No one knows for sure whether there's oil off the North Carolina coast.

But researchers believe there's a substantial cache of natural gas in an area about 45 miles off Cape Hatteras based on past experience, explains UNC-Chapel Hill geology professor Kevin Stewart.

The gas would have formed when layers of prehistoric organic matter — basically dead sea creatures from about 150 million years ago — were buried under limestone rock. Being closer to the earth's crust, they were heated over millions of years.

As the material became natural gas, it floated upward, filling giant pores in the rock, "like a big sponge," Stewart said. Shale on top of the limestone then acted as a cap that kept the gas from escaping.

Stewart said they do not know for sure whether there's natural gas off the coast, but sophisticated models comparing similar geological conditions give strong indications.

"No one really knows until they drill, but from their models they know it's likely," he said.

Democrats say "offshore drilling." Republicans say "deep-sea drilling."

Who's right? Kevin Stewart, a geology professor at UNC-Chapel Hill, says both terms are arguably correct, though both also overstate their case a little.

Any oil drilling that takes place in the water is "offshore," while "deep-sea" — or "deep-water" in the geologists preferred lingo — typically refers to drilling that takes place off the continental shelf.

The area under consideration in North Carolina is about 45 miles off Cape Hatteras in a zone known as the continental slope, which is between 2,000 and 4,000 feet deep. That is just past the shelf, which is 460 feet deep, but before the deepest ocean bottom, which can be 7,000 feet deep or more.

"Offshore drilling is a much broader term, while deep water is a very specific area," he said.

The connotations work in each side's favor. By calling to mind the coastline, "offshore drilling" makes it sound like it's happening closer to the beach, while "deep-sea drilling" sounds like something that happens far out in the ocean.