Australian Museum



Radiometric dating

Because the radioactive half-life of a given radioisotope is not affected by temperature, physical or chemical state, or radioactkve other influence of the environment outside the nucleus save radioactivr particle interactions with the nucleus, then radioactive samples continue to decay at a predictable rate and can be used as a clock.

This makes several types of radioactive dating feasible. For geologic dating, where the time span is on the order of the age of the earth and the methods use the clocks in the rocksthere are two main uncertainties in the dating process:. Starting with the simplest case where there are no daughter atoms present and no mass is lost from the rxdioactive, the age can be determined by measuring the relative amounts of the isotopes.

This can be done by chemical means, but for precise determinations, mass spectrometry can be used. From the radioactive decay equations, datingg expression for elapsed time can be developed. Using the common nuclear practice of calling the isotopes "parent" and "daughter", we use P and D to indicate the associated numbers of atoms.

The requirement of keeping the same number of nuclei gives. Now suppose that there was an original amount of the daughter element present at the formation time of the sample being studied. This adds an additional unknown in the process, and requires an additional piece of data to permit a solution for elapsed time. The requirement on the populations is now. Fortunately for radioactive dating processes, additional information is available in the form of other isotopes of the elements involved in the radioactive process.

If there is another isotope of the daugther element D' which is presumed to be constant how to find radioactive dating the process, then the population requirement can be expressed in terms of the ratios. We can be reasonably confident that the isotope D' is contant if it is not radioactive not part of one of the natural radioactive series. Using the radioactive decay equation as above, this becomes. Such a line is called an isochron since all the different minerals are presumed to have crystallized together and therefore have the same age since solidification.

The age can then be calculated from that slope as follows:. For geologic dating, the age calculation must take into account the presence of the radioactive species at the beginning of the time interval. If there is a non-radiogenic isotope of the daughter element present in the mineral, it can be used as a reference and the ratios of the parent and daughter elements plotted radioaxtive ratios with that reference isotope. The slope of the curve then gives the time interval.

Radioactive Dating Because the radioactive half-life of a given radioisotope is not affected by temperature, physical or chemical state, or any other influence of the environment how to find radioactive dating the nucleus save direct particle interactions with the nucleus, then radioactive samples continue to decay at a predictable rate and can be used as a clock. For geologic dating, where the time span is on the order of the age of the earth and the methods use the clocks in the rocksthere are two main uncertainties in the dating process: What was the amount of the daughter element when the rocks were formed?

Have any of the parent or daughter atoms been added or removed during the process? The requirement of keeping the same number of nuclei gives finc the radioactive decay adting is The elapsed time is then but with the use of the first expression above can be expressed in terms of how to find radioactive dating present concentrations of the parent and daughter isotopes. The requirement on the populations is now Fortunately for radioactive dating processes, additional information is available in the form of other isotopes of the elements involved in the radioactive process.

If there is another isotope of the daugther element D' which is presumed to be constant throughout the process, then the population requirement can be expressed in terms of the ratios We can be reasonably confident that the isotope D' is contant if it is not how to find radioactive dating not part of one of the natural radioactive series. The age can then be calculated from that slope as follows: Index Reference Krane Sec 6.

The data plotted here is from G.


How to Date a Dead Thing