Geologists often need to know the age of material that they find.
This is different to relative dating, which only puts geological events in time Most absolute dates for rocks are obtained with radiometric methods.
These use radioactive minerals in rocks as geological clocks.
The atoms of some chemical elements have different forms, called isotopes.
These break down over time in a process scientists call radioactive decay.
When ‘parent’ uranium-238 decays, for example, it produces subatomic particles, energy and ‘daughter’ lead-206.
Isotopes are important to geologists because each radioactive element decays at a constant rate, which is unique to that element.For example, if an area used for trash has modern refuse in it such as CDs and computers, and the layer underneath has cans made of tin, then it is safe to say the layer of tin cans have a greater relative age than the layer with modern refuse.However, this does not say anything about the absolute age of the layers.(Hint: The Law of Superposition might help you.) According to the Law of Superposition newer rock layers form on top of already existing layers.As more and more layers are deposited, the older rock layers end up at the bottom and the newer ones toward the top. What is the difference between relative and absolute age?Each original isotope, called the parent, gradually decays to form a new isotope, called the daughter.