The Final Frontier Below: What is Deep Sea Mining?
Introduction
Ever since early civilizations arose, the need for metals grew, mines were a cornerstone throughout human history and even now they are of the utmost importance. Yet land-based mines require vast amounts of acreage and leave behind irreparable damage, not only to the environment, but also to the people and ecosystems that surround them [1]. Even decades after the mines close and the minecarts stop hauling metals to the surface, their impact lingers leaving scars on its surroundings by leaving trails of pollution, deforestation, and habitat lost in its wake. Deep-sea mining offers a way to minimize terrestrial harm, while also gathering the critical resources we need most. While it does have its caveats that create its own problems, the future of resources may not be found in the ground anymore, rather in the dark abyss of the ocean.
The emerging idea of deep-sea mining is one that has only been around for a few decades, and at the center of it all lies potato-sized metal deposits known as polymetallic nodules [2], [3]. Unlike their terrestrial counterparts, they don’t need to be dug from layers of rock but instead lie scattered across the sandy seafloor.
These nodules are concentrated in a remote area of the Pacific Ocean known as the Clarion-Clipperton Zone, a stretch of seabed spanning millions of square kilometers [3], [5]. On the surface, it may seem like an easier, more efficient alternative to land-based mining since there’s no drilling or excavation. But as interest grows, so does the scrutiny. Global treaties, environmental watchdogs, and scientists are now debating whether this solution of the future could become a new problem, or a better path forward [2], [6].
What is Deep-Sea Mining?
Deep-sea mining is a broad term that refers to three different ways of gathering resources from the lightless deep [1], [2]:
Cobalt Crusts
The ocean holds mountain ranges and smaller mounds called seamounts. On their rocky slopes sits a mineral-rich layer containing cobalt, platinum, and other rare earth elements which are all vital for electronics, military technology, and renewable energy [2], [7]. Harvesting them, however, means scraping the crust from hard rock, a process that is both technically difficult and ecologically damaging due to the biodiversity found on these rocky outcrops [6], [7].Seafloor Massive Sulfides (SMS)
Hydrothermal vents on the seafloor spew superheated, mineral-laden water from cracks in the Earth. As this “black smoker” fluid cools in oxygen-rich seawater, dissolved minerals precipitate and coat the vents, creating deposits rich in copper, gold, silver, and zinc [2], [6]. These are essentially underwater ore veins formed by volcanic activity. But because vents host fragile and unique ecosystems, mining here risks wiping out species found nowhere else [2], [6].Polymetallic Nodules
Potato-sized lumps of metal-rich material sit loose on the seafloor, primarily in the Clarion-Clipperton Zone. They contain high concentrations of nickel, cobalt, manganese, and copper, making them highly attractive for clean energy technologies [3], [5]. Because they rest on the seabed rather than being buried, they’re seen as the most accessible, and potentially least disruptive, mining target [3], [7].
How Mining for Polymetallic Nodules Works
So how exactly do we get these nodules off the seafloor and onto a ship? The process involves three key steps [5], [7]:
Collection Vehicle
Robotic harvesters crawl along the seabed, using vacuums or scoops to gather nodules. Engineers try to design these machines to reduce sediment disturbance, but the plumes of silt they leave behind are one of the biggest environmental concerns [5], [7].The Riser System
Once gathered, the nodules are pumped up a long vertical pipe — the “riser” — which carries a slurry of nodules, seawater, and sediment 4–6 kilometers up to a ship on the surface. The pumps are specially engineered for these extreme depths [5], [7].The Surface Vessel
On board, the slurry is processed: nodules are separated from water and sediment. The nodules are stored for transport, while the leftover water and fine particles are discharged back into the ocean — raising questions about where and how to release them without harming ecosystems [5], [6].
Additional support systems, like remotely operated vehicles (ROVs), power supplies, and communications links, keep the whole process running smoothly [7].
