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Re: I need some dates and references
There are many ways to date rocks, but some of the best are
fission-tracking, in which case zircon or some other mineral is dated by
the use of "grooves" made in the crystal by escaping electrons as the
rock ages. Another is radioactive dating, probably the most widely used,
which involves parent/daughter ratio counts on such things as Rb:Sr
(bubidium/strontium), U:Pb (uranium/lead), and K:Ar (potassium/argon)
where the first is parent material and the latter daughter material (you
will often hear reference to half-lives when dealing with radioactive
dating). There are other methods and other elements which can be dated
(Ar40:Ar39) - in fact, a professor of mine and I along with a few other
students recently wrote an article highly dependent on radioactive dating.
Anyway, my point is that there are many ways in which things can be dated
with varying amounts of certainty. We can date things back to billions
of years. Books can be written (and have been) about this.