การเขียนเชิงบูรณาการ TOEFL

📖 เนื้อเรื่อง

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 massive volcanic eruptions in the Deccan Traps of India were the primary cause. First, the timing of the Deccan eruptions coincides with the extinction event. Radiometric dating shows that the main phase of volcanic activity began about 66 million years ago, exactly when the dinosaurs disappeared. Second, volcanic eruptions release vast amounts of sulfur dioxide and carbon dioxide, leading to severe climate change. Sulfur aerosols cause rapid global cooling, while carbon dioxide induces long-term warming, creating a 'double whammy' that disrupted ecosystems worldwide. Third, the fossil record reveals a gradual decline in dinosaur diversity in the last few million years before the extinction, consistent with the prolonged stress of volcanic activity rather than a sudden impact. Therefore, the Deccan Traps volcanism, not an asteroid, drove the dinosaurs to extinction.

🎧 การบรรยาย

The reading presents a compelling case for volcanism, but it overlooks critical evidence that supports the asteroid impact theory. First, while the Deccan eruptions began around 66 million years ago, their main phase actually occurred over a longer timescale—spanning hundreds of thousands of years. The extinction, however, was sudden, occurring within a very short geological instant. This mismatch suggests that the eruptions alone could not have caused the abrupt demise. Second, the claim about volcanic climate effects is exaggerated. Although volcanoes emit gases, the Deccan eruptions were intermittent, allowing the climate to recover between pulses. In contrast, the asteroid impact at Chicxulub released energy equivalent to billions of atomic bombs, triggering a global firestorm, a dust cloud that blocked sunlight for months, and a catastrophic collapse of photosynthesis. These effects were far more severe and immediate than any volcanic activity. Third, the gradual decline in dinosaur fossils may be an artifact of incomplete fossil preservation. Recent high-resolution studies show that dinosaur diversity remained high until the very end, and the decline observed in older records is due to sampling biases. Thus, the asteroid impact remains the most plausible cause of the mass extinction.