How is carbon-14 produced, and where does it exist naturally?

Question

How is carbon-14 produced, and where does it exist naturally?

Answer 1

Carbon 14 is produced in nature, and is 1percent abundant in all carbon. I think...

Answer 2

It is produced naturally in the upper atmosphere by the action of cosmic rays on nitrogen 14 atoms.  The reaction is given in the linked article.

Once produced, the atoms diffuse down to the biosphere, where it gets incorporated into all living things.  Rock deposits that contain carbon, including oil and gas deposits, do not contain any carbon-14: with a half life of 5730 years, it has already decayed.  It only makes up about 1 part-per-trillion of carbon on the Earth.