How are fossils dated using radiometric dating inter racial dating catholic
For instance, if a volcano erupts, like the super volcano that blew up to form the caldera in which Yellowtone Nat'l Park sits, then it left a lot of ash scattered over North America.THAT was a discrete instant in time geologically since the explosion occurred and the ash fall lasted for years not hundreds or millions So we can identify that layer of ash in the rock record and say..happened in such and such time.Cambrian and Ordivician and Silurian saw an increase in certain other organisms.So discrete lines were drawn and refined later as we got a better understanding and found more fossils delineating the periods in which they lived more clearly.So, it should be clear now that if you had a fossil shell in a rock in Virginia and found the same shell in a rock in Russia, that the shell found in both places was living during roughly the same time, not the same year, but within the geologic range of its existence. Just for example as if your bones are one day are found in the cemetery bone collection found in a sandstone a few million years from now by aliens exploring the earth.They would not know that you died in 2020, but only that you existed and lived during the several million years that homo sapiens inhabited the earth. In the Triassic period there was an excess of Iron and lots of oxygen so sediments are found world wide from this period and they are called Triassic Red Beds due to their bright red rusty appearance.Yes there are exceptions to this but we know in what environments of deposition they occur and can distinguish the exception from the rule.Now once we have established a relative age we can try to fine tune the age of the fossil itself by radiometric methods that are considered Absolute Age methods meaning they can give us a rough age in years before present.
One of the favorite ploys by Creationists is to say well how do you know the rocks haven't been turned upside down.
Well we do this pretty easily because bed forms form in sand and silts allowing us to tell if the rock has been folded or turned over.
We can look at grain size, larger grains usually settle first, followed by smaller and then finer grains so we look at the particle size distribution.
Another way we can split the geologic time line into intervals or periods are based on fossil evidence of certain organisms.
The Jurassic period the time of the Dinosaurs is an example.