It is 2018, and a group of international scientists are about to make a dazzling discovery. The team identify a curious anomaly, in fact, while analyzing how sound moves deep beneath the surface of the Earth. So the experts then design and execute a research project – and before long, they arrive at an extraordinary conclusion. The scientists therefore posit that hidden far below our feet is an enormous cache of precious diamonds.
Of course, diamonds consist of one of the most abundant and versatile elements on the planet: carbon. And from carbon comes carbohydrates, which are essential for the growth, repair and functioning of organic tissue. The element is also prevalent in fossil fuels and plastics as well as carbon dioxide, which plants require for respiration. In diamonds, however, carbon is arranged in a rare crystalline atomic structure – a so-called diamond cubic.
And thanks to their crystalline structures, diamonds have high optical dispersions. This means that they have the capacity to fragment white light into an array of colors, which we perceive as a characteristic sparkle. This is likely part of the reason why diamonds are prized for their ornamental value. The stones are also extremely old – between 1.5 and 3.5 billion years old, in fact. Diamonds are often therefore marketed as symbols of eternal love.
But the precious gems are not merely sparkly stones. They are also exceptionally hard and make good conductors of heat. That’s why diamonds are sometimes used in industrial machinery – particularly in polishing and cutting. They are additionally a key component in diamond anvil cells. These are scientific instruments capable of exerting the same immense pressures found deep within the strata of planets.
So the unique ornamental, industrial and scientific applications of diamonds are part of the reason they fetch such high prices. However, it is really the gems’ relative scarcity that makes them so valuable. Though diamonds can be created in laboratories, you see, synthetic diamonds tend to be worth considerably less than their natural counterparts. For that reason, then, diamonds continue to be mined from the Earth.
The trove of subterranean diamonds discovered by scientists in 2018 consequently represents a value of unimaginable vastness. If ever extracted, in fact, the precious gems could transform the world economy in radical and unpredictable ways. For now, however, the discovery has made a rich contribution to our understanding of geological processes.
In many ways, though, our modern understanding of the Earth and its processes began with the scientific and technological advances of the 1960s and ’70s. NASA photos of the Earth from outer space, for instance, popularized the concept of Gaia. That is, the idea of the Earth as a single entity. But it was the advent of plate tectonics – the theory that the planet’s surface layer or lithosphere consists of shifting plates – that completely transformed our scientific understanding of the world.
Thanks to the theory of plate tectonics, then, we understand how mountains and volcanos rise, what causes earthquakes and how continents form – among other natural phenomena. Yet our planet still holds untold unsolved mysteries. For example, scientists still don’t know where water originally came from. And while one theory suggests that it arrived on the Earth via ice-covered asteroids, there is no fossil evidence to support this.
Likewise, scientists remain puzzled about what lies at the center of the Earth. Once upon a time, you see, it was believed that the Earth’s core was composed like meteorites – and that they contained an abundance of nickel and iron. Subsequently, however, measurements of the Earth’s gravitational field contradicted that hypothesis. Yet today the composition of the Earth’s core remains a mystery.
And one of the most profound unsolved mysteries concerns the origins of life itself. Without any surviving fossil record from that earliest of periods, scientists don’t know if our most remote, single-celled ancestors emerged from the Earth itself or whether they arrived here on meteors and other interstellar objects. In fact, there is evidence to support both theories.
Earth science – also known as geoscience – represents an attempt to answer these and other great unsolved mysteries. And since the processes that constitute the Earth are multifaceted in nature – for example, they involve chemical, physical and biological phenomena – geoscience is interdisciplinary. Its four main objects of study are the planetary dimensions of earth (lithosphere), air (atmosphere), water (hydrosphere) and biological life (biosphere).
Yet despite incorporating diverse fields of research, geoscience does have several unifying themes. For one thing, many of the objects and processes it studies exist at places beyond the physical access of humans – including deep within the Earth and high above it. For another, much geoscience focuses on processes that occur on vast and epochal timescales of millions of years.
