Final answer:
The extinction of the dinosaurs is largely attributed to global climate effects caused by a thick cloud of dust and smoke from an asteroid impact, which blocked sunlight and disrupted the food chain.
Step-by-step explanation:
If the hypothesis tracing the extinction of the dinosaurs to an impact is correct, the dinosaurs died off largely because of global climate effects initiated by dust and smoke that entered the atmosphere after the impact. This dust and smoke created a thick cloud that blocked sunlight, leading to a shutdown of photosynthesis, which then resulted in widespread plant death. This chain of events would have disrupted the food chain and caused massive die-offs, not only of dinosaurs but of many species. The impact hypothesis mentions that a large meteorite, or asteroid, striking the Earth was the primary cause of the mass extinction event at the end of the Cretaceous Period, around 65 million years ago. Evidence supporting this includes a sharp spike in iridium levels, a metal not commonly found on Earth's surface, at the geological boundary between the Cretaceous and Paleogene periods, and the discovery of a large impact crater off the Yucatán Peninsula.