Marine Mining
Marine mining involves the extraction of valuable minerals and natural resources from oceanic environments. This practice ranges from near-shore operations, where materials like sand, gravel, and salt are harvested, to deeper waters that hold oil, natural gas, and strategically important metals such as manganese and cobalt. Historically, marine mining has roots in ancient salt collection and has evolved significantly since the first offshore oil wells were drilled in the late 19th century. The extraction techniques vary, utilizing advanced technologies like floating platforms and submersible rigs for oil and gas, while large dredges are employed for near-shore resources.
As the demand for construction materials, energy resources, and strategic metals grows, marine mining is gaining attention. However, environmental concerns and regulatory challenges accompany these advancements. The International Seabed Authority has begun to draft regulations to oversee mineral exploration and address the potential impacts on marine ecosystems. With rising sea levels and increased beach erosion due to climate change, the need for marine mining may continue to expand, particularly in sectors like beach nourishment. Yet, the complexities of sharing profits from seabed resources between developed and developing nations remain contentious issues that could shape the future of marine mining practices.
Marine Mining
Summary
Marine mining is mining minerals and other natural resources from the ocean. Valuable resources in the near-shore zone include sand and gravel for construction, salt, phosphate deposits needed for fertilizers, coral for marine aquariums, carbonate sands, diamonds, gold, tin, and other minerals in placers. Farther out are oil and natural gas deposits, sulfur for industry, and gas hydrates. On the seafloor are nodules and crusts containing strategically important metals, such as manganese and cobalt, and sulfide deposits around the black smokers in the rift zones, which contain gold, silver, and other useful metals.
Definition and Basic Principles
Marine mining deals with the extraction of economically valuable substances from the ocean. These may be gases, liquids, minerals, rocks, base and precious metals, or ornamental stones, such as pearls, diamonds, and coral. Near-shore mining has been done for centuries, and drilling for oil and gas at sea began in the 1890s. Still, the mineral deposits on the seafloor have been largely ignored because of the technological difficulty in obtaining them. The substances obtained by marine mining fall into three categories: rocks and minerals found in shallow, near-shore waters; oil and gas deposits found in waters up to thousands of feet deep; and metal-rich deposits found on the seafloor, two miles or more down. Near-shore sand and gravel and the minerals in placers can be scooped or suctioned up by giant dredges, salt can be evaporated in shallow coastal ponds, and divers can obtain pearls and ornamental coral for aquariums. Oil wells have been drilled in the ocean for more than one hundred years, and during that time, marine oil and gas production has grown so rapidly that by the twenty-first century, over 30 percent of the world's oil and 28 percent of the world's natural gas came from below the seafloor. Someday the gas hydrates, manganese nodules, and sulfide deposits may be tapped as well.
Background and History
The ocean has provided salt for human dietary purposes since ancient times, so the evaporation of salt from seawater represents one of the earliest examples of marine mining. Another early example was the collection of minerals that were washed into the sea by rivers to form placers. Shoreline tin was mined in Indonesia in the early 1900s using dredges, and diamonds carried into the sea by the Orange River were mined along the coast of South Africa at about the same time. Oil has been produced on land using dug or drilled wells for hundreds, if not thousands, of years, but the first offshore oil wells were drilled in the early 1890s, using piers or pilings driven into shallow water.
Oil drillers did not venture more than a mile from shore until the 1930s and the immense floating platforms used in the twenty-first century were not introduced until the 1960s. The first manganese nodules were discovered on the seafloor by the HMS Challenger expedition in the 1870s. However, the techniques for mining them and the related sulfide deposits are still being developed.
How It Works
Near-Shore Resources. Humans must have found early on that the salt crystals in dried-up lagoons near the ocean were useful as a seasoning and for the curing and preserving of foods. The construction of evaporating ponds was a logical next step, and these are common in countries with access to the ocean and lack underground salt deposits. The mining of placers uses large, floating dredges that either suck the minerals up in long tubes or scoop them up in a series of circulating buckets. Other valuable substances found in shallow water include phosphate for fertilizer, pearls for jewelry, live coral for aquariums, and pure carbonate sand. Although phosphate deposits are widely present in the ocean, they are not mined because phosphate deposits on land can be tapped at a lower cost. The pearls are grown from oysters in pearl farms, which consist of floating wooden rafts or posts driven into the bottom of the sea. A few pearls are still brought up by divers in the twenty-first century. Divers also bring up live coral, which is popular among marine aquarium hobbyists. In the Bahamas, shallow-water shoals of pure carbonate sand are mined as a source of lime for industry.
