Scientific controversy with radioisotopic dating
In this way, multiple trees can be used to build a master chronology for a forested region.
Geologists have found annual layers in ice that are easily counted to multiple tens of thousands of years, and when combined with radio isotope dating, we find hundreds of thousands of years of ice layers.
It’s hard to find rocks on the surface of the Earth that have not been altered over time.
Most old rocks have been eroded by wind and water or submerged by continental plates.
Some isotopes are unstable, and over time these isotopes “decay” into isotopes of other elements.
For example, Potassium-40 is unstable and decays into Argon-40.
The annual ice layers in glaciers provide a similar method that goes back much further in history.