Quaternary Period

Quaternary period (kwətûr`nərē), younger of the two geologic periods of the Cenozoic era of geologic time (see Geologic Timescale, table) from 2 millon years ago to the present. Comprising all geologic time from the end of the Tertiary period to the present, it is divided into the Pleistocene and Holocene, or Recent, epochs. It was named (1759) by Giovanni Arduino, an Italian scientist who thought that the biblical great flood was responsible for its deposits. During the early Quaternary, Europe and North America were covered by the glaciers of the Pleistocene epoch. Retreat of the glaciers led to isostatic rebound (see continent) of the crust in the Holocene. In the Quaternary the climate and present physical features of the earth continued to develop. Significant changes in sea level within historic times are demonstrated by the submergence of the temple of Jupiter Serapis near Naples and by the rising of the shores of the Baltic. The life of the Quaternary has been marked by the rise and dominance of humans.

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Quaternary Period

Interval of geologic time, approximately 2.6 million years ago to the present. The Quaternary follows the Tertiary Period and is the more recent of the two periods of the Cenozoic Era. The Quaternary is subdivided into the Pleistocene Epoch and the Holocene Epoch and is characterized by major cyclical changes of climate on a global scale. These led to repeated invasions of vast areas by ice sheets. Its major biologic feature is the evolution and dispersion of humans. The dramatic changes of climate and environment in the Quaternary led to high rates of evolution and extinction, particularly among the mammals. The extinction of many large mammals toward the end of the last ice age may also be related to the rapid territorial expansion of humans.