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    Question about geologic column

    I have a question about the geologic column. And a radio metric dating. Why do we get older dates for rocks on the bottom of the column and younger ones at the top if the soil composing these layers is simply material blown or washed from other places and these layers are composed of atoms that go back to the beginning whenever it was anyway. Thanks

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    Quote Originally Posted by BH View Post
    I have a question about the geologic column. And a radio metric dating. Why do we get older dates for rocks on the bottom of the column and younger ones at the top if the soil composing these layers is simply material blown or washed from other places and these layers are composed of atoms that go back to the beginning whenever it was anyway. Thanks
    Not all atoms "go back to the beginning". That's exactly the basis of radio dating. If we find a lot of thorium in places where due to their chemical properties we only expect uranium, we conclude that it used to be uranium when the rock formed.

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    Please be my friend and explain in more detail. Are you saying we should find older elements in only older strata and younger elements only in the top strata,assuming there has been no shifting due to faulting, one section of rock being pushed under another,ect.

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    Quote Originally Posted by BH View Post
    Please be my friend and explain in more detail. Are you saying we should find older elements in only older strata and younger elements only in the top strata,assuming there has been no shifting due to faulting, one section of rock being pushed under another,ect.
    Dating of a rock sample is determined by the ratio of radioactive elements to their decay products. For example, basalt is cooled lava. Any U235 in the rock will be fixed in the matrix. As time passes the Uranium will continually decay building up an increasing amount of lead associated with the remaining U235. Since we know the half life of Uranium, the ratio of U235 to associated lead can tell us how long ago the lava flow cooled to form solid basalt.


    ETA:
    Here's a Wiki article that likely explains it a bit better:
    https://en.wikipedia.org/wiki/Radiometric_dating

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    Uranium turns into Thorium. What element did the Uranium used to be?

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    Elements heavier than Hydrogen and some Helium up to Iron were created by fusion in a star's core. Uranium and all elements heavier than Iron were created in a supernova explosion. This explosion scattered the elements into space to become interstellar gas clouds (nebula) which were mostly hydrogen but included the higher elements created by the star and subsequent supernova. A section of this gas cloud eventually collapsed under mutual gravity to become our solar system, including the Earth.

    So the Uranium we see today was created through several fusion steps by a massive star that went supernova starting from hydrogen.

    ETA:
    Here's a short description of nucleogenesis, the process of the creation of the elements:
    http://www.dynamicscience.com.au/tes...eogenesis.html
    Last edited by skepticalbip; 10-16-2019 at 05:47 AM.

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    Quote Originally Posted by BH View Post
    I have a question about the geologic column. And a radio metric dating. Why do we get older dates for rocks on the bottom of the column and younger ones at the top if the soil composing these layers is simply material blown or washed from other places and these layers are composed of atoms that go back to the beginning whenever it was anyway. Thanks
    Dating sedimentary rock doesn't produce information that is of much use most of the time.

    Quote Originally Posted by BH View Post
    Uranium turns into Thorium. What element did the Uranium used to be?
    It was created in a supernova or a neutron star. On Earth it's primordial. It's just long enough lived that some of it is still around.

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    If all the uranium came from a supernova several billion years ago why does it show different ages in the various rock strata.

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    Quote Originally Posted by BH View Post
    If all the uranium came from a supernova several billion years ago why does it show different ages in the various rock strata.
    It isn't uranium that is used to date rock. It is the ratio of the amount of uranium with respect to the amount of its associated decay products locked in the rock matrix around it.

    There is no way to tell how old a sample of uranium is unless all its decay products are kept with it so a ratio of the two can be measured..
    Last edited by skepticalbip; 10-17-2019 at 04:10 AM.

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    Quote Originally Posted by BH View Post
    I have a question about the geologic column. And a radio metric dating. Why do we get older dates for rocks on the bottom of the column and younger ones at the top if the soil composing these layers is simply material blown or washed from other places and these layers are composed of atoms that go back to the beginning whenever it was anyway. Thanks
    Quote Originally Posted by BH View Post
    Uranium turns into Thorium. What element did the Uranium used to be?
    Quote Originally Posted by BH View Post
    If all the uranium came from a supernova several billion years ago why does it show different ages in the various rock strata.
    Radioactive material does not reveal a date. Rather, it's the ratio of the material to other material in the sample that gives the date. In most cases this is the radioactive material and it's decay product, but you also see things like carbon dating that are based on a known original ratio (the ratio of C-14::C-12 when the material was laid down) and seeing what the ratio is now. We typically identify radioisotope dating methods by naming only the radioisotope, but that doesn't mean it uses only the radioisotope.

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