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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.
The emissions of volcanoes into the atmosphere
The extinction of many oceanic biological species
The eruption of volcanoes
The release of carbon dioxide into the atmosphere
The release of methane from the bottom of the ocean
| 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" |
|
"The emissions of volcanoes into the atmosphere"
"The extinction of many oceanic biological species"
"The eruption of volcanoes"
"The release of carbon dioxide into the atmosphere"
"The release of methane from the bottom of the ocean"
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