The Cretaceous-Paleogene (K-Pg) boundary marks a significant event in Earth's history, occurring about 66 million years ago. This period is known for the mass extinction that wiped out approximately 75% of all species, including the non-avian dinosaurs. The cause of this extinction is widely believed to be a combination of volcanic activity and a massive asteroid impact. The impact created the Chicxulub crater in present-day Mexico, leading to drastic environmental changes. These changes included wildfires, tsunamis, and a "nuclear winter" effect, which drastically reduced sunlight and disrupted ecosystems. The aftermath allowed mammals and other species to thrive and evolve in the absence of dinosaurs.