GSA Geologic Time Scale, Latest Version
GSA Geologic Time Scale, Latest Version

The geologic time scale is the “calendar” for events in earth history. It subdivides all time into named units of abstract time called—in descending order of duration—eons, eras, periods, epochs, and ages.

Geologic time, the extensive interval of time occupied by the geologic history of earth. Formal geologic time begins at the start of the archean eon (4.0 billion to 2.5 billion years ago) and continues to the present day. Modern geologic time scales additionally often include the hadean eon, which is an informal interval that extends from about 4.6 billion years ago (corresponding to earth’s initial formation) to 4.0 billion years ago. Geologic time is, in effect, that segment of earth history that is represented by and recorded in the planet’s rock strata. Read more here.

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