A study of fossils from South Africa and Australia has revealed that mass extinction that killed nearly 70%of the Earth’s land animals 252 million years ago may occur at different times on land and in the sea.Researchers from the University of California (UC) Berkeley in the US have revealed that ecosystem alterations during this mass extinction event started hundreds of thousands of years earlier on land than in the sea. The study revealed that marine extinction, which killed nearly 95 percent of ocean species may have occurred over the time span of 10,000 years. Until now scientists believed that a series of volcanic eruptions were the principal cause of the mass extinction from the earth.