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 intense volcanic activity in the Deccan Traps of India was the primary cause. First, the timing of the Deccan eruptions aligns closely with the extinction event. Radioisotopic dating places the main phase of volcanic activity at approximately 66 million years ago, coinciding with the Cretaceous-Paleogene boundary. Second, volcanic emissions of sulfur dioxide and carbon dioxide would have caused severe climate perturbations, including rapid global cooling (volcanic winter) followed by long-term warming, which could have disrupted ecosystems worldwide. Third, the fossil record shows a gradual decline in dinosaur diversity during the last few million years of the Cretaceous, suggesting that environmental stress from volcanic activity weakened dinosaur populations before the proposed asteroid impact. This gradual pattern is inconsistent with a sudden catastrophic extinction.

🎧 Bài giảng

The reading presents a compelling case for volcanic activity, but it overlooks key evidence that strongly supports the asteroid impact theory. First, while the Deccan eruptions began before the extinction, the most intense phase of volcanic activity actually occurred about 200,000 years after the extinction event. The precise dating of the Chicxulub impact crater in Mexico, at 66 million years ago, matches the extinction horizon exactly, whereas the major volcanic pulses do not. Second, the climate effects of volcanic emissions are not as severe as those of an asteroid impact. The impact would have ejected vast amounts of dust and sulfur aerosols into the stratosphere, causing a sudden and prolonged impact winter that blocked photosynthesis globally. In contrast, volcanic gases are released gradually and would have allowed ecosystems to adapt. Third, the claim of a gradual dinosaur decline is based on incomplete fossil records. Recent high-resolution studies in North America show that dinosaur diversity was stable until the very end of the Cretaceous, with a sudden disappearance at the boundary. This pattern strongly favors a catastrophic, instantaneous event like an asteroid impact, not prolonged volcanic stress.