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Absolute dating of rocks

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  • Absolute dating of rocks

    Relative dating was developed by early geologists in the 18th century.
    Although they had no way to measure the exact age of a rock, they were able to figure out by simple observation that some rocks were higher or lower on the geological column that others.
    From this they were able to deduce that the lower rocks were generally older than the higher rocks.
    They also observed that certain fossils were found in certain layers, and were not found in other layers. These fossils were useful for determining the relative age of sedimentary rocks, so they came to be called "index fossils".
    Although these index fossils were useful for determining if a layer was formed in the mid jurasic, or the early permian, they could not tell anyone the actual age of the layers in question.
    Nobody knew whether the cretaceous era was five million years ago, or ten million years ago.

    In the late 19th century Lord Kelvin devised an experiment to try to calculate the age of the earth.
    Kelvin's experiment set the age of the earth at between 100 million years old, and 105 million years old.
    His results were astonishing. Until then, geologists had placed the age of the earth at about 50 to 60 million years old.
    Of course Kelvin's experiment rested on one assumption... that there was no new heat being produced inside the earth.
    The discovery of radioactivity changed all that. And pushed the Earth's age back into the billions of years.

    The discovery of radioactivity by physicists in the very late 19th century, allowed geologists to discover the absolute age of a particular rock. Thus was born absolute dating.
    The only assumption made with absolute dating by radioactive decay... is that American capitalist physicists, and Soviet communist physicists, are not collaborating in a bizzare international conspiracy.
    It is by absolute dating by radioactive decay that we are able to know how old the index fossils, and the rock they are in, are.

    When paleontologists claim that a fossil is XYZ years old, they are not taking a wild guess. they are basing the age on index fossils in the same layer as their fossil. Index fossils of KNOWN age. Of course this is not perfect. It only gives a ballpark figure. For more precise dates paleontologists still send samples to physicists to be tested.
    When evil is powerful, good men are silenced.

  • #2
    Exactly! I copied the following from the September 2001 issue of National Geographic.

    Isotopic techniques:

    a Uranium to Lead (minerals), 1 million to 4.5 billion years.

    b Rubidium to Strontium (minerals), 60 Million to 4.5 billion years.

    c Potassium to Argon (minerals), 10000 to 3 billion years.

    d Uranium series disequilibrium (minerals, shell, bone, teeth, coral), 0 to 400,000 years.

    e Carbon 14 (minerals, shell, bone, teeth, water), 0 to 40,000 years.

    Radiation Exposure techniques:

    a Fission Track (Minerals, natural glass), 500,000 to 1 billion years

    b Thermoluminescence (Minerals, natural glass), 0 to 500,000 years

    c Electron Spin Resonance (Minerals, tooth enamel, shell coral), 1,000 to 1 million years.

    Other techniques:

    a Geomagnetic polarity timescale (minerals), 780,000 to 200 million years.

    b Amino Acid racemization (shells, other bicarbonates), 500 to 300,000 years.

    c Obsidian hydration (natural glass), 500 to 200,000 years.

    d Dendrochronology (tree rings), 0 to 12,000 years.

    e Lichenometry (lichens), 100 to 9,000 years.

    "Life is not measured by the number of breaths we take, but by the moments that take our breath away"


    • #3
      The silence of the creationists
      When evil is powerful, good men are silenced.