end-Cretaceous extinction

The end-Cretaceous extinction, about 66 million years ago, was a major event that caused the rapid extinction of about 75% of Earth's species, including the dinosaurs. Scientists believe a large asteroid or comet struck Earth, creating a massive impact crater and throwing debris into the atmosphere. This blocked sunlight, disrupted climate, and reduced plant life, affecting animals that relied on plants and other animals for food. The dramatic environmental changes led to the collapse of many ecosystems, resulting in the widespread extinction that marked the boundary between the Cretaceous and Paleogene periods.