The Ordovician–Silurian extinction event, or quite commonly the Ordovician extinction, was the second-largest
of the five major extinction events in Earth's history in terms of percentage of genera that went extinct and
second largest overall in the overall loss of life. Between about 450 Ma to 440 Ma, two bursts of extinction,
separated by one million years, appear to have happened. This was the second biggest extinction of marine life,
ranking only below the Permian extinction. At the time, all known life was confined to the seas and oceans