This chapter focuses on two aspects of mass extinction – the fact that mass extinctions do indeed occur, and the cause of these extinctions. According to Charles Darwin, extinction is a continuous and gradual process, with a uniform rate, and species which succumb to it do so because of some inferiority causing them to fail to survive. Scientist have grouped the top biotic crisis in which at least 65 percent of such species became extinct in a brief geological instant as the “Big Five.” The five crises resulted in such catastrophes as marine regression, global climate change, asteroid or comet impact, etc.
