The old song says “diamonds are a girl’s best friend,” but the gemstone might be super important to our planet’s internal structure, too. In fact, deep within the earth, there may be literally a quadrillion ton of diamonds. That number sounds fake, but it’s very real: just take 1 and add 15 zeros.
Scientists developed their diamond theory during a study on seismic activity. Seismic activity is basically when earthquakes, explosions, tsunamis, and so on cause sound waves to travel through the earth. Humans have seismic receivers all over the globe to pick up and record these waves so we can figure out where an earthquake began and other useful information. We’ve collected decades’ worth of this info, but scientists have been puzzled by something. Over 100 miles beneath our planet’s surface, there’s a section of ancient, stable rock known as a craton. These rocks can stretch down all the way into the outer crust and mantle, which is 200 feet deep. Because of their tapering shape which resemble upside-down mountains, the deepest part of a craton is called a “root.”
So, what’s the odd thing about seismic activity that’s puzzling scientists? When sound waves move through cratonic roots, the waves speed up. While a faster speed isn’t weird in itself – the colder and less dense cratons would allow waves to move faster than through other materials – the waves are moving too quickly. There’s something else going on.
Using a 3D model of virtual rocks made from a variety of minerals, scientists tried to mimic what’s going on with sound waves and craton roots. They realized that when 1-2% of the craton roots were made of diamonds, they got the results they were seeing in the real world. While 1-2% is a really small percentage, it translates into a quadrillion tons.
Diamonds aren’t that rare, it turns out! However, they’re found deeper in the earth than any drill could ever go. They might appear since diamonds that deep come to the surface during volcano eruptions, but happens very rarely, as in, once in ten million years. For now, scientists just have their 3D model and a theory.