A period that encompasses at least the last 3 × 10⁶ years of the Cenozoic Era, and is concerned with major worldwide glaciations and their effect on land and sea, on worldwide climate, and on the plants and animals that lived then. The Quaternary is divided into the Pleistocene and Holocene. The term Pleistocene is gradually replacing Quaternary; Holocene involves the last 7000 years since the Pleistocene.