What is the half life of potassium argon dating Totally free cams
So for example, potassium can come in a form that has exactly 20 neutrons. And 39, this mass number, it's a count of the 19 protons plus 20 neutrons. But this is also the isotope of potassium that's interesting to us from the point of view of dating old, old rock, and especially old volcanic rock.
And this is actually the most common isotope of potassium. This accounts for about 6.7% of the potassium on the planet. And as we'll see, when you can date old volcanic rock it allows you to date other types of rock or other types of fossils that might be sandwiched in between old volcanic rock.
The potassium-argon dating method has been used to measure a wide variety of ages.
The potassium-argon age of some meteorites is as old as 4,500,000,000 years, and volcanic rocks as young as 20,000 years old have been measured by this method.
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.
Scientists in the 20th century developed a number of interesting ways to determine how old the rock formations around the world really are.