SUMMARY

Geological timescale is the time showing the possible age of the Earth and its associated life forms.

. Geologists employ three basic principles (rules) during the study of the relative age of rocks:

• The principle of original horizontality
• The principle of superposition
• The principle of cross-cutting relationships

Absolute age refers to the actual age of rocks given in numerical values through the analysis of the spontaneous decay of radioactive isotopes.

Radioactive decay stands for the conversion of unstable (Parent) elements into daughter (Stable) elements through the gaining or losing of particles in their nucleus.

Based on the geological timescale, the history of the formation of the Earth is classified into four longer geological periods named Eons. Hadean, Archean, Proterozoic, and Phanerozoic are four major sub-divisions of the known Eons.