| A | B |
|---|
| uniformitarianism | the geologic principle that the same geologic processes that operate today operated in the past to change Earth's surface |
| erosion | the process by which water, ice, wind, or gravity moves weathered particles of rock and soil. |
| weathering | the chemical and physical processes that break down rock and other substances |
| mechanical weathering | the type of weathering in which rock is physically broken into smaller pieces |
| chemical weathering | the process that breaks down rock through chemical changes |
| abrasion | the grinding away of rock by other rock particles carried in water, ice, or wind |
| frost wedging | process that splits rock when water seeps into cracks, then freezes and expands. |
| oxidation | a chemical change in which a substance combines with oxygen, as when iron oxidizes, forming rust. |
| permeable | characteristic of a material that contains connected air spaces, or pores, that water can seep through easily |
| soil | the loose, weathered material on Earth's surface in which plants can grow. |
| bedrock | the solid rock layer beneath the soil |
| humus | dark-colored organic material in soil |
| fertility | a measure of how well soil supports plant growth |
| loam | Rich, fertile soil that is made up of about equal parts of clay, sand, and silt. |
| pH scale | a range of values used to indicate how acidic or basic a substance is |
| soil horizon | a layer of soil that differs in color and texture from the layers above or below it |
| topsoil | the crumbly, topmost layer of soil made up of clay and other minerals and humus (nutrients and decaying plant and animal matter) |
| subsoil | the layer of soil below topsoil that has less plant and animal matter than topsoil and contains mostly clay and other minerals |
| decomposer | an organism that gets energy by breaking down wastes and dead organisms, and returns raw materials to the soil and water. |
| natural resource | anything naturally occurring in the environment that humans use |
| soil conservation | the management of soil to limits its destruction |
| crop rotation | The planting of different crops in a field each year to maintain the soil's fertility. |
| contour plowing | plowing fields along the curves of a slope to prevent soil loss |
| conservation plowing | soil conservation method in which weeds and dead stalks from the previous year's crop are plowed into the ground. |
