Definition of relative age dating
Principle of later continuity: The principle of lateral continuity says that rocks continue in all lateral directions, even if you can't see them on the surface.
This is because the rocks were deposited laterally in continuous flat layers and can be covered with vegetation or eroded in some places.
Geologists have studied the order in which fossils appeared and disappeared through time and rocks. Fossils can help to match rocks of the same age, even when you find those rocks a long way apart.
This matching process is called correlation, which has been an important process in constructing geological timescales.
Correlation can involve matching an undated rock with a dated one at another location.
Once the rocks are deposited flat, forces can act upon them to tilt or fold them.
Law of superposition: This is one of the most basic techniques of relative dating geologists use.
So, instead of saying when something happened, it puts events in the order they happened.
So, basically it's the difference between saying 'I'm 25 years old, and my sibling is 20 years old' and 'I'm older than my sibling.' Geologists use a variety of techniques, or principles, to determine the relative age of a rock unit.