The greatest mass extinction in Earth's history happened some 251 million years ago. In this cataclysm at least 90% of life was killed, both on land and in the sea, almost bringing evolution to a halt. What caused destruction on such an unimaginable scale? Was it the impact of a huge meteorite, or prolonged volcanic eruption in Siberia? In this acclaimed book, now updated to include the most recent research and findings, Michael Benton assembles all the evidence and gives his verdict.