But the value is not really known

Different types of radiocarbon dating

So these small particles of

There can also be argon or other daughter products added from the air or from other rocks. It is claimed that the argon that enters from the atmosphere or other rocks, is less tightly bound to the crystal lattice, and will leave the rock at a lower temperature. All its argon will either remain inside and give an old age to the flow, or will travel through surrounding rock, where it can be absorbed by other rocks. We also need to know that no parent or daughter has entered or left the system in the meantime.

But if we really understand what is going on, then we should be able to detect discrepant dates as they are being measured, and not just due to their divergence from other dates. In addition, some kinds of rocks are not considered as suitable for radiometric dating, so these are typically not considered. But isochrons might be able to account for pre-existing daughter elements. The rate of diffusion is proportional to the gradient of argon concentration, and increases rapidly with temperature. It takes a long time to penetrate the confusion and find out what is the hard evidence in this area.

Rubidium decays to

This is especially true as the lava is cooling. This is about one ten millionth of the mass of the rock, a very tiny percentage. It is also possible that parent and daughter elements could be present in boundaries between regular crystal domains. This is when the dinosaurs are assumed to have become extinct. So even if the crystal excludes the daughter element, it could be present in impurities.

So these small particles of lava cool very fast. Rubidium decays to strontium.

Trees of the same species that simultaneously grew within a few hundred miles of each other may have similar patterns. Again, the percentage of anomalies means nothing for the reliability of radiometric dating. Thus modern lava flows are not subject to the same mechanism of artificial increases in their K-Ar ages as are ancient ones. Also, they appear to have been covered over quickly. And since this agreement is the strongest argument for the reliability of radiometric dating, such an assumption of agreement appears to be without support so far.

So it must be possible for that excess argon to get in, even though the crystal is supposed to exclude it. Then the more questionable links are established based on the judgment of a tree-ring specialist. Another factor is that rocks absorb argon from the air. In areas where tremendous tectonic activity has taken place, highly discordant values for the ages are obtained. This does not include dates from minerals that are thought to yield bad dates, or from igneous bodies with wide biostrategraphic ranges, where many dates are acceptable.