* O Horizon (Organic Layer): This is the uppermost layer and is composed of decomposed plant and animal matter, called humus. It's often found in forests and grasslands.

* A Horizon (Topsoil): This layer is a mixture of minerals and organic matter, and it's where most plant roots grow. It's typically darker in color than the lower horizons.

* B Horizon (Subsoil): This layer is less rich in organic matter and is often denser than the topsoil. It contains clay, iron, and other minerals that have been leached from the A Horizon.

* C Horizon (Parent Material): This layer is made up of the original rock that the soil formed from. It's often broken down rock fragments and may contain very little organic matter.

It's important to note that not all soils have all 4 horizons. Some soils may have only 2 or 3 horizons, depending on factors like climate, vegetation, and time. Additionally, there are other layers that may be present, such as the E horizon (eluviated horizon) which is a layer of highly leached minerals.