Mid age dating
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.
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.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.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 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.
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.
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.
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.