Why are the rocks big at the bottom of the soil profile?

Answer 1

Rocks are formed initially as one large slab, then are broken down by various processes. Most of the processes that will break rocks down into smaller rocks require the rock be exposed to the weather (wind, rain, freeze/thaw cycle, mechanical separation by roots growing into the cracks), so the further the rocks are from the surface, the larger they are likely to be.

Answer 2

The larger rocks at the bottom of the soil profile are often a result of a process called rock weathering. Over time, physical and chemical processes break down larger rocks into smaller pieces, which accumulate at the bottom of the soil profile due to gravity. This creates layers of different-sized particles within the soil.