Numerical absolute geologic age dating

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.

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.

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.

The same rock formation also contains a type of trilobite that was known to live 415 to 425 million years ago.

Since the rock formation contains both types of fossils the ago of the rock formation must be in the overlapping date range of 415 to 420 million years. There are two main methods determining a fossils age, relative dating and absolute dating.Relative dating is used to determine a fossils approximate age by comparing it to similar rocks and fossils of known ages.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.The example used here contrasts sharply with the way conventional scientific dating methods are characterized by some critics (for example, refer to discussion in "Common Creationist Criticisms of Mainstream Dating Methods" in the Age of the Earth FAQ and Isochron Dating FAQ).

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