At Focus on the Family, we’ve offered a range of resources and expert advice bringing biblical principles to bear in this area.Some of the messages we’ve presented have taken the position that Christians can apply their faith in such a way that they can still work within the system they’ve inherited.Dating a rock involves uranium-lead measurements on many zircons, then assessing the quality of the data.Some zircons are obviously disturbed and can be ignored, while other cases are harder to judge.Other minerals sometimes used for uranium-lead dating include monazite, titanite and two other zirconium minerals, baddeleyite and zirconolite.However, zircon is so overwhelming a favorite that geologists often just refer to "zircon dating." But even the best geologic methods are imperfect.The straight line takes the zircons off the concordia. The disturbing event affects the zircons unequally, stripping all the lead from some, only part of it from others and leaving some untouched.The results from these zircons therefore plot along that straight line, establishing what is called a discordia. If a 1500-million-year-old rock is disturbed to create a discordia, then is undisturbed for another billion years, the whole discordia line will migrate along the curve of the concordia, always pointing to the age of the disturbance.
If you took rocks of all ages and plotted their two Pb/U ratios from their two isotope pairs against each other on a graph, the points would form a beautiful line called a concordia (see the example in the right column).
Uranium comes in two common isotopes with atomic weights of 235 and 238 (we'll call them 235U and 238U).
Both are unstable and radioactive, shedding nuclear particles in a cascade that doesn't stop until they become lead (Pb).
People attempting to follow a courtship model within today’s culture, however, often run into a lot of practical questions, such as, “What if her dad is unavailable or uninterested in being involved?
” or “What do you do when you live hundreds of miles from your family?
But now imagine that some geologic event disturbs things to make the lead escape.