"Plastic rocks" found on Trindade Island in the state of Espirito Santo is seen at the laboratory of the Federal University of Parana, in Curitiba, state of Parana, Brazil March 7, 2023. [Source: Reuters]

The geology of Brazil’s volcanic Trindade Island has fascinated scientists for years, but the discovery of rocks made from plastic debris in this remote turtle refuge is sparking alarm.

Melted plastic has become intertwined with rocks on the island, located 1,140 km (708 miles) from the southeastern state of Espirito Santo, which researchers say is evidence of humans’ growing influence over the earth’s geological cycles.

Santos and her team ran chemical tests to find out what kind of plastics are in the rocks called “plastiglomerates” because they are made of a mixture of sedimentary granules and other debris held together by plastic.

Trindade Island is one of the world’s most important conservation spots for green turtles, or Chelonia mydas, with thousands arriving each year to lay their eggs. The only human inhabitants on Trindade are members of the Brazilian navy, which maintains a base on the island and protects the nesting turtles.

The discovery stirs questions about humans’ legacy on the earth, says Santos.