, for example, employs lengths of time so great as to be meaningless in human terms.
In this way, it suggests eternity through the awe of large numbers.
These eras were referred to as the Paleozoic (meaning ancient life), the Mesozoic (meaning middle life), and the Cenozoic (meaning recent life) based on their relative similarity with modern taxa.
Much of the relative geologic time scale had been constructed prior to the 20th century, but much progress has been made in the last half-century toward defining the absolute ages of the rocks on which the relative time scale is based.
Moreover, these geologists recognized that the fossilized biota demonstrated rather large changes in overall composition and showed both similarities with, and differences from living taxonomic groups.
The majority of fossil organisms, however, did not match with modern groups; this led to the classification of three major eras within the period of time when the Earth's surface was populated with advanced life forms.
Dating of rocks is usually carried out by the measurement of radioactive decay.
In a related article on geologic ages (Ages), we presented a chart with the various geologic eras and their ages.Built into each dating method is a particular range of uncertainty; thus a specimen age doesn't always equal an exact age. Dating geological specimens involves an interdisciplinary approach using more than one dating method and cross-validating the results.Absolute dating methods include radiometric, luminescence and incremental dating.the Paleozoic, Mesozoic and Cenozoic Eras) representing the period of Earth's history with advanced life forms, and the Pre Cambrian (or Proterozoic and Hadean Eras) representing the period before advanced life.Within the context of the Phanerozoic Eon, geologists beginning in the late 1700's recognized that fossils appeared in an orderly fashion in stratigraphic units.The biblical chronology was sufficient for people who had no need to concern themselves with geologic time.