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“geological time scale”
geological time scale
A system of measuring the history of the earth by studying the rocks of the earth's crust.
Since new rocks are generally deposited on top of existing material, those lower down are oldest.
The strata of rock are classified according to their age, and a time scale corresponding to this can be constructed.
The main divisions (eras) are the Paleozoid, Mesozoic, and Cenozoic. These are further subdivided into periods and epochs.
geological time scale, geologic time scale
An arbitrary chronological arrangement of geological events; usually represented, in the form of a chart, showing the names of various rock layers and indicating the estimated period of each geological unit of geological time.