A rock sample from Nigeria was dated at 95 million years by the potassium-argon method, 750 million years by the uranium-helium method, and less than 30 million years by the fission-track method.
If the clock is not set to zero when a deposit forms, then there can be no starting point from which to calculate the age of a deposit.
A further example from a lava flow off the coast of Hawaii shows similar discrepancies.
If dated with the carbon-14 method, the flow appears to be less than 17,000 years old, but dating with the potassium argon method gives dates of 160,000 to 43 million years.
Radiometric dating techniques are thus based on sound scientific principles, but rely on so many basic assumptions that Bible believers need not have their faith shattered by data derived from these techniques.