The extinction of the dinosaurs at the end of the Cretaceous period has long been attributed to a massive asteroid impact. However, recent evidence suggests that volcanic activity, specifically the Deccan Traps in India, may have been the primary cause. First, the timing of the Deccan Traps eruptions coincides with the extinction event. Radiometric dating shows that the main phase of volcanic activity occurred around 66 million years ago, exactly when the dinosaurs disappeared. Second, volcanic eruptions release vast amounts of sulfur dioxide and carbon dioxide, which can cause rapid climate change. The Deccan Traps would have emitted enough gases to create a global cooling effect followed by warming, stressing ecosystems over hundreds of thousands of years. Third, the fossil record indicates a gradual decline in dinosaur diversity before the impact, suggesting that environmental stress from volcanism was already underway. This gradual pattern is more consistent with volcanic-induced climate change than with a sudden asteroid strike.
🎧 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 lecture challenges the volcanic theory presented in the reading. While the Deccan Traps were active around 66 million years ago, the most intense eruptions actually occurred about 300,000 years before the extinction. The final, smaller pulses of volcanism do not align precisely with the mass die-off, whereas the Chicxulub impact in Mexico occurred exactly at the boundary layer. Second, although volcanic gases can alter climate, the Deccan Traps would have released gases over a long period, allowing ecosystems to adapt gradually. In contrast, an asteroid impact would have injected dust and aerosols into the atmosphere suddenly, causing a dramatic and immediate temperature drop and blocking photosynthesis worldwide—effects far more catastrophic than gradual volcanic emissions. Third, the reading claims a gradual dinosaur decline, but this is based on incomplete fossil data. In many regions, dinosaur fossils are abundant right up to the boundary, indicating that they were thriving until the impact. The apparent decline in some areas can be explained by sampling biases or sea-level changes, not by volcanism. Therefore, the asteroid impact remains the most plausible cause.
📝 ライティング指示 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).
