#horizon  a specific layer or stratum of soil or subsoil in a vertical cross section of land
  supertype:  stratum  one of several parallel layers of material arranged one on top of another (such as a layer of tissue or cells in an organism)
  part of:  profile.cross_section
  subtype:  soil_horizon  a layer in a soil profile
     subtype:  A-horizon__A_horizon  the top layer of a soil profile; usually contains humus
     subtype:  B-horizon__B_horizon  immediately below the A-horizon; contains deposits of organic matter leached from surface soils
     subtype:  C-horizon__C_horizon  beneath the B-horizon and above the bedrock; consisting of weathered rock
  subtype:  geological_horizon  a layer of rock with a particular composition (especially of fossils); for dating the stratum

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