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Plastic trash is evolving into new types of rocks

Monday, June 24th 2019, 3:36 pm - Since the 1950s, an estimated 1 billion tonnes of plastic have been thrown out. Research suggests it will take up to 500 years for some forms to biodegrade.

Researchers at the Environmental Research Center on the Portuguese island of Madeira have identified one way that plastic trash is interfering with the environment. In a recent study, marine ecologist Ignacio Gestoso and his team have identified something called "plasticrust" which acts as a layer of plastic coating shoreline rocks.

Earther says the crust resembles "old chewing gum grafted onto a sidewalk," but it can't be peeled away. One year after Gestoso found the sample it was still there.

Within three years, the plasticrust had grown from a single specimen to covering nearly 10 percent of rocks in the area. Chemical analysis shows it's made of polyethylene, which is commonly used in plastic packaging.


Gestoso's team says it's the first time this type of pollution has ever been documented. The researchers think the crust formed by crashing against the rocky shore.

plasticrust Evidence of plasticrust. Photo credit: Ignacio Gestoso

The ecological implications of plasticrust are unknown, but the study notes the substance is replacing natural films that form on rocks. That could be problematic for some snail and barnacle species because they rely on those films to adhere to rocks in order to eat.


Caption/Photo courtesy: Patricia Corcoran: Photographs of clastic plastiglomerate on Kamilo Beach. (A) Subrounded fragment containing basalt clasts, molten plastic, yellow rope, and green and red netting. (B) Portions of black and green plastic containers adhered to basalt fragments and connected by netting. (C) Fragment containing plastic pellets and “confetti” with woody debris. (D) Adhered mixture of sand, black tubing, a bottle lid, “confetti,” netting, and part of a plastic bag.

In 2014 researchers from the University of Western Ontario found evidence of plastic mixing with organic debris in Hawaii, forming a new type of rock they called plastioglomerate.

At the time they said it has a "good potential to persist" in nature and may become part of the planet's rock record, creating a permanent "marker of human pollution."


Sources: Earther | Science of the Total Environment

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