With the exception of Carbon-14, radiometric dating is used to date either igneous or metamorphic rocks that contain radioactive elements such as uranium. Now when the uranium or thorium disintegrates, the alpha particles which are emitted are slowed down by the crystals in which the grains of the uranium- or thorium-bearing minerals are embedded.
And even though various radioactive elements have been used to "date" these rocks, for the most part, the methods are basically the same. This means that if you had some pure uranium-238 with no lead in it, 4.5 billion years later one half of it would have decayed into its stable daughter product (lead-206). Where these alpha particles finally stop, crystal deformation occurs (and) shows up as a discolouration or a darkening of the crystals.
datingbatsigns com - Dating of zircons
And since the only rocks which yield ages in excess of 100,000 years are of volcanic origin, this method of dating the earth is not based on science, but rather speculation and subjective reasoning.
Unfortunately, the public is rarely informed of these facts. * "Allende" is the name given to the meteorite that was used to "date" the age of the earth. It is the site where the famous 1470 skull was found.
They consist of measuring the amount of radioactive (mother) element and comparing it to the amount of stable (daughter) element. Uranium is radioactive, which means it is in the process of changing from an unstable element into a stable one. And after 9 billion years there would be 75% lead and 25% uranium, and so on. (an) episode of drastically accelerated decay has ... When the crystal is looked at under a microscope, these discolourations appear as dark ringshence the name "pleochroic halo".
Few people realize it but all radiometric dating methods require making at least three assumptions. Now the magnitude of the radius of a pleochroic halo in a particular mineral depends on the amount of energy that the alpha particle has ... depends on the half-life of the particular decay responsible for this alpha particle emission.
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.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.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.That's because radiometric dating (with the exception of Carbon 14) is almost always performed on igneous rocks (i.e. Also because, when different substances are in a liquid state, something known as mixing almost always takes place: meaning that whenever a liquid (or molten) rock is erupted out of the earth, both the mother and daughter elements will be "mixed" together, thus making it virtually impossible to determine the time that an eruption took place.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?