The extinction of the dinosaurs at the end of the Cretaceous period has long been attributed to a massive asteroid impact. However, a growing body of evidence suggests that volcanic activity, specifically the Deccan Traps in present-day India, was the primary driver. First, the timing of the Deccan Traps eruptions coincides closely with the extinction event. Radiometric dating shows that the main phase of volcanic activity occurred around 66 million years ago, within the same narrow window as the dinosaur extinction. Second, volcanic emissions would have caused severe environmental stress. The Deccan Traps released enormous quantities of sulfur dioxide and carbon dioxide, leading to acid rain, global cooling followed by warming, and ocean acidification—all of which could disrupt ecosystems long before any asteroid struck. Third, the fossil record reveals a gradual decline in dinosaur diversity in the millions of years leading up to the extinction, consistent with the prolonged effects of volcanic activity rather than a sudden catastrophic impact. In contrast, the asteroid impact theory predicts a sudden, instantaneous extinction, which does not match the observed pattern of gradual decline.
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The reading argues that volcanic activity was the main cause of dinosaur extinction, but this view is flawed. First, the claim about timing is misleading. While the Deccan Traps began erupting about 66 million years ago, the most intense phase of eruptions actually occurred about 100,000 years before the extinction event, and the eruptions continued for another 500,000 years after. In contrast, the asteroid impact at Chicxulub happened exactly at the boundary, and the extinction occurred within a very short period, likely just years to decades. Second, the environmental effects of the Deccan Traps were not as severe as the reading suggests. Recent climate models indicate that volcanic sulfur emissions were largely buffered by the oceans and atmosphere, and while they caused some cooling, the magnitude was not enough to trigger a mass extinction. Moreover, the Deccan Traps emitted carbon dioxide over a long period, allowing ecosystems to adapt gradually. Third, the fossil record does not support a gradual decline. When corrected for sampling biases and the incompleteness of the fossil record, dinosaur diversity appears to have been stable right up to the end of the Cretaceous. The apparent decline is an artifact of poor preservation. In fact, the sudden disappearance of dinosaurs aligns perfectly with the asteroid impact, which caused immediate global fires, tsunamis, and a nuclear winter—effects incompatible with gradual volcanic processes.
📝 Hướng dẫn viết 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).
