Soil Profiles
Geography: KS3, topic 7.1.7
Soil Profiles
A soil profile is a cross-section of the layers of soil in an area. The layers of a soil profile are called ‘horizons’ and there are four main horizons.
The O horizon
- This is the organic layer. It is organic because it is made up of dead plant and animal parts.
- The O horizon is thickest in forests where soil is undisturbed.
- The thickest of the O horizon in forests depends on how quickly decomposition happens.
- Some soils don’t have an O horizon at all.
The A horizon
- The A horizon is where the plant roots are.
- It can also be called the topsoil.
- You also find lots of microorganisms here- as they are decomposing material.
The B horizon
- The B horizon is also called the sub soil.
- The B horizon contains lots of minerals that have leached (moved / been washed down) from the A horizon and built up here.
The C horizon
- This is the parent material. It is the parent material from the Earth’s surface that the soil has formed from.
Test yourself on Soil Profiles
Which section of a soil profile is made up of parent material?