They observed that every rock formation, no matter how ancient, appeared to be formed from still older rocks.Comparing these rocks with the products of present erosion, sedimentation, and earth movements, these earliest geologists soon concluded that the time required to form and sculpt the present Earth was immeasurably longer than had previously been thought.We will deal with carbon dating first and then with the other dating methods.
To see how we actually use this information to date rocks, consider the following: Usually, we know the amount, N, of an isotope present today, and the amount of a daughter element produced by decay, D*.
By definition, D* = N-1) (2) Now we can calculate the age if we know the number of daughter atoms produced by decay, D* and the number of parent atoms now present, N.
So, we have a “clock” which starts ticking the moment something dies.
Obviously, this works only for things which were once living.
Cosmic ray protons blast nuclei in the upper atmosphere, producing neutrons which in turn bombard nitrogen, the major constituent of the atmosphere.
When neutrons collide, a nitrogen-14(seven protons, seven neutrons) atom turns into a carbon-14 atom (six protons, zero neutrons) and a hydrogen atom (one proton, zero neutrons.
Familiar to us as the black substance in charred wood, as diamonds, and the graphite in “lead” pencils, carbon comes in several forms, or isotopes.
One rare form has atoms that are 14 times as heavy as hydrogen atoms: carbon-14, or C ratio gets smaller.
In 1960, he was awarded the Noble Prize in Chemistry for this work.