Watch NOVA Season 50 Episode 14 Online

252 million years ago, the most devastating mass extinction of all time abruptly wiped out around 90% of all species on Earth. The culprits were the biggest volcanic eruptions the world has ever seen, emitting some 700 thousand cubic miles of magma and rock. Volcanic gasses permeated the atmosphere and acidified the oceans while toxic gasses destroyed the ozone layer, bathing the planet in destructive UV radiation. The event—now called "The Great Dying"—came close to wiping out all life on the planet. Follow scientists as they piece together geologic evidence from the deep past and clues from today’s ecosystems to discover how life made it through and evolved into the astonishing variety we see around us today.