Contrary to the impression that we are given, radiometric dating does not prove that the Earth is millions of years old. The vast age has simply been assumed.2 The calculated radiometric ‘ages’ depend on the assumptions that are made. The results are only accepted if they agree with what is already believed.
Laboratory tests on rock formed from the 1980 eruption of Mt St Helens gave ‘ages’ of millions of years. Critics claimed that ‘old’ crystals contained in the rock contaminated the result. However, careful measurements by Dr Steve Austin showed this criticism to be wrong.
More on Radiometric dating and why its unreliable, but i guess it will through one ear and out the other.
"Some information from the book Uranium Geochemistry, Mineralogy, Geology provided by Jon Covey gives us evidence that fractionation processes are making radiometric dates much, much too old. Geology contributing author Massimo Cortini cites a very interesting anomaly regarding the U 238 decay chain, which is U-238, U-234, Th-230, Ra-226, Rn-222, Po-218 Po-214, Po-210, Pb-210, Bi-210, Pb-206. The half life of U-238 is 4.47 x 10^9 years and that of Ra-226 is 1.6 x 10^3 years. Thus radium is decaying 3 million times as fast as U-238. At equilibrium, which should be attained in 500,000 years for this decay series, we should expect to have 3 million times as much U-238 as radium to equalize the amount of daughter produced. Cortini says geologists discovered that ten times more Ra-226 than the equilibrium value was present in rocks from Vesuvius. They found similar excess radium at Mount St. Helens, Vulcanello, and Lipari and other volcanic sites. The only place where radioactive equilibrium of the U-238 series exists in zero age lavas is in Hawiian rocks. Thus instead of having 1/(3 million) as much radium as uranium, which we should expect, there is ten times as much, or 1/(300,000) times as much radium as uranium.
We need to consider the implications of this for radiometric dating. How is this excess of radium being produced? This radium cannot be the result of decay of uranium, since there is far too much of it. Either it is the result of an unknown decay process, or it is the result of fractionation which is greatly increasing the concentration of radium or greatly decreasing the concentration of uranium. Thus only a small fraction of the radium present in the lava (at most 10 percent) is the result of decay of the uranium in the lava.
This is interesting because both radium and lead are daughter products of uranium. If similar fractionation processes are operating for lead, this would mean that only a small fraction of the lead is the result of decay from the parent uranium, implying that the U-Pb radiometric dates are much, much too old. Cortini, in an article appearing in the Journal of Volcanology and Geothermal Research also suggests this possibility. He says:
"The invalidity of the Th-230 dating method is a consequence of the open-system behaviour of U and Th. By analogy with the behaviour of Ra, Th and U it can be suggested that Pb, owing to its large mobility, was also fed to the magma by fluids. This can and must be tested. The open-system behaviour of Pb, if true, would have dramatic consequences...." J Vol Geotherm Res 14 (1982) 247-260.
On the other hand, even if such a process is not operating for lead, the extra radium will decay rapidly to lead, and so in either case we have much too much lead in the lava and radiometric dates that are much, much too ancient! So this is a clue that something is not right with U-238/Pb-206 radiometric dates. It is also a convincing proof that some kind of drastic fractionation is taking place, or else an unknown process is responsible. Since most lavas have excess radium today, it is reasonable to assume this has always been true, and that all U-238/Pb-206 radiometric dates are much, much too old. Cortini says high Ra-226/U-238 ratios are a common feature of primitive magmas, which magma-generating processes produce. He says this is inexplicable in a closed-system framework and certainly invalidates the Th-230 dating method. And it is also possible that something similar is happening in the U-235 decay chain, invalidating U-235 based radiometric dates as well.
In fact, U-235 and Th-232 both have isotopes of radium in their decay chains with half lives of a week or two, and 6.7 years, respectively. Any process that is concentrating one isotope of radium will probably concentrate the others as well and invalidate these dating methods, too. Radium 226 has a low melting point (973 degrees K) which may account for its concentration at the top of magma chambers.
What radiometric dating needs to do to show its reliability is to demonstrate that no such fractionation could take place. Can this be done? With so many unknowns I don't think so.
I even read something about geologists trying to choose crystals without impurities (by visual examination) when doing radiometric dating. Thus we can assume that zircons would incorporate some lead in their impurities, potentially invalidating uranium-lead dates obtained from zircons.
Here is yet another mechanism that can cause trouble for radiometric dating: As lava rises through the crust, it will heat up surrounding rock. Lead has a low melting point, so it will melt early and enter the magma. This will cause an apparent large age. Uranium has a much higher melting point. It will enter later, probably due to melting of materials in which it is embedded. This will tend to lower the ages.
Concerning the geologic time scale, Brown writes:
"The construction of this time scale was based on about 380 radioisotope ages that were selected because of their agreement with the presumed fossil and geological sequences found in the rocks. Radioisotope ages that did not meet these requirements were rejected on the basis of presumed chemical and/or physical modifications that made the "ages" unreliable indicators of real time. About 85% of the selections were K-Ar date s, 8% rubidium-strontium dates, and 4% uranium-lead dates."
So we see that only a tiny proportion of these dates on which geologic time was based, were uranium-lead dates. Maybe only 15 in all. Why is this? It is possible that the reason is that uranium-lead dates so rarely agree with the correct dates. So there may not be anything to explain.
We haven't even considered the fact that uranium is highly water soluble and lead is not, which could make the dates too old, too. Another factor to consider.