Our Plastic Trash Is Turning Into These Bizarre Rocks

Even in paradise, trash can be found—and it’s usually plastic debris. Kamilo Beach, on Hawaii’s Big Island, is one of the dirtiest beaches in the world. It recently became the discovery site of a new formation: a rock made of plastic, sediment, lava, and organic debris.

When oceanographer Charles Moore first saw it, he thought that lava had caused the plastic to melt and form rock with surrounding debris. But scientists, who call the formation plastiglomerate, learned that lava hasn’t flowed to that area since our pre-plastic years. They later concluded that local people who were camping or fishing have been unwittingly building the rocks by burning plastic.

“It’s possible other people have found [the plastic conglomerates] at other locations before Captain Moore did, but nobody had thought to report it,” Patricia Corcoran, a geologist from the University of Western Ontario, told Live Science.

“I would say that anywhere you have abundant plastic debris and humans, there will probably be plastiglomerates,” she said. “It definitely shows how humans have interacted with Earth’s biophysical system.”

Just as alarming is that the plastiglomerates are denser than plastic-only materials. This means the new rocks are more likely than regular plastic to sink and become preserved underground—so they could easily become our generation’s geological legacy.

“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 said. “But that’s not a legacy we really want.”