Correct Response: A. Radiometric dating techniques, including those used to date lava flows, compare the amount of radioactive parent isotope to the amount of stable daughter product in a sample of the rock. Radioactive decay of a particular isotope into its daughter products occurs at a known rate called the isotope's half-life. Once the lava flow has cooled, radioactive isotopes are locked into the crystal structure and the daughter products begin to build up in the rock. Measuring the lava's radioactivity (B) or measuring alpha and beta particle emissions and the change in the isotope's atomic number (D) do not provide an age estimate tool because the amount of isotope originally in the rock is unknown and the amount of radioactive material in the rock may be extremely small. Ionizing radiation can alter the composition of a rock (C) and this fact is used in thermoluminescence dating, but not radiometric dating.
