Therefore, in virtually every case, scientists do not know what the original condition of the rock was; and, even if they did know, they don't any more due to heat contamination, mixing, and leaching. Snelling in an article on this topic Note: As for the few cases where scientists do know what the "original" condition (or date of eruption) was, they still have not been able to come up with the correct "date" for the age of the rock without all sorts of fancy footwork and massaging of data.

The third assumption is that the sample has remained in a closed system.

This is necessary due to outside influences such as heat and groundwater that can seriously alter the original material.

Although these eruptions were less than 200 years old, the radiometric "dates" obtained from them were 140 million to 2.96 billion years for one, and from 0 to 29 million years for the other -- depending upon the (ocean) depth at which the lava sample was obtained. This also brings up an important question: If radiometric dating methods are unable to produce the correct date in cases where the actual date of eruption is known, why should we believe that these same methods can produce accurate dates when the date of eruption is unknown?

The point is simply this: radiometric dating is known to produce grossly erroneous dates when heat is involved in the formation or fossilization process.

This is because "common" lead contains both radiogenic (lead 206, 207 and 208) and non-radiogenic lead (204) but it does not contain any uranium.

In fact, about 98% of common lead is "radiogenic" (containing lead 206, 207, 208) and only 2% non-radiogenic.For Uranium/Lead dating this means that some of the uranium that was initially present would be "leached" out of the rock.Leaching can also cause uranium to be leached into rocks that have little or no uranium in them.College Board Standards for College Success: Science ES.3 Earth’s History: Relative and Absolute dating.Students understand that various dating methods — relative and absolute — have been used to determine the age of Earth. Between Earth Science and Other Disciplines: Evidence of Common Ancestry and Divergence (LS.1.1); Living Systems and the Physical Environment (LS.3.1); Nuclear Chemistry (C.1.6); Nuclear Interactions and the Conservation of Mass–Energy (P.2.3) Benchmarks: American Association for the Advancement of Science.However, not as well known is the fact that such methods have serious flaws which are often glossed over, or ignored when writing on, or discussing this subject in public. that (the) half-lives (of uranium-thorium-lead) are not constant but vary with time. comes from the study of pleochroic haloes which form in a rock in the following way.