For example, in North America, the Lower Cambrian is called the Waucoban series that is then subdivided into zones based on succession of trilobites.In East Asia and Siberia, the same unit is split into Alexian, Atdabanian, and Botomian stages.Dominantly fluid planets, such as the gas giants, do not preserve their history in a comparable manner.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.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.Leonardo da Vinci (1452–1519) concurred with Aristotle's interpretation that fossils represented the remains of ancient life.Older periods which predate the reliable fossil record are defined by absolute age.
The three million year Quaternary period, the time of recognizable humans, is too small to be visible at this scale.
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.
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.
For example, the boundary between the Cretaceous period and the Paleogene period is defined by the Cretaceous–Paleogene extinction event, which marked the demise of the non-avian dinosaurs and many other groups of life.