Radioactive dating example problems

Assuming we start out with pure parent, as time passes, more and more daughter will be produced. A ratio of infinity (that is, all daughter and no parent) means an age of essentially infinity.

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For isochrons, which we will discuss later, the conditions are different.

If these conditions are not satisfied, the error can be arbitrarily large.

We are told that of all the radiometric dates that are measured, only a few percent are anomalous.

This gives us the impression that all but a small percentage of the dates computed by radiometric methods agree with the assumed ages of the rocks in which they are found, and that all of these various methods almost always give ages that agree with each other to within a few percentage points.

In two half-lives, half of the remainder will decay, meaning 3/4 in all will have decayed.

In general, in n half-lives, only 1/(2^n) of the original parent material will be left.

We can assume that the Precambrian rocks already existed when life began, and so the ages of the Precambrian rocks are not necessarily related to the question of how long life has existed on earth.

The Cambrian period is conventionally assumed to have begun about 550 million years ago.

Perhaps the earth was made from older pre-existing matter, or perhaps decay rates were briefly faster for some reason. Geologic time is divided up into periods, beginning with the Precambrian, followed by the Cambrian and a number of others, leading up to the present.

When one considers the power of God, one sees that any such conclusions are to some extent tentative. Some fossils are found in Precambrian rocks, but most of them are found in Cambrian and later periods.

For potassium 40, the half-life is about 1.3 billion years.

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