The Permian-Triassic extinction event, occurring around 252 million years ago, is the most significant mass extinction in Earth's history. It marked the end of the Permian period and led to the disappearance of approximately 90% of marine species and 70% of terrestrial vertebrates. This event drastically altered ecosystems and paved the way for the rise of the dinosaurs in the following era. Several factors contributed to this extinction, including massive volcanic eruptions in the Siberian Traps, which released large amounts of carbon dioxide and sulfur dioxide into the atmosphere. This caused severe climate changes, ocean acidification, and a decrease in oxygen levels, creating inhospitable conditions for many species.