The number of parent atoms originally present is simply the number present now plus the number of daughter atoms formed by the decay, both of which are quantities that can be measured.
Samples for dating are selected carefully to avoid those that are altered, contaminated, or disturbed by later heating or chemical events.
Official publications say these rocks are more than a billion years old, but when the methods used to date them are carefully examined, a totally different story is discovered.
But the quest to test this belief by sampling rocks from deep within Grand Canyon has found it is not true.
During several raft trips through Grand Canyon, many samples of these “Brahma” amphibolites were collected from various outcrops in the Inner Gorge.6 These included seven samples from a single amphibolite body (figure 5).7 All the samples were sent to two well-respected commercial laboratories for radioisotope testing.8 Both laboratories use standard, best-practice procedures on state-of-the-art equipment and routinely provide accurate and repeatable measurements of the required isotopes.
The calculated ages for all the individual samples from the dating method turned out to be vastly different (see box, “Calculating the ages”, below), even for those closely spaced samples from the same outcrop of the same lava flow.
The results are not even close to each other, although the samples should all have given the same age.
It is important to realize that the laboratories do not measure the “age” of the rocks but the isotopes in them at the present time.
Geologists calculate an “age” using the measured amount of a “daughter” isotope (e.g.All rocks and minerals contain long-lived radioactive elements that were incorporated into Earth when the Solar System formed.These radioactive elements constitute independent clocks that allow geologists to determine the age of the rocks in which they occur.The latter are former sedimentary and volcanic layers that have been transformed (metamorphosed) by heat and pressure during intense geologic upheavals in the past.Among these volcanic layers are distinctive dark-coloured rocks called amphibolites3 (figure 3). Its crust is continually being created, modified, and destroyed.