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5. CHEMICAL WEATHERING DISSOLUTION Water removes ions or ion groups from a rock or mineral and carries them away. Precipitate later when water evaporates. Due to the bipolar nature of water molecules, ions become dissolved and are transported in solution. WEATHERING and the BREAKDOWN of ROCKS

6. CHEMICAL WEATHERING DISSOLUTION Halite Na + is attracted to OH - side of water molecules Cl - is attracted to the H + side of water molecules Water can also react with another compound to form an acid. H 2 O + CO 2 H 2 CO 3 (Carbonic acid) The acid can then decompose minerals. H 2 CO 3 + CaCO 3 Ca +2 + 2HCO 3 - (Bicarbonate) Removed by erosion WEATHERING and the BREAKDOWN of ROCKS Calcite

7. CHEMICAL WEATHERING DISSOLUTION Dissolution is the process by which caves are formed. Calcite is dissolved, Ca +2 and HCO 3 - end up in the ocean. Then removed from the ocean by marine organisms in the production of skeletal material. WEATHERING and the BREAKDOWN of ROCKS

8. CHEMICAL WEATHERING OXIDATION Positive ions in minerals combine with oxygen to produce oxides. 4Fe +3 + 3O 2 2Fe 2 O 3 (hematite) If the reaction takes place in water, limonite (FeOOH) is produced. Collectively called RUST. WEATHERING and the BREAKDOWN of ROCKS

9. CHEMICAL WEATHERING OXIDATION WEATHERING and the BREAKDOWN of ROCKS Also affects other metals such as copper.

10. CHEMICAL WEATHERING OXIDATION WEATHERING and the BREAKDOWN of ROCKS Oxidation has the same result with iron-rich rocks and minerals. Affects olivine, pyroxenes, amphiboles, gabbros and basalts.

11. CHEMICAL WEATHERING HYDROLYSIS WEATHERING and the BREAKDOWN of ROCKS H + and OH - ions in water displace other ions in a mineral structure producing a new mineral. Feldspars are readily changed by hydrolysis. 2KAlSi 3 O 8 + 2H + + 9H2O Al 2 Si 2 O 5 (OH) 4 + 4H 4 SiO 4 + 2K + Orthoclase Feldspar Kaolinite Silicic Acid

12. Hydrolysis of orthoclase, other feldspars and mafic minerals produces clays and clay minerals. Clays become incorporated in soils or wash to the sea by erosion. Dissolved materials produced can cement sedimentary grains Or, be utilized by plants (K + ). CHEMICAL WEATHERING HYDROLYSIS WEATHERING and the BREAKDOWN of ROCKS

13. So…… What are the factors that influence CHEMICAL WEATHERING?

14. FACTORS THAT INFLUENCE CHEMICAL WEATHERING WEATHERING and the BREAKDOWN of ROCKS CLIMATE Water drives all three reactions discussed. Heat also speeds reactions. Warm, humid climates are most suitable for chemical weathering reactions. Warm, humid climates also tend to have more plants. When plants die, decomposition increases the production of organic acids and increases chemical weathering.

15. FACTORS THAT INFLUENCE CHEMICAL WEATHERING WEATHERING and the BREAKDOWN of ROCKS LIVING ORGANISMS Mix up soil exposing more material to surface for weathering reactions.

16. FACTORS THAT INFLUENCE CHEMICAL WEATHERING WEATHERING and the BREAKDOWN of ROCKS TIME The longer a rock or mineral is exposed to weathering the more weathering takes place.

17. FACTORS THAT INFLUENCE CHEMICAL WEATHERING WEATHERING and the BREAKDOWN of ROCKS MINERAL COMPOSITION The effect of chemical weathering in rocks is related to the stability of the minerals in the rock. Since most rock-forming minerals are silicates, the strength of the bonds between the silica tetrahedra influences how they are weathered. The more silicon-oxygen bonds between the tetrahedra, the more resistant to weathering is the mineral.

18. WEATHERING and the BREAKDOWN of ROCKS

19. PRODUCTS OF CHEMICAL WEATHERING WEATHERING and the BREAKDOWN of ROCKS Or….What’s left after dissolution, oxidation and hydrolysis. Clay Minerals Produced by hydration of feldspars and mafic minerals (olivine, pyroxenes, and amphiboles).

20. PRODUCTS OF CHEMICAL WEATHERING WEATHERING and the BREAKDOWN of ROCKS CLAY MINERALS Type of clay formed depends on climatic conditions during hydrolysis. Kaolinite forms in warm, humid climates. Smectite forms in cool, dry climates. Uses of clay minerals: Agricultural fertilizersLubricants in oil drilling Bricks and cementPaper production Cat litterKaopectate Filtering impurities from beer and wine

21. PRODUCTS OF CHEMICAL WEATHERING WEATHERING and the BREAKDOWN of ROCKS METAL ORES Aluminum Forms from chemical weathering of feldspar- rich rocks in warm, humid climates. Leads to the concentration of aluminum in Bauxite (Al 2 O 3. nH 2 O).

22. PRODUCTS OF CHEMICAL WEATHERING WEATHERING and the BREAKDOWN of ROCKS SPHERIODAL WEATHERING Mechanical weathering breaks up rocks into smaller pieces. Chemical weathering rounds off corners.

23. SOILS AND SOIL FORMATION WEATHERING and the BREAKDOWN of ROCKS Mechanical and chemical weathering of sediment and pre-existing bedrock below produces REGOLITH. REGOLITH is all the material above the bedrock. SOIL is the upper part (up to a few meters) of regolith that supports plant life. Soil contains both mineral and organic matter (decaying vegetation). Soil also contains air and water.

24. SOILS AND SOIL FORMATION WEATHERING and the BREAKDOWN of ROCKS REGOLITH

25. SOILS AND SOIL FORMATION WEATHERING and the BREAKDOWN of ROCKS SOIL

26. INFLUENCES ON SOIL FORMATION WEATHERING and the BREAKDOWN of ROCKS PARENT MATERIAL The bedrock or sediment from which soil forms. Influences nutrient richness of the soil. Quartz-rich sandstone Basalt

27. INFLUENCES ON SOIL FORMATION WEATHERING and the BREAKDOWN of ROCKS CLIMATE Precipitation and temperature influence soil formation. Influences the rate of chemical weathering. Also influences plant growth. Soil formation is most rapid in warm, moist climates.

28. INFLUENCES ON SOIL FORMATION WEATHERING and the BREAKDOWN of ROCKS TOPOGRAPHY Physical features of the landscape. Influences the availability of water. Influences the rate of soil accumulation. Steep slope vs. gentle slope

29. INFLUENCES ON SOIL FORMATION WEATHERING and the BREAKDOWN of ROCKS VEGETATION Contributes organic matter to soil. Produces CO 2 and O 2 involved in chemical weathering. Plants contribute H + that helps weather soils. Aids in hydrolysis Degrades feldspars and other minerals into clay minerals. Clays increase nutrient supply to plants.

30. INFLUENCES ON SOIL FORMATION WEATHERING and the BREAKDOWN of ROCKS TIME The longer the time Earth materials are weathered, the thicker the soil produced.