This is Horizon A, otherwise known as Topsoil. It is the best layer of soil for planting, and consists of sand, silt, clay, and broken down organic matter (Humus).
This is Horizon B, also known as subsoil. It is where clay and other materials accumulate- so it is mostly made up of clay particles and iron materials (as well as organic matter washed down by rainwater).
Yo, I'm Clay
This is Horizon C, otherwise known as the Substratum. It is a layer of weathered parent rock, so the layer consists mostly of large rocks and