Absolute vs relative dating techniques
In a way this field, called geochronology, is some of the purest detective work earth scientists do.
There are two basic approaches: relative age dating, and absolute age dating.
On the other hand, the half-life of the isotope potassium 40 as it decays to argon is 1.26 billion years.
So carbon 14 is used to date materials that aren’t that old geologically, say in the tens of thousands of years, while potassium-argon dating can be used to determine the ages of much older materials, in the millions and billions year range.
The narrower a range of time that an animal lived, the better it is as an index of a specific time.
No bones about it, fossils are important age markers.
You might have noticed that many of the oldest age dates come from a mineral called zircon.But one must be careful by interpreting the results of excavations since stratigraphical layers may present abnormalities.In some cases inversion of stratigraphical layers may occur, with older layers being on top of younger ones.That’s because zircon is super tough – it resists weathering. Each radioactive isotope works best for particular applications.
The half-life of carbon 14, for example, is 5,730 years.
Pretty obvious that the dike came after the rocks it cuts through, right?