To derive ages from such measurements, unprovable assumptions have to be made such as: There is plenty of evidence that the radioisotope dating systems are not the infallible techniques many think, and that they are not measuring millions of years. For example, deeper rocks often tend to give older “ages.” Creationists agree that the deeper rocks are generally older, but not by millions of years.Geologist John Woodmorappe, in his devastating critique of radioactive dating, points out that there are other large-scale trends in the rocks that have nothing to do with radioactive decay.
That is, they take up less than would be expected and so they test older than they really are.
Furthermore, different types of plants discriminate differently.
These techniques, unlike carbon dating, mostly use the relative concentrations of parent and daughter products in radioactive decay chains.
For example, potassium-40 decays to argon-40; uranium-238 decays to lead-206 via other elements like radium; uranium-235 decays to lead-207; rubidium-87 decays to strontium-87; etc.
Familiar to us as the black substance in charred wood, as diamonds, and the graphite in “lead” pencils, carbon comes in several forms, or isotopes.
One rare form has atoms that are 14 times as heavy as hydrogen atoms: carbon-14, or C ratio gets smaller.
The strength of the Earth's magnetic field affects the amount of cosmic rays entering the atmosphere.
A stronger magnetic field deflects more cosmic rays away from the Earth.
Also, the Genesis flood would have greatly upset the carbon balance.
The flood buried a huge amount of carbon, which became coal, oil, etc., lowering the total C ratio in plants/animals/the atmosphere before the flood had to be lower than what it is now.
We will deal with carbon dating first and then with the other dating methods.