Radiometric Dating Techniques
Radiometric Dating Techniques - How Do Other Kinds of Radiometric Dating Work?
Radiometric dating techniques measure the rate of decay of radioactive isotopes into stable chemical elements and the concentrations of these same radioactive isotopes and chemical elements found within specimens of igneous and metamorphic rock. For example, Uranium-238, an unstable radioisotope, decays into Lead-206, a stable chemical element, with thirteen intermediate unstable radioisotopes in between (Uranium-238 decays into Thorium-234, which decays into Protactinium-234, and so on to Lead-206). In this case, Uranium-238 is called the "parent" and Lead-206 is called the "daughter."
Radiometric Dating Techniques – Three Basic Assumptions
Radiometric dating (with the exception of Carbon Dating) can only be used to date igneous and metamorphic rock. There are three basic assumptions fundamental to every radiometric dating technique.
First, we must assume the rate of decay does not change. This is a fair assumption. Scientists have not been able to vary the decay rates, despite their attempts to do so.
Second, we must assume there has been no loss or gain of parent or daughter elements, or any of the intermediate concentrations. This has been found to be a poor assumption. Many of the intermediate products are highly mobile gases. The majority of dates obtained through radiometric dating are in conflict, labeled contaminated and thrown out. It is assumed that the "uncontaminated dates" are legitimate.
- Finally, we must assume that we know the amounts of "daughter" elements present at the beginning of the "parent" decay process. This is the least reasonable assumption. If there are daughter elements present at formation, the rock would have an artificial appearance of age. The "isochron" technique indicates there are always daughter elements at the formation of rocks.