The geologic time scale (GTS) is a system of chronological dating that relates geological strata (stratigraphy) to time.
It is used by geologists, paleontologists, and other Earth scientists to describe the timing and relationships of events that have occurred during Earth's history.
Geologic units from the same time but different parts of the world often look different and contain different fossils, so the same time-span was historically given different names in different locales.
Apart from the Late Heavy Bombardment, events on other planets probably had little direct influence on the Earth, and events on Earth had correspondingly little effect on those planets.
Construction of a time scale that links the planets is, therefore, of only limited relevance to the Earth's time scale, except in a Solar System context.
In East Asia and Siberia, the same unit is split into Alexian, Atdabanian, and Botomian stages.
A key aspect of the work of the International Commission on Stratigraphy is to reconcile this conflicting terminology and define universal horizons that can be used around the world.
Therefore, the second timeline shows an expanded view of the most recent eon.
In a similar way, the most recent era is expanded in the third timeline, and the most recent period is expanded in the fourth timeline.Other subdivisions reflect the evolution of life; the Archean and Proterozoic are both eons, the Palaeozoic, Mesozoic and Cenozoic are eras of the Phanerozoic eon.The three million year Quaternary period, the time of recognizable humans, is too small to be visible at this scale.For example, the lower Jurassic Series in chronostratigraphy corresponds to the early Jurassic Epoch in geochronology.The adjectives are capitalized when the subdivision is formally recognized, and lower case when not; thus "early Miocene" but "Early Jurassic." Evidence from radiometric dating indicates that Earth is about 4.54 billion years old.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.