Dating rocks using radioactive isotopes is called essex chronicle dating
The starting isotope is called the parent and the end-product is called the daughter.
The time it takes for one half of the parent atoms to decay to the daughter atoms is called the half-life.
The reason this age may not be a true age—even though it is commonly called an absolute age—is that it is based on several crucial assumptions.
Most radiometric dating techniques must make three assumptions: The major problem with the first assumption is that there is no way to prove that the decay rate was not different at some point in the past.
Carbon-14 dating is another common technique, but it can only be used on carbon-containing things that were once alive.
Knowing this first: that scoffers will come in the last days, walking according to their own lusts, and saying, “Where is the promise of His coming?
For since the fathers fell asleep, all things continue as they were from the beginning of creation.” For this they willfully forget: that by the word of God the heavens were of old, and the earth standing out of water and in the water, by which the world that then existed perished, being flooded with water.
There is also a difference in the timescale used to explain the layers.
Determining the relative age of a rock layer is based on the assumption that you know the ages of the rocks surrounding it.