What process involves the smoothing and rounding of stones carried in the load of a river?

The process that involves the smoothing and rounding of stones carried in the load of a river is known as attrition. As riverbed materials, including rocks and pebbles, move downstream, they collide with one another and with the riverbank. These collisions cause the edges and surfaces of the stones to wear away, leading to a reduction in size and the formation of smoother, rounded shapes.

In contrast, hydraulic action refers to the force of water impacting the riverbanks and beds, causing erosion through pressure. Abrasion occurs when the load of the river physically scours the riverbed and banks, further shaping the landscape by removing material. Solution involves the chemical dissolution of minerals and rocks in water, contributing to the alteration of water's composition rather than the physical characteristics of the stones.

The key distinction with attrition is its specific focus on the mutual impact between the stones themselves, which is crucial for understanding river transport and sediment dynamics.