Sound waves reveal huge cache of diamonds inside the Earth

Sound waves reveal diamond cache deep in Earth’s interior

Study finds 1–2 percent of Earth’s oldest mantle rocks are made from diamond.

From MIT:

There may be more than a quadrillion tons of diamond hidden in the Earth’s interior, according to a new study from MIT and other universities. But the new results are unlikely to set off a diamond rush. The scientists estimate the precious minerals are buried more than 100 miles below the surface, far deeper than any drilling expedition has ever reached.

The ultradeep cache may be scattered within cratonic roots — the oldest and most immovable sections of rock that lie beneath the center of most continental tectonic plates. Shaped like inverted mountains, cratons can stretch as deep as 200 miles through the Earth’s crust and into its mantle; geologists refer to their deepest sections as “roots.”

In the new study, scientists estimate that cratonic roots may contain 1 to 2 percent diamond. Considering the total volume of cratonic roots in the Earth, the team figures that about a quadrillion (1016) tons of diamond are scattered within these ancient rocks, 90 to 150 miles below the surface.

“This shows that diamond is not perhaps this exotic mineral, but on the [geological] scale of things, it’s relatively common,” says Ulrich Faul, a research scientist in MIT’s Department of Earth, Atmospheric, and Planetary Sciences. “We can’t get at them, but still, there is much more diamond there than we have ever thought before.”

Faul’s co-authors include scientists from the University of California at Santa Barbara, the Institut de Physique du Globe de Paris, the University of California at Berkeley, Ecole Polytechnique, the Carnegie Institution of Washington, Harvard University, the University of Science and Technology of China, the University of Bayreuth, the University of Melbourne, and University College London.

A sound glitch

Faul and his colleagues came to their conclusion after puzzling over an anomaly in seismic data. For the past few decades, agencies such as the United States Geological Survey have kept global records of seismic activity — essentially, sound waves traveling through the Earth that are triggered by earthquakes, tsunamis, explosions, and other ground-shaking sources. Seismic receivers around the world pick up sound waves from such sources, at various speeds and intensities, which seismologists can use to determine where, for example, an earthquake originated.

Scientists can also use this seismic data to construct an image of what the Earth’s interior might look like. Sound waves move at various speeds through the Earth, depending on the temperature, density, and composition of the rocks through which they travel. Scientists have used this relationship between seismic velocity and rock composition to estimate the types of rocks that make up the Earth’s crust and parts of the upper mantle, also known as the lithosphere.

However, in using seismic data to map the Earth’s interior, scientists have been unable to explain a curious anomaly: Sound waves tend to speed up significantly when passing through the roots of ancient cratons. Cratons are known to be colder and less dense than the surrounding mantle, which would in turn yield slightly faster sound waves, but not quite as fast as what has been measured.

“The velocities that are measured are faster than what we think we can reproduce with reasonable assumptions about what is there,” Faul says. “Then we have to say, ‘There is a problem.’ That’s how this project started.”

Diamonds in the deep

The team aimed to identify the composition of cratonic roots that might explain the spikes in seismic speeds. To do this, seismologists on the team first used seismic data from the USGS and other sources to generate a three-dimensional model of the velocities of seismic waves traveling through the Earth’s major cratons.

Next, Faul and others, who in the past have measured sound speeds through many different types of minerals in the laboratory, used this knowledge to assemble virtual rocks, made from various combinations of minerals. Then the team calculated how fast sound waves would travel through each virtual rock, and found only one type of rock that produced the same velocities as what the seismologists measured: one that contains 1 to 2 percent diamond, in addition to peridotite (the predominant rock type of the Earth’s upper mantle) and minor amounts of eclogite (representing subducted oceanic crust). This scenario represents at least 1,000 times more diamond than people had previously expected.

“Diamond in many ways is special,” Faul says. “One of its special properties is, the sound velocity in diamond is more than twice as fast as in the dominant mineral in upper mantle rocks, olivine.”

The researchers found that a rock composition of 1 to 2 percent diamond would be just enough to produce the higher sound velocities that the seismologists measured. This small fraction of diamond would also not change the overall density of a craton, which is naturally less dense than the surrounding mantle.

