Tuesday, March 30th, 1999
Announcements:

Lecture notes:

• Example questions on the exam: 
  Describe where the Badlands fall on the rock cycle.
              answer: sedimentation
  
  Give an example of mechanical weathering in a glacial environment
              answer: mechanical weathering due to water melting and flowing

I. Themes for Exam II
    A.Collisional mountains--normal outcome of subduction; when continents passively move along with the ocean crust
    (ex. Australia, Japan)

    B.Metamorphism--growth of new minerals; change in minerals of any rock; bonds breaking and forming due to thermal
    reactions; diffusion of chemical species that form new minerals

    C. Weathering
            1. Mechanical weathering (physical weathering)
                    a. Physical break-up of rock; needs water because it's the only compound that has a change in volume
                    when it freezes and therefore it forces and splits apart rocks in low temperatures
 
                    b. Crack expansion caused by plants and roots; roots split the rock apart
 
            2. Chemical weathering--the making of new minerals by any chemical process
                    a. Hydrolysis--chemical breaking apart of rock by water; gradual replacement of unstable materials by
                    stable ones

                    b. Acid-enhanced--a little faster today than in earlier years; any acid speeds up the process of weathering

    D. Mass wasting--sediment transport; rapid transport of unconsolidated material (ex. landslide, Gros Ventre Landslide)

    E. River processes

    F. Deltas
 
    G. Floods

    H. Groundwater
            1. Karst
                    a. Groundwater you get when water flows through cracks in caves
                    b. It's an area where ground water flows through caves
                    c. Series of erosional features caused by water that can only occur in calcium carbonate rocks (ex.
                    limestone)
                    d. Forms through pre-existing cracks
 
            2. Aquifer
                    a. An underground well
                    b. An underground layer of sand, gravel, porous rock, etc. that holds ground water

            3. Conductivity--the speed at which water flows through a certain mineral (ex. shale has a low conductivity)

    I. Uniforitarianism--uniform, slow processes that occur everyday; rivers carrying sediments (ex. plate tectonism is
    uniforitarian)

    J. Catastrophism--every once in awhile there is a huge earthquake, volcano, etc. that causes a huge change in
    geography and/or topography; in the later part of the 18th century, this was the principle way of thinking

    K. Atmospheric chemistry--(know the problem set data dates for CO2 at Mauna Loa)

    L. "The Rock Cycle" (refer to March 4th notes for diagram)

II. Miscellaneous
    A. How were the Rockies formed?
            1. The Rockies are the only mountain range in the world that didn't form at the margin of a continent

            2. Rockies are special in two (2) ways
                    a. Rockies consist of little fragments of sediment

                    b. For 200 millions years it's been warm near the California coast, very much like the asthenosphere
                    therefore nothing could fracture and break and form mountains; all the stress was directed at the land so
                    the mountains formed where they were closest to area where they could fracture--->the Rockies present
                    location today

    B. Point Bar--place within a meandering river where sediment is deposited; sediment deposited in river meanders
    (the inside curve of the river)

    C. Proto-Atlantic--an ocean that existed where the Atlantic Ocean is presently but it consisted of totally different
    sediments and rocks

    D. Plastic flow/creep
                1. Glaciers usually move in the direction that the surface slopes (usually downhill)
                2. The weight of the glacier makes it move; large masses "want" to move downhill
                3. If the glacier comes within 20% of its melting temperature the bonds begin to move and loosen and the
                glacier then begins to move

    E. Sediments
                1. Glacial sediments--involve only mechanical weathering; not characterized by size
                2. River sediments--carry sediments and are sorted by size; chemical and mechanical weathering involved

    F. Diagenesis--first step of lithification; first step of taking sediment towards rocks; "cementation" (individual pieces
    of sediment get "glued" to each other)

    G. Why is Happy Valley older than the original data calculated?
                1. The original calculation was only the amount of sandstone missing from the top of the mountain to the
                bottom of the valley
 
                2. BUT the top sandstone wasn't the "top" of the mountain; there was a higher point before it was measured

    H. Mississippi River (know the junctions between all of the major rivers; know deltas and time scales of deltas)
                1. Crevasse splay--it's a break in the river; an artificial levee

    I. Continental collision--when continents collide; once the continents collide it thickens the continental crust by
    moving a large quantity of rock on top of other rock

 
    J. Folding instead of Faulting
            1. Folding occurs at higher temperatures than faulting
            2. SO, it happens below the earth's surface
            3. SO, they deform instead of break