Saturday | November 18, 2017
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Plastic rocks on Big Island beach?

Plastic debris is doing more than cluttering Kamilo Beach.

According to a new study, it’s also becoming part of its geologic record.

The report published in this month’s issue of GSA Today notes the presence of plastiglomerate on the Big Island beach, formed by melted plastic mingling with beach sediment, basalt fragments and other types of debris. The researchers identified camp fires as being the source of the melted material.

The result is a new rock, the study notes, and could be seen as a marker for human pollution, similar to methane concentrations in ice cores.

According to the study, plastic can persist in the environment for hundreds to thousands of years.

The rocks will last the longest if buried or if they make their way to the bottom of the ocean, where cooler temperatures and protection from ultraviolet light slows the process of disintegration.

“We observed that some of the plastiglomerate had been buried by sand and organic debris, as well as having been trapped within vegetation, which demonstrates the potential for preservation in the future rock record,” the study said.

The report also notes that plastiglomerate can more easily become buried and preserved than plastic-only particles.

The largest amount of plastic was identified as “confetti,” essentially the embrittled remains of products.

Partial lid containers contributed to 22 percent of the fragments, while fishing equipment was found in 20 percent of the samples.

Kamilo Beach was the focus of the study due to its location on the southeast side of the island, which receives the largest deposits of ocean debris, including plastic.

Three researchers from the University of Western Ontario in Canada and Algalita Marine Research Institute in California authored the report.

GSA Today is the journal of the Geologic Society of America.

Email Tom Callis at


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