The Permian Extinction, occurring around 252 million years ago, was the most severe mass extinction event in Earth's history. It is estimated that about 90% of marine species and 70% of terrestrial vertebrate species went extinct. This event marked the end of the Permian period and the beginning of the Triassic period. Several factors contributed to the Permian Extinction, including massive volcanic eruptions, climate change, and ocean anoxia, which is a lack of oxygen in the oceans. These changes disrupted ecosystems and led to the collapse of food chains, significantly altering life on Earth for millions of years.