Radiometric dating instruments pure love dating site
Fortunately, we are able to date older fossils using the radiometric breakdown of other elements (Potassium-Argon dating, Argon-Argon dating, and Rubidium dating [I'm writing this without any refs - so this last one might be wrong]).
Usually the radioactive 'clocks' for these elements are started when the elements are deposited by a volcanic eruption (usually in the form of ash).
During the 19th century, and even well into the twentieth, geological chronology was very crude.
Dates were estimated according to the supposed rate of deposition of rocks, and figures of several hundred million years were bandied out; usually arrived at through inspired guesswork rather than anything else.
By comparing the proportion of the two, one can work out how old the deposit is.
If the sample is 75% U-235 and 15% Lead (and 10% other), then the sample is approximately 300 mya.
Of course C-14 would never be of any use for dating dinosaur bearing deposits, unless you want everything to date to around 40,000 years!
Radiometric dating works on the principle that certain atoms and isotopes are unstable.
However, the error range increases drastically once you pass 50,000 years.