5 deep-sea sources of critical minerals essential to technology, and the fragile marine life at risk
You may be hearing a lot lately about critical minerals and rare earth elements. These natural materials are essential to industry and modern technology – from cell phones to fighter jets.
These include lithium and cobalt used in batteries, neodymium for magnets in motors and hard drives, and rare earths essential for defense systems, lasers and medical imaging. Critical minerals are also essential for renewable energy systems, energy storage and digital infrastructure. Without them, modern society – and any realistic path to a net-zero emissions world – would not be possible.
Critical minerals get their name because they are also highly vulnerable to supply chain disruptions due to global events, trade tensions, or economic instability. And today, one country dominates many critical mineral supply chains: China.
With this in mind, many governments are looking for alternative sources of essential minerals, and several companies are considering the seabed as a potential new frontier for their extraction.
As a marine geologist, I know the potential for seabed minerals is vast. But that doesn’t mean these minerals are easy to harvest. They come in many forms, from potato-sized rocks scattered on the seafloor to seafloor crusts at hydrothermal vents and underwater brine pools. And they are often found in sensitive places that support fragile marine life, raising questions about the damage being done to some of the least explored and least understood regions of our planet.
Polymetallic nodules on the seabed
When you imagine seabed mining, it’s probably polymetallic or manganese nodules that come to mind.
The rock-like nodules are about the size of a potato and are scattered across large, deep-water plains, typically between 3,000 and 6,000 meters deep, in several regions, including a large area of the Pacific Ocean southeast of Hawaii.
They are primarily made of manganese and iron, although they can contain significant amounts of other metals, including nickel, cobalt, copper, and small amounts of rare earth elements and platinum.
Nodules form from metals that enter the ocean through erosion or from seafloor hydrothermal vents in active volcanic areas. Metal ions attach to a core, such as a rock or shell fragment. Over time, layers form around this core. Growth is very slow – only a few millimeters in a million years – so larger nodules can be several million years old.
There are more than 17 exploration permits, primarily in the Clarion-Clipperton area of the Pacific. The tests involved sucking up nodules from the seafloor to ships above. But as of early 2026, large-scale commercial mining has yet to begin.
Massive seafloor sulfides in hydrothermal vents
Seafloor massive sulfides, which form near hydrothermal vents along ocean ridges, are another source of critical minerals. Volcanic activity reacts with seawater, fueling surges of marine life at these vents and also forming rocks rich in copper, gold, zinc, lead, barium and silver.
These hot springs form where water rises through the ocean crust at high temperatures, up to about 750 degrees Fahrenheit (400 degrees Celsius). The metals in these solutions precipitate on contact with cold, oxygen-rich seawater, forming vent-like structures called “black smokers” because they resemble factory chimneys.
The technology to exploit these deposits is currently under construction. The first deep sea tests were carried out by Japanese miners in their coastal waters.
Cobalt-rich crusts on seamounts
Ferromanganese crusts are another source. They form on the slopes and peaks of underwater mountains called seamounts and contain manganese, iron and a wide range of trace metals such as cobalt, copper, nickel and platinum.
Over millions of years, metals in the surrounding seawater form layers of iron and manganese oxides, with thicknesses ranging from a few millimeters to a few decimeters, depending on the age of the seamounts.
Scab extraction is technically much more difficult than nodule extraction. The nodules lie on soft sediments. Crusts, on the other hand, are attached to bedrock. To successfully mine the crusts, it would be essential to recover the crusts without collecting too much substrate, which would dilute the quality of the ore.
However, little is known about the marine life found on seamounts, particularly in regions most suitable for crustal exploration and mining.
Underwater brine pools
Another possible ocean source of lithium and potentially rare earth elements could lie in unusual underwater lakes called hypersaline brine pools. These salt pools are found on the seabed in many parts of the world, but they are particularly common in the Gulf of Mexico.
Brine is already the source of much of the lithium used today. Companies extract it from salt water produced during oil and geothermal operations.
Lithium concentrates in brines over millions of years. As water moves through deep rocks, minerals dissolve along the way and elements like lithium can accumulate.
Extracting lithium from deep sea brines, if its presence is confirmed, could be simpler than traditional deep sea mining. Technologies already exist to separate lithium from salt water.
In the Gulf, this approach could potentially utilize existing offshore oil and gas infrastructure, reducing the need for new construction. The brine could be pumped out, treated to remove lithium, then returned to the basement.
Deep Mud
In the central Pacific Ocean and off Japan, deep-sea mud enriched with rare earth elements and yttrium has been recognized as another new resource.
These deposits form from the very slow accumulation of fish debris, composed of biogenic calcium phosphate, in the deepest parts of the ocean. In 2026, a Japanese research vessel successfully drilled and recovered deep-sea sediments containing rare earth minerals from the seabed near Minamitorishima Island, and the Japanese government announced that a deep-sea mud mining trial would begin in 2027.
Disadvantages for marine life
Although these regions likely hold vast resources, scientists know very little about the ecological conditions at the boundary between deep waters and seafloor sediments, particularly the microbial communities that live there.
Microorganisms are the most widespread and fundamental form of life on Earth. They play a central role in ecosystems, nutrient cycles and the long-term stability of the planet. The potential impacts of mechanical removal of nodules from the seafloor – by cutting, scraping or lifting – on these microscopic ecosystems remain largely unknown.
In the Pacific Ocean, an experimental mining test carried out in 1978 was re-examined more than two decades later. Even after 26 years, the traces left by mining vehicles were still visible on the seabed. Disturbed areas had fewer bottom-dwelling organisms and less diversity than neighboring undisturbed areas. Notably, no detailed assessment of microbial communities has been carried out, leaving a significant gap in understanding.
Further complicating the situation is that many potential areas of deep sea mining are in international waters, beyond the jurisdiction of individual countries.
The International Seabed Authority is responsible for regulating mining activities in the deep ocean, but there is no global consensus on the rules, safeguards or acceptable risks associated with seabed mining. Some countries, including the United States, are discussing creating their own mining licenses in international areas, while around 40 others are calling for a mining moratorium until the risks are better understood.
Critical minerals are the invisible foundation of modern life. As interest in deep-sea mining increases, these scientific uncertainties and governance challenges will be at the heart of the debate.
This article is republished from The Conversation, an independent, nonprofit news organization that brings you trusted facts and analysis to help you make sense of our complex world. It was written by: Leonardo Macelloni, University of Mississippi
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