“They are like pieces of wood, floating on water,” Faul says. “Cratons are a tiny bit less dense than their surroundings, so they don’t get subducted back into the Earth but stay floating on the surface. This is how they preserve the oldest rocks. So we found that you just need 1 to 2 percent diamond for cratons to be stable and not sink.”

In a way, Faul says cratonic roots made partly of diamond makes sense. Diamonds are forged in the high-pressure, high-temperature environment of the deep Earth and only make it close to the surface through volcanic eruptions that occur every few tens of millions of years. These eruptions carve out geologic “pipes” made of a type of rock called kimberlite (named after the town of Kimberley, South Africa, where the first diamonds in this type of rock were found). Diamond, along with magma from deep in the Earth, can spew out through kimberlite pipes, onto the surface of the Earth.

For the most part, kimberlite pipes have been found at the edges of cratonic roots, such as in certain parts of Canada, Siberia, Australia, and South Africa. It would make sense, then, that cratonic roots should contain some diamond in their makeup.

“It’s circumstantial evidence, but we’ve pieced it all together,” Faul says. “We went through all the different possibilities, from every angle, and this is the only one that’s left as a reasonable explanation.”

This research was supported, in part, by the National Science Foundation.

116 thoughts on “Sound waves reveal huge cache of diamonds inside the Earth

  1. Journey to the Center of the Earth! Let’s go!!!

    seriously, I know author Vernor Vinge (among others) have postulated that there may be large, near planetary size diamonds floating through interstellar space, the remnants of burnt out white dwarves and other stellar decays.

  2. There “may be” diamonds. Then again there may not be diamonds. I always look on with skepticism when I here “my be” in a study.

    • A sad fact is that we know very little about properties of rocks under extreme pressures and temperatures – the material we know most about are diamonds, because they are used to approximate these conditions.

      We don’t know yet what causes very deep earthquakes (hundreds of miles deep) where the material should be half-melted. One theory is a sudden phase shift in a huge volume of material.

      • Here’s the weakest statement in the article (bold is mine)-
        “Next, Faul and others, who in the past have measured sound speeds through many (but not all), different types of minerals in the laboratory, used this (incomplete) knowledge to assemble virtual (GIGO) rocks, made from various combinations of minerals (they are familiar with).”

      • Curious G

        That is an interesting postulation. It could also be oil forming from its precursors, changing in volume as the reaction cascades through the material.

        I always found it fascinating that marble under high pressure can be shaped like putty, then depressurized to retain its new shape.

      • Could be those Cratonic Roots. We should mine them away to lessen tectonic resistance and decrease the potential for sudden dramatic slippage

        • They’re only lonely because their friends all got deported… Oh, wait! You said neutrinos!

  3. > cratonic roots made partly of diamond makes sense. Diamonds are forged in the high-pressure, high-temperature environment of the deep Earth

    Carbon, heat, pressure yields “diamonds.” Less heat and pressure yields oil. Hmmmm.

    • That would be the abiogenic petroleum origin theory. It seems logical that the presence of vast quantities of carbon as diamonds 100 miles into the Earth should bolster that theory.

      Any pushback against this new deep diamond theory would come from people opposed to the abiogenic petroleum origin theory. I’m waiting with bated breath to see if it happens.

      • The “abiogenic” hypothesis relies on a false narrative about the conventional theory of crude oil formation.

        Diamonds or any other high pressure/temperature species of carbon is totally irrelevant to hydrocarbons.

      • The end result of prolonged heat and pressure on Carbon and Hydrogen is probably methane(natural gas), not petroleum. Google the term “Oil Window” — which is the combination of time, heat and pressure thought to control whether a well into hydrocarbon rich rocks will yield oil, or gas or a mixture. Petroleum geologists seem to think that the concept works.

        Problem is that if the Earth contains large amounts of abiotic methane, one would expect a respectable number of seeps of natural gas from igneous rocks. Some are known, but not a lot. And it is plausible (but far from proven) that many of those result from near surface, low temperature, processes.

        Overall — we just don’t know. But there isn’t much evidence for abundant deep abiotic hydrocarbons” on the modern Earth.

