Relative dating in geological time
Suppose you find a fossil at one place that cannot be dated using absolute methods.
That fossil species may have been dated somewhere else, so you can match them and say that your fossil has a similar age.
A fundamental principle of geology advanced by the 18th century Scottish physician and geologist James Hutton, is that "the present is the key to the past." In Hutton's words: "the past history of our globe must be explained by what can be seen to be happening now." The principle of intrusive relationships concerns crosscutting intrusions.
In geology, when an igneous intrusion cuts across a formation of sedimentary rock, it can be determined that the igneous intrusion is younger than the sedimentary rock.
Relative dating is used to arrange geological events, and the rocks they leave behind, in a sequence.
Photo from Glen Canyon National Recreation Area, Utah.Correlation with them has helped geologists date many New Zealand rocks, including those containing dinosaurs.Bring relative dating principles to life with the activity Rock layers and relative dating.Different species of ammonites lived at different times within the Mesozoic, so identifying a fossil species can help narrow down when a rock was formed.Correlation can involve matching an undated rock with a dated one at another location.