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No longer the stuff of science fiction, the deep-sea mining industry is speeding up efforts to mine precious minerals in international waters. But some countries are looking to do so within their national boundaries. Norway, for example, became the first country to allow mining exploration in its own waters, and the United States may not be far behind.

In early March, the Department of Defense will deliver a report on the emerging deep-sea mining industry and its potential in the United States. Mining licenses for the high seas are out of reach for US companies, as their government has not signed the United Nations Convention on the Law of the Sea, an international agreement governing marine activities. But the United States can develop a seabed mining industry in its national waters. A new study highlights four regions in federal waters where deep-sea mining would be possible: the Blake Plateau off the southeastern United States, the Hawaiian Islands, the offshore region of California, and the Gulf of Alaska. These locations may contain nodules and ferromanganese crusts—unique features of the ocean floor that hold valuable minerals.

The Blake Plateau, offshore California, Hawaiian Islands, and Gulf of Alaska are prospective areas for deep-sea mining. Map courtesy of González Ortiz et al. with data from USGS

Formed over millennia and resting in the seabed, these nodules are tennis-ball-sized rocks containing copper, manganese, cobalt, and other minerals. Ferromanganese crusts that contain cobalt are mineral deposits found in underwater mountains that are remnants of long-extinct volcanoes. Researchers say it’s likely that nodules exist around the Hawaiian Islands and that all four areas of interest have ferromanganese crusts.

But these prospective regions are also hotbeds of biodiversity and human activity.

In the Gulf of Alaska, mining seamounts could endanger populations of groundfish—such as black cod—corals, and sponges. In California’s offshore region, shipping traffic and submarine cables intersect with areas where ferromanganese crusts likely exist. Mining there could also risk collisions with fishing vessels or oil tankers.

Researchers expect deep-sea mining around Hawai‘i to generate sediment plumes, which can travel several hundred to thousands of kilometers. Mining operations could threaten the lucrative bigeye tuna fishery and affect ray-finned fishes, sharks, sea turtles, and other endangered species.

But despite the federal government’s interest, states such as California and Oregon have already introduced legislation to ban deep-sea mining, citing the high risk to biodiversity, fisheries, and the rights of Indigenous peoples. The study authors argue that more data about the interactions between marine habitats and mining is urgently needed for stakeholders to better evaluate the risks of deep-sea mining.