So in 2018 a group of geoscientists came together to scrutinize certain unsolved questions. They included researchers from world-class universities such as Harvard, the University of California at Berkley, MIT, the Institut de Physique du Globe de Paris, the Carnegie Institute of Washington, the University of Science and Technology of China and several others.
The researchers, who collaborated for a month over the summer, worked within an organization known as the Cooperative Institute for Dynamic Earth Research (CIDER). Dedicated to unraveling the mysteries of global processes, CIDER is an interdisciplinary research center, supporting and mentoring the next generation of Earth scientists.
But while examining records of global seismic data, the group noticed a strange anomaly. In fact, various international organizations such as the U.S. Geological Survey (USGS) have been collecting seismic data for several decades. The data consists of measurements of the subterranean sound created by tsunamis, earthquakes, volcanic eruptions and other geological phenomena. Seismic receivers are responsible for capturing and measuring the sound.
The density, temperature and composition of rocks causes the speed of the sound waves – that is, their seismic velocity – to change. Therefore, it is possible to use seismic data to extrapolate an image of the Earth’s interior. Specifically, scientists are able to infer the types of rocks in the lithosphere, their abundance and distribution. Naturally, these rocks are so deep they would normally be unobservable.
The group discovered that sound waves tend to accelerate when moving through so-called cratons – and this was the starting point for their research. Located hundreds of miles beneath the surface of the Earth, cratons resemble enormous, upside-down mountains. As geological structures, their functions include supporting the continental landmasses at the surface above them.
In fact, cratons represent the most ancient part of continental plates. And they are considerably older than the geologic structures above them. For example, the cratonic lithosphere is up to four billion years old. Meanwhile, the oceanic lithosphere is just 180 million years old. Cratons are normally found in the center of tectonic plates and their mineral composition is an enduring mystery.
In fact, there is a good reason why sound waves ought to travel faster in cratons. For one thing, they are cooler and less dense than neighboring structures in the mantle. However, the velocities detected by the seismic receivers were much faster than would be expected from such factors alone.
So to determine exactly why sound accelerates when passing through cratonic roots, CIDER decided to construct a three-dimensional model of the waves as they passed through the Earth. This was a job for the team’s seismologists, who completed the task using data from various sources, including from the USGS.
Meanwhile, the next task was to extend the model. Essentially, the team created an array of “virtual rocks” to observe their impact on seismic velocity. Using measurements from previous lab experiments, they took multiple factors into consideration, including buoyancy, mineral composition and electromagnetism. And ultimately, they made a groundbreaking discovery.
Speaking to National Geographic in July 2018, Dr. Joshua Garber from Penn State University explained how their findings differed from previous research. He said, “What we found, in contrast to previous studies, is you can’t just use the main rock type in the mantle – that’s called peridotite – to explain these velocities. You need something that’s a little stiffer.”
In fact, according to the CIDER group, the only rocks capable of creating the observed velocities were those containing 1-2 percent diamonds. In addition to diamonds, the rocks were found to contain peridotite and trace quantities of eclogite, which is typically seen in oceanic crust. The mystery was solved – diamonds were causing the sound waves to accelerate.
Dr. Ulrich Faul, a CIDER researcher from MIT told The Independent in 2018 that diamond is a much better conductor of sound than most other cratonic rocks. He said, “Diamond in many ways is special. The sound velocity in diamond is more than twice as fast as in the dominant mineral in the upper mantle rocks…”
In fact, according to Dr. Faul, diamond is the only mineral that could have caused the observed changes in seismic velocity. He told Business Insider in 2018, “We went through all the possibilities, from every angle, and this is the only one that’s left as a reasonable explanation.” Of course, this would mean that the Earth’s cratons contain vast resources of the precious gem.
To estimate how many tons of diamonds might be hidden underground, the CIDER group simply calculated the total volume of the Earth’s cratonic roots and then used their estimated diamond content of 1-2% to arrive at a final figure. And the results were staggering. According to the group, the world’s cratons conceal a quadrillion – or 1,000,000,000,000,000 – tons of diamonds.
