First identified in 1969, komatiites are Earth's oldest known volcanic rocks and contain three times as much magnesium as do...
GMAT Reading Comprehension : (RC) Questions
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First identified in 1969, komatiites are Earth's oldest known volcanic rocks and contain three times as much magnesium as do most volcanic rocks. This chemical composition suggests that komatiites formed from the hottest lava known ever to have erupted: a high concentration of magnesium changes the physical properties of lava so that unusually high temperatures would be required for the lava to exist as a liquid.
Komatiites' discovery was surprising in light of then-current geological theories about magmas, moltenrock that forms in the Earth's mantle (the layer beneath the crust) and composes volcanic lava eruptions. Prior to 1960, geologists Bowen and Hess disagreed over whether or not the very high temperatures needed to produce magmas rich in magnesium could have existed on Earth. Hess suggested that the presence of water, probably released from minerals decomposing in the Earth's mantle, might have meant that a high-magnesium magma could have existed at a lower temperature. But Bowen showed experimentally that the high temperatures were indeed necessary. By 1960, it was generally accepted that volcanic rocks with such high levels of magnesium could not exist, and thus the discovery of komatiites changed geologists' assumptions about the characteristics of the Earth's mantle around the time of the formation of komatiites, between 2.5 and 4 billion years ago.
Ques. 1/3
Which of the following most accurately describes the organization of the passage?
Solution
1. Passage Analysis:
Progressive Passage Analysis
| Text from Passage | Analysis |
|---|---|
| First identified in 1969, komatiites are Earth's oldest known volcanic rocks and contain three times as much magnesium as do most volcanic rocks. | What it says: Scientists discovered special ancient volcanic rocks in 1969 that have much more magnesium than normal volcanic rocks. What it does: Introduces the main topic and establishes two key characteristics of komatiites. Source/Type: Factual information - discovery date and chemical composition. Connection to Previous Sentences: This is our opening sentence, establishing the foundation. Visualization: Normal volcanic rocks: 10% magnesium Komatiites: 30% magnesium (3x as much) Timeline: Discovered in 1969, but rocks are Earth's oldest What We Know So Far: Komatiites are unusual ancient rocks with high magnesium What We Don't Know Yet: Why this matters, what it tells us about ancient Earth Reading Strategy Insight: The author starts with concrete facts - a date and a specific comparison (3x). This gives us solid ground to build on. |
| This chemical composition suggests that komatiites formed from the hottest lava known ever to have erupted: a high concentration of magnesium changes the physical properties of lava so that unusually high temperatures would be required for the lava to exist as a liquid. | What it says: The high magnesium content means these rocks came from extremely hot lava - hotter than any other lava we know about. What it does: Explains the significance of the magnesium content mentioned in sentence 1. Source/Type: Scientific interpretation/conclusion based on chemical evidence. Connection to Previous Sentences: - This builds directly on sentence 1! - Sentence 1 told us: komatiites have 3x more magnesium - Sentence 2 tells us: WHY that matters - it means extremely hot lava Visualization: Normal lava temperature: 1000°C Komatiite lava temperature: 1600°C (much hotter due to high magnesium) Result: Hottest lava ever known What We Know So Far: Komatiites = high magnesium + hottest lava ever What We Don't Know Yet: Why this discovery was surprising to scientists Reading Strategy Insight: Feel confident here - this isn't new complexity! The author is simply explaining what the magnesium fact from sentence 1 actually means. |
| Komatiites' discovery was surprising in light of then-current geological theories about magmas, moltenrock that forms in the Earth's mantle (the layer beneath the crust) and composes volcanic lava eruptions. | What it says: Finding komatiites shocked scientists because it didn't fit what they believed about molten rock from deep in the Earth. What it does: Introduces the conflict between the discovery and existing scientific beliefs. Also provides helpful definitions. Source/Type: Author's explanation of scientific context + definitions. Connection to Previous Sentences: - This answers the 'so what?' question - We learned: komatiites came from extremely hot lava - Now we learn: scientists didn't think such hot lava was possible - The author helpfully defines 'magmas' for us Visualization: Before 1969: "Lava that hot is impossible" 1969 Discovery: "Wait, here's proof it existed" Scientists: "This changes everything we thought" What We Know So Far: Komatiites proved extremely hot lava existed, surprising scientists What We Don't Know Yet: What specific theories were challenged Reading Strategy Insight: The passage is becoming clearer, not more complex. We're getting the "story" of why this discovery mattered. |
