What is an important characteristic of sedimentary rocks?

Sedimentary rocks are characterized by their formation in distinct layers, a process known as stratification. This layering occurs as sediments are deposited over time, often in environments such as rivers, lakes, and oceans. As more layers accumulate, the weight of the overlying sediments exerts pressure on the lower layers, which leads to compaction and cementation. This layering not only provides clues about the geological history of an area but also influences the physical properties of the rock, including porosity and permeability.

The other options do not accurately describe the defining characteristics of sedimentary rocks. Volcanic activity is associated with igneous rocks rather than sedimentary ones. Crystalline structure is more typical of igneous and metamorphic rocks, while sedimentary rocks can be composed of particles that do not form a crystalline structure. Lastly, while sedimentary rocks can be formed from existing rocks through processes like weathering and erosion, this doesn’t define their key characteristic, which is the formation of layers during sediment deposition.