Explain potassium 40 dating


03-Feb-2020 19:44

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If the rock actually contained some argon-40 when it solidified then the calculated age would be too old. What he does is check his calculated age with the ages produced by other dating methods.

On the other hand, if the rock was later disturbed by a geological upheaval and lost argon the age would be too young. In other words, he checks to see if his calculated result falls into the range where he expects it to fall, given the geological situation of where he found his rock.

It is impossible to distinguish between them experimentally.

So, how do we work out how much excess argon we have? In this case the method is again salvaged by changing his assumptions about the past.

It explains what each of these were doing deep inside the earth millions of years ago. But wasn’t that what the dating method was supposed to be measuring?

The story explains that the behaviour of ‘excess argon’ (it even has a name) made the age too old. The problem is that although radiogenic argon and excess argon have different names they are exactly the same isotope—argon-40.

This means that the geologist can plausibly assume that all argon gas escapes from the molten magma while it is still liquid.

He thinks this solves his problem of not knowing the initial quantity of the daughter element in the past and not being able to go back in time and make measurements. He assumes that any argon-40 that he measures in his rock sample must have been produced by the radioactive decay of potassium-40 since the time the rock solidified.

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The scores of dates that have been produced have had a life like hens in a chicken coop.

We know that an element is defined by the number of protons it has. And when we talk about a given element, but we have different numbers of neutrons we call them isotopes of that element.

And I have a snapshot of it, of not the entire table but part of it here. Now, we also know that not all of the atoms of a given element have the same number of neutrons.

In this case the geologist assumes that everything went well, and he publishes his result as the crystallization age of the rock.

So although the potassium-argon method has been used for dating rocks for decades, the results it has produced have tended to reinforce the geological framework that already existed.By measuring the ratio of the two present in a rock, we can work out how long it is since the rock was formed from magma.