| Prior to 1960, geologists Bowen and Hess disagreed over whether or not the very high temperatures needed to produce magmas rich in magnesium could have existed on Earth. | What it says: Before 1960, two geologists argued about whether Earth could ever have been hot enough to create high-magnesium magmas. What it does: Provides specific historical context for the scientific debate mentioned in sentence 3. Source/Type: Historical fact about scientific disagreement. Connection to Previous Sentences: - This gives us the specific details of the "then-current theories" mentioned in sentence 3 - The timeline helps us understand the progression: debate before 1960, discovery in 1969 Visualization: Timeline: Before 1960 → 1960 → 1969 Before 1960: Bowen vs. Hess argument Question they debated: "Can Earth get hot enough for high-magnesium magma?" 1969: Komatiites discovered (proof it did happen) What We Know So Far: Scientists debated if high-temp magnesium magma was possible; komatiites later proved it was What We Don't Know Yet: What each scientist specifically believed and what resolved the debate Reading Strategy Insight: We're getting background story that makes the 1969 discovery more meaningful. This is context, not new complexity. |
| Hess suggested that the presence of water, probably released from minerals decomposing in the Earth's mantle, might have meant that a high-magnesium magma could have existed at a lower temperature. | What it says: Hess thought water from decomposing minerals might allow high-magnesium magma to form without needing extreme heat. What it does: Explains one side of the Bowen vs. Hess debate mentioned in sentence 4. Source/Type: Hess's scientific hypothesis/theory. Connection to Previous Sentences: - This gives us Hess's specific position in the debate from sentence 4 - Hess was trying to solve the temperature problem differently - he thought water could lower the temperature needed Visualization: The Debate - Hess's Position: Normal thinking: "High magnesium magma needs extremely high temperature" Hess's idea: "Water + decomposing minerals = same result at lower temperature" Hess's solution: Find a way around the extreme temperature requirement What We Know So Far: Hess thought water could enable high-magnesium magma without extreme heat What We Don't Know Yet: Bowen's position and who was right Reading Strategy Insight: We're just getting details of positions in the debate. This is filling in the story, not adding complexity. |
| But Bowen showed experimentally that the high temperatures were indeed necessary. | What it says: Through experiments, Bowen proved that you absolutely need extremely high temperatures - Hess was wrong. What it does: Gives us Bowen's position and indicates he won the scientific debate through experimental proof. Source/Type: Bowen's experimental results. Connection to Previous Sentences: - "But" signals contrast with Hess's theory from sentence 5 - This resolves the Bowen vs. Hess debate - Bowen had experimental proof - "Indeed necessary" confirms what we learned in sentence 2 about extremely hot lava Visualization: Scientific Method in Action: Hess: "Water might allow lower temperatures" (hypothesis) Bowen: "Let me test this experimentally" (experiment) Result: "High temperatures ARE necessary" (Bowen wins) What We Know So Far: Bowen proved experimentally that high-magnesium magma requires extreme heat What We Don't Know Yet: What conclusion this led to by 1960 Reading Strategy Insight: The debate is resolving, not getting more complex. Bowen's experimental proof gives us a clear winner. |
