The substance, referred to as plastic rocks or plastic stones by some, has been named plastiglomerate, and is a mixture of manufactured and natural materials.
Melted plastic binds sand, pebbles, shells, wood, coral, seeps or basalt into the cavities of bigger rocks to make a rock-plastic hybrid.
According to the researchers report in the periodical GSA Today, the resulting materials will possibly be long-lived, and can even become permanent markers in the earth's geologic record in the form of future fossils.
In 2006, plastiglomerate was discovered by Charles Moore, a sea captain and oceanographer at Algalita Marine Research Institute in Long Beach, California. He was examining plastic washed up on Kamilo Beach, which is a far-off, polluted stretch of sand on Hawaii?s Big Island.
Like other southeastern seashores in Hawaiian archipelago, Kamilo Beach gathers trash due to the circulation of currents. After noticing some peculiar plastic-covered rock collections, Moore took some photos and collected some samples.
The importance of that discovery was not understood until 2012, when Patricia Corcoran, who is an earth scientist at Western University in Ontario, requested Mr. Moore to give a lecture about plastic pollution.
Moore showed plastic conglomerates in one of his slides, though he had not given any name for them. Fascinated, Dr. Corcoran went to Hawaii to see the unusual anthropogenic stones for herself.
Dr. Corcoran and a colleague sampled 21 sites on a 2,300-foot strip at Kamilo Beach. They gathered all plastic-rock samples with a size of about an inch or more.
The majority of the melted plastic was difficult to identify, however traces of lids, ropes and nets appeared in some stones. They gathered 205 differently-sized pieces.
Firstly, Mr. Moore conjectured that lava from the close Kilauea volcano produced the plastiglomerates, but flows have actually not approached Kamilo Beach for at least a century. Interviews were conducted with local residents and it was found that bonfires were a more likely explanation.
The sand of Kamilo Beach is covered with pollutant particles known as plastic confetti. This makes it almost impossible to detect a bonfire spot devoid of plastic waste, according to Dr. Corcoran.
As scientists define rocks as things created by natural procedures, Corcoran prefers to mark the new materials as stones.