Millions of years ago the ancient oceans had microorganisms that lived and died in the oceans. When the microorganisms died there bodies fell to the ocean floor. After the bodies decomposed, what was left was almost pure carbon. The crust of the earth surface is in constant motion. Movement is due to tectonic plates and the continental drift.
When one of the tectonic plates was pushed under another the bodies of the microorganism, now carb...