Development of the geologic time scale and dating of formations and rocks relies upon two fundamentally different ways of telling time: relative and absolute.Relative dating places events or rocks in their chronologic sequence or order of occurrence.
Relative geologic age refers to the order in which geologic events occurred.
This idea is known as Plutonism, in reference to the God of the deep underworld.
Hutton viewed tilted strata as having been initially deposited horizontally, and then were subsequently deformed (tilted and folded) by the forces of Earth's internal heat engine.
Conversely, the igneous rocks are younger than the sedimentary rocks.
Other examples of cross crutting relationships can be related to faults (fault has to be younger than the rock it is found in) and unconformities (see below).