Relative dating of rock
Absolute dating is used to determine a precise age of a fossil by using radiometric dating to measure the decay of isotopes, either within the fossil or more often the rocks associated with it.
The majority of the time fossils are dated using relative dating techniques.
Using relative dating the fossil is compared to something for which an age is already known.
For example if you have a fossil trilobite and it was found in the Wheeler Formation.
Instead of invoking supernatural forces to explain fossils, Steno concluded that fossils were once parts of living creatures.Potassium-40 on the other hand has a half like of 1.25 billion years and is common in rocks and minerals.This makes it ideal for dating much older rocks and fossils.He then sought to explain how fossil seashells could be found in rocks far from any ocean.As in the Tyrannosaurus rex Figure 11.10, fossils resemble living organisms.