Relative dating of fossil
This process requires much more sophisticated chemical analysis and, although other processes have been developed, often utilizes the decay rates of radioactive isotopes to determine the age of a given material.
Using this process geologists are able to assign actual ages with known degrees of error to specific geologic events.
For example, rocks of the Phanerozoic eon are found on top of rocks from the Proterozoic eons therefore rocks of the Phanerozoic are younger than rocks of the Proterozoic.
Unlike relative time, absolute time assigns specific ages to events or formations and is typically recorded in years before present.
In either case, weathering and erosion are left free to work their mischief and erase some evidence of the geologic past. We’ll never know what happened during those 1.2 billion years? The Grand Canyon is not the only location with a rock record.
With out individual time stamps the process of dating these structures could become extremely difficult.
After my three-parter on fossils, I was sure you'd be sick of them, but there was a request (seconded by a few people) to talk about one particular aspect of paleontology that I didn’t cover yet: How do you know how old a fossil is? Misconception: Paleontologists directly date fossils. Correction: Most of the time, fossils are not mean we don’t have any idea how old it is. It’s just that we can’t run some kind of neat test (involving colored water, maybe? Instead, we have to rely on two methods of dating: relative dating and radiometric dating.
Relative dating—as the name suggests—is a method of determining the relative ages of rock layers and the fossils contained therein.
They get uplifted, tilted, faulted, squashed and squeezed, and magma gets injected into them.
It’s all a bit of a mess—but a mess that can be put in chronological order using relative dating principles.