The principle that tells us how rock layers are laid is the principle of Original Horizontality.
Explanation:
1. Original Horizontality states that sedimentary rock layers are initially deposited in horizontal layers. This means that when they are first formed, they are generally flat and parallel to the Earth's surface.
2. This principle helps geologists interpret the relative ages of rock layers. If rock layers are found to be tilted or folded, it indicates that some geological forces have acted upon them after their formation.
3. For example, if you observe a sequence of sedimentary layers that are vertical instead of horizontal, you can infer that some tectonic activity or deformation has occurred to change their original orientation.
In the context of the given options, Original Horizontality (B) is the principle that specifically addresses how rock layers are laid down initially in a horizontal fashion before any subsequent geological processes alter their orientation.
