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Earth Science Ch. 18
| Term | Definition |
|---|---|
| Chemical weathering | The breakdown of rock by the action of natural acids dissolved in water. It is a result of chemical changes in the minerals composing the rock |
| Mechanical weathering | The breakdown of rocks into smaller pieces by the action of physical forces such as freezing water, growing plant roots, or wind-driven sand |
| Frost wedging | The weathering process that occurs when water standing in cracks and pores of rock expands as it freezes, widening the cracks and eventually breaking up the rock into smaller pieces |
| Frost heaving | The pushing of rocks upward in soil by repeated freezing and thawing of water in the soil |
| blowout | An excavated desert basin caused by the wind carrying away loose material such as sand and silt |
| Desert pavement | The surface remaining after all the sand and other loose materials have been blown away |
| Sand dune | A mound or wavelike ridge of loose sand heaped up by the wind |
| exfoliation | A process by which thin slabs or flakes of rock are removed from larger rocks by mechanical and/or chemical weathering |
| talus | A sloping pile of weathered rock at the base of a cliff composed of rock pieces that have fallen from the cliff |
| soil | Ideally, a mixture of sand, silt, and clay containing some humus; proportions vary depending on the source and fertility of the soil. |
| horizon | A layer or zone of the soil that is relatively uniform in composition |
| humus | Decayed organic matter in soil. It is the constituent that makes soil “rich” in nutrients. |
| loam | An especially fertile soil that contains about equal parts of sand and silt, about half as much clay, and also humus |
| Mass wasting | The downhill movement of large masses of soil and rocks under the influence of gravity |
| creep | Slow movement of soil down a slope due to gravity |
| Rock glacier | A glacier consisting mostly of rock fragments held together with ice. It moves slowly under the influence of gravity, like a standard glacier |
| landslide | The rapid movement of a mass of soil and rock downward on a steep slope |
| rockslide | The rapid movement of a large mass of loosened bedrock down a steep slope |
| Debris slide | A landslide involving mostly loose soil and rocks lying on top of bedrock |
| erode | To wear away |
| stream | A confined body of water that flows either continuously or seasonally on the earth’s surface or underground |
| Headwaters/source | The highest point, or point of origin of a stream |
| gradient | The measure of the slope of a stream |
| mouth | The point at which a stream flows into another body of water |
| Base level | The lowest level to which a stream can flow |
| tributary | A smaller stream that feeds a larger stream |
| Drainage basin | The land drained by a system |
| divide | A ridge separating one stream’s drainage basin from another’s. |
| floodplain | A plain bordering a stream and composed of sediment deposited by the stream during floods |
| levee | Ridge of soil |
| meander | A sharp looping bend in the channel of a low-gradient stream |
| Neck cutoff | A shortcut across a meander that a low-gradient stream sometimes takes, turning the meander into an oxbow lake |
| Oxbow lake | A lake formed by the cutting off of a meander in a low-gradient stream |
| solution | A type of erosion in which groundwater dissolves minerals and removes them from rocks and soil |
| delta | A usually fan-shaped deposit of sediment where a stream enters a relatively quiet lake or the ocean |
| Alluvial fan | A fan-shaped deposit of sediments formed at the point where a stream emerges from a narrow valley onto a plain or other relatively flat surface. |
| Salt wedging | The precipitation of salts in joints as groundwater evaporates, a type of mechanical weathering |
| High-gradient stream | steep stream, usually has rapids and waterfalls |
| Low-gradient stream | flatter stream, usually has floodplains and natural levees |
| Silt | Fine-grained sediment deposited in stationary or very slowly moving water |
Created by:
jrasmussenheritage
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