What term describes the movement of very small rock particles suspended in water flow?

The term that accurately describes the movement of very small rock particles suspended in water flow is "suspension." This process involves finer materials, such as silt and clay, which are carried and held aloft within the water column due to the energy of the flowing water. These particles do not settle to the riverbed because they are light enough and small enough to be supported by the turbulence of the moving water.

Suspension plays an essential role in the dynamics of river systems as it allows for the transport of nutrients, sediments, and other materials that can influence the river's ecosystem. It also contributes to the river's overall sediment load, impacting the sedimentary environments and depositional processes downstream.

The other terms relate to different processes involving sediment movement. For instance, siltation refers to the accumulation of sediments in water bodies, which can affect water quality and aquatic habitats. Solution refers to the process where minerals dissolve in water and are carried in a dissolved state, whereas bedload transport describes the process of larger, heavier particles that move along the riverbed, often by rolling or bouncing, rather than being suspended in the water. Understanding these distinctions helps clarify the various ways sediment can move within a river system.