A rock made partially of plastic, found recently on a Hawaiian beach, inspired scientists to consider what role plastics will play in the geologic record many years from now.

More than 6 billion metric tons of plastic have been produced and relinquished to nature since the mid-20th century. And though a decent portion of it ends up in landfills or is recycled, large amounts are left littered throughout the natural world.

And some of that plastic is finding its way into rock formations, as recently happened on a beach of Hawaii's Big Island.

The plastic rock was found by geologist Patricia Corcoran, of the University of Western Ontario, and Charles Moore, captain of an oceanographic research ship called Alguita. The rock featured sand, seashells, volcanic rock, coral and, of course, plastic.

In the wake of their discovery, the two scientists decided to dub these types of rocks "plastiglomerates."

Corcoran and Moore detailed their discovery in the journal GSA Today earlier this month. In their study, they conclude that plastiglomerates likely form when plastic is melted in a campfire. The liquified plastic binds with a conglomerate of other materials to create a unique rock formation. The two scientists acknowledge that plastic rocks could form anywhere there is enough heat to melt plastic -- lava formations or forest fires.

The scientists say plastiglomerates have been found on other beaches as well, and that sometimes identifiable pieces of human debris is mixed in and embedded, like rope, forks and toothbrushes. The fact that real rocks, sand and coral are often fused with the plastic means the plastiglomerate has a better chance of sinking into the ocean or other bodies of water, insuring it will remain a preserved part of future geologic records.

"Plastics and plastiglomerates might well survive as future fossils," Jan Zalasiewicz, a geologist at the University of Leicester in England, told the New York Times. "If they are buried within the strata," Zalasiewicz added, "I don't see why they can't persist in some form for millions of years."

Some scientists say that plastiglomerates mark the beginning of new geological era, the Anthropocene -- the presence and proliferation of plastic rocks marking the point at which human activity began leaving its most visible and vast imprint on the earth via pollution.