The geologic time scale and geologic time scale is the framework to represent the events of Earth history in chronological order. Set divisions and subdivisions of the rocks according to their relative age and absolute time elapsed since the formation of the Earth to the present, in two dimensions: stratigraphic and chronological. These divisions are based primarily on faunal changes observed in the fossil record and have been dated by radiometric methods. The scale summarizes and unifies the results of work performed for centuries by naturalists, geologists, paleontologists and many other specialists. Since 1974 the formal elaboration of the scale is done by the International Commission on Stratigraphy of the International Union of Geological Sciences and the changes after several years of studies and discussions of specific subcommittees, must be ratified at conferences worldwide.
Geologic time scale
Schedule at
The diagram below shows the length scale of each geological period. The second and third schedule represent the subsections marked with asterisks in the immediately preceding it.
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