Permian-Triassic Extinction (252 million years ago)

The Permian-Triassic Extinction stands as the most catastrophic event in Earth’s history, annihilating 96% of marine species and 70% of terrestrial vertebrates. Triggered by massive Siberian volcanism, it acidified oceans and stripped the ozone layer, making it 20% more lethal than the next worst event on this list. This outpaced the Cretaceous-Paleogene extinction by a 20% higher species loss rate, marking it as the deadliest known extinction.