Radio dating wiki
If a fossil is found between two layers of rock whose ages are known, the fossil's age is thought to be between those two known ages.Because rock sequences are not continuous, but may be broken up by faults or periods of erosion, it is difficult to match up rock beds that are not directly adjacent.Favoriting this resource allows you to save it in the “My Resources” tab of your account.There, you can easily access this resource later when you’re ready to customize it or assign it to your students.The principle of radiocarbon dating is simple: the rates at which various radioactive elements decay are known, and the ratio of the radioactive element to its decay products shows how long the radioactive element has existed in the rock.This rate is represented by the half-life, which is the time it takes for half of a sample to decay.This is consistent with the assumption that each decay event is independent and its chance does not vary over time.
The half-life , specific to each nuclide, can be accurately measured on a pure sample, and is known to be independent of the chemical composition of the sample, temperature and pressure.
Symbolically, the process of radioactive decay can be expressed by the following differential equation, where N is the quantity of decaying nuclei and k is a positive number called the exponential decay constant.
The meaning of this equation is that the rate of change of the number of nuclei over time is proportional only to the number of nuclei.
The key is to measure an isotope that has had time to decay a measurable amount, but not so much as to only leave a trace remaining.
Given isotopes are useful for dating over a range from a fraction of their half life to about four or five times their half life.