Seven Hundred Trillion Reasons: The Unseen Scale of Cook Islands' Seabed Resources

Welcome to the latest instalments in our science series, brought to you by the Cook Islands Seabed Minerals Authority. We're on a mission to empower our readers by diving deep into the fascinating science behind the deep ocean seabed minerals. Through these articles, we aim to unravel the mysteries of the deep sea, spotlighting the sustainable and responsible exploration of these incredible resources. Join us on this journey to the ocean’s depths, where every discovery brings us closer to understanding our planet and safeguarding its future. For more insights, explore all our science articles on our website. 

Exploring the Hidden Treasure: Cook Islands' Polymetallic Nodules 

When you think of the Cook Islands, a few things might come to mind—relaxed holidays, vibrant tivaevae, and, less excitingly, the high price of fish. But ask a marine geologist, and they will tell you that the Cook Islands are famous for something much more significant: a massive deposit of polymetallic nodules.  

Individually, a nodule might not seem like much—certainly not something that would impress your girlfriend if you stuck one on a ring. But when you consider the vastness of the entire deposit, it is a different story. Nodules slowly grow on the seabed’s surface, where the right chemistry between the ocean and seabed exists. Over millions of years, metals from seawater and sediment accumulate, layer by layer, forming these nodules. They are not found everywhere, though. Only a few places in the world, including the Cook Islands, have had the perfect conditions over millions of years for these nodules to thrive.

A Sea of Nodules: Estimating the Mineral Wealth 

So, just how many nodules are we talking about, and how do we know? Given their depth, you cannot just peek down and count them. Surprisingly, it is not as difficult as it might seem. The process typically involves four steps:  

1. Find some – Identify the presence of nodules. 

2. Sample the seabed – Systematically collect samples across a grid to ensure they are widespread. 

3. Map the seabed – Understand where nodules are likely to be found, such as on flat seabeds, and where they are not, like on underwater volcanoes. 

4. Average the results – Use special statistical methods to estimate the total number of nodules, excluding areas without nodules. 

This method leads to what is known as a Mineral Resource Estimate [1]. These estimates are just that—estimates, produced with varying levels of confidence. The estimates are usually done by specially qualified persons [2], as it can be embarrassingly expensive if the estimates are seriously incorrect. “Inferred” estimates are less confident than “Indicated” estimates that are in turn less confident than “Measured” estimates 

However, if harvesting does occur, it is important to remember that not all the estimated nodules will be harvested. Some will be left behind for technical or economic reasons. The actual amount that could be harvested is called a "reserve estimate," which requires a more confident resource estimate and a detailed harvesting plan—something we do not yet have. 

Mind-Boggling Numbers: The Scale of the Cook Islands' Nodules 

So, what is the bottom line? How many nodules are out there? Current estimates suggest we have 6.7 billion tonnes of wet nodules. To put that into perspective, the container ships that visit Rarotonga have a cargo capacity of about 8,500 tonnes [3]. So, 6.7 billion tonnes are like loading over 780,000 of those ships to the brim. Or to put it another way, to carry that load, you would need a fleet three times larger than the total global cargo capacity of all the world’s ships combined [4]. 

If that is not enough to boggle your mind, try to imagine the number of dump trucks needed to haul all those nodules at one time. If you parked them nose to tail, they would circle Rarotonga over 120,000 times. Stack them up, and you would have a 30 km-high wall of trucks and nodules—the drivers at the top would need spacesuits! 

If we model it carefully it works out that the Cook Islands has between 33.5 trillion and 753 trillion individual nodules. If you prefer a precise average number, that is around 702,822,687,631,522 nodules—give or take. 

But beyond these mind-boggling figures, the real value lies in the metals within these nodules, particularly cobalt and manganese. By 2050, the world could need up to 525,000 tonnes of cobalt each year [5]. Our 6.7 billion tonnes of nodules could yield over 20 million tonnes of cobalt metal—enough to meet global demand for decades.  

What this works out to mean, is that there are so many nodules here in the Cook Islands, that market demand limits alone ensure that most of the nodules will never be minerals harvested, even before we apply measures to ensure protection of the environment and its biodiversity.

A Vast Ocean Treasure: The Extent of the Cook Islands' Nodule Deposit 

The most astonishing fact about the Cook Islands’ nodule deposit is its sheer size. Covering about 900,000 km², it spans 45% of our entire ocean-exclusive economic zone. That is over three times the land area of New Zealand. If we could magically gather all our nodules and lay them out between Rarotonga and Auckland, they would form a continuous strip over 75 km wide. 

Fun Fact: Counting Nodules with a Camera 

Did you know that seabed photographs can help estimate the number and weight of nodules? Because nodules grow under specific conditions, their sizes in each area are not random. By understanding their size distribution, scientists can estimate their weight just by looking at them. Of course, this requires some complex maths, but if you are into that sort of thing, you can dive deeper into the topic [6]. 

Conclusion: A Treasure Trove of Opportunity 

No matter how you look at it, the Cook Islands have a colossal number of nodules. Individually, they may seem modest, but collectively, they represent a fascinating and potentially significant source of wealth for our nation. And thankfully, we do not need to count every single one—because that would take a while! See if you can work out how long that would take if you counted one nodule every second… (the answer is below). 

References  

[1] Seabed Minerals Authority, “Seabed Mineral Resource Estimate completed for the Cook Islands,” Press Releases. Accessed: Aug. 03, 2024. [Online]. Available: https://www.sbma.gov.ck/news-3/article-110  

[2] Joint Ore Reserves Committee, “What is the JORC Code?” [Online]. Available: https://www.jorc.org/  

[3] Matson, “Matson’s Fleet - Imua/Liloa II.” Accessed: Aug. 03, 2024. [Online]. Available: https://www.matson.com/matnav/about_us/vessel_stats.html 

[4] N. Rasmussen, “Greek and Chinese companies own 34% of the global fleet’s cargo capacity,” BIMCO Shipping Number of the Week. Accessed: Aug. 03, 2024. [Online]. Available: https://www.bimco.org/News and trends/Market reports/Shipping number of the week/20231108 SNOW 

[5] International Energy Agency, “Critical Minerals Market Review 2023,” Paris, France, 2023. [Online]. Available: https://www.iea.org/reports/critical-minerals-market-review-2023/  

[6] G. Yu and J. Parianos, “Empirical Application of Generalized Rayleigh Distribution for Mineral Resource Estimation of Seabed Polymetallic Nodules,” Minerals, vol. 11, no. 5, p. 449, Apr. 2021, doi: 10.3390/min11050449.