What is the term for when fragments move along by rolling and sliding?

The correct term for when fragments move along by rolling and sliding is traction. This process occurs in settings like riverbeds or along shorelines where larger particles, such as gravel or cobbles, are moved by the force of water or wind. In traction, the particles maintain contact with the surface as they are displaced, mostly due to the sheer force of the moving water or wind acting upon them.

In contrast, saltation refers to the movement of smaller particles or sediments that bounce or hop along the surface rather than rolling or sliding. Deposition describes the process where materials carried by a fluid are dropped or settled out of the flow when the energy decreases. Sorting involves the separation of particles based on size or density, often occurring during transportation processes but not directly related to the manner in which fragments roll or slide. Understanding these terms is essential in grasping how sediment transport processes function in fluvial and coastal environments.