Plastic pollution is a worldwide problem - about 32 million tons of US plastic waste was generated in 2012, according to the Environmental Protection Agency. Now, researchers have discovered an unexpected way that some plastic waste is persisting: as a stone.

A team from the University of Western Ontario published a study in the journal GSA Today describing rocks made of plastic, called "plastiglomerates," found on the Big Island of Hawaii.

The substance is a fusion of both natural and manufactured materials, including sand, shells, pebbles, basalt, coral and wood. Melted plastic binds them all together or seeps into the cavities of larger rocks to form a rock-plastic hybrid.

"Most conventional plastic is relatively thin and fragments quickly," Richard Thompson, a marine biologist at Plymouth University in England who was not involved in the research, told The New York Times. "But what's being described here is something that's going to be even more resistant to the aging process."

Researchers say these materials will be long-lasting, and may even become permanent markers in the planet's geological record.

Charles Moore, a sea captain and oceanographer at the Algalita Marine Research Institute in Long Beach, Calif., was the one who discovered plastiglomerate in 2006. At the time, Moore was surveying plastic washed up on Kamilo Beach. This spots tends to be a garbage hub because of the way the currents circulate, Maine News reported.

Patricia Corcoran, an earth scientist at Western University in Ontario, heard of Moore's research, and was so intrigued she and her colleagues traveled to Hawaii, sampled 21 sites and gathered all plastic-rock specimens having a diameter of around one inch or more.

They collected 205 samples, most of them hard to identify and ranging from the size of a peach pit to the diameter of a large pizza, according to The Times.

Moore theorizes that lava from the nearby Kilauea volcano created the plastic marvels, but seeing as how such flows haven't reached the beach in over a century, it's not likely.

Regardless of their origin, scientists do agree that these stones will be around for some time.

"Plastics and plastiglomerates might well survive as future fossils," said Jan Zalasiewicz, a geologist at the University of Leicester in England, who was not involved in the discovery.

"If they are buried within the strata, I don't see why they can't persist in some form for millions of years."