The most compelling evidence supporting the theory that an asteroid collision contributed to the extinction of the dinosaurs approximately 66 million years ago includes the following:
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Iridium Layer: A layer of iridium-rich clay found in the geological record at the K-T boundary (Cretaceous-Paleogene boundary). Iridium is rare on Earth but more common in asteroids, suggesting a cosmic impact.
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Chicxulub Crater: The discovery of the Chicxulub crater in the Yucatan Peninsula of Mexico, which is approximately 150 kilometers in diameter and dates to the same time period as the extinction event. The size and impact of such a collision would have had catastrophic effects on the Earth's climate and ecosystems.
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Shocked Quartz: The presence of shocked quartz and tektites in sediment layers associated with the impact. Shocked quartz forms under high-pressure conditions typical of asteroid impacts, providing further evidence of such a catastrophic event.
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Global Climate Changes: The aftermath of the impact likely led to "nuclear winter" conditions, with debris blocking sunlight, causing drastic temperature drops, and disrupting photosynthesis. This would have led to mass extinction affecting many species, including dinosaurs.
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Fossil Records: The abrupt disappearance of many species, including the non-avian dinosaurs, in the fossil record at the K-T boundary correlates with the timing of the impact.
These points collectively provide strong support for the asteroid impact hypothesis as a significant factor in the mass extinction event that wiped out the dinosaurs.