# Radiometric dating sedimentary

All radiometric dating methods measure isotopes in some way.Most directly measure the amount of isotopes in rocks, using a mass spectrometer.What radioactive materials actually do is decay according to a law: Decays/Time = K * Number of atoms K is a constant called the decay constant.Let t stand for time and N(t) stand for the number of atoms at time t .For example, fission track dating measures the microscopic marks left in crystals by subatomic particles from decaying isotopes.Another example is luminescence dating, which measures the energy from radioactive decay that is trapped inside nearby crystals.

Isotopes are important to geologists because each radioactive element decays at a constant rate, which is unique to that element.Others measure the subatomic particles that are emitted as an isotope decays.Some measure the decay of isotopes more indirectly.In calculus terms, we write: d N(t)/dt = -K * N(t) or d N(t)/N(t) = -K dt The minus sign means that each decay decreases the total number of atoms.Integrating both sides, we get: ln N(t) = -Kt C C is the constant of integration that we can often ignore, but not here.

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