Radiometric dating Knowledge-Based Download PDF

Questions

1. 1.

   In the context of radiocarbon dating, by which nuclear reaction is carbon-14 continuously produced in Earth's upper atmosphere?

   • A) Capture of a cosmic-ray neutron by a nitrogen-14 nucleus accompanied by proton emission
   • B) Positron emission by an atmospheric carbon-13 nucleus induced by solar ultraviolet radiation
   • C) Capture of an alpha particle by an oxygen-16 nucleus accompanied by neutron emission
   • D) Spontaneous beta-minus decay of an atmospheric nitrogen-14 nucleus in the stratosphere
2. 2.

   In the radiometric dating of an igneous rock, what event corresponds to the initialization of the radiometric clock ($t = 0$)?

   • A) The initial formation of Earth's crust during planetary accretion
   • B) The cooling and crystallization of magma into solid mineral grains
   • C) The attainment of secular equilibrium between parent and daughter isotopes
   • D) The complete decay of all primordial radioactive isotopes in the melt
3. 3.

   During the thermal metamorphism of an igneous rock, gaseous daughter isotopes escape from the mineral lattice while the parent radioactive isotopes remain trapped. What is the effect of this daughter isotope leakage on a subsequent radiometric age determination of the mineral?

   • A) The calculated age will be older than the true crystallization age.
   • B) The nuclear half-life of the remaining parent isotope will increase.
   • C) The decay constant of the parent isotope will decrease due to elevated temperature.
   • D) The calculated age will be younger than the true crystallization age.
4. 4.

   Which isotope decay system is most suitable for determining the absolute age of an igneous rock formation estimated to be over one billion years old?

   • A) Uranium-238 decaying to lead-206
   • B) Carbon-14 decaying to nitrogen-14
   • C) Tritium (hydrogen-3) decaying to helium-3
   • D) Phosphorus-32 decaying to sulfur-32
5. 5.

   A sample of wood recovered from an ancient fire pit contains 12.5% of the carbon-14 concentration found in living organisms. Given that the half-life of carbon-14 is 5,730 years, what is the estimated age of the wood sample?

   • A) 5,730 years
   • B) 11,460 years
   • C) 17,190 years
   • D) 22,920 years