When was potassium argon dating first used dating while waiting for divorce
And the reason this is really useful is, you can look at those ratios.And volcanic eruptions aren't happening every day, but if you start looking over millions and millions of years, on that time scale, they're actually happening reasonably frequent. So let's say this is the ground right over here.This is going to have some amount of potassium-40 in it.And then let's say this one over here has more argon-40. And using the math that we're going to do in the next video, let's say you're able to say that this is, using the half-life, and using the ratio of argon-40 that's left, or using the ratio of the potassium-40 left to what you know was there before, you say that this must have solidified 100 million years ago, 100 million years before the present.Although it is a simple calculation the big question is whether his assumptions about the rock were correct.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.And let's say you feel pretty good that this soil hasn't been dug up and mixed or anything like that. It looks like it's been pretty untouched when you look at these soil samples right over here. Then, even though carbon-14 dating is kind of useless, really, when you get beyond 50,000 years, you see these fossils in between these two periods.
Let's say, you know it solidified about 150 million years before the present. So it allows you, even though you're only directly dating the volcanic rock, it allows you, when you look at the layers, to relatively date things in between those layer. It allows us to date things that are very, very, very old and go way further back in time than just carbon-14 dating.
But what's neat about argon-40 is that while it's lava, while it's in this liquid state-- so let's imagine this lava right over here. And so what you can do is you can look at the ratio of the number of potassium-40's there are today to the number that there must have been, based on this evidence right over here, to actually date it.
And in the next video I'll actually go through the mathematical calculation to show you that you can actually date it.
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.
He imagines that his radioactive hour glass sealed when the rock solidified, and his radioactive clock started running.