Cost of k ar dating
It's a pretty good indicator, if you can assume that this soil hasn't been dug around and mixed, that this fossil is between 100 million and 150 million years old.
Ages of geological formations or secondary events (i.e.
The apparent age may be affected by the post-depositional or post-formation history of the rocks.
Natural contamination of chemical sediments with detrital material can also affect the results of dating of diagenesis.
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.
The concentration of the mother and the daughter isotopes, as well as the apparent age can be determined with high precision.
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.
Because what's cool about argon, and we study this a little bit in the chemistry playlist, it is a noble gas, it is unreactive. And you know that it has decayed since that volcanic event, because if it was there before it would have seeped out.
And so when it is embedded in something that's in a liquid state it'll kind of just bubble out. So it erupts, and you have all of this lava flowing. So the only way that this would have been able to get trapped is, while it was liquid it would seep out, but once it's solid it can get trapped inside the rock.
It accounts for, I'm just rounding off, 93.3% of the potassium that you would find on Earth. You also have potassium-- and once again writing the K and the 19 are a little bit redundant-- you also have potassium-41. And then you have a very scarce isotope of potassium called potassium-40. And so what's really interesting about potassium-40 here is that it has a half-life of 1.25 billion years. So when you think about it decaying into argon-40, what you see is that it lost a proton, but it has the same mass number.
So the good thing about that, as opposed to something like carbon-14, it can be used to date really, really, really old things. So one of the protons must of somehow turned into a neutron. It'll just bubble out essentially, because it's not bonded to anything, and it'll sort of just seep out while we are in a liquid state. So right when the event happened, you shouldn't have any argon-40 right when that lava actually becomes solid.
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There are some techniques and calculations which can "look through" the post formation event.