Scientists discover 'quadrillion tons of diamond' beneath Earth's surface

Mindy Sparks
July 19, 2018

Cratons are ancient, unmoving sections in the center of tectonic plates.

Because they couldn't actually dig down and bring back a sample of the cratonic rock, the researchers used sound waves to arrive at their diamond-content estimate. According to the study, up to two percent of these roots may be composed of diamond - meaning there could be a whopping quadrillion tons (a staggering 15 zeroes) of diamonds scattered below our planet's surface.

"Diamonds are a flawless match because they're a little bit more dense, but we don't need a lot of them", said Ulrich Faul, a researcher in MIT's Department of Earth, Atmospheric, and Planetary Sciences and a senior participant in the study. "We can't get at them, but still, there is much more diamond there than we have ever thought before", explained Ulrich Faul, a scientist from the MIT.

Faul and his associates reached their decision subsequent to thinking about an abnormality in seismic information.

The diamonds were found by analysing seismic records - essentially sound waves travelling through the Earth triggered by ground-shaking forces. Seismic receivers around the globe get sound waves from such sources, at different rates and powers, which seismologists can use to figure out where, for instance, a quake started.

But, when studying the Earth's interior, the scientists faced something very puzzling.

Sound waves travel at different speeds depending on the composition of the rocks it has to travel through.

The scientists created virtual rock models to determine the material that allowed the sound waves to pass quickly through cratons.

Cratons are stable parts in the crust and mantle of the Earth that are usually less dense and colder than the parts surrounding them.

The researchers found that these sound waves tend to speed up when passing through the cratons' roots - much faster than they had previously thought.

'Then we have to say, "There is a problem".

Scientists later used this knowledge to gather virtual rocks, produced using different blends of minerals. The research team found only one composition of rock could support the speed measured: a material that contains 1 to 2 % diamond in addition to peridotite (the dominant rock type of the upper mantle) and small amounts of eclogite (which represents the subducted oceanic crust). About 1,000 times more common, according to the Massachusetts Institute of Technology.

Faul said, 'Diamond in many ways is special.

A postdoctoral student at UC Santa Barbara and lead author of the study, Joshua Garber said "When the waves pass through the earth, then diamonds will transmit them faster than other rocks or minerals, which are less rigid". In terms of sheer mass, that works out to around a quadrillion, or thousand trillion, tons of diamond.

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