Relative age dating geology
To think of it another way, the chocolate chips found in chocolate chip cookies must be made first before they are added to the cookie, right?
You can't make the cookie, then the chocolate chips, and then insert them into the cookie.
If we return to our example of the layered cake, the cake has to be there first before you can cut with a knife.
These fossils are found in rocks in chronological order in rock strata with the oldest being on the bottom and the youngest at the top.
This can best be explained by looking at fossils embedded in a rock column.
This is because the rocks were deposited laterally in continuous flat layers and can be covered with vegetation or eroded in some places.
So, when a valley or canyon cuts through these rock layers, the principle of lateral continuity says that rocks on either side of the canyon were once joined and continuous.