mass extinctions scientists have identified at least five major mass extinctions in earth’s history. during…

mass extinctions scientists have identified at least five major mass extinctions in earth’s history. during a mass extinction, large numbers of species die on different parts of earth during a relatively short period of time. scientists identify a mass extinction in the past by the disappearance of many species from the fossil record. the vast majority of all organisms that ever lived on earth are extinct. scientists are not certain what caused these mass extinctions. they think, however, that the extinctions may have resulted from global events such volcanic eruptions, climate warming or cooling, or meteorite impacts on earth’s surface. 19. scientists found many different types of fossils in a rock layer, which was dated at 251 - 299 million years old using an index fossil. in layers directly above that point, scientists found a large decrease in the number of fossils, particularly of marine and insect fossils. when did the extinction event occur?

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