level:Plants grow and animals live here. A thick cover of plants can keep
the soil cool and keep it from drying out.Decomposersrecycle
dead plants and animals intohumus.
Topsoil:Plants grow and animals live on top of the soil.
This is sometimes called the organic layer. A thick cover of plants
can keep the soil cool and keep it from drying out.Decomposersrecycle dead plants and animals intohumus.
Subsoil:This is a mix of mineral particles and some humus near the top. Subsoil is very low inorganic mattercompared to the topsoil. This is the layer where most of the soil's nutrients are found. Deep plant roots come here looking for water. Clays and minerals released up above often stick here as water drains down.
Weathered parent material:Thishorizoncan be very deep. There's no organic matter here at all. We're out of reach of all living and dead organisms down here. It's all rock particles, full of minerals.
The entiresoil profileused to look like this all the way to the surface. Physical weathering broke theparent materialup into small pieces. Don't be fooled! This layer may contain rock particles that are different from the bedrock below. A river or a glacier might have brought it from somewhere else.
Bedrock:We finally found solid rock! The bedrock formed before the soil above it. It will wait here until erosion or an earthquake exposes it to the surface. Then some of it will be weathered to become the next batch ofparent material. The soil-making process will start all over again.