You have carried out radiometric dating analysis on four ign

You have carried out radiometric dating analysis on four igneous rocks uncovered at several sites that you have been exploring. From the % lead you determine in each case, what is the appropriate age of the rock?

Solution

Radiometric dating is a technique used to date materials such as rocks or carbon in which trace radioactive impurities were selectively incorporated when they are formed.

Radioactivity can be used to date rocks. Rocks often contain traces of uranium. This is unstable and evenly distributes to lead, which is stable. The age of the rock can be calculated if its ratio of uranium to lead is known. The older the rock, the lower its uranium to lead ratio. Young rocks have a high uranium to lead ratio. Very old rocks have a low uranium to lead ratio.

This table shows how it works:

The half life of uranium is 4.46 billion years. If a rock has uranium to lead ratio of 1:1, one half-life must have passed since it formed. This would make it 4.46 billion years old.