Soil Formation and Weathering

1. Soil Formation and Weathering CH 10 uvm.edu

2. It’s not just dirt? • Medium for plant growth (food, feed, fiber) • Mechanical support for living organisms • Regulates water flow (runoff, infiltration, storage, recharge) • Provides nutrients & cycles nutrients • Acts as filter (physical, chemical & biological)

3. How is soil formed? • Parent rock material breaks down into smaller and smaller pieces. • Pieces are changed chemically by weathering. • Weathering changes rock at deeper and deeper levels. • Eventually different layers or zones (horizons) are noticeable

4. Soil • Loose material at Earth’s surface capable of supporting plants with root systems • Mixture of: • Small mineral fragments • Decaying organic material • Water • Air • Organisms physicalgeography.net

5. Soil http://www.organicgardeninfo.com/soil.html

6. Soil food web From Miller’s Living in the Environment

7. Soil horizons • O horizon • Leaf litter • A horizon • topsoil • B horizon • subsoil • C horizon • parent material eoearth.org

8. Soil texture • Clay < .002 mm • Silt < .06 mm • Sand .06 mm – 2 mm http://140.254.84.203/wiki/index.php/Fines

9. Soil texture chart

10. How is soil formed? • Mechanical weathering • Breakdown of rocks into smaller pieces by physical means • Chemical weathering • Breakdown of rocks into smaller pieces by chemical reactions

11. Mechanical weathering • Ice • Abrasion • Wind • Water • Gravity • Plants • Animals

12. Chemical weathering • Water • Acid in rainwater • Acid in groundwater • Air

13. Soil types in different biomes From Miller’s Living in the Environment

14. Soil types in different biomes From Miller’s Living in the Environment

15. Tropical Rain Forest • Thin, nutrient poor soils • Heavy rains leach nutrients from soil • Plants use nutrients very rapidly, so few nutrients are in soil

16. Desert • Slow rate of chemical weathering, so soil created slowly • Salts build up because there is little water to dissolve them & wash away

17. Temperate forest & grassland • Much weathering occurs due to much rain • Freeze/thaw breaks apart rocks • Rain causes chemical weathering • Most nutrient rich soils in the world

18. Arctic • Chemical weathering occurs slowly due to little precip. • Soils occur slowly • Thin soil = few plants • Decomposition happens slowly due to cold

19. Soil Erosion • http://www.maine.gov/dep/blwq/doceducation/dirt.htm http://www.otsego.org/conservationdistrict/erosion.htm

20. Erosion in Africa is widespread http://www.shef.ac.uk/research/stories/engineering/27.html

21. Soil erosion • Overused soils > fewer nutrients > fewer plants > exposed soils > wind & water carry away soil > people go hungry • Desertification = land degradation = areas that are now unable to support crops

22. Stream side erosion • http://www.newechotarivers.org/about-the-oostanaula/ecological-threats http://www.newechotarivers.org/about-the-oostanaula/ecological-threats

23. Soil Conservation • Contour plowing http://teachers.sduhsd.k12.ca.us/hherms/herms/GEOLOGY/conservation/desertification.htm

24. Soil Conservation • Buffers along streams http://www.treehugger.com/files/2010/10/the-global-battle-to-conserve-and-rebuild-soil.php

25. Soil Conservation • Terracing http://factoidz.com/terracing-an-environmentfriendly-agricultural-approach/

26. Satellite image of circular crop fields characteristic of center pivot irrigation in Kansas (June 2001). Healthy, growing crops are green. Corn would be growing into leafy stalks by late June. Sorghum, which resembles corn, grows more slowly and would be much smaller and therefore, possibly paler. Wheat is a brilliant gold as harvest occurs in June. Fields of brown have been recently harvested and plowed under or lie fallow for the year.

27. Vermicompostingturning kitchen scraps to soil • http://kids.niehs.nih.gov/worms.htm

28. Homework • Read pages 278 - 297

29. Output • Soil horizons activity