Absolute dating geology
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.
If a geologist claims to be younger than his or her co-worker, that is a relative age.
Gaps in the geologic record, called unconformities, are common where deposition stopped and erosion removed the previously deposited material.
Fortunately, distinctive features such as index fossils can aid in matching, or correlating, rocks and formations from several incomplete areas to create a more complete geologic record for relative dating.
The nuclear decay of radioactive isotopes is a process that behaves in a clock-like fashion and is thus a useful tool for determining the absolute age of rocks.
Radioactive decay is the process by which a “parent” isotope changes into a “daughter” isotope.