Researchers have finally determined with unprecedented confidence that extreme volcanism 252 million years ago is the likeliest cause of the greatest mass extinction the world has seen.
A quarter billion years ago (give or take a week or so), the world was not in a good way. It was undergoing the greatest series of extinctions that had ever happened. That record still stands today. This event goes by many names, The Permian-Triassic Extinction Event, The Great Permian Extinction or most floridly perhaps, The Great Dying. And dying is exactly what was happening.