5.2: Soil regolith: layer of rock and mineral fragments created from weathering soil: part of regolith that can support plant life

Soil Composition mineral matter (rock pieces) organic matter (humus) soil is made of four main parts: mineral matter (rock pieces) organic matter (humus) water air

Soil Formation type of soil formed is based upon: parent material (bedrock) time climate living organisms slope

parent material (bedrock) undergoes weathering to become regolith and soil

soil is a mixture of mineral and organic matter without any obvious rock structure regolith

soil horizon: over time, soil layers separate into distinct layers each horizon (layer) will vary based on climate and parent material

A horizon: top layer with organic matter (humus) usually dark in color due to the humus also called topsoil this layer supports plant life

B horizon: second layer down with more minerals & clay lighter in color also called subsoil this layer is the lower limit for plant roots

C horizon: third layer down made of weathered parent rock doesn’t really look like soil yet

parent rock: bottom layer of solid rock not yet weathered into regolith and soil

soil horizons A B C parent rock

soil profile: all the horizons in one area