What is the term for mostly coarse soils involved in slope movement?

The term that describes mostly coarse soils involved in slope movement is "debris." Debris flows or debris slides typically consist of a mixture of coarse materials, such as gravel, cobbles, and other fragmental solids, along with some finer materials. These types of movements are common in hilly or mountainous terrain where heavy rainfall or the rapid melting of snow can saturate the soil, leading to the flow of large volumes of mixed soil and rock materials down a slope.

In contrast, the terms rock, earth, and silt refer to specific types or classifications of soil and materials. Rock implies solid stone with little to no loose sediment, while earth generally refers to finer, cohesive materials that can behave differently under stress and are not inherently indicative of the rapid and chaotic movement associated with coarse materials. Silt, on the other hand, is a fine-grained soil that is too small to contribute significantly to the type of mass movement characterized by larger coarse particles. Understanding these distinctions is crucial for geologists when assessing slope stability and the potential for slope movement.