Radiometric dating of potassium
By measuring the amounts of Potassium and Argon present we can date volcanic rocks that are millions of years old.Carbon Dating Another important dating technique is Carbon-14 dating.A small percentage of this Carbon is the radioactive form, Carbon-14.While an organism is alive this exchange of Carbon continues, and the percentage of Carbon-14 in its body is the same as the percentage of Carbon-14 in the atmosphere.Radiometric dating methods are the strongest direct evidence that geologists have for the age of the Earth.All these methods point to Earth being very, very old -- several billions of years old.The original radioactive atom is known as a parent isotope, while the atom produced by the decay process is known as a daughter isotope. For example Uranium-235 and Uranium-238 are both Uranium atoms with the same number of protons, but they have a different number of neutrons.
All radioactive atoms decay to become a more stable kind of atom.These cases are due to trapped modern argon, either atmospheric argon or argon dissolved in ground water.The cure for this problem is pretty straightforward.Radioactive decay allows geologists and physicists to measure the age of ancient fossils, rocks and even the Earth.
This process is called radiometric or radioactive dating.
Well, there are a few complications: Potassium 40 has a branched decay: only 1/9 of all K-40 atoms decay to Ar-40.