Explained | Why have plastic rocks been found on the remote Brazilian island of Trindade?

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The story so far: A recent discovery of rocks made of plastic debris in the remote Brazilian Island of Tridade, which hosts a range of rare marine species, has sparked alarm among scientists. The fact that plastic had reached the secluded volcanic island known for its unique geology was “terrifying”, Fernanda Avelar Santos, a geologist at the Federal University of Parana told Reuters.

What are the geological features of Trindade Island?

General view of Trindade Island in Espirito Santo state, Brazil, on October 15, 2022.

General view of Trindade Island in Espirito Santo state, Brazil, on October 15, 2022. | Photo Credit: Reuters

Trindade Island is the easternmost and most remote point in Brazilian territory, located about 1,140 km from the southeastern state of Espírito Santo. Trindade surfaced owing to volcanic activity under the Atlantic Ocean about three million years ago. Trindade, along with the Martim Vaz archipelago about 40 km away, hosts many species of native flora and fauna including seabirds and marine creatures.

Trindade is known for being one of the most important conservation and nesting spots, both in Brazil and globally, for green sea turtles ( Chelonia mydas), hosting nearly 1,800 nests annually on a small stretch of land. It is also known for hosting native seabirds like the Trindade Petrel, and the great frigatebird, which is otherwise only found in the Indo-Pacific and not the Atlantic. The surrounding region also hosts species of sharks, dolphins, and corals.

Its formation due to volcanic activity makes its terrain unique, reaching a 600 m elevation at multiple points while having surrounding oceanic depths of 6000 m. The island is considered one of the most recent manifestations of alkaline volcanic activity in Brazil. It is at the eastern end of a chain of guyots, or submarine volcanic mountains with flat tops, extending east to west about 1,100 km from the continental shelf off Brazil’s coast.

The island was first sighted in 1502 by a Portuguese sailor and was first inhabited by humans only in 1730 when Azorean communities colonised the Island. Unsuccessful in their attempt, they left Trindade in the following years, abandoning their domestic animals like goats and pigs, which scientists blame for damaging much of the island’s original vegetation.

Currently, Trindade is a protected area not inhabited by any humans except for a small Brazilian Navy Crew which oversees the waters. It is also free of tourist activity.

How did plastic rocks get formed on the remote Island?

Parana University geologist Ms. Santos and her colleagues, who discovered the rocks made of plastic debris, say that melted plastic became intertwined with rocks on the island. Plastic reaching Trindade despite it being hundreds of miles away from the mainland was evidence of humans’ growing influence over the earth’s geological cycles, the geologists said.

Ms. Santos told Reuters that the team ran chemical tests on the rocks to determine what kind of plastics were in these rocks—called “plastiglomerates” since they are made of a mixture of sedimentary granules and other debris held together by plastic.

“We identified (the pollution) mainly comes from fishing nets, which is very common debris on Trindade Island’s beaches,” the geologist said. “The (nets) are dragged by the marine currents and accumulate on the beach. When the temperature rises, this plastic melts and becomes embedded with the beach’s natural material.”

The scientists also revealed that the spot where they found the plastic rocks is a “permanently preserved area in Brazil, near the place green turtles lay their eggs”.

How bad is marine pollution today?

While talking about the ecologically damaging discovery, the geologist said this was a clear manifestation of the Anthropocene, a term proposed by scientists to describe the current geological epoch, where humans are knowingly shaping the planet, instead of the usual geological processes which take millions of years.

The UN Human Development Report 2020 notes: “The Anthropocene: the age of humans. For the first time in our history the most serious and immediate, even existential, risks are human-made and unfolding at planetary scale.”

Referring to the rocks made of plastic, Ms. Santos said that garbage and plastic dumped incorrectly in the oceans are turning into “geological material” and getting preserved in the “earth’s geological records”.

According to the UN, decades of overuse and a surge in short-lived, single-use plastics, have led to devastating levels of marine pollution. Nearly 12 million tonnes of plastics are swept into the oceans annually and gyres, which are described as ‘islands of plastic’, have cropped up.

While most plastics remain intact for years and even centuries, some erode to form ‘microplastics’, which are then consumed by marine wildlife and finally humans. Microplastics are plastic particles less than 5mm in diameter. They contribute to over 80% of ocean debris.

Scientists have discovered microplastics in a host of places— from the remote Swiss mountains and fresh Antarctic snow to in human blood.

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