| A | B |
|---|
| humus | the dark, organic material in soil produced by the decay of plant and animal matter |
| soil | the portion of the Earth's surface that consists of organic matter, sediment, air, and water |
| soil profile | cross-section that shows the difference (or horizons) of soil in the ground |
| leaching | a process by which water dissolves substances and causes them to be removed from one location to another |
| topsoil | the top layer of soil that generally contains humus |
| subsoil | a layer of clay and small rocks where dissolved minerals collect |
| bedrock | the layer of rock beneath the soil |
| parent rock | rock that is the source of soil |
| permafrost | permanently frozen soil located from 25 to about 100 centimeters below Earth's surface |
