A rough diamond in a mine (Image credit: Getty Images)
LiveScience has a story about the formation of diamonds. Diamonds form deep in the Earth's crust at a depth of about 93 miles. They are brought to the surface by fast moving eruptions called kimberlites. Kimberlites travel at between 11 and 83 mph (18 to 133 km/h). They are most likely to occur during times of high tectonic activity, like the break up of Pangaea roughly about 190 million years ago. A recent paper in the journal Nature by Thomas Gernon, a professor of Earth and climate science at the University of Southampton in England, looks at the science of diamond formation.
Gernon and his colleagues began by looking for correlations between the ages of kimberlites and the degree of plate fragmentation occurring at those times. They found that over the last 500 million years, there is a pattern where the plates start to pull apart, then 22 million to 30 million years later, kimberlite eruptions peak. (This pattern held over the last 1 billion years as well but with more uncertainty given the difficulties of tracing geologic cycles that far back.)
For example, the researchers found that kimberlite eruptions picked up in what is now Africa and South America starting about 25 million years after the breakup of the southern supercontinent Gondwana, about 180 million years ago. Today's North America also saw a spike in kimberlites after Pangaea began to rift apart around 250 million years ago. Interestingly, these kimberlite eruptions seemed to start at the edges of the rifts and then marched steadily toward the center of the land masses.
