A solidified lava flow containing zircon mineral crystals is present in a sequence of rock layers that are exposed in a hillside. A mass spectrometer analysis was used to count the atoms of uranium-235 and lead-207 isotopes in zircon samples from the lava flow. The analysis revealed that 71% of the atoms were uranium-235 and 29% of the atoms were lead-207. Required:
a. About how many half-lives of the uranium-235 to lead-207 decay pair have elapsed in the zircon crystals?
b. What is the absolute age of the lava flow based on its zircon crystals? Show your calculations.
c. What is the age Of the rock layers beneath the lava flow?
d. What is the age Of the rock layers above the lava flow?