Videos radiometric dating
To determine the relative age of different rocks, geologists start with the assumption that unless something has happened, in a sequence of sedimentary rock layers, the newer rock layers will be on top of older ones. This rule is common sense, but it serves as a powerful reference point.Geologists draw on it and other basic principles ( to determine the relative ages of rocks or features such as faults.For example, in a given sample of rock, after 713 million years, half of the originally-present uranium-235 will be changed to lead: this is the "half-life" of uranium-235. Origin and Evolution of Earth System: Geologic time can be estimated by observing rock sequences at various locations.After another 713 million years, half of what was left will have decayed, etc. Current methods include using the known decay rates of radioactive isotopes present in rocks to measure the time since the rock was formed.A mass spectrometer is an instrument that uses a series of magnets to bend a beam of ions and then physically count how many there are, so with AMS radiocarbon dating, we can measure a carbon-12, 13 and 14 beam, and we measure the ratio of 14 to 13, and from that, we can tell how much C-14 is in the sample.So the most important things about AMS radiocarbon dating as opposed to conventional is that the sample size is much, much smaller.
The C-14 decays with the beta particle, and you have some detection equipment and you count the C-14s one by one.In a way this field, called geochronology, is some of the purest detective work earth scientists do.