In fact, this represents a global resource 1,000 times greater than previously thought. In a 2018 MIT statement, Dr Faul said, “This shows that diamond is not perhaps this exotic mineral, but on the [geological] scale of things, it’s relatively common. We can’t get at them, but still, there is much more diamond there than we have ever thought before.”
Of course, the scientists’ findings haven’t convinced everyone. According to Suzan van der Lee, a seismic expert at Northwestern University, the change in seismic velocities may have been caused by some unidentified factor. She told National Geographic in 2018. “I’m taking the conclusions, personally, with a grain of salt.”
Meanwhile, the research tends to corroborate our existing understanding of where and how diamonds form. Although diamonds consist of a relatively abundant chemical element, they form under exceptional circumstances and only in specific environmental conditions. Typically, their formation requires extreme pressures and temperatures such as can only be found deep below the surface of the Earth.
Specifically, diamonds form in so-called “diamond stability zones,” at depths of approximately 90 miles. They also require a minimum temperature of 2000 °F to form. However, diamond stability zones are not ubiquitous – they’re normally found underneath continental plates. In fact, diamond stability zones occupy exactly the same places where one would expect to find cratons.
Furthermore, when diamonds reach the surface of the Earth, they tend to be carried by volcanic eruptions that seem to originate in cratons. The eruptions are relatively rare and occur at intervals of tens of millions of years. They carry magma to the surface which then cools into igneous rocks known as Kimberlite pipes – which carry diamonds within them.
Kimberlite pipes have mostly been found at the edges of cratons. And they’ve specifically been discovered in South Africa, Canada, Australia and Siberia, places all well known for their diamond resources. Therefore, the CIDER group’s chief claim that cratons contain large reserves of diamonds appears to be consistent with our previous understanding of where and how diamonds are forged.
Furthermore, CIDER geochemist Dr. Megan Duncan explained to science news website Inverse how the quantity of diamonds believed to exist in the cratons does not exceed current estimates for the total carbon on Earth. She said, “While it is a higher concentration of diamonds than we would have expected…We’re not adding lots of extra carbon to the Earth’s overall budget.”
However, the research does promise several new insights, particularly with regards to craton formation and stabilization. And this should also improve our understanding of the Earth’s early geologic history. Dr. Duncan continued, “It does have some interesting implications for ancient Earth processes, like subduction, and how it may nor may not have changed with time.”
Meanwhile, aside from their scientific value, the diamonds have enormous economic potential. Indeed, they represent one of the most valuable resources on the planet. At current market prices, a ton of diamonds is worth approximately $3,800. That means the cratons contain gems to the tune of a staggering 191 septillion dollars, or $191,000,000,000,000,000,000,000,000.
Naturally, any dollar sum with 24 zeros is hard to visualize. However, to put it into context, the total value of the world economy, as calculated by the CIA’s World Factbook in 2014, is approximately US$78.28 trillion, or $78,280,000,000,000 – which is a figure many leagues lower than the value of the diamonds. Of course, all this assumes that markets are static, which they aren’t.
In fact, mining so many gems will almost certainly have a negative impact on their value. One historical precedent is the Spanish Price Revolution, in which the Spanish Empire flooded European markets with vast quantities of gold plundered from the New World. Along with several other factors, the Price Revolution caused the value of gold to plummet. And ultimately, Spain went bankrupt three times during the 1500s.
So should we all rush to rush to invest in diamond-mining corporations? Is a high-tech diamond rush now imminent? Will we soon all be wearing diamonds as casually as brass buttons? Apparently not – unfortunately, since the diamonds are located at depths of 90 to 150 miles, they are impossible to extract with current technology.
Indeed, it is doubtful that we will ever be able to reach such depths, at least not in our lifetime. At present, the deepest that humans have ever dug is 7.6 miles – a mere fraction of the necessary 100 miles. In order to reach the diamond stability zones, we would require machinery capable of withstanding extraordinary pressures and temperatures.
Still, the world is a richer place for the findings of the CIDER group. Not only do they enhance our scientific understanding of the planet, but they spark our imagination. Deep within the dark heart of the Earth, within inverted mountain ranges which support our world, a wealth of diamonds would glint and sparkle, if only light from the surface were ever to reach them.