CK12 Earth Science

(Marvins-Underground-K-12) #1
their daughter products are used to determine the age of rocks and organic remains.

Review Questions



  1. What four techniques are used to determine the absolute age of an object or event?

  2. A radioactive substance has a half-life of 5 million years. What is the age of a rock in
    which 25% of the original radioactive atoms remain?

  3. A scientist is studying a piece of cloth from an ancient burial site. She determines that
    40% of the original carbon-14 atoms remain in the cloth. Based on the carbon decay
    graph (Figure11.27), what is the approximate age of the cloth?


Figure 11.27: ( 21 )


  1. Which radioactive isotope or isotopes would you use to date each of the following
    objects? Explain each of your choices.
    (a) A 4 billion year old piece of granite.
    (b)A one million year old bed of volcanic ash that contains the footprints of hominids
    (human ancestors).
    (c) The fur of a woolly mammoth that was recently recovered frozen in a glacier.
    (d)A fossilized trilobite recovered from a bed of sandstone that is about 500 million
    years old.

  2. The principle of uniformitarionism states that the present is the key to the past. In
    other words, the processes that we see happening today probably worked in a similar

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