A New Threat to Oceans: Deep-Sea Mining for Precious Metals


This huge species of cnidarian in the genus Relicanthus with 8-foot long tentacles has attached itself to a dead sponge stalk on a polymetallic nodule in the CCZ. Image by Diva Amon and Craig Smith.


This box-core sample of the seabed is full of polymetallic nodules. Image by Craig Smith.


The International Seabed Authority has divided up the seabed of the Clarion Clipperton Zone into 15 different claim zones. Image courtesy International Seabed Authority.

Around 500 miles southeast of the bright turquoise waters at Honolulu Harbor, and two and a half miles down to the dark ocean floor, a massive carpet of potato-sized rocks stretches thousands of miles on the seabed. These rocks, called polymetallic, or manganese, nodules, are made up of manganese, nickel, copper, and cobalt. The nodules’ growth is one of the slowest geological processes in the world—it takes millions of years for one to grow a couple of millimeters: Tiny particles precipitate from the surface of the ocean to the seafloor and conglomerate around a core, like a rock or a shark tooth, and create a nodule.

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