biosphere

• what is soil made up of?

  mineral matter - product of weathering (natural process of the chemical, physical or biological breakdown of rocks and minerals) and comes from rocks

  air - carries gases to and from the plants roots and animals. it is in the empty pore spaces when water is not present

  water - held in pore spaces and carries dissolved salts (plant food)

  organic matter - largest component of soils and comes from the remains of plants and animals, this eventually breaks down into a brown material called humus
• eluviation


  minerals are dissolved into the pore spaces which takes them from the layer they originally came from, this is called leaching
• illuviation


  minerals get re-preticipated back into the soils as visible minerals which adds them to a layer that they don't normally get to creating an iron pan
• the Ao horizon


  closest to the surface and contains:

  leaf litter - undecomposed layer of plant material laying on the surface

  fermentation layer - first stage of rotting takes place

  humus layer - rotted material available as food for plants
• the A horizon


  'topsoil', usually nutrient rich and finely textured

  leaching can take place here - plant nutrients are moved down by excess precipitation

  an iron pan can be created here on the boundary with the B horizon - a dense layer of soil which is washed out from the upper layers and precpitated into a mineral deposit again
• the B horizon


  sub-soil, coarser that the layer above with little organic matter

  area of illuviation where material has been leached from the A to B horizon
• the C horizon


  regolith, made up of weathered bedrock from the parent material