Between a rock and an artistic place

Kamilo Beach is, arguably, the world’s dirtiest beach. Located on the southeastern coast on the island of Hawaii, the beach’s sands are littered with marine debris – most of it plastic waste washed up from the Great Pacific Garbage Patch.

Among this garbage, Patricia Corcoran and Kelly Jazvac have discovered something new.



Inspired by a lecture from renowned oceanographer Charles Moore, Corcoran, a geologist and Earth Sciences professor, and Jazvac, an artist and Visual Arts professor, headed to Kamilo Beach to discover what was there. What they found was an array of rock formations, with plastics fused within.

They called it ‘Plastiglomerate.’



“They’ve cleaned up most of it, but there’s still a lot of plastic material we find on the beach, a lot of larger intact fragments, strange things, bowls and cups and spoons and pails and slippers and flip-flops,” Corcoran said. “A lot of the big pieces of this material had already been taken away, but there were still a lot of fragments buried in the sand.

“Basically, in geology, a conglomerate is a rock made of many different fragments, and because this has plastic, I just thought Plastiglomerate was appropriate,” she added.

Plastiglomerate is the first type of rock formation influenced by humankind, and, so far, it has only been found on Kamilo Beach, though it is likely in existence elsewhere.

“Charles Moore thought it could be formed by lava flows because it’s the ‘Big Island’ of Hawaii and it’s volcanically active,” Corcoran said. “He thought the lava could have flowed to the beach and melted it.

“But in the end, when we went, we realized – quite easily actually – there are geological maps of the island and there haven’t been any flows that are active there for the last thousand years. The plastic we see in the environment is from the last 50 years or so.”

The pair soon learned people living in the vicinity of the beach often burned the plastic materials scattered on the sands.

“It’s so polluted you couldn’t have a campfire there without burning some plastic. The quantity is so high that if you’re living near this beach, and you want to live there, what else are you going to do with this material?” Jazvac asked.

“We knew then it was an anthropogenic influence, rather than a natural burning of the plastic,” Corcoran added.

Corcoran and Jazvac have written a paper, An anthropogenic marker horizon in the future rock record, which will appear in the journal GSA Today in June as its cover story. It is the first time this kind of rock formation has been reported in scientific literature.

The significance of Plastiglomerate is two-fold, the pair explained.

“Basalt has higher density than plastic. So, what happens when you melt the plastic, and it becomes stuck to the rock fragments, that makes the plastic heavier and more dense and it increases its potential to be buried,” Corcoran said.

“Once you do that, it will eventually become part of the rock record, a mark on the horizon. If someone came along a million years from now, and was looking at a stratigraphic section through the rock, they would be able to see this plastic along one horizon and say this was the time when humankind was using so much plastic and not disposing of it properly.”

Jazvac said the artistic and cultural implications are likewise melded into Plastiglomerate.

“I’m really excited about this. We did this – people made this. And that’s a cultural concern. As an artist, I’m interested in culture and the impact people have on the environment around them, and this is kind of an already made artwork that speaks to that,” she said.

“As a sculptor, I’m fascinated by these objects because of the way the plastic has flown through the ocean currents of the world and ended up in this weathered state on the beach. I couldn’t put my materials through a similar process and glue them together in a similar way. I couldn’t make it if I tried. All the history and politics crammed into these objects is fascinating.”