To find their age, two major geological dating methods are used.
These are called relative and absolute dating techniques.
Ice cores showed the age of a military plane buried in the artic as thousands of years old.
Similarly, dendrochronology measures the tree rings in trees and assumes they represent years.
Absolute age is more straight-forward and does not require any other objects for comparison.
The relative dating techniques are very effective when it comes to radioactive isotope or radiocarbon dating.