Earth Is Full Of Diamonds: A Quadrillion Tons In Fact

It turns out diamonds might be shockingly common with over a quadrillion tons of the precious rock potentially hiding under the Earth's surface.

Unfortunately, this endless diamond cache is entirely out of reach as it's buried over 100 miles deep underground.

Earth Is Chock-Full Of Diamonds

In the study published in the journal Geochemistry, Geophysics, Geosystems, researchers reveal that new seismic models suggest an abundance of diamonds in the Earth's cratonic roots. Cratons are ancient and immovable rock that extend through the crust and mantle, and their roots are known to be the deepest sections 

The team estimates that diamond may be 1 to 2 percent of the planet's cratonic roots, which means there are roughly a quadrillion tons of diamonds just lying among these ancient rocks.

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

Finding Earth's Diamond Cache

Faul and the other researchers discovered Earth's secret diamond stash by tracking seismic activity, which are sound waves moving through the planet as a result of ground-shaking events such as earthquakes and tsunamis. Since sound waves travel in varying speeds depending on the rock's temperature, density, and composition, geologists can put together a picture of the planet's interior with seismic data.

Cratons are expected to yield slightly faster sound waves due to their coolness and density, but the recent analysis produced sound waves that are much faster than it should be. The anomaly piqued the team's interest, leading them to hunt for the mysterious composition of cratonic roots.

According to MIT, the researchers created a three-dimensional model of the seismic wave velocities as it traveled underground. Then, they tested a number of rocks against the sound waves to see which one would match the velocities that the seismologists measured.

There was only one that did: a rock that contains 1 to 2 percent diamond, plus peridotite and even traces of eclogite.

This much diamond is 1,000 times more than previously believed, but it's not expected to alter the cratons' density.

An Intriguing Hypothesis, But There Are Some Skeptics

"It's circumstantial evidence, but we've pieced it all together. We went through all the different possibilities, from every angle, and this is the only one that's left as a reasonable explanation," Faul says, but also tells Gizmodo that it's still just a hypothesis.

After all, this would change a lot about what geologists know and understand about the Earth at the moment.

Wendy Panero, professor in the Ohio State University school of Earth Sciences, explains that this much diamond under our feet would almost double the carbon in the mantle. In turn, this would have an effect on scientists' knowledge of the evolution of Earth's interior.

"[Two percent volume] is far in excess of the amount of diamond found in kimberlite rock, which is on the order of carats per ton," Panero, who is not involved in the study, points out to Gizmodo. "I am eager to see more work in the area to see if this hypothesis holds up to further scrutiny."