RADIOMETRIC DATING

=Radiometric Dating= Radiometric dating techniques take advantage of the fact that radioactive isotopes decay at a very specific rate. Atomic clocks, which are the most accurate in the world, rely on the same principle. Materials such as rocks and carbon often contain small traces of radioactive isotopes. By comparing the relative amount of the isotope with that found in nature an estimate of the materials age can be obtained. [image:http://i.imgur.com/ZqR3Jrx.png?2] '''Potassium Argon (K–Ar) Dating''' Potassium-40 is a radioactive isotope that will spontaneously decay into argon-40, another radioactive isotope. Molten rock and volcanic ash emerge at such high temperatures that all the argon gas in driven out. Thus any argon-40 found in volcanic rocks is the result of radioactive decay. This decay occurs at a known rate (half-life of approx 1.3 billion years). By examining the ratio of potassium-40 to argon-40, scientists can get a fairly accurate idea of how old the rock or volcanic ash really is. [image:http://i.imgur.com/OvbPbMK.png?2] '''Carbon Dating''' Carbon-14 is a radioactive isotope that is incorporated into living things tissues in the same proportions as it occurs in the air. When an organism dies and is buried, the carbon-14 will decay at a constant rate. Thus scientists can estimate how long it has been since the organism died based on the proportion of carbon-14 that remains. However due to the shorter half-life of carbon-14 this technique is used to more accurately date more recent finds (less than 40,000 years ago).