The extinction of the dinosaurs at the end of the Cretaceous period, approximately 66 million years ago, has long fascinated scientists. While the asteroid impact theory is widely accepted, a competing hypothesis suggests that massive volcanic eruptions in the Deccan Traps of India were the primary cause. This volcanic theory rests on three main arguments. First, the Deccan eruptions were prolonged, lasting over a million years, and would have released vast amounts of sulfur dioxide and carbon dioxide. These gases could have caused severe climate fluctuations, including rapid cooling from sulfate aerosols and long-term warming from CO2, creating stress that gradually undermined ecosystems worldwide. Second, the timing of the eruptions appears to align with the extinction event. Geochemical dating indicates that the main phase of Deccan volcanism occurred just before and at the Cretaceous-Paleogene boundary, suggesting a causal link. Finally, volcanic activity would have produced global effects similar to those of an asteroid impact, such as acid rain, ozone depletion, and a drop in photosynthesis due to particulate blockage of sunlight. These environmental disruptions could have been sufficient to trigger a mass extinction without needing an extraterrestrial trigger.
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The reading presents the volcanic hypothesis as an alternative to the asteroid impact theory, but its arguments are not convincing when examined closely. First, while the Deccan eruptions were extensive, their duration actually weakens the case for extinction. The prolonged release of gases would have allowed ecosystems to adapt gradually, whereas the fossil record shows a sudden, catastrophic extinction. In contrast, the asteroid impact would have caused an abrupt, short-term event—like a global firestorm and a dust cloud that blocked sunlight for months—which is more consistent with the rapid demise of dinosaurs. Second, the timing of the Deccan volcanism is not as precise as the reading claims. High-resolution dating shows that the most intense volcanic phase occurred about 300,000 years *before* the mass extinction layer, not exactly at the boundary. This gap suggests that volcanic activity alone did not deliver the final blow; the asteroid impact, which occurred precisely at the boundary, is a more direct culprit. Third, the environmental effects of volcanism are not equivalent to those of an impact. Volcanoes emit gases gradually, but an asteroid impact vaporizes rock, producing iridium, shocked quartz, and spherules—signatures found in the boundary layer worldwide. These unique markers, along with a massive tsunami and a global layer of soot from wildfires, point to an instantaneous, high-energy event that volcanoes cannot replicate. Therefore, the reading's claims are overstated and fail to dethrone the asteroid hypothesis.
📝 Инструкция по письму Summarize the points made in the lecture, being sure to explain how they cast doubt on the specific points made in the reading passage.
📊 TOEFL Integrated Writing Rubric
Content Accuracy: Accurately capture the relationship between lecture and reading
Information Completeness: Cover all key counter-arguments from the lecture
Structure & Coherence: Logical organization and progression
Language Use: Grammar, vocabulary, expression accuracy
Scored 0-30 based on holistic scoring (original 0-5, scaled to 30).
