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Plastic Pollution Is Forming Plastiglomerate, A New Type Of Stone

Fused plastic jumbles may become a marker for human activity

by Carmen Drahl
June 23, 2014 | A version of this story appeared in Volume 92, Issue 25

Credit: Patricia Corcoran
Plastiglomerates are, in general, a few centimeters in size.
Different examples of plastiglomerates, a new kind of stone formed with melted plastic, sand, shell bits, rock, and other debris
Credit: Patricia Corcoran
Plastiglomerates are, in general, a few centimeters in size.

Chemists have developed all kinds of plastics over the years. But that legacy might unintentionally end up in the geologic record, if a new type of stone sticks around as long as its discoverers think it could. The stone is called plastiglomerate. It forms when plastic waste, melted by a heat source such as a campfire, mingles with sediment, coral, shell fragments, and other debris. Geologist Patricia L. Corcoran of the University of Western Ontario found the new stone with help from Charles J. Moore, the oceanographer known for bringing attention to the Great Pacific Garbage Patch, an area of the Pacific Ocean awash in plastic trash. They canvassed a 700-meter swath of shoreline on Hawaii’s Kamilo Beach and found plastiglomerates everywhere they looked (GSA Today 2014, DOI: 10.1130/gsat-g198a.1). Corcoran thinks the plastic hodgepodges are likely to be found elsewhere and that they might persist if they’re buried. “My best guess is that incorporation of the plastics into rock will make them even more recalcitrant” to biodegradation than they already are, says Darrell Jay Grimes, a bioremediation expert at the University of Southern Mississippi.


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