托福综合写作

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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, specifically the Deccan Traps in India, was the primary cause. Three main arguments support this volcanic hypothesis. First, the Deccan Traps eruptions occurred over a period of approximately 1 million years, coinciding with the gradual decline of dinosaur populations observed in the fossil record. This extended timeline aligns with a slow extinction, rather than a sudden catastrophe. Second, volcanic eruptions released enormous quantities of sulfur dioxide and carbon dioxide, leading to severe climate change, including global cooling and ocean acidification. These environmental stresses would have disrupted food chains and habitats, causing many species to dwindle before the final extinction event. Third, the fossil record shows that many dinosaur species were already declining in diversity well before the asteroid impact, suggesting that volcanic activity, not the impact, was the driving force. Thus, while an asteroid may have delivered the final blow, the Deccan Traps volcanism created the conditions that made dinosaurs vulnerable to extinction.

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The reading argues that volcanic activity was the primary cause of dinosaur extinction, but this view is flawed. While the Deccan Traps eruptions did span a long period, the most intense phase of activity occurred after the asteroid impact, not before. In fact, the majority of lava was erupted in the last 100,000 years, which is too short to explain the gradual decline seen in fossils. Moreover, the climate changes caused by volcanism, such as cooling and acidification, were not severe enough to cause a global extinction. For example, the oceans experienced only a minor pH change, and many marine species survived, unlike the selective extinction pattern seen at the end of the Cretaceous. Finally, the decline in dinosaur diversity observed before the impact can be explained by regional factors, such as the separation of continents and changes in sea level, not by volcanic stress. In contrast, the asteroid impact created a sudden, catastrophic event—ejecting dust that blocked sunlight, causing a dramatic drop in temperature and a collapse of photosynthesis. This rapid and severe environmental change matches the abrupt extinction of many species, including dinosaurs, much better than the prolonged volcanic effects.