| A | B |
|---|
| erosion | the movement of rock particles by wind, water, ice and gravity |
| mechanical | type of weathering that breaks rock into pieces by freezing and thawing, release of pressure, growth of plants, actions of animals and abrasion |
| abrasion | grinding away of rock by rock particles carried by water, ice, wind or gravity |
| ice wedging | splits rock when water seeps into cracks, then freezes and expands |
| chemical | type of weathering that breaks down rock through chemical changes |
| weathering | the process that breaks down rock and other substances at the Earth’s surface |
| permeable | material that is full of tiny connected air spaces that water can seep through |
| soil | loose weathered material on Earth’s surface in which plants grow |
| bedrock | sand layer of rock beneath the soil |
| humus | dark-colored organic material in soil |
| loam | rich, fertile soil that differs in color and texture from the layers above or below it |
| topsoil | mixture of humus, clay and other minerals that forms the topmost layer of soil |
| subsoil | layer of soil beneath the topsoil that contains mostly clay and other minerals |
| litter | loose layer of dead plant leaves and stems on surface of the soil |
| decomposers | soil organism that breaks down the remains of organisms and digests them |
| Dust Bowl | area of Great Plains where wind erosion caused destructive soil loss during the 1930’s |
| soil conservation | the management of soil to prevent its destruction |
| contour plowing | plowing fields along the curves of a slope to prevent soil loss |
| conservation plowing | method in which the dead stalks from the previous year’s crop are left in the ground to hold the soil in place |
