There have been five major extinctions around the end of each period: Ordovician, Devonian, Permian, Triassic and Cretaceous. Several from celestial impact, others with unknown triggers. Permian was the worst, with around 90% of all species perishing. The cause is unknown. The Earth began a volcanic frenzy around the globe, centering near today's Asian continent. Miles long fissures erupted lava for thousands of years and covering several million square miles. Accompanying the heat was an outpouring of dust and noxious gases resulting in a prolonged global Nuclear Winter.