Tuesday, March 16th, 1999

Announcements: Everyone has the opportunity to hand in 2 extra credit assignments before April 15th. Additional resources for extra credit are located at http://landslides.usgs.gov/htm_files/nlicsun.html; http://geohazards.cr.usgs.gov; http://www.usgs.gov/themes/flood.html. There will be a review session for the upcoming exam (April 1st) in class on Tuesday March 30th. There will be no out of class review session.

Lecture notes:

I. Exam #2 preview
    A. Topics (book topics)
            1. Rockies
            2. Appalachians
            3. Badlands
            4. Gros Ventre
            5. Mississippi River and delta
            6. Mammoth Cave
            7. Glacier National Park

    B. Themes
            1. Continental collision
            2. Erosion/weathering
            3. Transport of sediment
            4. Rivers
            5. CO2 at Mauna Loa
            6. Karst (will be disgusted in upcoming lectures)
            7. Rock cycle

II. Water (review of notes from March 4th)
    A. Agent of chemical weathering (polarized molecule)

    B. Agent of transport
 
    C. Agent of erosion

III. Rivers
    A. Meandering (wander)

    B. Braided

   C. River behavior
            1. Focus on "mature" rivers, not mountain streams
 
            2. "Mature" rivers run through low gradient, nearly flat topography

            3. Nearly all rivers in this kind of area will meander or "wander"

    D. Which directions do rivers flow?
            1. Always downhill

            2. They do not always flow from north to south
 
    E. Levies--natural borders of a river; all rivers have natural levies

    F. "Oxbow Lake"--when a river changes its channel and abandons its old course

    G. Wind gap--when a river stops flowing in its regular course; the river found a new path

IV. Miscellaneous
    A. How do sedimentary rocks form?
            1. Suspended (sediment floating in water) sediment

            2. Sediment deposited from suspension (settles to the bottom when water stops moving)

            3. After a long period of time passes, sediment compacts under its own weight (compaction)

            4. "Cementation" or diagenesis (individual pieces of sediments get "glued" to each other)

            5. Lithification (cement comes from within pore fluid)

    B. The entire process takes about 1-10 million years