Plastics break down in the environment at a very slow rate. As a result scientists say a build up of such materials has actually created a new type of "stone" that will be maintained in the rock record, possibly long enough for future generations to study.
A study about the material published in Geological Society of America Today details the new substance called "plastiglomerate," a mixture of melted plastic, beach sediments, basaltic lava fragments and organic debris. Plastiglomerate was first identified on Hawaii's Kamilo Beach, which is in a location that makes it prime target for plastic debris brought to it from the water and wind.
“Plastics and plastiglomerates might well survive as future fossils,” Jan Zalasiewicz, a geologist at the University of Leicester who was not involved in the study, told the New York Times. “If they are buried within the strata, I don’t see why they can’t persist in some form for millions of years.”
Types of plastiglomerate found on the beach. (Image source: Corcoran et al. via GSA Today)
"Our results indicate that this anthropogenically influenced material has great potential to form a marker horizon of human pollution, signaling the occurrence of the informal Anthropocene epoch," the study authors wrote.
"On a beach as dynamic as Kamilo, preservation of plastics in the sediment column could occur where trapped sediment is covered with sand or where a polymer is combined with a much denser material. We observed the results of this density increase on Kamilo Beach, where great quantities of melted plastic have mixed with the substrate to create new fragments of much greater density," the authors continued.
Plastiglomerate is a multi-composite material identified in nine of the 21 sample sites evaluated by researchers. The largest piece of plastiglomerate on the beach was about 70x32 inches, but researchers also believe similar materials could be forming in marine environments as well.
The formation of plastiglomerate by melting of materials on this beach is driven mainly by campfire burning, but the study authors said similar materials could form around the globe in areas experiencing volcanic eruptions, forest fires or extreme temperatures.
"I would say that anywhere you have abundant plastic debris and humans, there will probably be plastiglomerates," lead author Patricia Corcoran, a geologist at the University of Western Ontario, told Live Science.
"One day in the future, people can look at this material and use it as a marker horizon to see that in around 2010, humans were polluting the planet with plastic," Corcoran continued. "But that's not a legacy we really want."