Source - Economist, Nov 10, 2018: "The sea is lovely, dark and deep"
Business and economics: primary extraction (mining) of rare earths will begin soon on the ocean floor, the environmental consequences are unknown but may be severe and long-lasting.
The Clarion Clipperton Zone is a stretch of seafloor located a few hundred miles south and southwest of Hawaii. About three thousand feet down, on the surface of the ocean floor, are nodules of metal, usually iron or manganese. These nodules also contain rare earths like vanadium and molybdenum. As the nodules merely need to be scooped off the surface, their extraction is cost-competitive with that of traditional surface mines.
As the CCZ is more than 200 miles away from any nation's coast, it is governed by the United Nations Convention on the Law of the Sea and the UN International Seabed Authority or ISA. The ISA has issued 17 exploratory licenses for companies to begin mining the nodules. As the US is not a signatory to the UN Convention on the Law of the Sea, any US involvement must come through US-owned foreign subsidiaries who reside in a nation that has signed the Convention.
The environmental impacts are uncertain. The abyssal plain maintains a static environment, slow to respond to changes. Tracks from exploratory craft on the ocean floor can till be seen decades later. The mining should resemble a conveyor belt, with silt being returned to the seabed for minimal disruption. But profits can be increased if the silt is simply dumped back into the ocean from the surface, it will negatively impact life along the entire water column from seafloor to surface.