<human>:  When did the Permian-Triassic Mass extinction happen?
<bot>: The Permian-Triassic mass extinction happened 252 million years ago. It is the largest extinction event in Earth’s history. This extinction event is considered to be one of the most significant events in the history of life. It wiped out over 90% of marine species and 70% of terrestrial species. The cause of this extinction is still debated, but many scientists believe that a massive volcanic eruption in Siberia caused a release of carbon dioxide into the atmosphere. This carbon dioxide would have caused a rapid global warming that led to the extinction of most life on Earth.