Viết tích hợp TOEFL

📖 Đoạn văn

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 eruption of the Deccan Traps in present-day India, was the primary cause. First, the timing of the Deccan Traps eruptions overlaps with the extinction event. Geochemical dating indicates that the main phase of volcanic activity occurred around 66 million years ago, exactly when the dinosaurs disappeared. Second, volcanic emissions of sulfur dioxide and carbon dioxide would have caused severe climate change, including rapid global cooling followed by prolonged warming, which could have disrupted ecosystems worldwide. Third, the fossil record shows a gradual decline in dinosaur diversity in the millions of years before the impact, suggesting that environmental stress from volcanism was already taking a toll. In contrast, the asteroid impact theory relies on a single catastrophic event, which cannot easily explain the protracted decline observed in the fossil record. Therefore, the Deccan Traps volcanism, not the asteroid, was the main driver of the Cretaceous-Paleogene extinction.

🎧 Bài giảng

The professor challenges the volcanic theory presented in the reading. First, although the Deccan Traps eruptions began around 66 million years ago, the most intense phase of activity—the one that would have released the majority of gases—occurred about 200,000 years after the extinction event. In fact, the extinction horizon itself shows no significant volcanic spike. This timing mismatch undermines the claim that volcanism caused the extinction. Second, while volcanic gases can alter climate, the effects would have been gradual and less severe than the sudden impact winter caused by an asteroid. The asteroid would have ejected dust and aerosols into the stratosphere, blocking sunlight for months or years, leading to a rapid collapse of photosynthesis. Such a sudden and catastrophic event better explains the abrupt disappearance of many species, including dinosaurs, at the boundary layer. Third, the reading's claim of a gradual dinosaur decline is based on incomplete fossil sampling. In many regions, dinosaur fossils are abundant right up to the boundary, indicating that they were thriving until the impact. The apparent decline can be attributed to the scarcity of fossil sites from that period. Therefore, the asteroid impact remains the most plausible explanation.