1. Weathering and Soils (ch.3): Week 5, Friday; September 26, 2014

2. Kaolinite http://mineral.esci.umn.edu/node/1182 Illite http://sunbio.my/?page_id=121 Vermiculite http://www.vermiculite.org/what_is_vermiculite.php

3. Clay Minerals Building block: Si Tetrahedra SiO 4

4. Clay Minerals Building block: Al Octahedra Al(OH) 6

5. Clay Minerals SiSi O Al OH Octahedral Layer Tetrahedral Layer Dominantly formed by hydrolysis and hydration

6. Clay Minerals

7. http://faculty.yc.edu/ycfaculty/ags105/week08/soil_colloids/soil_colloids_print.html Scanning Electron Microscope (SEM) image of Kaolinite

8. http://greenfieldgeography.wikispaces.com/IGCSE+and+GCSE+Weathering Hydrolysis: H + replaces a cation in a mineral 4KAlSi 3 O 8 + 4H + + 2H 2 O  4K + + Al 4 Si 4 O 10 (OH) 8 + 8SiO 2 Weathering granite forms “grus” Potassium feldspar Kaolinite (clay) Formation of Clay Minerals via Weathering

9. Clay Minerals and Progressive Weathering O T T O T T Cations O T T O T T Weathering O T O T O O

10. Clay Minerals Why are clay minerals so important on Earth’s surface?

11. Clays exhibit “shrink-swell” behavior because of their ability to hold water Clay Function #1: They Hold Water!

12. Cation Exchange: Exchange of cations between minerals and solutions http://www4.uwsp.edu/geo/faculty/lemke/geomorphology/ Commonly exchanged cations: H +, K +, Na + Ca 2+, Mg 2+ Al 3+ Clay or organic compound Clay or organic compound http://elements.geoscienceworld.org/content/6/6/375/F2.expansion.html Clay mineral Exchangeable cations Clay Function #2: They Hold Nutrients!

13. Beware: “Clay” versus “Clay” …or to a specific grain size (<2μm) Exchangeable water or cations versus “Clay” can refer to a specific family of minerals…

14. Soil Profiles O A E B C

15. Soil Development http://thegrowingseason.wordpress.com/2013/05/10/soils-management-the-old-jar-test/

16. Description of Soil Pit on Huntington River Terrace #X Names 0 cm 100 cm 50 cm 25 cm 75 cm O A E B C A Horizon (x – x cm): Describe here…. Use this for a gradational transition Use a dashed line for a more diffuse contact… … and use a solid line for a more defined contact