How does soil form layers?

Answer 1

Soil is made of 3 main layers: topsoil, subsoil and the layer of parent material.

The topsoil contains most of the humus (which is a dark organic material of the soil), it is formed from the decay of various organisms

The thick layer of soil below topsoil is subsoil, it is lighter in colour in comparison with the topsoil and often contains a lot of clay. Water carries minerals an other materials down into this layer and most tree roots grow down into the subsoil

The bottom layer contains large rocks, this is the material from which the soil above is partly formed. The bottom layer is the parent material, these rocks break down into gravel, sand and clay that become part of the subsoil