Errors in radiometric dating
Here it is possible to use two decay processes, the decay of uranium-238 into lead-206 and the decay of uranium-235 into lead-207.
Hence, by measuring the amount of lead-204 in a rock, geologists can estimate the amount of lead originally present.
Given this value of Dit is then possible to use either decay process to calculate the age of the rock.
If the results agree, they are said to be concordant, and geologists are usually confident that concordant ages are the true ages of the rocks under consideration.
For if extra daughter element were added, then we should arrive at too large a figure for the amount of the parent element that has decayed, and thus produce too high a value for the age of the rock.) Geologists are not unaware of these assumptions, and they take great pains to construct ways of cross-checking them.
Argon is an inert gas, so that it does not occur in chemical compounds in original rocks.