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The following four timelines show the geologic time scale.The first shows the entire time from the formation of the Earth to the present, but this gives little space for the most recent eon.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.Leonardo da Vinci (1452–1519) concurred with Aristotle's interpretation that fossils represented the remains of ancient life.The 11th-century Persian geologist Avicenna (Ibn Sina, died 1037) and the 13th-century Dominican bishop Albertus Magnus (died 1280) extended Aristotle's explanation into a theory of a petrifying fluid.The existence, timing, and terrestrial effects of the Late Heavy Bombardment are still debated.In Ancient Greece, Aristotle (384-322 BCE) observed that fossils of seashells in rocks resembled those found on beaches – he inferred that the fossils in rocks were formed by living animals, and he reasoned that the positions of land and sea had changed over long periods of time.

Older time spans, which predate the reliable fossil record (before the Proterozoic eon), are defined by their absolute age.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.Some other planets and moons in the Solar System have sufficiently rigid structures to have preserved records of their own histories, for example, Venus, Mars and the Earth's Moon.Dominantly fluid planets, such as the gas giants, do not preserve their history in a comparable manner.

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