Geochronology

a system of chronological dating that classifies geological strata (stratigraphy) in time

evolution of Earth throughout times

subdivision of geological time; short than a supereon and longer than an era

scientific dating of the age of the Earth

thumb|right|300px|An artistic depiction of the major events in the history of Earth

calendar era that uses 10,000 BC as 1 HE

calendar era

process of determining an age on a specified chronology in archaeology and geology

processes by which organisms evolved on Earth

unit in chronostratigraphy

major geological occurrences in Earth's past

determining the relative order of past events

sequence of rock depositions defining a chronostratigraphic unit corresponding to a specific epoch on the geologic time scale

A chronozone or chron is a unit in chronostratigraphy, defined by events such as geomagnetic reversals (magnetozones), or based on the presence of specific fossils (biozone or biochronozone). According to the International Commission on Stratigraphy, the term "chronozone" refers to the rocks formed during a particular time period, while "chron" refers to that time period.

250px|thumb|right|Tephra horizons in south-central Iceland. The thick and light coloured layer at the height of the [[volcanologist's hands is rhyolitic tephra from Hekla.]]

In stratigraphy, paleontology, geology, and geobiology, an erathem is the total stratigraphic unit deposited during a certain corresponding span of time during an era in the geologic timescale.

thumb|200px|right|Horseshoe Canyon Formations exposed in Horseshoe Canyon (Alberta)|Horseshoe Canyon near [[Drumheller, Alberta.]] thumb|200px|right|Oxfordian (Upper Jurassic) cyclic sediments at Péry-Reuchenette, near Tavannes, kanton Bern, Switzerland. Alternating layers are limestone (light, more competent) and [[marl/clay; dominant cycle is the 200000 year-cycle.]]

idealized composite unit of the geologic record representing the totality of rock strata laid down during a certain period of the geologic time scale

geologic time

entirety of the layers of rock strata

radionuclide formed by nucleosynthesis before formation of the Solar System

Geochronologist