Stratigraphy is used to determine the sequence of geological events by studying rock layers.
There are six principles of stratigraphy: uniformitarianism, original horizontality, superposition, cross-cutting relationships, inclusions, and faunal succession.
Relative age talks about what is older or younger than something else, while absolute age gives the actual age.
There are several methods for finding the absolute age of something, including:
Radiometric dating is used to find the absolute ages of rocks and fossils using the radioactive properties of elements (such as uranium) and their known half-lives. Uranium's half-life is 700 million years.
Incremental dating provides year-to-year time frames by measuring the addition of new material to older material. Dendrochronology, the study of ice cores, and the study of varves are all types of incremental dating.
Correlative dating involves mapping and comparing rocks and fossils in various areas to look for physical continuity, in order to draw conclusions on geologic trends and timeframes
