Radiometric dating rock strata
The tables of geologic time spans, presented here, agree with the nomenclature, dates and standard color codes set forth by the International Commission on Stratigraphy (ICS).The primary defined divisions of time are eons, in sequence the Hadean, the Archean, the Proterozoic and the Phanerozoic.He also formulated the law of superposition, which states that any given stratum is probably older than those above it and younger than those below it.While Steno's principles were simple, applying them proved challenging.
The three million year Quaternary period, the time of recognizable humans, is too small to be visible at this scale.
The geology or deep time of Earth's past has been organized into various units according to events which took place.
Different spans of time on the GTS are usually marked by corresponding changes in the composition of strata which indicate major geological or paleontological events, such as mass extinctions.
The first three of these can be referred to collectively as the Precambrian supereon.
Eons are divided into eras, which are in turn divided into periods, epochs and ages.
Leonardo da Vinci (1452–1519) concurred with Aristotle's interpretation that fossils represented the remains of ancient life.