Which term represents fine particles that can be moved by wind and water?

Loess refers to a specific type of sediment that consists of fine particles, primarily silt, which can be easily transported by wind and water. This material forms in areas where dust accumulates, such as near deserts or glacial regions. Loess deposits are often characterized by their ability to form steep, vertical cliffs as they are less consolidated than other soil types, making them particularly susceptible to erosion.

The other terms, while related to soils and sediment, do not encompass the same characteristics as loess. Colluvial refers to material that is transported downslope primarily by gravity, not by wind or water. Alluvial pertains to sediment deposited by flowing water, often found in riverbeds and floodplains, but it does not specifically refer to fine particles that can be transported by wind. Clay describes a type of soil with very fine particles as well, but it does not specifically capture the broader movement of particles by wind and water like loess does. Thus, loess is the term most accurately representing fine particles easily moved by these natural forces.