June 4, 2014 Sciencemag
As a material plastic may last longer than we expected. Besides filling up landfills and being trapped in Arctic ice, a part of the material is becoming rock hard.
“The article is intriguing and fascinating,” says geophysicist Douglas Jerolmack of the University of Pennsylvania, who was not involved in the work. “If these things can be preserved, then they might be a nice marker around the world of when humans came to dominate the globe and leave behind their refuse in mass quantities.”
Geologist Patricia Corcoran of the University of Western Ontario in London, Canada, and Charles Moore, captain of the oceanographic research vessel Alguita, stumbled upon the new rocks on a beach on the Big Island of Hawaii. These stones, which they’ve dubbed “plastiglomerates,” most likely formed from melting plastic in fires lit by humans who were camping or fishing, the team reports this month in GSA Today. Although anywhere there is a heat source, such as forest fires or lava flows, and “abundant plastic debris,” Corcoran says, “there is the potential for the formation of plastiglomerate.” When the plastic melts, it cements rock fragments, sand, and shell debris together, or the plastic can flow into larger rocks and fill in cracks and bubbles to form a kind of junkyard Frankenstein.
Corcoran says some of the plastic is still recognizable as toothbrushes, forks, ropes, and just “anything you can think of.” Once the plastic has fused to denser materials, like rock and coral, it sinks to the sea floor, and the chances it will become buried and preserved in the geologic record increase.