Before radiometric dating all we could do were estimated dates based upon minimal estimated times for deposition based upon observation.
Radiometric dating involves the process of a radioactive element, such as uranium, decaying into another element, such as lead.
Uranium-lead radiometric dating would be a good clock for estimating the age of rocks if we knew the following.
(A.) The rate at which uranium decays into lead.
(B.) How much lead was in the rock when it was formed.
(C.) All of the lead that was not in the rock when the rock was formed came from decaying uranium.
(D.) There is no way any extra lead or uranium could have gotten into the rock from the outside.
(E.) There is no way any of the original lead or uranium could have gotten out of the rock, such as by differential leaching.
(F.) The process has always been uniform. In other words, A, C, D, and E have each always remained constant throughout the age of the rock.
However, most of these requirements are either unknown, or are known not to be true. But there is a flip-side to the uranium-lead dating method. Uranium decays into lead, which is a very common element on the earth. When the uranium decays, it also produces helium-4 as a by-product. But unlike lead, helium-4 is very rare. Rocks which the uranium-lead dating method estimates to be more than 100 million years old, contain only enough helium to account for a tiny fraction of that time. The evolutionists claim that the helium must have escaped from the rocks. But if that were the case, we should be able to find vast amounts of helium-4 in the atmosphere. But the tiny amount of helium-4 present on the earth indicates only a few thousand years of uranium decay, not 4 to 5 billion years. Even uranium-lead radiometric dating provides evidence that the earth is young when one considers the lack of helium-4 on the planet.
Another radiometric dating method is the
Potassium-Argon method. With this method, ages found from samples taken from a single rock may differ drastically. Rocks formed from the active Kilauea volcano in Hawaii were found to increase in age as the depth of the rock increased. Lava flows known to be less than 200 years old yielded dates of up to 22 million years using this method. Part of the problem is that argon, which is abundant in the atmosphere, can be incorporated into the rocks under pressure, making the Potassium-Argon method yield older dates.
The
radio-carbon (C-14) dating method is another very inaccurate dating method. Results differ greatly even in the same rock layer. In rocks that are supposed to be 110 million years old, dinosaur bones and wood were taken and dated to 19,000 years old and 890 years old respectively using this method. In addition, the shells of living mollusks regularly date to more than 2000 years old using the radio-carbon method. One other interesting note about C-14 is that its level on the earth is presently increasing exponentially, and is now 30 per cent short of equilibrium. It has been estimated that it would have taken less than 8000 years for the C-14 to reach its present level of concentration.
Ref.: http://www.matthewmcgee.org/creation.html