The Ordovician–Silurian extinction events, also known as the Ordovician extinction, were, combined, 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 447 Ma to 443 Ma (million years ago), two pulses of extinction, separated by four million years, appear to have happened. They were the second biggest extinction of marine life, ranking below only the Permian–Triassic extinction event, and as they occurred, all known life was confined to the seas and oceans.