How is potassium argon dating used
One problem with argon-argon dating has been a slight discrepancy with other methods of dating.) reports that a correction of 0.65% is needed.Thus the Cretaceous–Paleogene extinction (when the dinosaurs died out) - previously dated at 65.0 or 65.5 million years ago - is more accurately dated to 66.0 Ma.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's not bonded to anything, and so it'll just bubble out and just go out into the atmosphere. That lava will contain some amount of potassium-40. And so you know the only way this argon-40 can exist there is by decay from that potassium-40. So you know for every one of these argon-40's, because only 11% of the decay products are argon-40's, for every one of those you must have on the order of about nine calcium-40's that also decayed. 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.
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.And in the next video I'll actually go through the mathematical calculation to show you that you can actually date it.And the reason this is really useful is, you can look at those ratios.Modern methods of analysis allow individual regions of crystals to be investigated.This method is important as it allows crystals forming and cooling during different events to be identified.