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Weathering and Soil
| Term | Definition |
|---|---|
| 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 wedgeing | 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 | Rock that makes up Earth's crust; also 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; expresses the concentration of hydrogen ions in a solution. |
| 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 limit 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. |