  4. Don’t tell my wife that diamonds can be the size of planets.
    NOVA (God forbid) has an episode about gems and go on to theorize when continental drift began, in where the tectonic plate forces generated diamonds. Earth formation, 4.2B years ago, plate tectonics, about 3.2B years ago. They surmised this by studying inclusions held in diamonds which are like time capsules. Thought it was interesting 🙂

  5. An interesting article, but once again no hat tip to pre-existing knowledge that there is a huge store of diamonds beneath Archean (>2.5 bya) at what is known as the Diamond Stability Field (DSF)some 150km depth. The kimberlite is a high potassium magma that arises from about 180-200km depth. It contains no diamonds itself but when it begins to erupt, it punches through the diamond stability field and samples it.

    The remarkable journey to the surface takes only a few hours. It rises at average~ 20kph to the base of the crust where it attains ~40kph and once it cracks into the crust it begins to accelerate, driven by volatiles – water, CO2, F, etc, reaching ~1200kph when it breaks the surface.It tosses material from 300_400m deep up above the clouds and it falls back into the crater and surroundings along with trees and other debris that toppleinto the temporarily empty crater. Timber was found in a number of South African pipes and more recently, perfectly preserved redwood chunks were found at 300m depth in the Ekati dimond mine at the Arctic Circle in Canada. Hows that for “precedented”? A California climate in the Canadian barren lands. Now thats some Climate Change 53 million years ago. Here are some pics of the still red and sappy redwood.

    • A California climate in the Canadian barren lands. Now thats some Climate Change 53 million years ago.

      Yabut … that part of Canada may not have been in the Arctic. The continents have moved a lot since then. link

    • There is an old joke that every generation of teenagers thinks they are the first to discover sex. It would seem that every generation of newly-minted PhDs think that they are the first to discover anything new.

      • You are absolutely right. The thing is that their thesis advisors, and their committees are equally removed from reality. It’s very common that ten different PhDs of varying ages don’t know things that a lot of supposedly uneducated people would think are common knowledge. Otherwise the crap would be nipped in the bud.

        • In my years as a facility operations engineer for SIUE, I encountered many PhDs who were unable to understand that the placement of their office furniture blocking HVAC vents was detrimental to their staff’s comfort. Simple stuff just doesn’t click for some of academia, once a young math prof asked me if I could help him because his bicycle chain had come off and he was not sure how to reinstall it.

          • I had reloaded a few boxes of 12-gauge shotgun shells with no problems. I had just come back from the hospital from abdominal surgery, and didn’t feel up to doing a lot of work. I invited two PhD co-workers, who I regularly shot trap with, to come over and load shells while I sorted hulls. I left the two of them to their own devices operating the re-loader, which seemed reasonable. The next time we went trap shooting, about half of all their shot-shells failed to discharge the pellets from the barrel, apparently lacking any powder! Just saying!

    • That is so like UK PM Tony Blair’s vision for more students and more universities.

      Noting that University graduates on average earned 50% more than mere mortals, he decided to borrow enough money to turn all et the technical colleges into universities so that more than half the UK population could attend, and double their salaries.

      What resulted of course was an unemployable generation on the social security convinced they were entitled to better, and having of tens of thousands of pounds student loan debts.

      • Where I live, community colleges are a bargain. Compared with universities they have around half the students. link Graduates from community colleges are more likely to end up working in the field for which they trained.

        The shocker for me:

        … only about 30 per cent of employed individuals in Ontario who held a bachelor’s degree or higher in engineering were working as engineers or engineering managers. Fully two-thirds of engineering-degree holders were not working in engineering at all. link

        Compare that with +90% in-field employment for two year engineering technicians and three year engineering technologists. That means that a three year community college engineering technology graduate much more easily meets the experience requirements necessary to become a professional engineer.

        Why aren’t people flooding the community colleges?

        Parents perceive that a college diploma lacks the prestige of a university degree. Because of that, the Ontario government has granted colleges the right to grant four year degrees. The trouble is that they are effectively supervised by the universities. The result hasn’t been wonderful and students still don’t flood the community colleges.

        Given the choice of sending my child to a university to do Women’s Studies or college to do Graphic Design or Law and Security, the choice would be easy.

        Sadly, given the PEO survey, I wouldn’t advise a young person to take Engineering at University. These days I would suggest a three year engineering technology diploma. With an additional eight years of part-time courses, the three year grad can become a Licensed Professional Engineer. It’s not easy but it’s a heck of a lot more certain and, as an additional benefit, it’s way cheaper.

