Which characteristic defines sedimentary rocks?

Sedimentary rocks are primarily defined by their formation process, which involves the accumulation and compaction of sediments. These sediments can originate from the weathering and erosion of pre-existing rocks, the accumulation of organic material, or precipitation of minerals from solution. Over time, layers of these sediments build up, and through processes such as lithification—where sediments are pressed together and cemented—they transform into sedimentary rock.

The other characteristics mentioned do not apply to sedimentary rocks. For example, the formation from volcanic activity describes igneous rocks, while the notion of being composed of minerals from a single source typically pertains to certain metamorphic or igneous rocks. Additionally, the description of forming from extreme heat and pressure is specifically associated with metamorphic rocks. Thus, the pivotal characteristic that distinctly identifies sedimentary rocks is their origin from the accumulation of sediments.