Now, when I did that, I made a pretty big assumption, and some you all have touched on this in the comments on You Tube on the last video, is how do I know that this estimate I made is based on the assumption that the amount of carbon-14 in the atmosphere would have been roughly constant from when this bone was living to now?And so the question is, is the amount of carbon-14 in the atmosphere and in the water, and in living plants and animals, is it constant?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.And so it's kind of a record of the atmosphere up to 10,000 years. Those are the speleothems that are coming from the top of the cave.If you want to go even further back, you can look at cave deposits, and the fancy word for these cave deposits are speleothems. But the reason why these are useful is these are formed by calcium carbonate, so they have carbon in them, and slowly over, really, tens of thousands of years, the water in the cave deposits that calcium carbonate.
For example if you have a fossil trilobite and it was found in the Wheeler Formation.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.Relative age dating also means paying attention to crosscutting relationships.Say for example that a volcanic dike, or a fault, cuts across several sedimentary layers, or maybe through another volcanic rock type.
Familiar to us as the black substance in charred wood, as diamonds, and the graphite in “lead” pencils, carbon comes in several forms, or isotopes.