The Permian-Triassic Extinction, occurring around 252 million years ago, is the most significant mass extinction event in Earth's history. It marked the end of the Permian period and the beginning of the Triassic period. Approximately 90% of marine species and 70% of terrestrial vertebrate species went extinct, drastically altering ecosystems. Several factors contributed to this extinction, including massive volcanic eruptions in the Siberian Traps, which released large amounts of carbon dioxide and sulfur dioxide. This led to climate change, ocean acidification, and a decrease in oxygen levels, creating harsh conditions for many species and disrupting food chains.