Potassium argon dating wiki
Radiometric dating utilizes the decay rates of certain radioactive atoms to date rocks or artifacts.
Uniformitarian geologists consider this form of dating strong evidence that the Earth is billions of years old.
The proportion of argon to radioactive potassium in the sample today is observable, and the decay constant of potassium is readily calculable by measuring the amount of argon produced from the decay of K after a specified time.
Other isotopes with shorter half-lives can also be used to date objects- however, each method has its own drawbacks. The formula below is a proper model that admits the possibility that some daughter isotope was present when the rock formed: where D is the amount of daughter isotope present at start.In order to simplify the formula, scientists generally assume that igneous rock contains no argon when it forms, because the argon, being a noble gas, would escape from the cooling lava. Fresh volcanic rock is routinely found to have argon in it when it first cools.If the concentration of argon-40 is almost zero, then the rock was formed recently.If it is high relative to the amount of potassium-40 present, then the rock is old.