Definition for relative dating
They then go further by interpreting the formation of each feature to be the consequence of a speciﬁc geologic event.Examples of geologic events include: Deposition of sedimentary beds; erosion of the land surface; intrusion or extrusion of igneous rocks; deformation (folding and/or faulting); and episodes of metamorphism.
If today you find a sedimentary layer cut by a canyon, then you can assume that the layer once spanned the area that was later eroded by the river that formed the canyon.
The succession of events in order of relative age that have produced the rock, structure, and landscape of a region is called the geologic history of the region.
We can use these principles to determine relative ages of the features.
If a fault cuts across and displaces layers of sedimentary rock, then the fault must be younger than the layers.
But if a layer of sediment buries a fault, the sediment must be younger than the fault.
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Once the relative ages of a number of fossils have been determined, the fossils can be used to determine the relative age of the beds containing them.