In which geological principle are sediments deposited horizontally?

The principle that sediments are deposited horizontally is known as the Law of Original Horizontality. This geological principle was formulated by the 17th-century geologist Nicolas Steno. It asserts that layers of sedimentary rock are originally deposited in a flat, horizontal orientation. This is significant because it helps geologists understand the deposition environment and interpret the geological history of an area. If layers of sediment are found to be tilted or folded, it suggests that they have undergone subsequent geological events, such as tectonic forces.

The other principles mentioned pertain to different geological concepts. For example, the Law of Superposition refers to the idea that, in an undisturbed sequence of rocks, the oldest layers are at the bottom and the youngest are at the top. The Principle of Crosscutting Relationships states that if a geologic feature cuts through another, the feature that has been cut is older. Lastly, the Principle of Uniformitarianism posits that the processes observable today, like erosion or sedimentation, also operated in the past. Thus, while these concepts are essential in understanding geological processes, the Law of Original Horizontality specifically addresses the initial arrangement of sedimentary deposits.