        • I tend to agree. We have the same dichotomy in Sweden with ”Civilingenjörer” and ”Högskoleingenjörer”.

          At my workplace we hired almost exclusively “Högskoleingenjörer”, it took a slightly longer time before they could work independently as consultants, true, but they were more work-focused and considerably cheaper. The only real drawback was that once they had accumulated some experience they became very attractive on the market, and our customers would often try to hire them away from us.

      • “….unemployable generation on the social security…” So that’s where all the protesters come from. Don’t have to work so go protest.

  6. Diamonds are a form of carbon, right ? … and this makes them evil.

    If ever there were a case to cease the tradition of giving diamonds as a gesture of love, then this is it. I mean, would you give your most cherished love a chunk of pollution as a gesture of your affection ? I think not. We need to rewrite a familiar saying as, “Carbon pollution is a girl’s best friend.”

    Nothing says “I love you” like a chunk of carbon pollution, … right ?

  7. Signals and inference outside of a limited frame of reference in time and space helps us discover patterns in the clouds. That doesn’t mean there is nothing there or even poorly characterized. It’s a beginning to something. Perhaps something real.

  8. Then we have to say, ‘There is a problem.’ That’s how this project started.

    I believe I hear echoes of my science teachers.

  9. “quadrillion (10^16) tons ”
    err, no.
    IQ test:
    million 10^6 ; billion 10^9 ; trillion 10^12 ….. fill in the next term in this sequence.

  10. “… and this is the only one that’s left as a reasonable explanation.”

    Ah the post-scientific era’s best argument : what else could it be ?


    “On Europa, Van der Berg and Chris Floyd take the shuttle William Tsung (nicknamed Bill Tee) to study Mount Zeus. Near Mount Zeus, van der Berg relays the message “LUCY IS HERE” to his uncle Paul. It is revealed that Van der Berg’s hypothesis, now proven true, was that Mount Zeus is one huge diamond, a remnant from the core of the exploded Jupiter.”

  12. Seems like the usual optimization routine for filling in structure or density. In an optical CAD program it’s easy to set up arguments that either drive material property (index of refraction) or object parameters (radius of curvature, thickness, or departures from sphericity) to create an quality or effect seen some other way. Substituting materials or objects and so on to drive the error function down. I used this to reverse engineer optical systems when there was incomplete knowledge.

    I imagine these scientists have elaborate geophysical models that can be rigged for optimization relatively easily.

  13. “We went through all the different possibilities, from every angle, and this is the only one that’s left as a reasonable explanation.” Good logic except for the other unknown variables that could increase the speed of sound slightly. This is still a big maybe.

  14. I’m not a geologist, is this why volcanoes toss out eruption diamonds? Am I barking up the wrong peice of compressed carbon?

    • Yes, but not any old volcano. Only kimberlite eruptions can carry diamonds from the mantle to the surface. And they are rare, none has occurred in historical times as far as is known. And only a small fraction of all kimberlite pipes actually contain diamonds.

  15. “Cratons are known to be colder and less dense”
    Since the Cratons have existed for centuries in close (relative) proximity to the core material (at whatever temperature that is) I don’t follow why it is colder at all. Thermal soak for a long time brings everything to the SAME temperature.
    Different densities are expected as long as the composition is different but NOT colder!

  16. Why do you think DeBeers created the ‘Diamonds are Forever’ message? Because they didnt want a second hand market in them which would expose DeBeers as massively manipulating the price. The fact is diamonds are abundant on the surface in some parts of the world, and not at all rare.

    • ” The fact is diamonds are abundant on the surface in some parts of the world,and not at all rare.”
      So Matt tell us where they all are. Worked as an exploration geologist, including deep drilling at Argyle and I can tell you they are not common, especially gem quality. You will make a fortune if you know where the next supply is.

      • Kimberlites are more common than DeBeers would prefer… Otherwise, yeah… Gem quality minerals are, by definition, rare.

  17. It is very similar to the process of reasoning that gives us global warming. It is modeled and makes predictions that cannot be tested in lifetimes of those making the predictions. This is theory, not an objective finding. It might be true and might not but the evidence is all circumstantial as they admit and there may be many other explanations that they have failed to consider. Fortunately this theory doesn’t lead to an expectation that civilization regress to the hunter gatherer stage.