| By 1960, it was generally accepted that volcanic rocks with such high levels of magnesium could not exist, and thus the discovery of komatiites changed geologists' assumptions about the characteristics of the Earth's mantle around the time of the formation of komatiites, between 2.5 and 4 billion years ago. | What it says: By 1960, scientists agreed that high-magnesium volcanic rocks were impossible. So finding komatiites (which proved they DID exist) forced scientists to rethink what ancient Earth was like. What it does: Completes the historical timeline and explains the full significance of the komatiite discovery. Source/Type: Scientific consensus and author's conclusion about impact. Connection to Previous Sentences: - This completes our timeline: Before 1960 (debate) → 1960 (consensus) → 1969 (shocking discovery) - This brings us full circle back to why the discovery was "surprising" (sentence 3) - 1960 consensus: "impossible" vs. 1969 reality: komatiites exist Visualization: Complete Timeline: Before 1960: Bowen vs. Hess debate 1960: Scientific consensus = "High-magnesium volcanic rocks CANNOT exist" 1969: Komatiites discovered = "Wait, they DO exist!" Result: Scientists had to completely rethink ancient Earth (2.5-4 billion years ago) What We Know So Far: Complete story from scientific debate to consensus to revolutionary discovery Reading Strategy Insight: This is the satisfying conclusion! The passage has walked us through a complete scientific story. We should feel confident - we understand the whole narrative now. |
2. Passage Summary:
Author's Purpose:
To explain how a surprising scientific discovery changed what geologists believed about ancient Earth by walking through the historical debate that preceded the discovery.
Summary of Passage Structure:
In this passage, the author walks us through a complete scientific story that shows how one discovery can overturn accepted theories:
- First, the author introduces komatiites and their unusual chemical makeup, explaining that their high magnesium content means they came from extremely hot lava.
- Next, the author tells us this discovery was shocking because it contradicted what scientists believed was possible.
- Then, the author gives us the background story of the scientific debate, showing us how two geologists disagreed about whether such hot conditions could exist, and how experiments settled the debate by 1960.
- Finally, the author explains that by 1960 scientists agreed these rocks were impossible, which made finding them in 1969 so revolutionary that it forced scientists to completely rethink what ancient Earth was like.
Main Point:
The discovery of komatiites forced scientists to change their understanding of what conditions were like on ancient Earth because these rocks proved that extremely hot volcanic activity occurred billions of years ago, even though scientists had concluded such conditions were impossible.
3. Question Analysis:
This question asks us to identify the organizational structure of the passage - how the author arranged and presented the information from beginning to end.
Connecting to Our Passage Analysis:
From our detailed analysis, we can see the passage follows a clear pattern:
- The author introduces komatiites as a discovered phenomenon with unique characteristics (high magnesium content)
- The author explains the scientific significance of this chemical composition (indicating extremely hot ancient lava)
- The author describes why this discovery was surprising to the scientific community
- The author provides historical context about previous scientific debates and consensus
- The author concludes by explaining how the discovery changed scientific understanding of ancient Earth
Our passage analysis shows this is fundamentally about describing a phenomenon and discussing its scientific significance, rather than tracing a discovery process, reconciling views, or examining theories.
Prethinking:
The passage structure moves from what komatiites are → why they matter scientifically → why they surprised scientists → what scientists believed before → how the discovery changed scientific thinking. This is a classic pattern of describing a phenomenon and then exploring its scientific importance and implications.
Answer Choices Explained
A
Two divergent views of a scientific phenomenon are reconciled.
Why It's Wrong:
• The passage doesn't reconcile the Bowen-Hess disagreement - Bowen simply won through experimental proof
• The divergent views mentioned (Bowen vs. Hess) were resolved by 1960, but this isn't the main focus
• The passage is primarily about komatiites, not about resolving the historical scientific debate
Common Student Mistakes:
• The passage doesn't reconcile the Bowen-Hess disagreement - Bowen simply won through experimental proof
• The divergent views mentioned (Bowen vs. Hess) were resolved by 1960, but this isn't the main focus
• The passage is primarily about komatiites, not about resolving the historical scientific debate
Common Student Mistakes:
- Does the Bowen-Hess debate make this about reconciling views?
