Twenty Thousand Leagues under the Sea

Natural resources are becoming scarce. Deep-sea mining would therefore seem to be an increasingly realistic option for extracting mineral wealth. The new Deep Sea minor (3mE) launched this month unravels the mysteries of the fathomless depths.

It is pitch-black. Two hundred metres below sea level you can just see a shimmer of sunlight in the water, but further down, at depths of many kilometres, there is hardly any visibility. Nevertheless the submersible continues to descend, searching for the bottom. Caught in its lights, tube worms several metres long dance in their quest for food. An octopus is hunting shrimps.

If you imagine that the water is not there, it is as if the vehicle is landing on a desolate mountain landscape full of steep cliffs and deep caverns. But the water is there. In the deep ocean the pressure on the material is a few hundred bar. The salt water will erode thick steel plates in the space of a few months with no problem. Ocean currents and underwater hurricanes fling down heavy structures dozens of metres with ease. The deep ocean is an environment that is – at best – hostile to man and machine.

Violent conditions

And yet the deep sea exercises a powerful attraction on us: a wealth of valuable natural resources is to be found where parts of the earth’s crust in the ocean rub up against one another. In regions such as the Ring of Fire and Solwara in New Guinea gigantic chimneys (black smokers) spew out hot water towards the surface. The earth’s crust is so thin there that sea water seeps through the rock, entering red-hot regions of the earth, where it is forced upwards. It is not only water that finds its way out, however: large concentrations of gold, silver, cobalt, magnesium, zinc and rare earth elements such as yttrium, which is used in smartphones, are deposited on the sea bed and the chimney. And with natural resources becoming ever more scarce there is growing interest in extracting them from these ‘seafloor massive sulphide’ (SMS) deposits in the deep ocean.

The new Deep Sea minor at the Faculty of Mechanical, Maritime and Materials Engineering (3mE) is a response to this trend, enabling forty students to seek solutions to the problems of mining in the deep ocean. “The conditions in the deep sea are unique. The other extreme is space,” says Frederik Brauer, an Aerospace Engineering student who has just started taking the minor. “It’s difficult to control mining equipment under such violent conditions. And how do you maintain it in good repair and replace parts at such extreme depths?”

These are questions that interest a lot of students and professors – questions to which there are no ready answers. Deep-sea mining is still in its infancy. But the inquisitive child is straining at the leash to investigate the deep oceans. “Two-thirds of the world is under water and still untouched”, says Prof. Mirek Kaminski. The deep sea is a mystery. As Kaminski points out, “We’ve been on the moon several times, but hardly ever on the deepest sea floor, which lies eleven kilometres below sea level.”

“This is exciting for the students, especially since there’s a great future in it,” says Prof. Ian Richardson. “They’re learning completely new things, they need to push their knowledge to the limits as the conditions are so extreme. There’s a big demand for natural resources and deep-sea mining, but we don’t know precisely what we’re going to come up against: it takes a lot of money and we’re working in uncharted waters, so we need to come up with responsible solutions.”

Six hundred bar

At the Royal Netherlands Institute for Sea Research (NIOZ) on the island of Texel they know just how extreme the deep oceans can be: they have been doing deep-sea research there for decades now, making NIOZ the authority in the Netherlands. Marck Smit, who heads up its Netherlands Deep Sea Science & Technology Centre, holds out a weight. “Grab hold of it,” he says. It’s fairly heavy, feels like a few kilos. “Now put the tip on your finger. Now you know what six thousand bar, or six thousand metres deep, feels like.” There wouldn’t be much left of my finger, let alone if a few more hundred bar were to be added, as in the deep ocean. Smit then shows me a piece of stainless steel that has been left kilometres below sea level for nine months. It is covered in rust and has broken like a matchstick. “You might think that stainless steel is pretty resistant to sea water, but the salt attacks everything.”

NIOZ’s showpiece is RV Pelagia, a vessel that has been sailing the world’s high seas for years doing deep-sea research, a floating scientific command centre. The hold has space for five containers of measuring equipment. On deck are winches with thick cables full of copper and optical fibre to enable communication to take place even at depths of several kilometres. “There is a hatch under the vessel that can be opened,” Smit explains. The Hipap 100 USBL acoustic direction finder, a huge dish, then descends into the ocean to listen and thereby locate the equipment in the water. “As it is so dark in the depths and GPS doesn’t work under water, a lot of instruments use sound, so we also look using sound.”


