Process of relative dating
In terms of paleontology, if an earthquake occurs and moves a fossil to another layer of the earth, one would think that fossil is older or younger than it is. By burying our dead, we impose them into geologic layers that we, ourselves, did not actually live in.
Erosion could also take a mineral or fossil out of position and place it in another layer, thus causing humans to incorrectly assume an older or different age.
Making this processes even more difficult is the fact that due to plate tectonics some rock layers have been uplifted into mountains and eroded while others have subsided to form basins and be buried by younger sediments.
However, forces that can disturb relative dating or at least make it more challenging include multiple geological processes occurring over a short period of time.
If the layers you're examining are very small, it can be hard to determine for sure which occurred first.
The ten strata systems that compose the “standard geologic column” are the familiar Cambrian, Ordovician, Silurian, Devonian, Carboniferous, Permian, Triassic, Jurassic, Cretaceous, and Tertiary periods.
Although no absolute methods were available to establish actual dates, Lyell needed to assign very old dates to the strata to make them consistent with the long eons of time that would be necessary to meet the new uniformitarianism theory developed by James Hutton and himself.