The potassium-argon method is attractive for dating volcanics since it can be applied to rocks of Pleistocene age and older, thus encompassing important periods of general volcanic activity.
However it has been found that dates obtained on whole rocks and on included minerals frequently show gross discordances.
However, this causes a problem for those who believe based on the Bible that life has only existed on the earth for a few thousand years, since fossils are found in rocks that are dated to be over 500 million years old by radiometric methods, and some fossils are found in rocks that are dated to be billions of years old.
If these dates are correct, this calls the Biblical account of a recent creation of life into question.
Teach your students about absolute dating: Determining age of rocks and fossils, a classroom activity for grades 9-12.A Summary of the Million Dollar RATE Research Project (Radioisotopes and the Age of The Earth) Introduction: Rocks and fossils do not come with dates on them.In fact, the very concept of strata representing long ages does not come from the rock strata themselves.In the minerals from Mauna Kuwale sporadic occurrences of inclusions have been noted in biotites and hornblendes, and crushing of the mineral releases the excess radiogenic argon.The determination of the age of such a material would give an old age, and thus account for the anomalies found.
We have found that gas released from such inclusions by crushing contains radiogenic argon, and that the constituent minerals give very old potassium-argon ages (circa 800 million years).