What is being measured in radiometric dating
This method should also be applied only to minerals that remained in a closed system with no loss or gain of the parent or daughter isotope.Uranium-Lead Dating Uranium-Lead (U-Pb) dating is the most reliable method for dating Quaternary sedimentary carbonate and silica, and fossils particulary outside the range of radiocarbon.
The original atom is referred to as the parent and the following decay products are referred to as the daughter.
For example: after the it forms a component of all organic compounds and is therefore fundamental to life. Libby of the University of Chicago predicted the existence of carbon-14 before it was actually detected and formulated a hypothesis that radiocarbon might exist in living matter.
The Potassium-Argon dating method is the measurement of the accumulation of Argon in a mineral.
It is based on the occurrence of a small fixed amount of the radioisotope Ar with a half-life of about 1,300 million years.
If the rock containing these minerals is heated, the tracks will begin to disappear.
If the rock is heated high enough, 120C for apatite, all tracks will disappear.
Any material which is composed of carbon may be dated.
Herein lies the true advantage of the radiocarbon method.
Zircons will loose their tracks at higher temperatures of 200.
The tracks will then begin to accumulate when the rock begins to cool.
By measuring the C concentration or residual radioactivity of a sample whose age is not known, it is possible to obtain the number of decay events per gram of Carbon.