Complex sentence: This led Cuvier to become an active proponent of the geological school of thought called catastrophism that maintained that many of the geological features of the earth and the history of life could be explained by catastrophic events that had caused the extinction of many species of animals.
Split into simpler sentences: This led Cuvier to become an active proponent of the geological school of proposed a theory called catastrophism. Catastrophism it maintained that many of the geological features of the earth and the history of life could be explained by catastrophic events that had caused the extinction of many species of animals.