The Impossible Carbon Reservoir

A lake of molten carbon the size of Mexico was recently discovered under western USA. That is a heck of a lot of carbon, and it makes one wonder how many dinosaurs it must have taken to fill it.

With so much carbon locked in deep under the mantle of our planet, a large percentage of ancient life must have turned into carbon rather than dirt after death. It must have been the rule rather than the exception that dead plants and animals did not rot, but became instead locked in under clay or mud so that they could turn into carbon of various sorts.

And to end up many hundred kilometers down, this huge lake of carbon has mysteriously managed to subduct under the American continent where it has slid along in an easterly direction for hundreds of miles. Because something as light as carbon will always tend to slide in under granite?

The story makes no sense, but is nevertheless presented as the truth. No alternative explanation is offered. Let me therefore make some suggestions:

Could it be that the carbon has been where it is today ever since the formation of our planet? Could it be that most carbon on our planet has nothing to do with dinosaurs or other fossil sources? Could it be that carbon was simply one of a large number of different materials that came together to form our planet when it was originally created?

Oil rig - By Joshua Doubek - Own work, CC BY-SA 3.0, Link