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CM Earth Science 4-2
Unit 4 Mr. Wilbur/Barbis: Chapter 14/ RB 4
| Question | Answer |
|---|---|
| Weathering | Natural process where atmospheric & environmental agents (wind, rain, temperature) disintegrate & decompose rocks (ex. ice, plants, animals, gravity, running water, wind); a slow process |
| Mechanical weathering | process that breaks rocks down into smaller pieces by physical means |
| Agents of mechanical weathering | Frost action (ice wedging);Organic;Wetting & drying;Abrasion |
| Frost action (Ice wedging) | Water seeps into rock cracks; freezes; expands; breaks rocks |
| Organic | Plant roots & animals digging break down and expose rocks to other forces |
| Wetting & drying | Especially effective in rocks with a lot of clay; can result in exfoliation; outer layer of rocks peel off |
| Abrasion | Grinding & wearing away of rock surface; sand, water, gravity |
| Chemical weathering | Changes composition of rock; decompose through chemical reaction |
| Agents of chemical weathering | Oxidation; Carbonation; Hydrolysis; Plants & animals |
| Oxidation | Oxygen reacts with minerals to form rust; faster with water present |
| Carbonation | Carbon dioxide reacts w/ minerals; faster with water present; carbon dioxide reacts with water to from carbonic acid |
| Hydrolysis | Reaction with water to form new compounds (ex. feldspar + water = clay + soluble minerals (dissolving) |
| Plants & animals | Produce organic acids released into ground; reacts w/ rock materials; ex. lichen, moss |
| Mechanical weathering vs. Chemical weathering | Mechanical weathering allows chemical weathering to proceed faster; Chemical weathering makes it easier to mechanically weather rocks too |
| Increased surface area | Breaking up rocks; rocks break down faster |
| How chemical weathering makes mechanical weathering take place faster | Weakened bonds between mineral grains; Forms solutions that break down rocks; Forms new minerals |
| What determines how fast a rock will break down | Composition of rock; Surface area exposed from fractures /joints;Climate: warm & humid = faster; Cold & dry = slower; Topography: steep vs. gentle slope |
| Soil | Dirt; a loose mixture of rock fragments & organic matter |
| Mixture of 4 major components in soil | Mineral materials; Organic matter (humus); Water; Air |
| Mineral materials | Sand, silt, clay-sized particle;45% of average soil volume; Helps anchor plants;Determines soil texture |
| Organic matter (humus) | 5% of average soil volume; Keeps soil loose; Increases soil’s ability to retain water; Food source for microbes |
| Water | About 25% of average soil volume;Found in pore spaces;Dissolved salts & water provide nutrients |
| Air | About 25% of average soil volume;Found in pore spaces;Needed by roots of plants |
| Factors affecting formation of soil | Climate;Parent rock type;Topography;Time |
| Climate | Includes temperature and moisture;determines types and rates of weathering; types of vegetation |
| Parent rock | Influences weathering rate;Determines soil texture;Porosity;Permeability |
| Topography | slope of land;soils are better developed where land is flatter |
| Time | It takes time to break down materials into soil |
| Soil profile | Cross-section of the soil from the surface to the parent rock material (bedrock) |
| Soil horizons | Soil layers making up profiles |
| A-horizon | topsoil;most fertile nutrients;most humus |
| B-horizon | subsoil;lighter in color than A;more clay than A |
| C-horizon | partially weathered rock |
| Soil types | mature soil; immature soil;transported soils |
| Mature soil | In all three horizons |
| Immature soil | Lacks 1 or 2 horizons |
| Transported soils | Form from materials brought into area by erosional agents (wind, water, glaciers, etc) |
| Classification of soil types | Tropical;Grasslands (prairie);Forest; Desert; Arctic |
| Tropical soil | warm, wet climate;infertile;red to yellow color |
| Grasslands (prairie) soil | cool, wet climates;dark A-horizon; very fertile |
| Forest soil | cool, wet climates (wetter than grasslands);light to medium brown soil;good for farming (not as good as grasslands) |
| Desert soil | dry;not many nutrients (very little humus);too warm or too cold;poor soil= not a lot of break down |
| Arctic soil | high elevation/high latitude;poorly developed soil;often layer of permafrost |
| Erosion | Movement of weathered material |
| Agents of erosion | water (surface, ground, precipitation, glaciers);gravity;wind |
| Balanced soil formation | Normally soil forms at the same rate as it erodes (balanced). Changes in use and weather can increase rate of erosion |
| What plant root systems do | “Hold” soil in place; clearing land and overgrazing can take protection away |
| Gullying | Crop furrows that widen due to water erosion |
| Sheet erosion | Rain washes topsoil away; wind can do this if it is real dry (ex. Dust Bowl 1930’s American Midwest) |
| Conservation of soil (ways to “save” the soil from erosion) | contour farming;strip-cropping;terracing;crop rotation |
| Contour farming | Plowing following the shape or contour of the land |
| Strip-cropping | Farming cover crops and alternating the “plow crops” such as corn |
| Terracing | Farming on steps to reduce water and gravity erosion |
| Crop rotation | Similar to strip farming; but on an annual basis, cover crops are alternated with plow crops each year |
| Mass movements gravity can cause | mass wasting;slump;creep;Talus;Solifluction |
| Mass wasting | movement;large amounts of moving soil;gravity can cause land and mudslides |
| Slump | movement of large “chunk” of ground |
| Creep | downhill movement that is barely noticeable (fences/poles move);Talus |
| Talus | accumulation of fragments at bottom of a slope |
| Solifluction | slow movement landslide |
| Miscellaneous erosion facts | all surfaces are affected by erosion;mountains, plains, and plateaus are erosion and deposition are two opposing forces working to breakdown & build up the landscape |
| Plain | Relatively flat landform near sea level |
| Plateau | Broad, flat landform that has high elevation |
| Mesa | Table-like areas from eroded plateaus |
| Buttes | Small, narrow-topped formations from eroded mesas |
Created by:
vbarbis
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