    • They haven’t designed a reproducible experiment yet? That’s something someone should ‘dig’ into. I suggest all the ‘warmists’ that will, hopefully, find an end to their supply of grant money. That should keep them both busy and warm.

    • Precisely – we tried all the things we could think of in our climate models, but only got correlation with our data when we included CO2 forcing and amplification. Therefore, it must be CO2.

  18. “Cratons are known to be colder and less dense than the surrounding mantle, which would in turn yield slightly faster sound waves.”

    Guess that should say

    less dens yield slightly slower sound waves.

    • Any geophysicist care to comment? I don’t think density is the only parameter, but i’m not a geophysicist.

        • But it’s the specific modulus, right? The colder less dense rock may have a combination of enough shear modulus and low density to have higher seismic wave velocity. Denser rocks usually have higher shear modulus but maybe not in hot or semi melted states. Diamonds are low density but the modulus is sky high. That’s like, makes for really really high speed of sound. The seismic waves are going to really speed up in the diamond zone.
          Gad, come on people, don’t make me work. David you are a reference animal, just do it! Speed of sound is proportional to the specific modulus. Proportional to the shear modulus and inversely proportional to density. There is an equation somewhere, in my seismology notes from 1982 buried out in the shed.

        • Ugh, went off to Wikipedia. Yeah yeah, basically vel ~ modulus/density. The S and P waves use different modulus qualities, therefore propagate at different speeds. Speed of sound in diamond is about 12000 m/s or 2X common craton rock.

  19. Regrettably, this article is feeding into the mystique of natural diamonds, to the benefit of a cartel. “Wow: Diamonds diamonds everywhere but not a hole so deep!”. Diamonds, nearly flawless of any color and size you wish, should be no more $200/carat, but the cartel pressures and does worse to anyone who would create this fair price market. When the deep state enablers of the corrupt diamond industry are stripped of their power, I’ll be looking forward to decorating my wife with tiaras, chokers, and all sorts of diamond jewelry in every color for all clothes and occasions.

  20. DeBeres isn’t going to be happy about this. If someone can reach this cache of diamonds, cost of diamonds will drop drastically worldwide!

    • I doubt that de Beers will be worried. It would be vastly simpler to make artificial gem-quality diamonds. It can be done already for small stones, but the cost is comparable to de Beers prices.

    • Drilling a borehole to a depth of 90-150 *miles* would be… There really isn’t a word to describe how DUMB this idea is.

      This is about as worrisome for DeBeers as the collected works of Thomas Gold are worrisome to ExxonMobil… Is my sarcasm obvious?

      • De Light (Beer) Fully obvious. Is there any way to pitch it to the Flat Earth Society? Or get a grant to develop a 3-D printing process for diamonds? Or sell asteroid belt maps with the ‘likely to contain’ asteroids marked?

    • There’s diamonds ’nuff already in the vicinity.

      People tend to think the bridal ring with small diamonds from Grandma must yield good money.

      Forget about it: a new bridal ring for the daughter costs more than you got for Grandma’s.

  21. Sorry for commenting in this given subject a bit too late, and also for the following simple and probably silly question.

    If when this 1-2% figure considered as per addressing the given mass estimation of diamonds under “there”, and if this considerd as a volume expression…
    How much bigger and larger that “diamond volume” will be if and when compared to the entire land mass above sea level, when the later considered as expressed per a volume metric????

    probably just a silly question!

    My wild and most probably estimation guess consist as somewhere around of a figure round about 3x;
    at the very least!!

    and please do not mind any grammar errors….commenting by my “smart phone” 🙂


    • Need a big backhoe and a big dump truck for all those diamonds. Probably a lot of spare buckets and an arm extension or two. And a big island, or maybe a continent for storage. Simple is best! No such thing as a silly question. Silly answers, on the other hand ………….

  22. “Diamonds, render her speechless! — DeBeers advertisement.
    “Diamonds: That’ll shut her up!” — Ron White

  23. “Diamonds, render her speechless” — DeBeers advertisement
    “Diamonds…that’ll shut her up!” — Ron White

Comments are closed.