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 eruptions in present-day India, was the primary driver of this mass extinction. Three main arguments support this volcanic hypothesis. First, the Deccan Traps eruptions released enormous quantities of sulfur dioxide and carbon dioxide over a period of roughly one million years, leading to severe global cooling followed by prolonged warming. Such climate perturbations would have disrupted food chains and stressed ecosystems long before any asteroid struck. Second, the fossil record shows a gradual decline in dinosaur diversity and abundance in the last few hundred thousand years of the Cretaceous, consistent with a slow, volcanically induced deterioration of habitats rather than a sudden catastrophic kill. Third, recent high-precision dating of Deccan lava flows reveals that the most intense phase of volcanism occurred just before the mass extinction boundary, suggesting a causal link between the peak of eruptions and the extinction event itself. These lines of evidence challenge the asteroid impact theory and point to volcanism as the more plausible culprit.
🎧 听力讲座
🎯 模拟考试环境：先点「播放讲座」听完内容，再作答。听力原文默认隐藏。
The reading makes a case for volcanism as the main cause of dinosaur extinction, but the evidence actually supports the asteroid impact theory more strongly. First, while the Deccan Traps did release gases, the timing of the most intense volcanic phase does not align well with the extinction. High-precision dates show that the peak eruptions occurred about 300,000 years before the impact layer, and the extinction event is precisely at the impact boundary. If volcanism were the cause, we would expect the extinction to coincide with the volcanic peak, not with the asteroid strike. Second, the claim of a gradual dinosaur decline is misleading. Recent studies of dinosaur fossils from the last 100,000 years before the extinction show that dinosaurs were thriving, with diverse assemblages and healthy populations. The apparent decline in some regions is an artifact of incomplete fossil sampling, not a real trend. When corrected, the fossil record indicates sudden extinction, which is more consistent with an impact. Third, the Deccan Traps eruptions, though massive, released gases over a long period, allowing ecosystems to adapt gradually. In contrast, the asteroid impact caused a sudden, short-term cooling and darkness from dust, which would have been far more devastating in a matter of months. Thus, the volcanic arguments do not hold up under scrutiny; the impact remains the best-supported explanation.
📝 Instrucciones de escritura 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).
