Chapter 7 section 1

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Chapter 7 section 1

  1. 1. Weathering<br />Chapter 7: Section 1<br />
  2. 2. I. Weathering<br />Weathering and It’s Effects<br />Surface processes that work to break down rock are called weathering. <br />Weathering breaks down rocks into smaller and smaller pieces. <br />Two forms of weathering<br />Mechanical (with some biological)<br />Chemical (with some biological)<br />Weathering can reduce mountains to hills and boulders to pebbles. <br />
  3. 3. Mechanical Weathering<br />The breakdown of rocks without changing their chemical composition. <br />Fragments of parent rock formed without changing chemical composition. <br />Fragments have exact characteristics as parent rock.<br />Mechanical weathering is caused by many factors<br />Tree roots, ice expanding, crystal growth, lightning, expansion and contraction, heating and cooling, friction, and wind erosion. <br />
  4. 4. Plants and Animals (Mechanical Weathering)<br />Roots grow into cracks in rocks. <br />Start out thin as hair, then grow larger and larger. <br />Act as a wedge forcing rock to crack into pieces. <br />Example: Sidewalks buckling due to tree roots.<br />Animals burrowing increases weathering of soil. <br />Burrowing allows water and air to act on rock below the surface. <br />Animals also bring un-weathered materials to the surface where weathering occurs. <br />
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  7. 7. Ice Wedging<br />A natural process of breaking rocks down quickly. <br />Process:<br />Water seeps into the cracks of rocks/sidewalks<br />Water expands as it freezes. <br />Crack begins to widen. <br />More water is able to seep in and freeze.<br />Crack in rock widens even more. <br />The process repeats until pieces break off the parent rock. <br />
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  9. 9. Wind Action<br />Wind picks up dust particles. <br />These particles act as abrasives, wearing away rock surfaces. <br />Very similar to sand blasting. <br />
  10. 10. II. Chemical Weathering<br />Chemical Weathering is the process when water, air, or other chemicals wear away rocks and change their chemical composition. <br />Water is called the universal solvent. <br />Oxygen and hydrogen in water reacts with minerals. <br />The minerals change into much different compounds. <br />Example: Oxidation of Iron casues RUST<br />
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  12. 12. Acid (Chemical Weathering)<br />Acids react with minerals, usually dissolving them over time. <br />Acids form naturally in many ways. <br />Carbonic Acid forms from carbon dioxide and water (very weak acid) and wears away limestone to make caves. <br />Carbonic acid also wears away granite to make clay. <br />Sulfuric Acid: formed when sulfur and water combines to form a strong acid that can wear away marble and concrete. <br />Nitric Acid: (Strong Acid) produced by some plant roots and mosses; breaks down rocks and causes acid rain. <br />
  13. 13. pH Scale<br />The strength of acids and bases is measured by the pH scale. <br />Scale goes from 0 (extremely acidic) to 14 (extremely basic or alkaline)<br />7 is neutral on the scale (water)<br />Most minerals are more soluble in acidic soils than in neutral or slightly alkaline soils. <br />Different plants grow better in different soil types. <br />Peanuts grow better in soils with a 5.3 to 6.6 pH.<br />Alfalfa grows best in soils having a pH of 6.2 to 7.8<br />
  14. 14. Oxygen and Oxidation<br />Oxidation is the bonding of oxygen to other elements that changes the chemical composition. <br />Almost all elements oxidize. <br />Iron  Iron Oxide (Rust)<br />Aluminum  Aluminum Oxide white powder on window sills<br />Sulfur  Sulfur Dioxide- Acid Rain Most comes from power plants.<br />Copper Oxide – Turns copper green (Statue of Liberty)<br />
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  16. 16. III. Effects of Climate<br />Climate plays a big part in how quickly mechanical and chemical weathering occur. <br />Climate is the weather patterns for a given area over long periods of time. <br />Mechanical and Chemical Weathering occur everywhere. <br />
  17. 17. Cold Climate Weathering<br />Freezing and thawing cycles allow ice wedging to break down rocks quickly. <br />Warm/Wet Climate Weathering<br />Chemical weathering acts more quickly and occurs more often. <br />Dry Climate Weathering<br />Wind action is the prevalent form of weathering. <br />

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