| A | B |
|---|
| soil | a loose mixture of mineral fragments and organic material |
| bedrock | the layer of rock under the soil |
| parent rock | the rock that is the source of soil |
| residual soil | soil remaining above the bedrock from which it formed |
| transported soil | soil blown or washed away from its parent rock |
| humus | decayed plant and animal material |
| organic | coming from living things |
| topsoil | the upper layer of soil |
| horizon | layer of soil |
| horizon A | the top layer, containing organic material |
| horizon B | subsoil--contains clay and dissolved minerals |
| horizon C | partially weathered bedrock--the first soil layer to form |
| leaching | dissolved minerals and nutrients carried down into lower soil layers by water |
| tropical climates | topsoil is thin due to leaching from heavy rain |
| desert climates | high evaporation leads to salts in the topsoil which don't support plant growth |
| temperate climates | a lot of weathering contributes to thick, fertile topsoil |
| arctic climates | cold temperatures and low precipitation lead to thin topsoil that doesn't support much plant growth |
