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Weathering

Prepared by: Rana Faizan Saleem BS-Applied Geology Institute of Geology, Universty of The Punjab. Weathering. Is to explain you about: What is Weathering? Agents of Weathering Types of Weathering Types of Mechanical Weathering Types of Chemical Weathering

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Weathering

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  1. Prepared by: RanaFaizanSaleem BS-Applied Geology Institute of Geology, Universty of The Punjab Weathering

  2. Is to explain you about: • What is Weathering? • Agents of Weathering • Types of Weathering • Types of Mechanical Weathering • Types of Chemical Weathering • Factors that Effects rate of Weathering Aim of This Presentation

  3. Weathering is the Physical and Chemical breakdown of pre-existing rocks into small particles , called sediments. Weathering

  4. Water • Wind • Ice • Gravity Agents of Weathering

  5. There are following types of Weathering: • Mechanical Weathering • Chemical Weathering Types of Weathering

  6. The Physical breakdown of rocks into sediments, but their Chemical composition does not change. Mechanical Weathering

  7. Frost Wedging • Salt Wedging • Exfoliation • Frost Heaving • Organic Activity • Abrasion Types of Mechanical Weathering

  8. When water peels into the cracks of rocks, it freezes and causes the rock to crack. Frost Wedging

  9. This occurs when rain water fills cracks in rocks; then water evaporate and with the passage of time salt crystals grow into cracks and expands,finally break the rocks. Salt Wedging

  10. When a rock has heat exerted upon it, along with pressure, it separates into layers. It is also called Onion Skin Weathering because rock layers separate like onion layers. Exfoliation

  11. Upward or Vertical movement of soil due to freezing of water in soil. Frost Heaving

  12. Organic weathering is the breakdown of rocks by plants or animal action or by chemicals formed from plants and animals. Organic Activity

  13. Abrasion occurs when rocks rub against each other and become rounded. Abrasion

  14. The process by which rocks break down into sediments and their chemical composition will also changed. Chemical Weathering

  15. Hydrolysis • Oxidation • Carbonation • Hydration • Reduction • Acid Rain • Plant Acid Types of Chemical Weathering

  16. When rocks sit in water for extended periods of time they begin to break down and have a clay-like texture. 2KAlSi3O8+ 2H+ + H2O → Al2Si2O5(OH)4 +2K +4SiO2 (Orthoclase)(Kaolinite) Hydrolysis

  17. When oxygen reacts with iron in rocks, they rust, and change the compositon. • 4FeO (Ferrous oxide) + O2    2Fe2O3 (Ferric oxide) • 4Fe3O4 (Magnetite) + O2      6Fe2O3 (Hematite)  • 2Fe2O3 (Hematite) + 3H2O   2Fe2O3 .3H2O (Limonite) Oxidation

  18. The carbon dioxide dissolved in water forms carbonic acid that reacts with many common minerals.e.g Limestone and Calcite. • CO2 + H2O  H2CO3 carbonic acid • H2CO3 + CaCO3Ca++ + 2HCO3- (bicarbonate ions) Carbonation

  19. The process of removal of oxygen and is the reverse of oxidation is called Reduction. i. 2Fe2O3  4FeO + O2 (Hematite) ( Ferrous oxide) Reduction

  20. Chemical combination of water molecules with a particular substance or mineral leading to a change in structure. • Al2O3 + 3HOH   Al2O3 .3H2O (Bauxite)              (Hyd. aluminium Oxide) • CaSO4 + 2H2O    CaSO4 .2H2O (Anhydrite)(Gypsum) Hydration

  21. Water in the atmosphere absorbs sulfur oxides and nitrogen oxides and forms Sulfuric Acid and Nitric Acid which falls in the form of rain on earth called Acid Rain. • It changs the composition of minerals and rocks. Acid Rain

  22. Plant Acid- When plants decay they release acids that react with the minerals in rocks. Plant Acid

  23. Climate • Rock Composition • Surface Area Factors that affecting rate of Weathering

  24. Weathering occurs fastest in hot, wet climates. It occurs very slowly in hot, dry climates. Without temperature changes, ice wedging cannot occur. In very cold, dry areas, there is little weathering. Climate

  25. Some minerals resist weathering. Quartz is a mineral that weathers slowly. Rocks made up of minerals such as feldspar, calcite, and iron, weather more quickly. Rock Composition

  26. The more surface area a rock has, the more quickly it will weather. • When a block is cut into smaller pieces, it has more surface area. So, therefore, the smaller pieces of a rock will weather faster than a large block of rock Surface Area

  27. Thank You For Your Attention

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