Most absolute dates for rocks are obtained with radiometric methods. These use radioactive minerals in rocks as geological clocks. These break down over time in a process scientists call radioactive decay. Each original isotope, called the parent, gradually decays to form a new isotope, called the daughter.

What rock layers are used for absolute dating?

So in order to date most older fossils, scientists look for layers of igneous rock or volcanic ash above and below the fossil. Scientists date igneous rock using elements that are slow to decay, such as uranium and potassium.

How are rock layers dated?

To establish the age of a rock or a fossil, researchers use some type of clock to determine the date it was formed. Geologists commonly use radiometric dating methods, based on the natural radioactive decay of certain elements such as potassium and carbon, as reliable clocks to date ancient events.

How can you determine the absolute age of rock layers?

Absolute age is the numeric age of a layer of rocks or fossils. Absolute age can be determined by using radiometric dating.

Which type of rock is best for radiometric dating?

igneous rocks Of the three basic rock types, igneous rocks are most suited for radiometric dating. Metamorphic rocks may also be radiometrically dated. However, radiometric dating generally yields the age of metamorphism, not the age of the original rock.