Half life radiometric dating
These radioactive elements constitute independent clocks that allow geologists to determine the age of the rocks in which they occur.The radioactive parent elements used to date rocks and minerals are: Radiometric dating using the naturally-occurring radioactive elements is simple in concept even though technically complex.This means that zircon data can tell us not only when a rock formed, but also when significant events occurred during its life.The oldest zircon yet found dates from 4.4 billion years ago.The 235U–207Pb cascade has a half-life of 704 million years and the 238U–206Pb cascade is considerably slower, with a half-life of 4.47 billion years.So when a mineral grain forms (specifically, when it first cools below its trapping temperature), it effectively sets the uranium-lead "clock" to zero.If we know the number of radioactive parent atoms present when a rock formed and the number present now, we can calculate the age of the rock using the decay constant.
Consider the concordia: as zircons age, they move outward along the curve.Uranium comes in two common isotopes with atomic weights of 235 and 238 (we'll call them 235U and 238U).Both are unstable and radioactive, shedding nuclear particles in a cascade that doesn't stop until they become lead (Pb).The above equation makes use of information on the composition of parent and daughter isotopes at the time the material being tested cooled below its closure temperature.
This is well-established for most isotopic systems.
The probability of a parent atom decaying in a fixed period of time is always the same for all atoms of that type regardless of temperature, pressure, or chemical conditions. The time required for one-half of any original number of parent atoms to decay is the half-life, which is related to the decay constant by a simple mathematical formula.