| A | B |
|---|
| weathering | The process that breaks down rock and other substances at Earth's surface |
| erosion | The removal of rock particles by wind, water, ice, or gravity |
| permeable | Material that has tiny, connected air spaces that allow water to seep through it. |
| uniformitarianism | A principle that states that the same process that operates today operated in the past |
| mechanical weathering | The type of weathering in which rock is physically broken down into smaller pieces |
| abrasion | The grinding away of rock by rock particles carried by water,ice, wind or gravity |
| ice wedging | Water freezes and pushes against rock and cracks it; it then thaws and water seeps into cracks and freezes again. |
| chemical weathering | Process which breaks down rocks through chemical changes |
| oxidation | Iron combines with oxygen in the presence of water and the product is rust |
| soil | The loose, weathered material on Earth's surface in which plants can grow. |
| bedrock | The solid layer of rock beneath the soil. |
| humus | A dark colored substance that forms as plant and animals decay. |
| soil fertility | A measure of how well the soil supports plant growth. |
| loam | Soil that is made up of equal parts clay, sand, and silt. |
| soil horizon | A layer of soil that differs in color and texture from the layers above it and below it. |
| topsoil | A crumbly, dark brown soil that is a mixture of humus, clay, and other minerals. |
| subsoil | soil that consists of clay and other particles washed down from the A horizon. |
| decomposers | Organisms that break down the remains of dead organisms into smaller pieces and digest them with chemicals. |
| litter | A loose layer of leaves that have fallen to the ground. |
| sod | The thick mass of tough roots at the surface of the soil. |
| natural resources | Anything in the environment that humans use. |
| Dust Bowl | Area in southern Plain states where erosion was most serious in the 1800's. |
| soil conservation | management of soil to prevent its destruction |
| contour plowing | Plowing a field along the curves of a slope. |
| conservation plowing | plowing so that the plants covering the soil are disturbed as little as possible |
| crop rotation | Planting crops in a different field each year. |
