1. HCDE-LPI Workshop on Sedimentary Processes Good Morning!!

2. Weathering… Let’s break it down…

3. Weathering Chemical and physical alteration of rock and minerals when exposed to air, moisture, and organic matter –Chemical weathering - minerals in a rock are chemically altered or dissolved –Physical weathering - solid rock fragmented by mechanical breaking University of Georgia Examples?

4. What Controls the Rate of Weathering? Parent Material (minerals and structure) Climate (rainfall and temperature) Biology Slope Presence / Absence of Soil Exposure Time

5. Chemical Weathering Chemical weathering - minerals in a rock are chemically altered or dissolved Minerals weather at different rates because of differences in chemical stability; the resistance of a mineral to change

6. Which Minerals are More Stable? Less?

7. Our Hero Bowen & His Reaction Series Skinner and Porter, 1992

8. Physical Weathering Physical weathering - solid rock fragmented by mechanical breaking Factors affecting: –Slope –Zones of weakness - joints –Organisms - flora (and fauna) –Freeze/thaw (frost wedging) –Crystal growth –Heat / Cold

9. Slope Things move downhill …. Why? Gravity aids in the breakdown and transport of material Slope starts it all!

10. Mass Movements (Mass Wasting) Mass movement is the down slope movement of earth materials under the influence of gravity www.physicalgeography.net

11. Rock Mass Movements Fall - fast; rocks break and fall www.physicalgeography.net

12. www.geology.com

13. Rock Mass Movements Slide - (land slide) moderate; rocks slide as a unit Source: USGS

14. Unconsolidated Mass Movements Creep - very slow flow downhill; top moves faster than base Source: North Dakota State University

15. Unconsolidated Mass Movement Slump - moderate; slide of material as a unit along a lower surface (spoon-shaped)

16. Why Do We Care? Human Impacts of mass wasting … Year LocationTypeFatalities 1916It/AustLandslide10,000 1920 ChinaEarthquake triggered landslide200,000 1945 JapanFlood triggered landslide1,200 1949 USSREarthquake triggered landslide12-20,000 1954 AustriaLandslide200 1962 PeruLandslide4,000-5,000 1963 ItalyLandslide2,000 1970 PeruEarthquake related debris avalanche70,000 1985 ColumbMudflow related to volcanic eruption23,000 1987 EcuadorEarthquake related landslide1,000 In a typical year in the United States, landslides cause over $1.5 billion in damages and 25 to 50 deaths http://www.tulane.edu/~sanelson/geol204/masswastproc.htm

17. Joints http://www.geo.duke.edu/geo41/st045.gif

18. http://www.geo.duke.edu/geo41/wea017.gif

19. Chemical Weathering Along Joints ….. Where the Water Goes ….. http://www.geo.duke.edu/geo41/wea017.gif Spheroidal Surfaces

20. http://www.geo.duke.edu/geo41/wea003.gif Roots and Critters

21. Crystal Growth http://www.geo.duke.edu/geo41/wea001.gif

22. http://www.usd.edu/esci/figures/150651.JPG Frost Wedging

23. In what environments will chemical weathering be greatest? Physical?