What is the main cause of the grading of rocks on rocky shores?

The grading of rocks on rocky shores is primarily influenced by the pounding effect of the sea. As waves crash against the rocks, they exert a significant amount of force that leads to mechanical weathering and erosion. Over time, this process shapes the rocks, causing larger boulders and fragments to break down into smaller, smoother pebbles or gravel. This continuous action not only alters the size and shape of the rocks but also creates a distinct gradient where larger rocks are often found higher on the shore and smaller ones closer to the water. This natural sorting, driven by the consistent impact of waves, plays a critical role in defining the geological characteristics of rocky shore environments.