An hourglass is a helpful analogy to explain how geologists calculate the ages of rocks.When we look at sand in an hourglass, we can estimate how much time has passed based on the amount of sand that has fallen to the bottom.It is mainly determined by the uranium distribution in rocks of a water-bearing complex.Therefore, the uranium isotope ratio serves as some kind of natural indicator of water of a certain water-bearing complex.The amount of time required for half of a given quantity of a parent radioactive element to decay into the daughter product is referred to as the half-life.
The values of the radiogenic isotopes in waters are practically independent of chemical factors.
Statistical probablity is the only thing we can know exactly.
Often students get bogged down in the fact that they don't "understand" how and why radioactive elements decay and miss the whole point of this exercise.
Therefore using measured decay constants and the rate at which radionuclides decay, geochronologists can harness this relationship to calculate the amount of time that has passed since an assumed volume of material began accumulating radiogenic material.
The rate at which radioactive elements decay is governed by the exponential decay constant.
Radioisotope geochronology in its present form is made possible by radioactive decay.