Sediment columns giving an unbroken history for more than 25,000 years have been identified in about 30 locations around the world.
Age estimates can be cross-tested by using different isotope pairs.
Results from different techniques, often measured in rival labs, continually confirm each other.
Radiometric dating is the method for establishing the age of objects by measuring the levels of radioisotopes in the sample. It decays to nitrogen 14 with a half life of 5730 years.
Carbon 14 is created by cosmic rays in the upper atmosphere.
In fact, they track because radiometric data is accurate.
An expert scientist summarizes: "The first radiometric dates, generated about 1920, showed that the Earth was hundreds of millions, or billions, of years old.
There are three reasons why radiometric data is known to be accurate: 1.
It depends upon radioactive decay, which is known to be extremely stable, not influenced my chemical processes, and which can be measured quite accurately.
For dating back to about 35,000 years, sediment layers are precise. Sediments include different types of pollen depending upon the season.