Question: what are earth's 5 mass extinctions?
Answer: Ordovician-silurian Extinction: 440 million years ago., Devonian Extinction: 365 million years ago., Permian-triassic Extinction: 250 million years ago., Triassic-jurassic Extinction: 210 million years ago., Cretaceous-tertiary Extinction: 65 Million Years Ago.