Геология

Геологическая эпоха

Геологическая эпоха (геологический отдел) — единица геохронологической шкалы, часть геологического периода, подразделяется на геологические века. Текущая геологическая эпоха — голоцен, начавшийся около XII тысяч лет назад, с концом последнего ледникового максимума. Несмотря на совсем недавнее в геологических масштабах начало последней эпохи, некоторые учёные предлагают время, с которого деятельность человека начала оказывать серьёзное воздействие на окружающую среду, выделить в отдельную новую эпоху — антропоцен.

Эон является крупнейшей (формальной) геохронологической единицей времени, и является эквивалентом хроностратиграфической эонотемы. По состоянию на апрель 2022 года, существует три формально определенных "эона/эонотемы":

• Катархей (неформальный эон);

• Архей;

• Протерозой;

• Фанерозой.

An eon is the largest (formal) geochronologic time unit and is the equivalent of a chronostratigraphic eonothem. As of April 2022 there are three formally defined eons/eonothems: the Archean, Proterozoic, and Phanerozoic. The Hadean is an informal eon/eonothem, but is commonly used.

An era is the second largest geochronologic time unit and is the equivalent of a chronostratigraphic erathem. As of April 2022 there are currently ten defined eras/erathems.

A period is a major rank below an era and above an epoch. It is the geochronologic equivalent of a chronostratigraphic system. As of April 2022 there are currently 22 defined periods/systems. As an exception two subperiods/subsystems are used for the Carboniferous Period/System.

An epoch is the second smallest geochronologic unit, between a period and an age. It is the equivalent of a chronostratigraphic series. As of April 2022 there are currently 37 defined and one informal epochs/series. There are also 11 subepochs/subseries which are all within the Neogene and Quaternary. The use of subseries/subepochs as formal ranks/units in international chronostratigraphy was ratified in 2022.

An age is the smallest hierarchical geochronologic unit and is the equivalent of a chronostratigraphic stage. As of April 2022 there are currently 96 formal and five informal ages/stages.

A chron is a non-hierarchical formal geochronology unit of unspecified rank and is the equivalent of a chronostratigraphic chronozone. These correlate with magnetostratigraphic, lithostratigraphic, or biostratigraphic units as they are based on previously defined stratigraphic units or geologic features.