Scientists from the Massachusetts Institute of Technology (MIT) in the US and colleagues said the findings are unlikely to set off a diamond rush.
Shaped like inverted mountains, cratons can stretch as deep as 200 miles through the Earth's crust and into its mantle; geologists refer to their deepest sections as "roots."
"This shows that diamond is not perhaps this exotic mineral, but on the (geological) scale of things, it is relatively common," said Ulrich Faul, a research scientist in MIT.
"We can't get at them, but still, there is much more diamond there than we have ever thought before," Faul said.
came to the conclusion after puzzling over an anomaly in seismic data.
For the past few decades, agencies such as the US Geological Survey have kept global records of seismic activity - essentially, sound waves travelling through the Earth that are triggered by earthquakes, tsunamis, explosions, and other ground-shaking sources.
Scientists have used this relationship between seismic velocity and rock composition to estimate the types of rocks that make up the Earth's crust and parts of the upper mantle, also known as the lithosphere.
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