more yellow in Antarctic waters, that supports the idea it could turn blue ice green
Blue icebergs and green icebergs are rarely found near each other.
✗ Incorrect
- Geographic proximity doesn't directly challenge the chemical explanation
- Blue and green icebergs could form in different locations for various reasons unrelated to the dissolved organic carbon hypothesis
Blue icebergs and green icebergs contain similarly small traces of dissolved organic carbon.
✓ Correct
- If both blue and green icebergs contain similar amounts of dissolved organic carbon, then dissolved organic carbon cannot be what's causing the difference in color
- This directly contradicts the core assumption of the hypothesis