The Environmental Concerns With Deep-Sea Mining
The risks of harvesting nodules overlap with other forms of seabed mining, but they also carry unique challenges [6], [7].
One of the biggest concerns is seafloor ecosystem damage. Nodules are among the only hard surfaces on the abyssal plain, making them the anchor for life in these deep habitats. Corals, anemones, sponges, and brittle stars depend on them to survive. By removing nodules, we erase this foundation [2], [6].
The collector’s intake and heavy tracks also disturb the sediment layer, which hosts worms, crustaceans, and countless microbes. Some of these smaller creatures may recover in decades, but species that depend on nodules cannot return — because nodules take millions of years to form. While a single vehicle only impacts a small patch, large-scale mining could mean widespread ecosystem loss [3], [6].
Another major concern is sediment plumes. These come in two forms [5], [7]:
Near-Bottom Plumes: Harvesters stir up fine sediment that currents can spread far beyond the mining site. Settling particles can smother organisms, clog filter feeders, and alter the oxygen-rich top layer of sediment that microbes rely on [5], [7].
Discharge Plumes: After nodules are processed on the ship, the waste water and fine particles are released back into the ocean. Where it’s discharged matters as the effects differ depending on its depth: [5], [6]:
Deep release: Keeps impacts near the seabed but risks further smothering the ecosystem.
Mid-water release: Avoids the seafloor but disrupts mid-ocean ecosystems and can spread over thousands of square kilometers [5], [6].
Companies and international bodies argue these risks can be managed. For example, plume size could be reduced by carefully choosing discharge depths, and no-mining zones could preserve key habitats. The challenge is that none of these solutions have been proven at commercial scale. The technology is still ahead of the science [6], [7].
Conclusion
Deep-sea mining will likely play a role in the future of resource acquisition. With the vast stores of critical metals on the ocean floor, someone at some point will attempt to gather them [1], [2].
While the current means of using a dredging-based system has its flaws, it is the only proven method to harvest these nodules as of right now. With time this could change, but the environmental problems with this way of extraction cannot be ignored.
For now, polymetallic nodule mining sits at the center of the debate. Its outcome could reshape industries from clean energy to electronics. Yet the environmental consequences remain serious, and the solutions are still unproven [3], [6].
References
[1] International Seabed Authority, “Deep-seabed minerals,” 2021. [Online]. Available: https://www.isa.org.jm/minerals
[2] C. L. Van Dover et al., “Scientific rationale and international obligations for protection of active hydrothermal vent ecosystems from deep-sea mining,” Marine Policy, vol. 90, pp. 20–28, 2018. [Online]. Available: https://www.sciencedirect.com/science/article/pii/S0308597X17306061
[3] C. Muñoz-Royo et al., “Extent of impact of deep-sea nodule mining midwater plumes is influenced by sediment loading, turbulence and thresholds,” Communications Earth & Environment, vol. 1, 2021. [Online]. Available: https://www.nature.com/articles/s43247-021-00181-3
[4] “Deep-sea mining impacts visible 44 years on,” Reuters, Mar. 27, 2025. [Online]. Available: https://www.reuters.com/business/environment/deep-sea-mining-impacts-still-felt-forty-years-study-shows-2025-03-27
[5] MDPI Water Special Issue, “A Review of Plume Research in the Collection Process of Deep-Sea Mining,” Water, 2024. [Online]. Available: https://www.mdpi.com/2073-4441/16/23/3379
[6] M. Levin et al., “Ecological and ethical considerations of deep-sea mining,” Nature Sustainability, vol. 1, no. 9, pp. 544–550, 2018. [Online]. Available: https://www.nature.com/articles/s41893-018-0141-6
[7] D. Wedding et al., “Managing mining of the deep seabed,” Frontiers in Marine Science, vol. 5, 2018. [Online]. Available: https://www.frontiersin.org/articles/10.3389/fmars.2018.00313/full
