Radioactive dating using potassium argon
Potassium is about 1/40 of the earth's crust, and about 1/10,000 of the potassium is potassium 40.
Uranium decays to lead by a complex series of steps. Thus we obtain K-Ar dating, U-Pb dating, and Rb-Sr dating, three of the most common methods.
For isochrons, which we will discuss later, the conditions are different.
If these conditions are not satisfied, the error can be arbitrarily large.
We can assume that the Precambrian rocks already existed when life began, and so the ages of the Precambrian rocks are not necessarily related to the question of how long life has existed on earth.
The Cambrian period is conventionally assumed to have begun about 550 million years ago.
Since there doesn't seem to be any systematic error that could cause so many methods to agree with each other so often, it seems that there is no other rational conclusion than to accept these dates as accurate.
However, there may be other explanations for this apparent age. I also believe that the evidence indicates that the earth has recently undergone a violent catastrophe.
How radiometric dating works in general Why methods in general are inaccurate Why K-Ar dating is inaccurate The branching ratio problem How Errors Can Account for the Observed Dates Why older dates would be found lower in the geologic column especially for K-Ar dating Do different methods agree with each other on the geologic column?