Oil and Natural Gas. A fixed or floating platform is built to extract oil and natural gas so that a hole may be drilled into the seabed. The first wells used fixed platforms, either built on pilings at the ends of piers or on artificial islands. The first true offshore well in the Gulf of Mexico was spudded in 1937, one mile from shore in the then-intimidating water depth of fourteen feet. The first well, located out of sight of land in the Gulf of Mexico, was drilled in 1947. It was 10 miles from shore and was 18 feet in water. In the twenty-first century, companies drill wells in the Gulf of Mexico that are fifty miles out and in nearly ten thousand feet of water. The drilling platform rests on a concrete structure or a steel tower for wells in moderate water depths. Deeper waters necessitate semisubmersible rigs in which the platform rests on underwater pontoons, moored to the bottom by steel cables, or kept in place by dynamic positioning.
Related Products.Sulfur is commonly associated with oil deposits, especially when salt domes are present. As the salt moves upward because of its lesser density, it arches up the sediments, and chemical reactions between the salt and the sediments may form a cap rock rich in sulfur. The sulfur is mined by drilling into the cap rock, melting the sulfur with high-pressure steam, and bringing it to the surface as a liquid for processing. The methane gas hydrates in the ocean, which contains a large amount of natural gas, and has yet to be mined in the twenty-first century. In these hydrates, the gas is bonded with water as ice instead of being associated with oil.
Deep-Sea Resources. Technology for mining the manganese nodules and sulfide deposits found on the seafloor is still in developmental stages in the early twenty-first century. The nodules are lumps about the size of hamburgers and are scattered about. Someday it may be possible to vacuum them up with suction hoses or scoop them up with a series of buckets. The sulfide deposits around the black smokers present a greater challenge. They are welded to the seafloor and would have to be broken loose.
Applications and Products
Sand and Gravel. Sand and gravel for construction purposes are in short supply in many parts of the world. When available deposits on land have been exhausted, the only other supplies are in the ocean. This situation is particularly true for some of the older countries in Europe, such as England, where construction has gone on for hundreds of years and real estate values are so high that the few remaining deposits on land are prohibitively expensive. Deposits of sand and gravel in the ocean have the advantage of being well sorted, with grains all of the same size, so they are suitable for building purposes once the salt has been washed out of them. Sand and gravel are mined along the coast of the United States (US) to rebuild beaches that have lost their sand because of erosion. The sand is pumped directly onto the beach from the offshore zone in a process known as beach nourishment. The cost of nourishing a beach may exceed several million dollars for each mile of beach treated, and a significant problem is that if the sand is fine-grained, it may wash away quickly in storms. In the Bahamas, shallow-water shoals of carbonate sand are mined as a source of lime for making cement and for separating iron from its ore in blast furnaces.
Placers. Gold, tin, and diamonds are the most sought-after substances found in placers, but platinum, iron minerals, and other gemstones may also be found in them. The gold, platinum, and gems are used in the manufacture of jewelry, with the gold also being needed for dentistry, coinage, and monetary purposes. Both gold and platinum have electrical properties that are useful for industry, and platinum is required in the manufacture of catalytic converters for automobiles. Tin was highly prized in ancient times because it was needed for the manufacture of bronze and pewter. In modern times, it is used in solder and for the tin plating of steel to prevent corrosion. The familiar so-called tin can used to package food is simply a steel container with a thin, protective coating of tin.
Salt. Because of its dietary importance and usefulness for food preservation, salt has been valued by humans throughout history. It is also widely used in the chemical industry as a water softener, for snow and ice removal, and by anyone who makes homemade ice cream. However, only 86 percent of the dissolved material in the ocean is table salt. The remainder includes bromine, which is used in medicines, chemistry, and antiknock gasoline; magnesium, an important light-weight metal used in fireworks and flares because it is flammable; potassium, which is used in fertilizers; and calcium sulfate (gypsum), an important component of wallboard.
Oil and Natural Gas. By far, the most valuable of the resources obtained from the sea are oil and natural gas. In addition to being used for fuels, such as gasoline, diesel fuel, kerosene, fuel oil for heating homes, and jet fuel, oil is the raw material that is the basis of grease, motor oil and other lubricants, asphalt and tar, and a variety of chemical products, including nylon fibers for stockings. Even the paraffin wax used to seal jars of homemade jelly comes from oil. The natural gas found with oil is used domestically for cooking and heating, in the power industry to generate electricity, and in the production of ammonia for making fertilizer. The methane gas hydrates deposited on the seafloor, which have not yet been exploited commercially, may someday have similar uses.
Sulfur. Although sulfur is not derived from the seafloor in the twenty-first century, it has been in the past. Sulfuric acid, which is widely used in chemistry and industry, is its most important product. Because of its toxicity to bacteria, sulfur is an ingredient in medicines, insecticides, fungicides, and pesticides. Sulfur is also flammable and is used in the manufacture of matches and gunpowder.