→ No, that debate was background context. The main focus is on komatiites and their significance - Wasn't the discovery a way to resolve their disagreement?
→ The disagreement was already resolved by 1960; komatiites were discovered in 1969 and challenged the consensus
B
A phenomenon is described and its scientific significance is discussed.
Why It's Right:
• The passage begins by describing komatiites as a phenomenon (ancient volcanic rocks with high magnesium)
• The scientific significance is thoroughly discussed (hottest lava ever, implications for ancient Earth conditions)
• The author explains why this discovery matters to geological science
• The passage structure moves from description to significance to implications
Key Evidence: "Komatiites' discovery was surprising in light of then-current geological theories" and "the discovery of komatiites changed geologists' assumptions about the characteristics of the Earth's mantle"
• The passage begins by describing komatiites as a phenomenon (ancient volcanic rocks with high magnesium)
• The scientific significance is thoroughly discussed (hottest lava ever, implications for ancient Earth conditions)
• The author explains why this discovery matters to geological science
• The passage structure moves from description to significance to implications
Key Evidence: "Komatiites' discovery was surprising in light of then-current geological theories" and "the discovery of komatiites changed geologists' assumptions about the characteristics of the Earth's mantle"
C
The discovery of a scientific phenomenon is traced and its implications for further research are suggested.
Why It's Wrong:
• The passage doesn't trace the discovery process - it simply states "First identified in 1969"
• No implications for further research are suggested - the focus is on past implications
• The passage is more about the significance of what was found than how it was found
Common Student Mistakes:
• The passage doesn't trace the discovery process - it simply states "First identified in 1969"
• No implications for further research are suggested - the focus is on past implications
• The passage is more about the significance of what was found than how it was found
Common Student Mistakes:
- Doesn't the historical timeline trace the discovery?
→ The timeline provides context for why the discovery mattered, not how it was made - Aren't there implications mentioned?
→ Yes, but past implications (how it changed thinking), not suggestions for future research
D
A long-standing scientific theory is examined and recently discovered evidence is shown to support it.
Why It's Wrong:
• The passage shows how komatiites contradicted and overturned established theory, not supported it
• By 1960, scientists concluded high-magnesium volcanic rocks "could not exist" - komatiites proved this wrong
• The discovery challenged rather than supported long-standing theory
Common Student Mistakes:
• The passage shows how komatiites contradicted and overturned established theory, not supported it
• By 1960, scientists concluded high-magnesium volcanic rocks "could not exist" - komatiites proved this wrong
• The discovery challenged rather than supported long-standing theory
Common Student Mistakes:
- Didn't komatiites support Bowen's experimental findings about high temperatures?
→ While consistent with Bowen's work, komatiites overturned the 1960 consensus that such rocks were impossible - Isn't this about examining geological theory?
→ The focus is on the phenomenon itself and how it changed theories, not on examining existing theory
E
The ways in which a particular geological phenomenon is exceptional are detailed and classified.
Why It's Wrong:
• The passage doesn't classify different ways komatiites are exceptional
• While exceptional characteristics are mentioned (age, magnesium content, temperature), they aren't detailed and classified systematically
• The organization focuses on significance rather than categorizing exceptional features
Common Student Mistakes:
• The passage doesn't classify different ways komatiites are exceptional
• While exceptional characteristics are mentioned (age, magnesium content, temperature), they aren't detailed and classified systematically
• The organization focuses on significance rather than categorizing exceptional features
Common Student Mistakes:
- Aren't multiple exceptional characteristics mentioned?
→ Yes, but they're mentioned to explain significance, not to create a detailed classification system - Doesn't the passage detail how komatiites are special?
→ The details serve the purpose of explaining scientific importance, not systematically cataloging exceptions
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