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HCDE-LPI Workshop on Sedimentary Processes

HCDE-LPI Workshop on Sedimentary Processes. Good Morning!!. Weathering…. Let’s break it down…. 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

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HCDE-LPI Workshop on Sedimentary Processes

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  1. HCDE-LPI Workshop onSedimentary 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 Examples? University of Georgia

  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 Location Type Fatalities • 1916 It/Aust Landslide 10,000 • 1920 China Earthquake triggered landslide 200,000 • 1945 Japan Flood triggered landslide 1,200 • 1949 USSR Earthquake triggered landslide 12-20,000 • 1954 Austria Landslide 200 • 1962 Peru Landslide 4,000-5,000 • 1963 Italy Landslide 2,000 • 1970 Peru Earthquake related debris avalanche 70,000 • 1985 Columb Mudflow related to volcanic eruption 23,000 • 1987 Ecuador Earthquake related landslide 1,000 • 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. http://www.geo.duke.edu/geo41/wea017.gif Chemical Weathering Along Joints….. Where the Water Goes ….. Spheroidal Surfaces

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

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

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

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

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