Two methods of dating rocks Konnys pussy nude
By experimentation, scientists have determined which rocks are suitable for various dating techniques.
For K-Ar, for example, igneous rocks are good candidates for testing because they formed directly from molten magma and have a simple history.
Metamorphic rocks do not work well because heating events in their history have allowed the escape of Argon (daughter element) and thus will indicate an age too young for the sample.
Sedimentary rocks do not work because they are made up of a mixture of deposits of many other types of rocks, each of which would point to a different age.
At any rate, scientists have devoted a great deal of effort to determining exactly which dating methods are appropriate for which types of rocks.
The other problem to avoid when dating rocks is the possibility that changes to the rock have caused loss or gain of either the parent or daughter element - this would lead to a false date (too old if parent element were lost, too young if daughter element were lost).
Since radioactive decay is known to occur at a constant rate, the age of a rock can be determined from the ratio of the parent element to the daughter element.
The concerns about these dating methods were exactly the same that creationists continue to raise - presence of the daughter element at the time the rock was formed and possible loss / gain of either the parent or daughter element at some point in the history of the rock.
For this reason, the tests were designed to account for those possibilities.
Initial daughter element can often be accounted for by either measuring the amount of an isotope of the daughter element (the ratio of isotopes are almost always constant).
Another possibility is (as in the case of the potassium - argon - K-Ar method) that because the daughter element is gaseous, it would escape from the rock when the rock was molten.