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.
In other words, the magnitude of the radius of a pleochroic halo in a particular crystal depends on the half-life of the decay responsible for the alpha particle emission. the radii of pleochroic haloes corresponding to a definite decay in a particular mineral are ...
(the same) size, then it can be safely assumed that the half-life of that decay is a constant.
When scientists at the University of Regina, Saskatchewan were asked what the results would be if these roots were dated by Potassium Argon method.
Their response was that the results: Two well-documented examples of "heat contamination" are the 18 eruptions from two Hawaiian volcanoes.
For example, with the uranium/lead method scientists have attempted to estimate what the original ratio (of uranium-238 to lead-206) was when the Earth formed.Another problem that calls into question the credibility of radiometric dating is heat contamination.For example, In 1973, in Alberta, Canada (near the town of Grand Prairie) a high voltage line fell which caused nearby tree roots to fossilize almost instantly.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.
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.