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WEATHERING

WEATHERING. Weathering - Breakdown of rocks into particles called Sediment. Weathering occurs when rocks are exposed to: 1. Atmosphere 2. Hydrosphere 3. Living things. TYPES OF WEATHERING. 1. Mechanical or Physical - Breakdown of rock into smaller pieces without chemical change. EXAMPLES:.

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WEATHERING

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  1. WEATHERING

  2. Weathering- Breakdown of rocks into particles called Sediment Weathering occurs when rocks are exposed to: 1. Atmosphere 2. Hydrosphere 3. Living things

  3. TYPES OF WEATHERING 1. Mechanical or Physical - Breakdown of rock into smaller pieces without chemical change. EXAMPLES: • Biological Activity : Plant roots grow through cracks and break the rock. • (Root Action)

  4. b) Frost wedging water freezes and expands in cracks. As this happens over and over again the rock breaks. c) Uploading: Changes in temperature cause the rock to expand and contract. Surface of the rock begins to peel away (exfoliation).

  5. ADD TO YOUR NOTES d) Abrasion: When rocks or sediments rub against another rock ex: sandblasting

  6. Mechanical or Physical Weathering VIDEO

  7. 2. Chemical - Breakdown of rock by chemical action that results in a change in mineral composition ADD TO YOUR NOTES EXAMPLES: a) Oxidation - When elements in the rock react with O2 (oxygen) Fe (iron) + O2 (oxygen) = |Fe2O2 (iron oxide or rust)

  8. b) HYDRATION- When elements in the rock react with H2O (water- the “universal dissolver”) Feldspar (common mineral) + H2O = Clay Clay = fine particles that are usually wet

  9. c) CARBONATION- When elements are dissolved by acid rain. Carbon Dioxide + Water = Carbonic Acid or Sulfur Dioxide + Water = Sulfuric acid Example: Marble grave stone dissolved by acid rain

  10. Chemical Weathering VIDEO

  11. RATE OF WEATHERING DEPTH FACTORS AFFECTING THE RATE AND TYPE OF WEATHERING Rocks near the surface are weathered faster than rocks deep under ground.

  12. SAME OVER ALL VOLUME RATE OF WEATHERING MORE EXPOSED AREA PARTICLESIZE 1. PARTICLE SIZE- The smaller the particle size, the greater the total surface area that is exposed to weathering.

  13. RATE OF WEATHERING MINERAL HARDNESS 2. Mineral Composition - Different minerals have different resistances to weathering. EXAMPLES: Quartz is hard, takes a long time to weather. Talc is soft, takes a short time to weather.

  14. RATE OF PHYSICAL WEATHERING RATE OF CHEMICAL WEATHERING TEMPERATURE TEMP. AND MOISTURE 3. Climate - In warm, moist climates chemical weathering is dominant. Cold climates frost action most effective form of weathering. A lot of freezing and thawing - frost action is the most effective form of weathering In dry climates very little weathering happens.

  15. Differential Weathering Different parts of a rock will weather at different rates

  16. PRODUCTS OF WEATHERING Weathering results in four types of sediment: 1. Solid sediment - sand and pebbles. 2. Colloids clay sized particles (small sediment) 3. Ions - Particles dissolved in water (salty oceans) 4. Soil - a mixture of sediment and organic matter

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