Subsoil

Beneath the topsoil is the subsoil. It is thicker than the topsoil but it does not contain organic materials. Instead, it is made up of lots of pebbles and big pieces of rocks. It also has very little or no humus at all, making it lighter in color than the topsoil.

Bedrock

Below the subsoil is the bedrock, which is composed of big fragments of rocks and gravel from which the topsoil is produced through weathering.

Weathering is the process by which rocks are broken into smaller pieces, with some pieces turning into powder form. Animals, chemicals, plants, people, the wind, and water are among the causes of weathering. For instance, strong ocean currents carry rocks with them and throw these about, causing the rocks to break. People use rocks to build different structures and they break the rocks to suit their building needs. The roots of some plants may grow in a crack in a rock, causing the rock to break into smaller pieces as the roots grow. The bedrock contains the rocky particles that are products of weathering and that give rise to the topsoil.