Which principle states that if sedimentary rock layers are not found in a relatively horizontal pattern they have been rearranged by the action of forces within the earth?

The principle that states this is known as the "Principle of Original Horizontality." It asserts that sedimentary rock layers are originally deposited in horizontal or nearly horizontal layers. If these layers are found to be tilted, folded, or otherwise rearranged, it indicates that geological forces, such as tectonic activity, have acted upon them after their formation.