Parent Decay and Daughter Growth Curves Radiocarbon Dating Dating Rocks with the Rb-Sr "Isochron" Method Getting a Rock Sample Ready for the Mass Spectrometer A Mass Spectrometer is used to Measure Isotopic Ratios A numerical (or "absolute") age is a specific number of years, like 150 million years ago.
For example, decay of the parent isotope Rb-87 (Rubidium) produces a stable daughter isotope, Sr-87 (Strontium), while releasing a beta particle (an electron from the nucleus).
("87" is the atomic mass number = protons + neutrons.
Numerical ages have been added to the Geologic Time Scale since the advent of radioactive age-dating techniques. In theory, the age of any of these minerals can be determined by: 1) counting the number of daughter isotopes in the mineral, and 2) using the known decay rate to calculate the length of time required to produce that number of daughters.
It illustrates how the amount of a radioactive parent isotope decreases with time. For example when 42% of the parent still remains, 1.23 Half-Lives of time has passed.
This amount is a percentage of the original parent amount. Parent Decay and Daughter Growth Curves The half-life of U-235 decaying to Pb-207 is 713 million years.