Flawed diamonds reveal the shape of a lost Earth

A tiny, blood-red flaw inside a diamond can reveal what was happening to Earth 3 billion years ago. A recent scientific study of thousands of flawed diamonds like this one have given us a window into our planet's strange and violent past.

We have a pretty good understanding of the continental plates' behavior on Earth now, but what did they look like billions of years ago? That's a difficult question that goes far beyond simply reconstructing ancient mega-continent Pangaea. But now researchers from the Carnegie Institution's Department of Terrestrial Magnetism and the University of Cape Town have figured out how to better understand how Earth's surface behaved in the distant past — by analyzing its most precious elements.

See that diamond in the shot above? The red spot in the middle is a garnet inclusion, with a significant amount of nitrogen present. While that makes it a less valuable diamond for the market, it provides a huge amount of information if you're the right type of scientist. Diamonds have impurities — often too small to be seen — but by tracking the impurities of these ancients stones, you can begin to see how the continents behaved.

The inclusions are perfectly preserved inside the diamonds, and can give the age and chemical information about the environment in which they were formed.

By examining thousands of diamond samples, the researchers discovered that around three billion years ago, there was a major change on our planet. The ocean floor was mixing with the Earth's mantle, a layer liquid rock deep beneath the planet's surface.

How do they know? Inclusions in the diamonds stopped showing traces of peridotite rocks (commonly found in the Earth's mantle) to ecologite (a rock from the Earth's surface crust). This change can be found in diamonds all across the globe, and indicates that three billion years ago, the ocean's continental plates started hitting the land, breaking up the original supercontinent, and starting the cycle of continents drifting apart then smashing together that has carried on until today.

Just how long ago was that? Think of it this way: we all know about the supercontinent Pangaea, right? Well, before that was Pannotia, and before that Rodinia, and onwards backwards through Columbia, Kenorland, Ur, and finally Vaalbara. Think of how slowly the continents move, how long ago Pangaea was, and how long it will be before the next supercontinent is formed when the continents smash into each other again. Now repeat that cycle five times in the past. That's how long ago this whole system started.