Journalist: The end of the Triassic, the geologic period that extended from about 250 to 200 million years ago, has...
GMAT Two Part Analysis : (TPA) Questions
Journalist: The end of the Triassic, the geologic period that extended from about 250 to 200 million years ago, has traditionally been blamed on volcanic eruptions that went on for 600,000 years. However, a researcher has recently suggested that these eruptions were only an indirect cause. By analyzing the isotopic composition of hydrocarbon molecules from plant waxes from the period, he discovered what looks like a spike in the amount of non biological carbon in the atmosphere, lasting between 10,000 and 20,000 years. The researcher believes that the release of methane—a carbon-containing greenhouse gas much stronger than carbon dioxide—stored at the bottom of the ocean was the direct cause of the end of the Triassic.
The journalist suggests that a certain causal sequence may have brought about the end of the Triassic period. Identify in the table the sequence of cause and effect most strongly suggested by the journalist to have resulted in the end of the Triassic. Make only two selections, one in each column.
Phase 1: Owning the Dataset
Argument Analysis Table
| Passage Statement | Analysis & Implications |
|---|---|
| "The end of the Triassic... has traditionally been blamed on volcanic eruptions that went on for 600,000 years" |
|
| "However, a researcher has recently suggested that these eruptions were only an indirect cause" |
|
| "spike in the amount of non-biological carbon in the atmosphere, lasting between 10,000 and 20,000 years" |
|
| "The researcher believes that the release of methane... was the direct cause of the end of the Triassic" |
|
Key Patterns Identified
- Causal Chain: Volcanic eruptions (indirect) → Release of methane (direct) → End of Triassic
- Time Scales: Volcanic eruptions (600,000 years) vs. Carbon spike (10,000-20,000 years)
- Role Reversal: Volcanoes go from direct to indirect cause in new theory
- Evidence: Isotopic analysis supports sudden carbon release consistent with methane
Phase 2: Question Analysis & Prethinking
Understanding Each Part
- Part 1 (Cause): We need the initial trigger in the causal sequence
- Part 2 (Effect): We need what resulted from the cause (but still led to the end of Triassic)
- Relationship: These must form a logical sequence within the researcher's theory
Valid Inferences from Prethinking
- The volcanic eruptions must have triggered something else (they're indirect causes)
- The methane release was caused by something and then caused the extinction (it's the direct cause)
- The sequence is: Volcanoes → Methane Release → End of Triassic
Phase 3: Answer Choice Evaluation
Analyzing Each Option:
"The emissions of volcanoes into the atmosphere"
- What it claims: Volcanic gases entered the atmosphere
- Fact Support: Not specifically mentioned; passage focuses on eruptions themselves
- Part Suitability: Could be Part 1, but "eruptions" is more directly stated
"The extinction of many oceanic biological species"
- What it claims: Ocean life died out
- Fact Support: Not mentioned in the passage at all
- Part Suitability: Neither - this is speculation beyond the passage
"The eruption of volcanoes"
- What it claims: Volcanoes erupted
- Fact Support: Directly stated as the indirect cause
- Part Suitability: Perfect for Part 1 (Cause)
"The release of carbon dioxide into the atmosphere"
- What it claims: CO2 was released
- Fact Support: Not mentioned; passage discusses methane, not CO2
- Part Suitability: Neither - incorrect gas
"The release of methane from the bottom of the ocean"
- What it claims: Methane escaped from ocean floor
- Fact Support: Directly stated as the direct cause of the end of Triassic
- Part Suitability: Perfect for Part 2 (Effect of volcanoes, cause of extinction)
Answer Selection
Part 1 (Cause): "The eruption of volcanoes"
- This is the indirect cause that started the chain of events
Part 2 (Effect): "The release of methane from the bottom of the ocean"
- This resulted from the volcanic eruptions and was the direct cause of extinction
Verification
- ✓ Both answers are directly supported by passage facts
- ✓ They form a logical cause-and-effect sequence
- ✓ They represent the journalist's presentation of the researcher's theory
- ✓ No speculation beyond what's stated