Using sound waves, geologists have discovered a gigantic cache of gems deep in the bowels of the Earth, possibly in the volume of a quadrillion tons.
The exploration began when an international team of researchers decided to uncover a long-standing geological mystery. Scientists can determine which rocks form different parts of the planet by studying seismic activity. Basically, the sound waves created by earthquakes or the rumble of volcanoes will travel at different speeds through different types of rocks, painting a picture of what lies below.
But one area does not behave as expected. Cratons are the oldest and most immobile stone slabs on Earth (more precisely, in the Earth), with roots extending from the center of tectonic plates to a depth of 320 km. The estimated composition of these pillars will produce faster sound waves, but not up to the speeds that have been seen.
To find out what "cratonic roots" might be, geologists studied seismic data collected by various organizations to create a 3D model of the propagation of these waves through cratons.
They then modeled sound waves traveling through a wide range of different combinations of rock types to find one that matches the observed speeds.
After all, only one particular breed recipe produced the same sound wave velocities. To do this, the cratons require a diamond content of one to two percent of the total volume, and otherwise they consist of peridotite and a small amount of eclogite.
It may not sound very much like a diamond, but given the entire volume of cratons in Earth, geologists estimate that there could be up to a quadrillion tons of material - about 1,000 times more diamonds than was previously known.
The find is an addition to an already large collection of inaccessible diamonds and shows that gems are not all that rare. They were previously found in meteorites hitting Neptune, in clouds around distant stars, and may even make up entire planets.
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