Relative versus absolute dating techniques
Studying the layers of rock or strata can also be useful. If a layer of rock containing the fossil is higher up in the sequence that another layer, you know that layer must be younger in age. This can often be complicated by the fact that geological forces can cause faulting and tilting of rocks.
By measuring the ratio of the amount of the original (parent) isotope to the amount of the (daughter) isotopes that it breaks down into an age can be determined.
Then after another 5,000 years half of the remaining parent isotope will have decayed.
While people are most familiar with carbon dating, carbon dating is rarely applicable to fossils.
It is a less advanced technique when compared to absolute dating.
Some methods used in relative dating are stratigraphy, biostratigraphy, and cross dating.
This uses radioactive minerals that occur in rocks and fossils almost like a geological clock.