In the Texel labs, scientists in white coats walk around doing experiments on materials from the deep sea. In the workshop sea-floor landers and systems to investigate the bottom of the sea, looking a lot like giant corkscrews, are being worked on. Outside, ready for shipping, are immense orange-red buoys filled with tiny glass spheres in synthetic foam to improve flotation. “Cork would shrivel up immediately under the pressures in the deep sea,” Smit explains.

In a month’s time they will be dropped into the sea attached to an anchor so as to measure the ocean currents a few hundred metres below the surface down to the bottom. Smit: “We know a lot about surface ocean currents but not very much about the currents at deeper levels. Deep down the currents could be very different, and we need to take them into account.”

Black smokers

As well as darkness, enormous pressure, salt and corrosion, unforeseen currents and underwater hurricanes cause extreme conditions. Smit shows me a globe with all the underwater prominences. At the Bay of Biscay the sea bottom descends to great depths, and along the fissures in the midst of the oceans are deep trenches and high mountain ridges. It is at these places that we find black smokers, areas rich in precious metals and minerals. “It’s just in this kind of area that you’re trying to guide a large, unwieldy mining machine along the bottom with the utmost precision even though you can hardly see anything,” says Floris Groenendijk of Imares. He works together with Robbert Jak and Sander Lagerveld at the research institute affiliated with Wageningen University, which specialises in strategic and applied marine ecological research. One of the things Imares is working on with NIOZ is a case study in the Lucky Strike region off the Azores. The institute is trying to find out what the ecological effects of mining would be.

Various scenarios are being considered. “Black smokers have a unique ecosystem,” says Jak. The area around them is red-hot, around 400º Celsius. The sea water further away is at about freezing point. Nearby are bacteria. “They look for a spot that is not too hot and not too cold. The area around the black smokers is a kind of deep-sea campfire at which they warm themselves,” says Lagerveld. Waving around the bacteria are tube worms that can grow to one metre in length. “You won’t find this ecosystem anywhere else,” Groenendijk adds.

What effect mining would have on the rest of the ocean is not clear. “Twenty-five years ago manganese nodules – a bit like billiard balls full of iron and other metals – were harvested for the first time,” says Groenendijk. “Those places still look just as they did 25 years ago, the traces have still not been erased.” Things that live deep down grow slowly, say scientists. “It takes millions of years for new manganese nodules to form,” Smit stresses. “Two-thirds of the earth is ocean, whereas we have only taken samples from the bottom amounting altogether to a few football pitches, so we still know very little about it.”

Ecological issues

Drilling for minerals deep under the sea therefore needs to be done responsibly, say scientists at Imares and NIOZ. “It makes a lot of difference whether you dump the material left over from mining into the sea at surface level or take it back to the same depths. If the residual material comes into contact with warmer water and oxygen it can form compounds that are harmful to the environment. Or it can cause big dust clouds in the water that destroy life deep in the ocean.”

Metals and other natural resources are already being brought up, for example in the Solwara field off New Guinea. The Canadian company Nautilus Minerals is extracting gold and copper from the bottom at 1,600 metres depth. “They are already expecting an annual turnover of a billion dollars,” says Lagerveld.

This is just the beginning. “Clever engineers will come up with new pieces of equipment that can cope with the extreme pressures and the salt,” thinks Smit, who for the past year has been fielding a whole lot of questions from companies interested in deep-sea mining.

Staff of Imares and NIOZ find that the companies concerned take the ecological issues of deep-sea mining seriously. “Nobody wants an ecological disaster. All the scenarios must be clear before drilling begins. It takes an awful lot of time and money to bring up a mining machine from the bottom half-way through the operation,” says Groenendijk.

The importance of the environment is instilled in the Deep Sea students right from day one of the minor. “By involving various faculties in organising this minor we can combine everything we know,” says Mirek Kaminski. “We want to make use of the natural resources on the sea floor without damaging the environment. Extracting them provides opportunities for society; the Netherlands, with all its knowledge of science and the industry, can lead the way.”

Editor Redactie

Do you have a question or comment about this article?

Comments are closed.