Layers of Soil. O Horizon. A Horizon. B Horizon. C Horizon. Bedrock. Soil is composed of 5 distinct layers. O Horizon. This layer is dark in color. This layer consists of decomposed leaves, organic matter and humus, which makes the soil fertile. A Horizon. This layer is called as top soil. It is a soft porous layer and is very rich in humus and nutrients. It is a shelter for living organisms like worms and rodents. Plant roots grow in this layer. B Horizon. This is a hard and compact layer. Roots of bigger plants extend till this layer. Minerals. This layer consists of many minerals. This layer is also known as sub soil. C Horizon. Welcome to C Horizon. Hi, we are slightly weathered parent rocks. We have cracks and crevices. Bedrock. Bedrock is the last layer of soil. This layer is very hard. It consists of unweathered parent rocks. This vertical section through which the different layers of the soil are visible is called soil profile. The End.