What forms layers that can eventually become sedimentary rock?

The formation of layers that can eventually become sedimentary rock primarily occurs through the accumulation of sand, mud, or organic material. These materials are deposited in various environments, such as riverbeds, lakes, and ocean floors. Over time, as additional layers are deposited, the weight of the overlying material compresses the layers beneath, leading to lithification, which is the process that transforms sediment into rock.

Sand, mud, and organic remnants, such as plant and animal materials, contribute to the variety and richness of sedimentary rock types. Their deposition can encapsulate and preserve evidence of past environments and life forms, making sedimentary rocks critical to understanding geological history.

The other options, while related to geological processes, do not directly form the layers that become sedimentary rock. Weathering and erosion are processes that break down rocks and transport sediments but do not themselves create layers. Volcanic activity typically leads to the formation of igneous rocks rather than sedimentary rocks, and metamorphic pressure affects existing rocks rather than contributing to layer formation for sedimentary rock. Therefore, the role of sand, mud, and organic material is central to the development of sedimentary layers.