There are enormous deposits of diamonds deep underneath the Earth's surface. Man is unlikely to ever reach them, but they can help us have a better understanding of how the planet is made.
In order to understand the structure of the planet underneath its surface, scientists use sound waves. Unlike light, sound passes through rock, which gives scientists an opportunity to learn a lot about the insides of our planet.
Usually, scientists analyse the sounds that come from earthquakes or volcanic explosions to find out what materials lie under the ground. Scientists used this method to study a strange anomaly that occurs when seismic waves pass through the structures called cratonic roots. These are very ancient structures that represent very dense rock formations, reminiscent to mountains turned upside down. These rocks rest hundreds of kilometres under tectonic plates.
Because of their density, sound waves pass through cratonic roots much faster than they do through most other rocks. Over the past few decades, it has become clear that sound waves move at a faster rate than simulations had showed. A group of scientists from the Massachusetts Institute of Technology analysed this oddity and suggested that it was a certain material inside cratonic roots that made sound waves pass through them faster.
US scientists used computer modelling to see how sound waves pass through cratonic roots of different types of rock. Only one simulation coincided with the results that the scientists obtained. A faster speed of sound waves could thus be achieved only if cratonic roots consisted not only of rock, but also of diamonds, the content of which should be at least one or two percent.
Cratonic roots constitute a significant part of the Earth's lithosphere. Even if two percent of those deposits consist of diamonds, it means that there are quadrillion tons of precious rocks buried about 200 kilometres underneath the Earth's surface.