Manganese Nodules. Although the manganese nodules or polymetallic nodules (PMN or PN) and crusts found on the seafloor are not being mined commercially, the US has an interest in them because of the metals they contain. Three of the metals—iron, needed for making steel; copper, used in wiring; and nickel, important in the manufacture of stainless steel—are already available on land. The other two metals, strategically important in wartime, are not available in the US and must be imported. They are manganese, used in making armor plate, and cobalt, which is needed for the high-temperature steel used in tools and aircraft engines.
Sulfide Deposits. The sulfide deposits found on the seafloor have not been mined yet in the early decades of the twenty-first century but are of interest because of their metal content. They contain not only the five metals found in the manganese nodules but also zinc, which is needed for galvanizing and for alloys, such as brass; lead, which is used in batteries, scuba divers' weight belts, and as shielding for atomic reactors; silver, which is needed for coinage and in industry; and gold, with its monetary and industrial uses.
Coral. In an aquarium, coral is used to provide breeding grounds for bacteria, which benefits the fish. Mushroom corals are used for fish, crustaceans, and motile invertebrates; crushed corals to maintain the pH level of an aquarium; leather corals to add bulk to an aquarium. Besides aquariums, corals are also used in the surgical replacement of bone, spinal fusions, and dental surgeries.
Careers and Course Work
The only marine mining done in the US in the early twenty-first century is the dredging of sand and gravel for beach nourishment and oil and gas production in the Gulf of Mexico, along the Southern California coast, and off the north slope of Alaska. Dredging jobs are limited because the work is intermittent and seasonal and takes place largely in resort areas where beach erosion is a problem. Advanced training and professional degrees are not required. A captain is needed to run the dredge, a hydrographic surveyor has to chart the bottom and locate the deposits of sand and gravel, a mechanic has to keep the equipment running, and deckhands are required to do routine tasks. By contrast, a wide variety of jobs are available in the oil and gas industry, both on land and at sea.
A good place for the beginner to start is with an undergraduate, college-level course in geology. This could lead to graduate work in geology and a career in oil and gas exploration, or to a degree in petroleum engineering and a job designing, constructing, and maintaining offshore drilling platforms. The oil industry also offers jobs doing seismic surveying, drilling and logging wells, and producing, refining, and marketing the oil that is produced. Management positions also are available, so courses in business management are also recommended.
Courses, such as oceanography, the study of the physical and biological aspects of the ocean; mining and mineral engineering; metallurgical engineering; marine biology, to study marine environmental management, marine animals, and to assess human impact, can be undertaken.
Social Context and Future Prospects
As glaciers and ice sheets melt because of global warming, the water added to the sea by this melting will result in rising sea levels. This, in turn, will increase the amount of beach erosion around the world and consequently the need to nourish beaches in resort areas. Jobs in the dredging industry should continue to be available as a result. Jobs in the oil and gas industry will continue to be available as well. More than three-quarters of world oil production goes into powering cars, trucks, ships, and planes, so the demand for oil is likely to grow as more and more people in the developing nations are able to afford to buy cars.
One problem that may lie ahead in marine mining involves the manganese nodules and sulfide crusts found on the seafloor. The developed nations are already investigating ways to mine these deposits. They are the only nations with the technological expertise to bring up these nodules and crusts. However, the law of the sea states that the profits from mining minerals in the area in which the nodules and crusts are found must be shared with the developing nations, and the developed nations may find it hard to agree to this condition. In 2021, the International Seabed Authority (ISA) drafted the mining code, a set of rules to regulate the exploration of marine minerals, examine the effect of manganese nodules on the seabed and marine creatures, and undertake large-scale mining operations.
Bibliography
Drew, Lisa W. “The Promise and Peril of Seafloor Mining: Can Minerals Be Extracted from the Seafloor Without Environmental Impact?” Oceanus 47.3 (2009): 8–14.
Drew, Lisa W. “Who Regulates Mining on the Seafloor?” Oceanus 47.3 (2009): 15.
"11 High Paying Marine Careers." Maritime Manual, 1 Apr. 2021, www.maritimemanual.com/high-paying-marine-careers/#4‗Marine‗Archaeologist. Accessed 5 June 2021.
Garrison, Tom. Oceanography: An Invitation to Marine Science. Belmont: Thomson, 2007.
Kiel, Rov. “What We Know About Deep-sea Mining — and What We Don't.” World Resources Institute, 23 Feb. 2024, www.wri.org/insights/deep-sea-mining-explained. Accessed 4 June 2024.
Lau, Bon. "The Detrimental Effects of Deep-Sea Mining on Marine Ecosystems." Earth.org, 4 June 2021, earth.org/detrimental-effects-of-deep-sea-mining. Accessed 5 Jun. 2021.
McLachlan, Anton, and Alec Brown. The Ecology of Sandy Shores. Burlington: Elsevier, 2006.
Rice, Tony. Deep Ocean. Washington, DC: Smithsonian Inst., 2009.
Welland, Michael. Sand: The Never-Ending Story. Berkeley: U of California P, 2009.