Which process involves materials becoming smaller and rounder as they collide with each other in the sea?

Attrition is the process where materials, such as pebbles and sand, undergo wear and tear from colliding with each other in the sea. This constant movement in the water causes the edges of these materials to chip away, leading to a gradual reduction in size and making them rounder over time.

In coastal environments, this process is significant as it contributes to the overall shaping and smoothing of sediment. As these particles collide during wave action, they lose sharp edges and transitions towards a more rounded form. This is essential for understanding sediment transport and the evolution of coastal landscapes, as rounded materials can be easily transported by water currents.

The other processes listed, while related to erosion and sediment movement, do not specifically describe the action of materials colliding with each other to become smaller and rounder.