Thursday, April 8th, 1999

Announcements: none

Lecture notes:

I. Overview
    A. To have sedimentary rocks, you need water
    B. Sedimentary rocks are deposited (or formed) underwater
    C. Sedimentary rocks tell us about:
            1. Paleo-environment
            2. Animals, plants
            3. Temperature

     D. Topography
            1. "Source area"--what was eroding
            2. Old mountains

II. Kinds of sedimentary rocks
    A. Shale ----->
    B. Sandstone ---->                *grain size varies so it tells you the energy of transport
    C. Limestone
    D. Conglomerate ---->
    E. Moraines (glacial) ---->
    F. Point bar (fluvial)---->  *depositional environment
    G. Deltas----->

III. Neptunism and Plutonism
    A. 18th century
            1. No global fossil record
            2. No magnetic dating
            3. No radiometric dating
            4. Poor global communication

    B. Prussian A. Werner
            1. His goal was to find order to the rock system
            2. So he developed the first classification scheme for minerals (this was used for the past 200 years)
            3. First stratigraphy (making sense of layers) for the world
            4. His classification for the world:
                    a. Granites, gneisses (oldest rocks)
                    b. Limestone (many continental margin sediments)
                    c. Chalk, limestone (most sediment)                   --------> *based entirely on superposition and relative age
                    d. Unconsolidated (ex. Death Valley, alluvial fans)
                    e. Volcanics (youngest rocks)
 
    C. Neptunism (said the is young; Werner's model to make sense of the rocks; this theory was popular for at least 100 years)
            1. Water is an extremely important agent in the scheme of rocks

            2. Sedimentary rocks needs water, granites do not therefore if granites are the oldest rocks then there wasn't
            any water on early earth

            3. His theory was that the "Great Flood" brought water which then left all of the sedimentary rocks; he said
            "Great Flood" occurred within the past 200 years, very recently

    D. Pliny (AD 79)
            1. Brought up the idea that basalt was hot and that it came from the center of the earth

            2. He was the "grandfather" of Plutonism

            3. Agreed that granite was the first and most important rock

    E. Hutton
            1. First to popularize the idea of earth's internal heat

    F. Charles Darwin
            1. First to take the ideas of uniformitarianism and Neptunism and try and see which one was correct and more
             reasonable

            2. Calculated the age of the earth to be 300 million years old based upon erosion rates (this calculation was not
            openly accepted)

    G. Phillips
            1. Calculated the age of the earth to be 96 million years old based upon deposition rates

    H. Lord Kelvin
            1. He was an expert on the conduction of heat and wrote about this in 1862

            2. He was not in favor of "eternity" and assumed all energy on earth was of gravitational origin

            3. He believed there were no internal sources of heat within the earth

            4. He did believe in a meteoritic accretion model

            5. His first calculation of the age of the earth came out to be 98 million years old or in the range of 20-400
            million years

    I. At approximately 1900, Pierre and Marie Curie discovered that radioactive elements release heat therefore the
    conclusion was that the earth produces its own heat and therefore Kelvin was wrong

    J. At approximately 1911 the first radiometric dating was used

    K. At approximately 1930 scientists had the first believable dates on rocks and finally decided that the earth was
    greater than 1 billion years old