Sedimentary rocks lie uppermost in the crust. By piecing together the histories of enough areas we can determine the geological evolution of a continent.
Relative time deals with the order of events.
For most people in this course the list on the right is the sequence that represents the relative order of these events. When using relative time it is not important that we know when an event occurred, but only that we know if it occurred before or after another event. The image below shows beds at Dead Horse Point, Utah. Using the principle of superposition we can assume that the beds at river level are older than the beds higher on the slopes. Older rocks may be cut by younger rocks or other geological features.