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The Treasure Trove at the Bottom of the Ocean: The Promise & Perils of Deep Sea Mining

Deep sea mining for polymetallic nodules promises metals but raises environmental concerns. Learn the history, geology, pros & cons of mining the seafloor.

Lying over 3,000 m (~9,843 ft) below the ocean's surface are "nodules" that could help humans create the green energy and electrified future of our dreams, but can it be done in an environmentally friendly way?

Deep sea mining has dominated news headlines recently, with countries exploring these vast resources, and the International Seabed Authority striving to develop regulations. While focus is currently on the ocean, the idea to mine these nodules is far from new, originating over 100 years ago!

The History of Deep Sea Mining

In 1868, a dredging ship extracted a chunk of iron ore from the seabed north of Russia. Within 5 years, the HMS Challenger embarked to expand global knowledge of the ocean floor, first discovering polymetallic nodules during its 4-year voyage.

These revelations led to further studies and insights about the nodules, but little else was learned for almost 100 years. However, in the 1960s, systematic research began in earnest. J.L. Mero's Mineral Resources of the Sea proposed mining the nodules, asserting near limitless supplies of cobalt, nickel, and other metals throughout the oceans. Nations dispatched research vessels to locate deposits.

In 1974, billionaire Howard Hughes Jr. initiated the Glomar Explorer project to harvest manganese nodules from the seafloor. However, speculation swirled, and in 1975 the LA Times revealed Glomar's true purpose as a CIA vessel, not mining. In 2010, "Project Azorian" was declassified, exposing the mining cover story to salvage a Soviet submarine.

The feasibility of deep sea mining seemed exaggerated. By 1982, an estimated $650 million was spent for minimal returns, and interest mostly waned.


Activity remained dormant until recently, with revived zeal for the nodules. In 2022, The Metals Company tested pioneering mining tools in the Clarion Clipperton Fracture Zone, the first large-scale nodule collection since the UN Law of the Sea treaty.

Throughout 2023, deep sea mining has commanded global attention and vigorous debate. Multiple nations are revisiting this mining option, while research examines environmental impacts. Lobbying continues from all sides. In July 2023, the International Seabed Authority postponed regulations until 2024, targeting a decision by 2025. Currently, over 20 countries advocate pausing or banning deep sea mining, while proponents insist it's essential to meet green energy demands.

Geology of Polymetallic Nodules

Amid the surge of activity surrounding these nodules, it's worth examining what exactly they are.

These polymetallic nodules typically range in size but are on average potato size, and rest atop or partially buried in seafloor sediment. They harbor minerals including copper, nickel, cobalt, iron, manganese, and rare earth elements.

First discovered in the Kara Sea, nodules now appear ubiquitous across most of the world's oceans. Abundant deposits exist in regions like the Penrhyn Basin, the Clarion Clipperton Zone (CCZ), and the Indian Ocean Nodule Field. The CCZ alone may contain around 21 billion tons of these nodules.


So how do they form? Manganese nodules accumulate incrementally over eons around diminutive solid core on the seafloor. The core might be shark teeth or shell shards.

Two primary growth mechanisms exist:

  1. Hydrogenous - Manganese and other metals precipitate from the water column, congregating around the core. This predominantly produces the manganese mineral vernadite.
  2. Diagenetic - Metals precipitate from sediment pore water, accumulating on the core. This chiefly generates the manganese minerals todorokite and birnessite.

Most nodules grow through both processes. Hydrogenous nodules grow up to 10 mm per million years. Diagenetic nodules grow 10-100 mm per million years.

Nodules need stable conditions to grow over these long time spans:

        • Low sedimentation to avoid getting buried
        • Flow of oxygenated water to transport metals
        • Coarse sediment particles that don't cover the nodules
        • Porous, water-filled sediment for the diagenetic process

The extremely slow growth allows metals to concentrate in the nodules over millions of years.

Pros and Cons of Deep Sea Mining

There is extensive debate on both sides of the deep sea mining discussion. Deep sea mining has potential economic benefits but also significant environmental risks requiring further research. Policymakers face vital questions around mitigating ecological harm, addressing legal issues, and weighing if the rewards outweigh the possible irreparable damage to largely unexplored deep ocean ecosystems.

Some frequently cited advantages are:

      • Could provide access to valuable mineral deposits and reduce dependence on land-based mining

      • May stimulate economic growth and job creation for coastal communities

      • Could lead to advances in ocean exploration technologies

      • Might reduce environmental impacts of terrestrial mining operations

On the other hand, commonly stated disadvantages of deep sea mining are:

      • Poses risks of disturbing seabed habitats and releasing toxic sediments

      • Noise, vibration and light pollution could harm marine life

      • Effects on deep sea ecosystems and species are still poorly understood

      • Legal uncertainties exist around operations in international waters

      • Challenging and hazardous working conditions for miners

      • Lack of regulation and oversight is concerning

Globally, we are in a pivotal period for this mining method. Will it mirror the 1970s enthusiasm, or will technological advances enable it to progress responsibly? Only time will tell!


What are your perspectives on deep sea mining? If you seek more information to decide, we have several publicly disclosed deep sea mining projects in the Prospector database. Click the button below to check them out for free. 

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