| A | B |
|---|
| weathering | the processes that break down rock at Earth's surface |
| erosion | the process by which water, ice, wind or gravity moves fragments of rock and soil |
| mechanical weathering | the type of weathering in which rock is physically broken into smaller pieces |
| abrasion | the grinding away of rock by other rock particles like sandpaper |
| ice wedging | process that splits rock when water seeps into cracks, then freezes and expands |
| chemical weathering | the process that breaks down rock through chemical changes |
| permeable | characteristic of materials such as sand and gravel that allow water to pass easily through them |
| soil | the loose, weathered material on Earth's surface in which plants can grow |
| bedrock | the solid layer of rock beneath the soil |
| humus | dark-colored organic material in soil |
| loam | rich, fertile soil that is made up of about equal parts of clay, sand, and silt |
| soil horizon | a layer of soil that differs in color and texture from the layers above and below it |
| topsoil | mixture of humus, clay, and other materials that forms the crumbly, topmost layer of soil |
| subsoil | the layer of soil beneath the topsoil that contains mostly clay and other materials |
| litter | the loose layer of dead plant leaves and stems on the surface of the soil |
| decomposers | an organism that breaks down wastes and dead organisms |
| development | the construction of buildings, roads, dams, and other structures |
| desertification | the advance of desertlike conditions into areas that previously were fertile |
| sod | a thick mass of grass roots and soil |
| Dust Bowl | the area of the Great Plains where wind erosion caused 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 |
| no-till farming | soil conservation method in which the dead stalks are left in the ground to hold soil in place |
| cover crops | crops planted in off season to hold soil and replace nutrients |
| crop rotation | the planting of different crops in a field each year |
| land reclamation | the process of restoring land to a more natural state |
| plant growth | Roots of trees and other plants enter cracks then widen cracks as they grow |
| Animal actions | Burrowing animals like moles and gophers breaks apart rock in the soil |
| Living organisms | Plant roots produce weak acids that dissolve rocks. Lichens grow on rocks |
| carbon dioxide | Produces a weak acid called carbonic acid to break down marble and limestone |
| Oxygen in air | Combines with rock particles and undergoes oxidation (rust-red) |
| water | most important agent of chemical weathering which dissolves rock particles |
| Type of rock | Determines rate of weathering due to rock’s composition |
| freezing and thawing | Water seeps into cracks in rock then freezes when temperature drops |
| climate | Average weather conditions in an area |
| type of rock and climate | two most important factors in weathering |
| Temperature and humidity | warm and wet quickens chemical reactions for weathering |
| oxidation | process where oxygen combines with water in air producing rust |
