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Weathering, Erosion, & Soil

Weathering, Erosion, & Soil. Ch. 7: Part 1. Weathering. Weathering : Process by which rocks on or near Earth’s surface break down and change Types of Weathering :

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Weathering, Erosion, & Soil

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  1. Weathering, Erosion, & Soil Ch. 7: Part 1

  2. Weathering • Weathering: Process by which rocks on or near Earth’s surface break down and change • Types of Weathering: • Mechanical: process by which rocks and minerals break down into smaller pieces (does not change rocks composition, only size and shape. • Chemical: process by which rocks and minerals undergo changes in their composition as a result of chemical reactions

  3. Factors of Mechanical Weathering • Temperature: Drop in temperature causes water to begin to freeze, water then expands, taking up more space than in liquid form • - Frost Wedging: repeated thawing and freezing of water in the cracks of rocks causing them to break apart (example: Potholes)

  4. Factors of Mechanical Weathering • 2. Pressure: Layers of rocks put pressure on rocks below; when rock layers are removed (exfoliation), pressure is reduced, causing expansion of the rock and long, curved cracks to form • Exfoliation: outer rock layers are stripped away

  5. Factors of Chemical Weathering • Water: can dissolve many kinds of minerals and rocks; Can react with other substances (hydrolysis) which occurs during the decomposition of one mineral to another. • 2. Oxygen: can chemically react with other substances (oxidation); ex: oxygen in the atmosphere can combine with iron in rocks and minerals

  6. Factors of Chemical Weathering • 3. Carbon Dioxide: atmospheric gas when combined with water in the atmosphere produces weak carbonic acid; can react with certain minerals to dissolve rocks • 4. Acid Precipitation: caused by the oxidation of sulfur dioxide and nitrogen oxides in the atmosphere by human activity; has a pH below 5.6; creates problems for many organisms living in aquatic environments

  7. What affects the rate of weathering? • Climate: interaction between temperature and precipitation • -Chemical weathering: common in warm temps, abundant rainfall, lush vegetation • -Mechanical weathering: cool, dry climates where water undergoes repeated freezing and thawing • Rock Type and Composition: sedimentary rocks are more easily weathered than harder igneous and metamorphic • Surface area: more surface area=more weathering • Topography: slope of the landscape determines the weathering

  8. Erosion and Deposition

  9. Erosion • Erosion: removal of weathered rock and soil from its original location • Deposition: After the material is transported they are dropped into another location

  10. Gravity’s Role in Erosion • Force of gravity tends to pull all materials downslope. • Without gravity, glaciers would not move downslope and streams would not flow • Also an agent in mass movements: landslides, mudflows, and avalanches.

  11. Erosion by Running Water • **Swiftly flowing water has greater erosional power than wind and can also carry more material along with it and over a greater distance. • Rill Erosion: erosion by running water in small channels, on the side of a slope; form on a slope • Gully Erosion: when channel becomes deep and wide; can be more than 3 m deep and causes major problems in farming and grazing areas • **Weathering and Erosion occur also in oceans and islands: currents, waves, and tides carves out cliffs, arches, and more and a lot of the weathering and erosion occurs along the shorelines.

  12. Glacial Erosion • -Glaciers scrape and gouge out large sections of Earth’s landscape; they are so dense and have ability to carry huge rocks and other debris long distances • -Leave behind valleys with waterfalls, lakes, and variously shaped deposits of sediment

  13. Wind Erosion • Major erosional agent in areas with limited precipitation and high temperatures • Can easily pick up and move the fine, dry particles • Effects can be dramatic and devastating • Can damage natural features and human made structures • Very common in Death Valley • Shore areas also experience wind erosion • Running water and glacial activity still more powerful • Wind barriers can reduce the effects of wind erosion for farmers (trees and other plants)

  14. Erosion by Plants, Animals, and Humans • -Plants and animals move Earth’s surface materials from one place to another • -Animals burrow, humans excavate areas and move soil, planting a garden, developing new athletic fields, building a highway all result in the moving of earth’s materials from one place to another • -Effects of erosion by plants, animals, or humans is minimal compared to water, wind, or glaciers.

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