What defines a bedding plane in geology?

A bedding plane in geology refers specifically to the horizontal surfaces that separate different layers of sedimentary rock. These planes represent the surfaces of deposition, where sediment was laid down over time. The bedding plane marks the transition between one layer of sediment and the next, indicating a change in sediment type, composition, or environment of deposition.

In contrast, a vertical fissure indicates a crack or break that runs vertically through rock formations, which does not provide information about the layered structure of sedimentary rocks. Similarly, a layer of volcanic ash would not define a bedding plane, as it represents a specific type of material rather than the interface between sedimentary layers. A shift in tectonic plates pertains to geological movements and processes that can affect the landscape but do not directly relate to the concept of a bedding plane. Thus, the correct understanding of a bedding plane focuses on its role in stratigraphy and sediment deposition, making the option that describes a horizontal gap in rock layers the best choice.