Geology

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Author:
lolita91
ID:
43839
Filename:
Geology
Updated:
2010-10-20 19:31:06
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Geology Geologic Time part
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Geology test 3
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  1. Determining the ages of rocks through their contained radioactive elements is known as
    ______________________ dating.
    isotopic dating or geochronology
  2. An isotope of a given element has the same atomic number as the element, but a different
    __________ ________________.
    atomic weight
  3. An isotope contains the same number of neutrons as the non-radioactive parent element. True
    or false
    false
  4. U-238 and U-235 are two naturally occurring isotopes of ____________________.
    uranium
  5. The spontaneous disintegration of the nuclei of an atom is called __________________
    ___________.
    radioactive decay or radioactivity
  6. The parent of the U-238/Pb-206 isotope system is ___________.
    U-238
  7. The daughter of the U-235/Pb-207 isotope system is ___________.
    Pb-207
  8. The time that it takes a given amount of a radioactive isotope to be reduced by one-half is called
    the isotopes ____________.
    half-life
  9. What is the name of the constant that reflects the rate at which a radioactive isotope decays per
    unit of time?
    decay constant
  10. The number of parent isotopes remaining at time t is what parameter in the equation N = No(e-
    t).
    N
  11. What is  in the equation N = No(e-t)?
    decay constant
  12. Given 100 atoms of an isotope, how many will be left after one half-life?
    50
  13. Given 100 atoms of an isotope, how many will be left after three half-lives?
    12.5
  14. What is the following equation called: t = (1/)(ln[(D/P)+1])?
    age equation or fundamental age equation
  15. What is D in the equation t = (1/)(ln[(D/P)+1])?
    amount of daughter product
  16. The amount of remaining original isotopic material is represented by what parameter in the
    equation t = (1/)(ln[(D/P)+1])?
    P
  17. What isotope system would you use to date a very young rock?
    C-14/N-14
  18. What isotope system would you use to date a Pleistocene tree trunk?
    C-14/N-14
  19. What isotope system would you use to date volcanic deposits containing a dinosaur?
    K-40/Ar-40
  20. Of the isotopic systems mentioned in this chapter which has the longest half-life?
    Rb-87/Sr-87
  21. Of the isotopic systems mentioned in this module which has the smallest half-life?
    C-14/N-14
  22. What kinds of rocks are found at Jack Hills, NW Australia and why are they significant?
    • Conglomerate. Detrital zircons were eroded, transported, and then deposited as part of the
    • conglomerate. A single detrital zircon was dated at 4.4 b.y. using the U-Pb method.
  23. Minerals such as K-feldspar, biotite, and hornblende all contain the element K. What isotopic
    system would you use to date these minerals?
    K-40/Ar-40
  24. What isotopic system would you use to date a crystal of zircon?
    U238/Pb206 or U235/Pb207
  25. What is the oldest material dated on planet Earth, and what is its age?
    Zircon, 4.4 b.y.
  26. Where is the oldest material dated on planet Earth?
    Jack Hills, NW Australia
  27. What and where is the oldest rock dated on planet Earth? What is its age?
    Acasta gneiss, NW Canada, 4.03 b.y.
  28. What mineral and isotopic system were used to date the oldest detrital crystal and rock on
    planet Earth?
    Zircon, U-Pb
  29. Can you date the age of the Earth from fossils?
    • No, the first evidence for life on Earth does not occur until the Archean. In other words, there
    • was no life on Earth until approximately 4.0 billion years ago. Without life there can be no fossils.

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